Analytical and Comparative Study for Solar Thermal Cooling ... · Cooling and Photovoltaic Solar Cooling in ... Study for Solar Thermal Cooling and Photovoltaic Solar Cooling

Analytical and Comparative Study for Solar Thermal Cooling and Photovoltaic Solar Cooling in the MENA

Region

By

Younis Yousef Abidrabbu Badran

A Thesis Submitted to the Faculty of Engineering at Cairo University

and Faculty of Electrical Engineering and Computer Science at Kassel University

in Partial Fulfillment of the Requirements for the Degree of

Master of Science in

Renewable Energy and Energy Efficiency

Faculty of Engineering

Cairo University Kassel University Giza, Egypt Kassel, Germany

March, 2012


Region

By






Renewable Energy and Energy Efficiency

Reviewers Supervisors

Prof. Dr. Adel Khalil Member Mechanical Power Engineering Department Faculty of Engineering, Cairo University

Dr.-Ing. Norbert Henze

Systems Engineering and Grid Integration Department Head of group. Engineering and Measuring Technology Fraunhofer Institute IWES, Kassel, Germany

Prof. Dr. Albert Claudi Member Faculty of Engineering and Computer Science Kassel University

Dipl.-Ing. Siwanand Misara Member Group of Engineering and Measuring Technology Fraunhofer Institute IWES, Kassel, Germany

March, 2012

http://www.iwes.fraunhofer.de/de/kompetenzen_abteilungen/anlagentechnik/anlagen-_und_messtechnik/personal/visitenkarten_mitarbeiter/norbert_henze_.html

http://www.iwes.fraunhofer.de/de/kompetenzen_abteilungen/anlagentechnik/anlagen-_und_messtechnik/personal/visitenkarten_mitarbeiter/siwanand_misara.html


Region

By






Renewable Energy and Energy Efficiency Approved by the Examining Committee:

Prof.Dr. Adel Khalil, Thesis main Advisor

Prof. Dr. Albert Claudi, Thesis main Advisor

Dr. Sayed Kaseb, Member

Faculty of Engineering

Cairo University Kassel University Giza, Egypt Kassel, Germany

March, 2012

IV

Acknowledgements

First and foremost I would like to thank God. This work could not have been possible

without the help of many people who supported my work.

I would like to show my gratitude to my family in Palestine for their continued love,

encouragement over the years of my education. This thesis is dedicated to them.

I am heartily thankful to my supervisor Dipl.-Ing. Siwanand Misara from Fraunhofer

Institute for Wind Energy and Energy System Technology (IWES) in Kassel, who has

guided and supported me in every phase of this thesis from the initial to the final level

and enlightened the work with his vast knowledge on the subject.

Deepest gratitude to my supervisor from Cairo university, Professor. Dr. Adel Khalil for

his support and giving me the chance to carry out this research. It has been a pleasure to

work with this professor who has a high scientific competence and professionalism. In

addition I would like to thank my supervisor from Kassel university, Prof. Dr.-Ing. Albert

Claudi for his available advice in this study. Thanks to Dr.-Ing Michael Krause from

Fraunhofer Institute of Building Physics - Kassel(IBP), who has guided and supported

me especially in the TRNSYS simulation and the thermal air-conditioning cooling design

in this study.

I am grateful to Mr. Salah Azzam and Mr. Firas Alawneh from The Higher Council for

Science and Technology National Center (NERC) in Jordan, who supported me in getting

the meteorological measurement data for Aqaba city.

Thanks to the German Academic Exchange Service (DAAD) for their financial assistance

which made it possible for me to pursue the REMENA master program and this study.

Thanks to my teachers, friends and staff of the REMENA master program and IWES

Fraunhofer Institute in Kassel for encouraging me during my work.

http://www.iwes.fraunhofer.de/de/kompetenzen_abteilungen/anlagentechnik/anlagen-_und_messtechnik/personal/visitenkarten_mitarbeiter/siwanand_misara.html

V

Abstract

In this thesis, a comparison and analyses of solar thermal and solar photovoltaic (PV)

air-conditioning technologies for a Typical Single Family House (TSFH) in two different

MENA climates, Aswan-Egypt and Aqaba-Jordan, are performed. The building cooling

demand is firstly obtained from annual building simulation in TRNSYS software. Based

on these simulation results, three scenarios are designed in order to compensate the

TSFH’s annual cooling demand in each selected climate. These scenarios are solar

thermal air-conditioning with storage (absorption chiller), PV air-conditioning without

storage and PV air-conditioning with storage. The cooling compensation is simulated by

Matlab-Simulink for each scenario.

TRNSYS simulations for Aswan-TSFH and Aqaba-TSFH respectively demonstrate that

the maximum cooling load demand during summer season are: 13.9 kW and 15.3 kW;

the annual cooling energy demands are: 44,330 kWh/year and 43,490 kWh/year which

represents 97.5 % and 96.3 % of the total annual energy consumption (heating and

cooling). On the other hand, Matlab-Simulink demonstrates that the total annual

percentage of cooling energy compensation (direct plus storage) difference between the

PV and thermal with storage scenarios does not exceed 1 % in both cases. However,

differences exist between the two scenarios. The performance of daily direct cooling

compensation by the PV air-conditioning scenarios is more efficient than in the thermal

air-conditioning scenario. The direct cooling compensation percentage for the Aswan-

TSFH and the Aqaba-TSFH respectively are 39.3 % and 35.8 % for the PV air-

conditioning scenarios and 30.8 % and 30.9 % for the thermal air-conditioning scenario.

The compensation by the storage are 10.7 % and 7.3 %, by the PV air-conditioning with

storage scenario and 20.1 % and 11.9 %, by thermal air-conditioning with storage

scenario for the two cases respectively.

The PV air-conditioning scenario with storage behaves and compensates the cooling

demand better than the solar thermal air-conditioning with storage scenario and needs

less storage to cover the same amount of cooling load demand. However, the storage

system in the PV air-conditioning scenario is minor and the direct compensation is

major. That is vice versa in the thermal air-conditioning scenario. This research can be

extended to compare and analyze the scenarios in terms of primary energy, economic

analysis and different buildings. Moreover, the future cost reduction by learning curves

of both technologies can influence the economic feasibility.

VI

Contents

Acknowledgements ............................................................................................................................... iv

Abstract ...................................................................................................................................................... v

List of Figures.......................................................................................................................................... ix

List of Tables .......................................................................................................................................... xii

List of Symbols ..................................................................................................................................... xiii

List of Abbreviations .......................................................................................................................... xvi

1. Introduction ......................................................................................................................................... 1

1.1 Background ................................................................................................................ 1

1.2 Objectives and Boundary Conditions ........................................................................ 2

1.3 Thesis Structure ......................................................................................................... 3

2. Determination of the Reference Building in MENA Regions ............................................. 4

2.1 Reference Location Climates ..................................................................................... 4

2.1.1 Meteorological Data for Reference Locations ..................................................... 5

2.2 Reference Building ..................................................................................................... 8

2.2.1 Architecture Design ............................................................................................. 9

2.2.2 Facade Stricter ................................................................................................... 10

2.2.2.1 Wall Construction ........................................................................................... 10

2.2.2.2 Windows ......................................................................................................... 11

2.2.3 Internal Gain ...................................................................................................... 11

2.2.4 Air Change Condition ......................................................................................... 12

2.2.5 Cooling and Heating Set Points ......................................................................... 12

3. Reference Building Thermal Cooling and Heating Load Simulation .......................... 13

3.1 TRNSYS Software Simulation Environments .......................................................... 13

3.2 Description of the Simulation .................................................................................. 14

3.2.1 Type 56 Mathematical Description ................................................................... 14

3.2.2 TSFH Modeling with Type56 and TRNBuild ..................................................... 16

3.2.3 TSFH Modeling with Type56 and TRNStudio ................................................... 18

3.3 Thermal Cooling Load Simulation Results and Analysis of Results ........................ 21

VII

3.3.1 The Annual Energy Consumption ..................................................................... 21

3.3.2 The Performance of Cooling Load ..................................................................... 23

4. Solar Air-Conditioning Technologies ...................................................................................... 26

4.1 Solar Photovoltaic Air-Conditioning Technology .................................................... 26

4.2 Solar Thermal Air-conditioning Technology ........................................................... 27

5. Solar Air-Conditioning Scenarios Design and Simulation .............................................. 29

5.1 Matlab-Simulink Simulation Environments ............................................................ 29

5.2 Solar PV Air -Conditioning Scenarios ...................................................................... 30

5.2.1 System Components and Design ....................................................................... 30

5.2.2 Systems Simulation and Methodology .............................................................. 37

5.2.2.1 PV air-conditioning Without Storage Scenario .............................................. 38

5.2.2.2 PV Air-conditioning with Storage Scenario.................................................... 40

5.3 Solar Thermal Air-conditioning Scenario(absorption chiller)................................ 41

5.3.1 System Components and Design ....................................................................... 41

5.3.1.1 Solar Thermal Heating System ....................................................................... 42

5.3.1.2 Absorption Chiller .......................................................................................... 47

5.3.3 System Simulation and Methodology ................................................................ 52

6. Simulation Results and Analysis for Solar Air-Conditioning Scenarios .................... 58

6.1 Solar Photovoltaic (PV) Air-conditioning Scenarios ............................................... 58

6.1.1The Influence of a Direct Cooling production .................................................... 59

6.1.2 Excess of Cooling Production and External Back-up Cooling for a Battery

Design ......................................................................................................................... 63

6.1.3 Annual Cooling Energy Compensation Analysis ............................................... 65

6.1.3.1 PV Air-conditioning Without Storage Scenario.............................................. 66

6.1.3.2 PV Air-conditioning With Storage Scenario ................................................... 67

6.2 Results and Analysis for Solar Thermal Air-conditioning Scenario ........................ 69

6.2.1 The Influence of Cooling Production ................................................................. 69

6.2.2 Annual Cooling Energy Compensation Analysis ............................................... 74

VIII

6.2.2.1 Excess Cooling Production and External Back-up Cooling Loads ................. 74

6.2.2.2 Annual Cooling Energy Compensation ........................................................... 76

6.2.2.3 Solar Fraction.................................................................................................. 79

6.3 Thermal Air-conditioning Scenario Versus PV Air-conditioning Scenarios ........... 81

6.3.1 The Direct Cooling Production Load Performance ........................................... 81

6.3.2 Annual Cooling Compensation Energy Percentage .......................................... 87

7. Conclusions and Future Research ............................................................................................ 90

7.1 conclusions ............................................................................................................... 90

7.2 Future Research. ...................................................................................................... 94

References .............................................................................................................................................. 95

Appendices ........................................................................................................................................... 102

Appendix A: Schematic vapour compression cycle ..................................................... 102

Appendix B: Solar Photovoltaic module data sheet .................................................... 102

Appendix C : Inverter data sheet, [45] ......................................................................... 103

Appendix D:Description of Wet Cooling Tower, [37] .................................................. 104

Declaration .......................................................................................................................................... 105

IX

List of Figures

Figure 2.1: Annual distribution of horizontal global solar radiation for Aswan and Aqaba

cities, [16], [17]. ......................................................................................................................................................6

Figure 2.2 Annual distribution of ambient air temperatures for Aqaba and Aswan cities,

[16], [17]. ...................................................................................................................................................................6

Figure 2.3:Annual distribution of ambient air relative humidity in Aswan and Aqaba

cities, [16], [17]. ......................................................................................................................................................7

Figure 2.4: sketch of Typical Single Family House(TSFH) in MENA regions plan, [20]. ......9

Figure 3.1: Zones of TSFH model in TRNBuild. .................................................................................... 16

Figure 3.2: Aswan-TSFH model (Type 56) with all the required components and

connections in TRNStudio. ............................................................................................................................. 18

Figure 3.3: Aqaba-TSFH model (Type 56) with all required components and connections

in TRNStudio. ........................................................................................................................................................ 19

Figure 3.4: Yearly cooling and heating energy demand for the Aswan-TSFH and Aqaba-

TSFH. ......................................................................................................................................................................... 21

Figure 3.5: Monthly cooling and heating energy demand in (kWh) for the Aswan-TSFH

and Aqaba-TSFH. ................................................................................................................................................. 22

Figure 3.6: Yearly Cooling and heating demands distribution(kW) for the Aswan-TSFH.

...................................................................................................................................................................................... 23

Figure 3.7:Yearly Cooling and heating demands distribution in (kW) for the Aqaba-

TSFH. ......................................................................................................................................................................... 24

Figure 3.8: Weakly Cooling load demand distribution in (kW) for the Aqaba-TSFH and

Aswan-TSFH. ......................................................................................................................................................... 25

Figure 4.1 :Basic structure of PV air-conditioning systems, [2]. .................................................. 26

Figure 4.2 :Basic structure of heat driven and desiccant air-conditioning systems, [2]. . 27

Figure 5.1: Schematic flow diagram for solar PV air-conditioning without storage. ......... 31

Figure 5.2: Schematic flow diagram for solar PV air-conditioning with storage. ................ 31

Figure 5.3: The dimensions of a typical single family house (TSFH) - roof area (1) for PV-

array installation. ................................................................................................................................................ 34

X

Figure 5.4: Solar thermal air-conditioning system scenario, coupling of an absorption

chiller with a solar heating system............................................................................................................. 42

Figure 5.5: Schematic diagram for an absorption chiller for chilled water production,

[37]. ........................................................................................................................................................................... 47

Figure 6.1: PV air-conditioning cooling production along the year for Aswan-TSFH. ...... 59

Figure 6.2: PV air-conditioning cooling production along the year for Aqaba-TSFH. ....... 59

Figure 6.3: Solar-PV air-conditioning cooling production in Summer week for Aswan-

TSFH. ......................................................................................................................................................................... 60

Figure 6.4: Solar-PV air-conditioning cooling production in Summer week for Aqaba-

TSFH. ......................................................................................................................................................................... 61

Figure 6.5: Solar PV air-conditioning cooling production in winter week for Aswan-

TSFH. ......................................................................................................................................................................... 61

Figure 6.6: Solar PV air-conditioning cooling production in winter week for Aqaba-

TSFH. ......................................................................................................................................................................... 61

Figure 6.7: PV air-conditioning without storage scenario, Excess cooling production and

external back-up cooling loads for Aswan-TSFH. ............................................................................... 63

Figure 6.8: PV air-conditioning without storage scenario, Excess cooling production and

external back-up cooling loads for Aqaba-TSFH. ................................................................................ 64

Figure 6.9: yearly cooling energy compensation by the solar PV air-conditioning system

with and without storage scenarios for the Aswan-TSFH and Aqaba-TSFH. ........................ 65

Figure 6.10: Monthly cooling energy compensation by solar PV air-conditioning system

with and without storage scenarios for Aswan-TSFH and Aqaba-TSFH. ................................ 66

Figure 6.11: Solar thermal air-conditioning cooling production along the year for

Aswan-TSFH. ......................................................................................................................................................... 69

Figure 6.12: Solar thermal air-conditioning cooling production along the year for Aqaba-

TSFH. ......................................................................................................................................................................... 70

Figure 6.13: Solar thermal air-conditioning cooling production in summer week for

Aswan-TSFH. ......................................................................................................................................................... 71


Aqaba-TSFH. .......................................................................................................................................................... 72

XI

Figure 6.15: Solar thermal air-conditioning cooling production in winter week for

Aswan-TSFH. ......................................................................................................................................................... 72

Figure 6.16: Solar thermal air-conditioning cooling production in Winter week for

Aqaba-TSFH. .......................................................................................................................................................... 72

Figure 6.17: Solar thermal air-conditioning excess cooling production and external

back-up cooling loads for Aswan-TSFH. .................................................................................................. 74


back-up cooling loads for Aswan-TSFH. .................................................................................................. 75

Figure 6.19: The cooling energy compensation by the solar thermal air-conditioning

system scenario for Aqaba-TSFH and Aswan-TSFH. ......................................................................... 76

Figure 6.20: Monthly cooling energy compensation by the solar thermal air-conditioning

system scenario for Aswan-TSFH and Aqaba-TSFH. ......................................................................... 77

Figure 6.21: Annual solar fraction for the solar thermal air-conditioning system scenario

in Aswan-TSFH and Aqaba-TSFH. ............................................................................................................... 79

Figure 6.22: Monthly solar fraction for the solar thermal air-conditioning system

scenario in Aswan-TSFH and Aqaba-TSFH............................................................................................. 79

Figure 6.23: PV air-conditioning versus solar thermal air-conditioning, cooling

production performance in Summer Week for Aswan-TSFH. ...................................................... 81


production performance in Summer Week for Aqaba-TSFH. ....................................................... 82

Figure 6.25:PV air-conditioning versus solar thermal air-conditioning, cooling

production performance in Summer day for Aswan-TSFH. ........................................................... 83


production performance IN Summer day for Aqaba-TSFH. ........................................................... 84

Figure 6.27: Percentage of cooling Energy compensation by the three scenarios for

Aswan-TSFH. ......................................................................................................................................................... 87

Figure 6.28: percentage of cooling Energy compensation by the three scenarios for

Aqaba-TSFH. .......................................................................................................................................................... 88

Figure A: Schematic vapour compression cycle, [2]. ...................................................................... 102

Figure D: Schematic drawing of an open type wet cooling tower, [37]................................. 104

XII

List of Tables

Table2.1 :Constructional components of the reference building (TSFH), [21], [20]. ........ 10

Table2.2 : Thermal properties of the Single glass window for the reference TSFH in

Aswan and Aqaba, TRNSYS library and [13]. ........................................................................................ 11

Table2.3 :Air change(ventilation and infiltration) rate for Aswan-TSFH and Aqaba-TSFH.

...................................................................................................................................................................................... 12

Table 5.1 : Parameters of the flat plate collector, [52]...................................................................... 44

Table5.2: Lithium Bromide-water (WEGRACAL SE 15ACS15) absorption chiller

parameters, compiled from [56] and [10]. ............................................................................................. 50

Table5.3: Technical parameters of the back-up heater, storage and cooling tower, ......... 51

Table6.1: Yearly cooling energy compensation by the solar PV air-conditioning system

with and without storage scenarios for Aswan-TSFH and Aqaba-TSFH. ................................ 66

XIII

List of Symbols

Variables Units Description

m2 PV-array area

AF - Autonomy factor

Acoll,Spec m2 Specific collector area

As m2 Storage surface area

Cnom,Batt Ah Nominal capacity of battery

C1 W/m2K linear heat transfer coefficient

C2 W/m2K2 Quadratic heat transfer coefficient

COPideal Ideal coefficient of performance

COPABCH Coefficient of performance for absorption chiller

Cw kJ/kg .K Specific heat capacity of water

Wh The average daily electric DC of the excess energy

Wh The back-up cooling energy

Gtilt W/m2 Global solar radiation on a tilted surface

G W/m2 Global radiation on horizontal surface

W Output electric power of PV-array

W Output electric power of Inverter

W Output cooling power of Compressed chiller

W Excess cooling power

W Back-up cooling power

W Demand Cooling power

W Electric power charged in the battery

W Cooling power produced by the battery

P hABCH h W Heat power required by the absorption chiller

W Heat power production by the absorption chiller

Pcollh W Heat power production from the collector

PST;loss h W Heat power losses of the storage tank

PhABHh W Heat power losses from the storage by the demand

of cooling system

W Direct heating power

W Back-up cooling power

XIV

W Compensated cooling power by the storage

W Direct cooling power

Wh Back-up cooling energy

Wh Cooling energy compensation by the storage

Wh Direct compensation of cooling energy

K , C Module’s operation temperature

TNOCT K, C Operation cell temperature

K Ambient temperature

K Inlet temperature of the generator

K Outlet temperature of evaporator

K Inlet temperature of condenser

TmaxSTH K Maximum temperature of the storage tank

T coll K Average fluid temperature in the collector

∆TS K The temperature difference of the storage tank

U W/m2K Storage heat losses coefficient

V storage m3 Volume of the storage

w kg/m3 Density of water

- Collector efficiency

- Optical efficiency

- Photovoltaic module efficiency

- Battery efficiency

- PV module efficiency at the standard test condition

- Temperature coefficient of the PV module

XV

Subscripts

Subscript Description

ABCH Absorption chiller

Amb Ambient temperature

BAH Back-up

Batt Battery

C Cooling

Coll Collector

Chrge Charging

Cond Condenser

Combined

Convection

D Diffuse

Electric

Evap Evaporator

Equivalent

Gen Generator

Inverter

I Internal

Ir Infrared radiation

Loss Losses

Max Maximum

Nom Nominal

o External

P Peak

R Radiative

S surface

T Time

W Water

XVI

List of Abbreviations

TSFH Typical Single Family House

MENA Middle East and North Africa

PV Photovoltaic

STC Standard Test Conditions

NOCT Operation Cell Temperature

SRE Standard Reference Environment

TRNSYS TRaNsient SYstem Simulation program

NERC National Energy Research Center

IWES Institute for Wind Energy and Energy System Technology

IBP Institute of Building Physics

EPW Energy Plus weather

DNI Direct Normal Irradiance

DOS Department Of Statistic

ETMY Egyptian Typical Meteorological Year

IWEC International Weather for Energy Calculations

DOD Depth Of Discharge

SF Solar Fraction

HCB Hollow Concrete Block

TFM Transfer Function Method

DC Direct current

AC Alternating Current

LiBr Lithium Bromide

H2O Water

1

1. Introduction

1.1 Background

Worldwide, the growing demand for traditional air-conditioning has caused a

significant increase in demand for primary energy resources. ‘‘This results in a

significant increase in peak electric power demand in summer reaching, in many cases,

the capacity limits of the network and causing the risk of blackouts’’ [1]. That due to,

increasing living standards, comfort expectations and global warming. In many

countries of Middle East and North Africa (MENA), air-conditioning is one of the main

consumers of electrical energy today. For example in Egypt, at least 32 % of the

electrical energy used by the domestic sector is for air-conditioning: [2], [3]. However,

there is a higher solar radiation in the MENA regions, with a potential that is larger than

the total electricity demand worldwide. The average daily sunlight exceeds 8.8 hours,

with an average DNI1 of 2,334 kWh/m2/year [4]. Solar air-conditioning is one of the

technologies which allows to obtain important energy savings compared to traditional

air-conditioning plants, by using the renewable solar source. This is definitely the case

for the hot and sunny regions in the MENA. In addition, the growing demand for air-

conditioning in typical single family houses (TSFH) and small office buildings is opening

new sectors for this technology in the MENA regions.

Today, there are two main solar air-conditioning technology options: solar thermal air-

conditioning, where the solar absorption cooling is the first type of this option and it is

still practical for remote building in places where there is an excess of heat energy

available. Another option is the solar photovoltaic air-conditioning, by using electricity

from renewable sources to power the conventional cooling equipment. ‘‘On the other

hand, the market introduction of photovoltaic systems is much more aggressive than

that of solar thermal power plants; cost reductions can be expected to be faster for

photovoltaic systems. But even if there is a 50% cost reduction in photovoltaic systems

and no cost reduction at all in solar thermal power plants, electricity production with

solar thermal power plants in southern Europe and North Africa remains more cost-

effective than with photovoltaic systems’’ [5].

1 Direct Normal Irradiance

2

A lot of papers have been published that describe the performance of thermal air-

conditioning technology under different climate conditions in the world: [6], [7], [8] and

[9]. In addition, there are also a number of publications available that cover the

performance of solar photovoltaic air-conditioning technology or different performance

between the two technologies such as [10]. However, there are very few research on the

solar air-conditioning technology under the MENA region climate conditions, for its

importance in this region. Therefore, there are areas in which one or the other of the

two technologies should be preferred for technical reasons under the MENA regions’

climates.

1.2 Objectives and Boundary Conditions

The performance of solar air-conditioning technology is strongly dependent on the

ambient climate conditions, the building standards and the users’ behaviour. The main

objective of this thesis is to analyze and compare the solar thermal air-conditioning

technology and the photovoltaic air-conditioning technology under different thermal

load profiles and under the MENA region climate conditions. Additionally, to evaluate

the cooling compensation by employing this technology to the cooling load demand of

the selected building (TSFH) in two different climate locations: Aswan-Egypt, Aqaba-

Jordan. In order to achieve the aforementioned objectives, the study focuses on the:

Determination of TSFH as a reference building for the two selected locations in

this study : Aswan city in Egypt and Aqaba City in Jordan.

Determination of the TSFH cooling load demand for the two selected locations

carried out by the TRNSYS Software.

Design and simulation of three solar air-conditioning scenarios to cover the

cooling load demand of a TSFH for the two respective locations where the

simulation is carried out by MATLAB-Simulink .

The considered scenarios are as following:

Solar photovoltaic air-conditioning without storage

Solar photovoltaic air-conditioning with storage

Solar thermal air-conditioning with storage (absorption chiller)

3

1.3 Thesis Structure

The climate of the selected location and a detailed description of the reference building

are given in chapter 2. The description of the reference building includes its

architectural design, orientation, wall construction, window type, indoor climate, air

change rate, internal gain, cooling and heating set points.

The thermal cooling and heating load demands for the reference building (TSFH) are

simulated by TRNSYS software for the two selected locations. A description of the

simulation environments, the models as well as the simulation results and their analysis

are given in Chapter 3. Chapter 4 includes a general description of available solar air-

conditioning technologies and its state-of-the-art.

In Chapter 5, three solar air-conditioning scenarios have been designed and simulated

for each TSFH in the selected locations. This chapter discusses three parts: simulation

environments, solar radiation on a tilted surface by TRNSYS software and then each of

the scenario components and design followed by the scenario simulations and

methodology.

Chapter 6 includes the simulation results and the analysis for each scenario. Then, the

comparison between the solar thermal air-conditioning with storage scenario and the

two solar PV- air-conditioning scenarios with and without storage is done. The

conclusions of this study are summarized in chapter 7. Moreover, an outlook for further

work that could be done is given.

4

2. Determination of the Reference Building in MENA Regions

To investigate the above objective two cities in two countries were selected from MENA

regions, Aqaba city in Jordan from Middle East(ME) and Aswan in Egypt from North

Africa(NA). The reference building model in this study was selected for the two

locations, namely typical single family house (TSFH). The aim of this chapter is to

determine the reference building TSFH, for various climate conditions of the selected

locations in MENA regions. For the locations climate conditions, solar radiation, ambient

air temperature and relative humidity. For the building, the construction (i.e. wall U-

values, type of window glazing), internal heat gains air exchange rate etc... were defined.

That in order to simulate the TSFH thermal load demand by using TRNSYS software.

The Simulation in more details will be further explained in next chapter.

2.1 Reference Location Climates

The building cooling and heating demands are strongly influenced by the outdoor

ambient air temperature and global solar radiation around it. In this study, the TSFH

cooling demand calculations depends on the selected locations climates Aqaba city in

Jordan and Aswan city in Egypt.

Jordan is located in Middle East (ME) regions its’ area is 9 X 104 km2, 80% of its area is

desert. The climate of Jordan may be divided into three main categories depending on

the altitude: low-, medium- and high-mean temperature regions [11]. Aqaba city is

located south of Jordan at latitude 29°31'N and longitude 35°E on the Aqaba Gulf of the

Red Sea. The meteorological station is 51 meters above sea level. It is located in the high

–mean temperature regions. This city is characterized by very hot and dusty weather in

summer; summer temperatures rise above 45 ◦C . Winter is mild therefore there is little

need for heating with extremely little amount of precipitation. The mean annual daily

average temperature is estimated at around 24.1 ◦C [12], [13].

5

Egypt is located in North Africa (NA) regions its area 1,001,450 km2 and it is mostly

desert. Aswan city is the 3rd biggest city in Egypt today and the biggest one in upper

Egypt located at latitude 23°54'N and longitude 32°E [14]. Aswan enjoys a relatively

high temperatures, dry weather and arid climate; Summers in Aswan grow unbearably

hot with the average temperature ranging from 31.6 °C to 33 °C and in July sear up to

almost 34 °C. In Winter the average temperature ranging from 23-30°C and rainfall

almost non-existent and no need for heating [15].

2.1.1 Meteorological Data for Reference Locations The meteorological data for the two reference locations (Aswan, Aqaba) had been

selected, these data sets were used to perform the calculations and generate the results

presented in this study.

The meteorological data file of Aqaba city contains measurement data in 15 minute

intervals for the year 2010. It is includes, the horizontal solar radiation (beam, diffuse

and global), ambient air temperature and relative humidity. The file was received in

Excel-format from the National Energy Research Centre (NERC) in Jordan.

The meteorological data of Aswan city, in Egyptian Typical Meteorological Year (ETMY)

format and in Energy Plus Weather (EPW) format Were received. This formats was

developed as a standard development for energy simulation by Joe Huang with data

provided by the U. S. National Climatic Data Center which for periods of record from 12

to 21 years, all ending in 2003. This file was hourly data included the horizontal solar

radiation (beam, diffuse and global), ambient air temperature and relative humidity

[16]. Figures 2.1 to 2.3 represent the horizontal global irradiation, ambient air

temperature and relative humidity data for each location Aqaba and Aswan.

http://en.wikipedia.org/wiki/North_Africa

http://toolserver.org/~geohack/geohack.php?pagename=Aswan&params=24_05_20_N_32_53_59_E_type:city(275000)_region:EG

6

Figure 2.1: Annual distribution of horizontal global solar radiation for Aswan and

Aqaba cities, [16], [17].

Figure 2.1 shows, distribution of the global horizontal solar radiation for Aswan city and

Aqaba city, in Aswan city has higher peak daily of global horizontal solar radiation than

Aqaba city along the year; in summer season reaches near to 1000 W/m2 ,1050 W/m2

and in winter 600 W/m2 , 700 W/m2 for Aqaba and Aswan respectively. In addition the

radiation difference between the two cities, in winter higher than in summer seasons.

Figure 2.2 Annual distribution of ambient air temperatures for Aqaba and Aswan

cities, [16], [17].

7

Figure2.2 illustrates, the annual distribution of ambient temperatures in Aqaba city and

Aswan. Approximately in both cities; in summer season the daily maximum peak

temperatures reaches to 40oc and in sometimes to 45oc, in winter changes between

25oC to 30oC. Aqaba city daily temperatures are fluctuated along the year higher than

Aswan, this means Aswan night temperatures higher than Aqaba night temperatures.

This leads to higher night cooling consumption by the buildings in Aswan city than in

Aqaba city.

Figure 2.3:Annual distribution of ambient air relative humidity in Aswan and Aqaba

cities, [16], [17].

As shown in Figure2.3,the relative humidity distribute along the year for both cites

Aqaba and Aswan. Generally Aqaba city has higher ambient air relative humidity along

the year than Aswan, especially in July, August and September. Additionally, it is

fluctuated in Aqaba more than in Aswan. The high relative humidity of location, leads to

increase building cooling consumption.

8

2.2 Reference Building

The reference building which has been selected in this study is a typical single family

house (TSFH) relates to the MENA locations, Aswan city in Egypt and Aqaba city in

Jordan. This section defines the TSFH and the definition include architecture design and

orientation, constriction building elements descriptions (walls, roof, floor and

windows), internal heat gain, the heating and cooling set points and the air change

conditions. This building data must be determined in order to simulate the thermal

cooling and heating demands for the building by using TRNSYS software. More details

about the thermal consumption simulation by TRNSYS software for TSFH will be further

explained in next chapter.

According to department of statistic (DOS), type of building (TSFH) called ‘’Dar’’ in

Jordan represents about 72 % of the total residential building in Jordan [18], [19]. As

mentioned by [11], 54.6 % of the dwellings in Jordan are detached as TSFH . In addition

the average useful living floor area per capita is about 20m2 and 6 persons residents per

dwelling. Hollow cement-blocks are most widely used for constructing walls: nearly

two-thirds of the total housing being built with such cheap blocks, followed by

reinforced concrete and white-stone. Nearly 95% of flat roofs, in Jordan are constructed

using reinforced concrete, and the remaining fraction employed roof tiling, asbestos

and/or corrugated steel-sheets.

Most of TSFH in MENA regions specially in Jordan and Egypt, has same building

architecture design, it has a flat roof, it consists Gust room , living room, kitchen, two or

three bedrooms and the bathrooms.

However a simplification was made in this study, the typical Single family house in

Jordan same that’s in Egypt. In order to simplify the comparison of solar thermal air-

conditioning scenarios and solar photovoltaic air-conditioning scenarios, which as the

major objective in this study, Figure 2.4 shows the TSFH sketch and It can be described

as follows [20], [13]:

9

2.2.1 Architecture Design The reference object (of TSFH) was taken from [20], [13] (see Figure 2.4). The floor area

is about 224 m2, perimeter is 60.35 m and ceiling internal height is 2.86 m. It is

rectangular shape and consists of three bedrooms, living room, guest room and Kitchen.

Number of occupants is 6 persons.

The sketch of TSFH in Figure 2.4 shows the building orientation where the Gust room

and the living room are facing to south. The zones dimensions were provided by Eng.

Tawfiq Al- Khamayseh (Architecture engineer works for Al-Bayader Company for

construction and engineering in Ramallah, Palestine). This architecture design of the

TSFH was considered for the two climate locations, Aswan and Aqaba cites.

Figure 2.4: Sketch of Typical Single Family House(TSFH) in MENA regions plan, [20].

10

2.2.2 Facade Stricter

2.2.2.1 Wall Construction The construction consists of typical stone walls(External walls), it consists of stone,

concrete, concrete blocks and plaster. The various material of the building envelope,

layers the thicknesses and energy performance data describing the reference building

(TSFH) listed in Table 2.1 [21], [20].

Table2.1 : Constructional components of the reference building (TSFH), [21], [20].

Assembly Layer Thickness

[m]

Density

[kg/m3]

Thermal

Conductivity

[kJ/h m K]

Specific

heat

capacity

[kJ/kg K]

U-Value of

component

[W/m2K]

External

wall

Cement plaster

H.C.B for wall

Reinforced

concrete

Stone

0.01

0.07

0.22

0.07

2000

1400

2300

2250

4.32

2.7

6.3

6.12

1.008

0.864

0.936

0.828

2.28020

Internal

wall

Cement plaster

H.C.B for wall

Cement plaster

0.01

0.15

0.01

2000

1400

2000

4.32

2.7

4.32

1.008

0.864

1.008

2.58621

Roof

Cement plaster

H.C.B for roof

Reinforced

concrete

Bitumen

0.01

0.2

0.1

0.001

1400

2300

1200

3.42

6.3

0.612

1.008

0.936

1.0

2.21286

Ground

floor

Tile

Cement tile

Sand

Reinforced

concrete

Under floor

0.02

0.03

0.1

0.1

0.2

2000

2100

1800

2300

1400

3.6

3.96

2.52

6.3

1.69

1.0

0.864

0.864

0.936

1.0

1.18581

11

2.2.2.2 Windows A single glazed window with U-value of 5.68 W/m2 Ok was selected for the reference

building TSFH. ‘‘This considered as one of the most popular windows type in the

selected locations. The U-value indicates the rate of heat flow due to conduction,

convection, and radiation through a window as a result of a temperature difference

between the inside and outside in (W/m2.K)’’ [13]. The windows parameter are

summarized in Table 2.2. This parameters According to TRNSYS library and [13].

According to [13], the optimum window area for the TSFH in Aqaba city, on the east and

on west facades amounts to 20% of the wall surface area. On the North facade, windows

area is 10% whereas 30% for the west facade. Same for Aswan-TSFH was assumed. The

TSFH windows were considered without any internal or external shading.

Table2.2 : Thermal properties of the Single glass window for the reference TSFH in

Aswan and Aqaba, TRNSYS library and [13].

Single glaze window Value Unit

U-Value 5.68 [W/m2oK]

g-value 0.855 [ - ]

Frame U-value 2.169 [W/m2 OK]

Frame fraction 0.15 [ - ]

Solar reflectance Of outer surface 0.075 [ - ]

Visible transmittance 0.901 [ - ]

2.2.3 Internal Gain Internal gain is thermal (sensible or latent) heat which dissipates from persons, lighting,

or electric equipments (computer, wash machine, ..etc.). This heat gains contributes in

the building cooling and heating load demands. The rate of internal heat gain is 150 W

from occupants and electric equipment. It is considered based on ISO 7730 standard

where the number of occupants is 6 persons in TSFH. The heat gain 120 W/person

(Seated, very light writing) was considered constant, which represents an average

activity could be done daily by the occupants in addition the heat gain from appliance

defined also as a constant (300 W/day) during the year that according to ISO 7730

standard in TRNSYS data library.

12

2.2.4 Air Change Condition The air tightness of Middle East and South East Asia buildings is less than European

standard, which leads to higher infiltration rate . According to the United Arab Emirates

UAE building regulations, the ventilation rate should be 0.4/h.

In this study, the TSFH for both locations Aswan and Aqaba have the same ventilation

and infiltration rates. Natural ventilation was considered for this building according to

MASDAR energy design guide line [22]as it regarded a proper code for efficient building

design where the natural ventilation is constant during the day and throughout the year.

The value of infiltration rate has been defined according to ASHRAE 90.1 standard [23].

The Iinfiltration and ventilation rats for TSFH are given in Table2.3.

Table2.3 : Air change (ventilation and infiltration) rate for Aswan-TSFH and Aqaba-

TSFH.

2.2.5 Cooling and Heating Set Points The initial step in the cooling and heating load consumption calculation is defending

indoor and outdoor conditions of TSFH. Indoor conditions depends on building use,

number and type of occupancy, and/or code requirements. In this study, the TSFH

indoor design conditions, the set-point temperature and relative humidity for cooling

and heating are set according to ASHRAE, Handbook Fundamental (2005) [24], [20]. For

cooling, it is 24 ◦C dry bulb and a maximum of 50–65% relative humidity. For heating, it

is 20 ◦C dry bulb and 30% relative humidity.

Parameter Unit Aswan-TSFH Aqaba-TSFH

Infiltration 1/h 0.16 0.16

Ventilation rate 1/h 1 1

Total air change 1/h 1.16 1.16

13

3. Reference Building Thermal Cooling and Heating Load Simulation

The major objective for this chapter is to calculate the thermal cooling and heating loads

for the two cases: Aswan-TSFH and Aqaba-TSFH cases. That is in order to investigate

the main objective of this study: to compare and to analyze the solar thermal air-

conditioning technology and PV air-conditioning technology in the MENA regions. This

chapter has two parts. The first part discusses and describes the thermal cooling and

heating loads simulation by using TRANSYS Software. The second part includes the

thermal cooling load simulation results and analysis of the results.

3.1 TRNSYS Software Simulation Environments

TRANSYS is a transient system simulation program. It is a well known software diffusely

adopted for both commercial and academic purposes. The software includes a large

library of built-in components, often validated by experimental data [8], [25]. It is a

component-based simulation engine. Components (or types) are individual engineering

systems such as a boiler, thermal storage tank, PV panels, or a pipe that are defined by a

discrete set of inputs, outputs, parameters, and the mathematical functions which

govern their operation. It is dynamic, transient building energy and energy supply

systems modelling tool which offers distinct advantages as well as disadvantages over

its alternatives (e.g. energy plus) [26]. It is a complete and extensible simulation

environment for the transient simulation of systems, including multi-zone buildings

[20].

The program allows the users to create and design complex energy engineering systems

by adding and dropping components from the software library to a simulation map and

connects this components’ inputs and outputs together [26]. This makes TRANSYS a

very capable tool to simulate the building cooling and heating loads. For the sake of the

aforesaid reasons, the TRANSYS software is selected in this study to simulate TSFH

cooling and heating loads for each case: Aswan-TSFH and Aqaba-TSFH. TRNSYS consists

of suitable of programs. In this study, only two of these programs have been deployed:

TRNSYS simulation studio and Multi-zone building (TRNBuild) [27].

14

3.2 Description of the Simulation

The first step before starting this simulation, which is done in Chapter 2, includes: the

selecting TSFH-indoor design conditions ( such as, number of occupancy, internal gains,

air change conditions ,heating and cooling set points etc. ), selecting TSFH-envelope

data ( e.g. architectural design, facade stricter data etc..) and selecting TSFH-outdoor

climatic data (solar radiation, ambient temperature, relative humidity).

TYPE 56 (Multi-zone building model) in TRNSYS is chosen to simulate the heat

conduction through opaque surfaces of the TSFH-envelop. In order to use this type, two

separate processing program must be carried out. The first process, TRNBuild program

reads in and processes a file containing the TSFH description and generate two files

(described later). The second process occurred in the TRNStudio program, the two

generated files will be used by the TYPE 56 component during a TRNSYS simulation.

3.2.1 Type 56 Mathematical Description The TRNSYS mathematical model calculations are influenced by the outdoor climatic

conditions, the indoor design conditions and the TSFH envelop structure. ‘‘The heat

balance method is used by TRNSYS as a base for all calculations. For conductive heat

gain at the surface on each wall, TRNSYS use Transfer Function Method (TFM) as a

simplification of the arduous heat balance method’’ [28], [29]:

-

-

……………….…..…..…………...…………..….....…(3.1)

..................................................(3.2)

‘‘ Where the surface temperatures and heat fluxes are evaluated at equal time intervals.

The k refers to the term in the time series, and it specified by the user within the

TRNBUILD description. within the TRNBUILD program the coefficients of the time

-

15

series (a's, b's, c's, and d's) are determined by the z-transfer function routines of

literature ’’[30]. The Heat gain by radiation and convection is calculated using [28]:

……………………………………………………..………………...….......(3.3)

…………………………………………………………………………………………………………...(3.4)

q comb,s,i/o is the combined convective and long wave radiation of the inside/outside surface [28]:

……………………………………………………………..….….….(3.5)

…………………………………………………………....………….….………………….......(3.6)

.......................................................................................(3.7)

......................................................................................(3.8)

In these equations the Ss,i, is the radiative heat flux absorbed at the inside surface, is

the inside surface area, is the view factor to the sky, artificial temperature

node, is referred to the resistance. The Latent heat gain by the ventilation or

infiltration is calculated by using [28], [31], [32]:

………………………………………………………………………..…………….…..(3.9)

For more details about the mathematical model which are used by TRNSYS simulation,

see TRNSYS16 manual [33].

16

3.2.2 TSFH Modeling with Type56 and TRNBuild TRNBuild is used to enter the TSFH input data and to create the TSFH description file

(*.bui). This file includes all the information required to simulate the building where

(*.bui) file used to generate three new files: the (*.bld)2, (*trn)3 files which are used by

TYPE 56 during the simulation process in TRNStudio program and information

file(*.inf)4)

As shown in Figure 3.1, TRNBuild allows the users to specify all the building structure in

details that is needed to simulate the thermal behaviour of the TSFH such as geometry

data, wall construction data, windows data, etc. Furthermore, it needs SCHEDUALE

information which define the internal heat gain from the equipment and occupants

during the day in the TSFH.

Figure 3.1: Zones of TSFH model in TRNBuild.

2 The file containing the Geometric information about the building. 3 The file containing the wall transfer function coefficients. 4 An informational file.

17

This section includes a brief description of steps for the TSFH modelling with TYPE 56

and TRNBuild which are followed in this study.

As shown in Figure 3.1, the TRNBuild manager defines the project details: TSFH

orientation, iconic properties which define the parameter value for software calculation

such as air density, specific heat of air etc. Inputs icon which is used to add the required

INPUTS to TYPE 56 (such as, control strategies etc.) whereas the outputs icon describe

the OUPUTS of TYPE 56 such as sensible energy demand of zone etc. where this is the

last step of the building description.

The TSFH zones thermal definition step include the adding zone walls and windows in

addition to its thermal description (see Tables 2.1 and 2.2): defining the materials that

will make up the layers of the wall (from internal zone to external) in addition to the

wall area, geography (external and internal), thermal conductivity etc., defining the

materials that will make up the layers of the window and adding (its thermal properties,

area and orientations etc.).

After the TSFH zones definition step, inserting the TSFH zones required regime, data

step has been followed which includes: infiltration and ventilation data, heating and

cooling set points, internal gain setting data, comfort and Humidity. In this study

,Chapter 2 includes all of the required data for the second step where the infiltration

and ventilation data listed in Table2.3, the internal gain is considered based on ISO 7730

standard. Cooling set point is 24 0C dry bulb and a maximum of 50–65 % relative

humidity . The Heating set point is 20 0C dry bulb and 30 % relative humidity.

Defining the outputs needed from TYPE 56, in this step the output can be selected from

the list such as, sensible energy demand (cooling and heating) of building, air

temperature of zone, etc. In this study, the sensible energy demand of three bedrooms,

living room, guest room and kitchen is defined as outputs for TYPE 56.

The final step in the running model is to generate the TYPE 56 files: (*.bui) file used to

generate three new files: the (*.bld)5, (*trn)6 files which are used by TYPE 56 during the

simulation process in TRNStudio program and information file (*.inf)7.

5 The file containing the Geometric information about the building 6 The file containing the wall transfer function coefficients

18

3.2.3 TSFH Modeling with Type56 and TRNStudio After the TSFH Model in TRNBuild is created and the TSFH description file (*.bui) is

generated, the TSFH modelling with Type56 and TRNStudio started to complete the

simulation of the TSFH thermal cooling and heating loads demands. The brief

description of the simulation steps which are followed in this software (TRNStudio) are

as described as follows:

The first step, creating a new Multizone building project and all its necessary

parameters have been entered (such as drawing TSFH plan, setting zone properties,

setting window,...etc). Once the created project has been finished the simulation studio

will create a multi zone building description (stored in a .BUI file), translate the TSFH

description file (*.bui) file to the internal files necessary for simulation (*.bld8, *trn9

files) from TRNBuild program, create a simulation project (stored in a .TMF file) and

open it in the simulation studio [33]. So a simulation with the important components

and links for the first run are automatically generated.

Figure 3.2: Aswan-TSFH model (Type 56) with all the required components and

connections in TRNStudio.

7 An informational file 8 The file containing the Geometric information about the building 9 The file containing the wall transfer function coefficients

19

Figure 3.3: Aqaba-TSFH model (Type 56) with all required components and

connections in TRNStudio.

Figure 3.2 and Figure 3.3 show that the TSFH model (Type 56) with all required

components and connections in simulation studio for Aswan and Aqaba respectively.

The studio simulation has been started to specify the values for the variables in the

components of the TSFH model then determines how data flows from one component to

another (such as solar radiation data flows from TYPE 16e to TYPE 56 ). This data flow

is indicated by a link between two components in the Assembly Panel window.

Assembly Panel window includes the simulation components as shown in the right hand

side in Figure 3.2 and Figure 3.3. However, the link shown on the assembly panel is

purely informational. So it must specify the details of the link between two components

to actually flow data from one component to another [33].

As known in Chapter 2, the meteorological data of Aswan city in TMY and EPW format

and its hourly horizontal solar radiation data. In addition, regarding the TSFH geometry,

the direct and diffuse radiation of every hour should be determined. Then it must be

converted into hourly tilted radiations depending on the sun position in the sky and on

the TSFH surface’s slope from the horizontal plan. So TYPE 15-3, weather data reading

and processing have been chosen for the Aswan-TSFH model in order to read the Aswan

20

meteorological data file and to calculate the hourly solar radiation (direct plus diffuse)

regarding to the TSFH surface’s slope and on the sun position in the sky. After that data

has been processed, it will be provided from TYPE 15-3 to TYPE 56 in order to simulate

the TSFH cooling and heating demands.

In the simulation case of Aqaba-TSFH, there is a difference because the metrological

data file has been in Excel format. So the TYPE 9e has been chosen in order to call and

read the excel data file which provides this data through the link to TYPE 16e. The TYPE

16e completes the data processing before delivering it to TYPE 56 as in Aswan-TSFH

case. In this step, the Reindl model has been chosen in TYPE 15-3 and TYPE 16e in order

to calculate the tilted solar radiation. For more details about Reindl mathematical

model, see the TRNSYS16 module [33].

As shown in the above figures, TYPE 33e has been chosen for both cases. ‘‘This

component takes as input the dry bulb temperature and relative humidity of moist air

from the processing data component and calls the TRNSYS Psychrometrics routine,

returning the following corresponding moist air properties: dry bulb temperature, dew

point temperature, wet bulb temperature, relative humidity, absolute humidity ratio,

and enthalpy’’ [33]. This data is transferred to TYPE 56 to use it in the cooling and

heating demand calculations.

TYPE 69b is selected for each model in order to determine the effective sky

temperature, which is used by TYPE 56 to calculate the long-wave radiation exchange

between an arbitrary external surface of the TSFH and the atmosphere. TYPE 65 is

online graphics component which is used to display selected system variables while the

simulation is progressing [33].

Final step in the TRNStudio simulation is the running step, where the cooling load is

calculated in 15 minutes time step by TRNSYS software for the two case studies. Then

the cooling and heating load demand simulation results for the TSFH has been provided

for both cases.

21

3.3 Thermal Cooling Load Simulation Results and Analysis of Results

As mentioned before, the major objective of this simulation is to determine the cooling

load of a typical single family house in two different climate locations in the MENA

regions: Aswan city in Egypt and Aqaba city in Jordan . The discussion and analysis on

simulation results concentrate mainly on sensible cooling load demand of TSFH (three

bedrooms, living room, guest room and Kitchen). The simulation results and the

analysis of the results are documented in subsequent subsections.

3.3.1 The Annual Energy Consumption

This section discusses the annual cooling load consumption for both cases, Aswan-TSFH

and Aqaba-TSFH. Figure 3.4 and Figure 3.5 below diagram the total annual and monthly

cooling and heating energy consumptions for the aforementioned cases respectively.

Figure 3.4: Yearly cooling and heating energy demand for the Aswan-TSFH and

Aqaba-TSFH.

The simulation result in Figure 3.4 shows the annual energy consumption where the

total cooling load energy are : 44,330 kWh/year and 43,490 kWh/year; the total heating

load energy are: 1114 kWh/year and 1635 kWh/year for the Aswan-TSFH and the

Aqaba-TSFH cases respectively. On the other hand, 97.5 % and 96.3 % of the annual

energy consumption are cooling load for the two cases respectively.

0 3000 6000 9000

12000 15000 18000 21000 24000 27000 30000 33000 36000 39000 42000 45000

Heating demand Cooling demand

En

ergy

[k

Wh

]

Aswan-TSFH

Aqaba-TSFH

22

Figure 3.5: Monthly cooling and heating energy demand in (kWh) for the Aswan-

TSFH and Aqaba-TSFH.

Figure 3.5 shows the cooling energy required during a long period throughout the year

which is ten months, from February to the end of November, while the heating energy

period is very short, three months (January, February and December) for both cases.

The previous results and discussion show the extent of a need and importance of

cooling compared to heating for both cases in the aforementioned locations.

The monthly cooling energy demand in Aswan-TSFH is higher than Aqaba–TSFH’s

throughout the year except for the months of June, July and August. Whereas, in Aqaba-

TSFH, there is a higher cooling energy consumption due to a higher humidity in Aqaba

city than in Aswan city as shown in Figure 2.3 for the reason that the ventilation

increases the inside building’s humidity and hence it causes the mentioned difference.

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

En

ergy

dem

and

[K

Wh

]

Aqaba-TSFH Heating demand

Aqaba-TSFH Cooling demand

Aswan-TSFH Heating demand

Aswan-TSFHCooling demand

23

3.3.2 The Performance of Cooling Load Now this section is dealing with the TSFH cooling power demand(real-time power kW),

not energy yields (kWh). Because this study going to compensate the power production

from the solar air-conditioning systems, not energy Production. However, Figure 3.6

and Figure 3.7 display the cooling load demand distribution throughout the year, for

Aswan-TSFH and Aqaba-TSFH cases. These loads follow the solar radiation load which

was shown in Figure 2.1. In addition, it follows the outdoor ambient air temperature

distribution throughout the year. Furthermore it follows the outdoor ambient air

relative humidity, where high relative humidity leads to increasing the cooling

demands. So it will be worth to compensate the solar irradiation to this cooling

consumption.

The maximum cooling load for Aswan-TSFH is 13.9 kW as viewed in Figure 3.6. As

shown in the Figure, the peak load takes place during the months of June and August. On

the other hand, the smallest cooling load occurs during January, February and

December. For Aqaba-TSFH, the simulation result diagrammed in Figure 3.7 shows that

the maximum cooling load is in the range 14.8 -15.3 kW and this load occurs during the

periods of June and August. Besides, the smallest cooling load happens during January

and December.

Figure 3.6: Yearly Cooling and heating demands distribution(kW) for the Aswan-

TSFH.

24

Figure 3.7: Yearly Cooling and heating demands distribution in (kW) for the Aqaba-

TSFH.

The cooling demand generally follows the outside ambient air temperature. Normally,

higher temperature leads to higher cooling load due to a heat transition through the

building’s envelope from hotter outside to a cooler inside of the building. In Aqaba city,

the outside average monthly ambient temperature varies from around 15 0C in January

to almost 35 0C in August. In addition, there are bigger daily ambient temperature

fluctuations compared with Aswan’s ambient air temperature (see Figure 2.2) which in

turn leads to a variation in cooling load throughout the year. In Aqaba-TSFH, as shown

in Figure 3.7, the highest cooling load occurs between June and August , which matches

the highest outside ambient temperature.

In comparison with Aqaba city, the ambient temperature in Aswan city does not vary a

lot throughout the year. The minimum monthly ambient temperature is 20 0C in January

and the maximum is 350C in August. In addition, it has low daily fluctuations (see Figure

2.2). A small variation in ambient temperature leads to a minor variation in the cooling

load demand in Aswan-TSFH (see Figure 3.6). The lower cooling load fluctuation of

Aswan-TSFH means higher night cooling load demand, compared with Aqaba-TSFH.

According to Figure 3.5; during the months of June, July and August; the cooling energy

consumption in Aqaba-TSFH is higher than Aswan-TSFH’s. Hence, identical results are

25

shown in Figure 3.6 and Figure 3.7. However, the solar radiation and the ambient air

temperature in Aswan city are higher than in Aqaba city because of the presence of a

higher ambient relative humidity in Aqaba-TSFH than in Aswan-TSFH (See Figure 2.3).

This in turn means, the ventilation during these months increases the inside building’s

cooling demand due to a prominent ambient air humidity which has entered the

building.

Figure 3.8: Weakly Cooling load demand distribution in (kW) for the Aqaba-TSFH

and Aswan-TSFH.

The High cooling load demand shows a less daily fluctuation and is dominated by the

external temperature conditions. The Performance of the cooling load during the day of

the week in July for both cases (see Figure 3.8), the maximum daily cooling demand

occurs at noon and the minimum occurs in the morning of the daytime. Additionally,

this Figure shows the extent needed for cooling in huge amounts (approximately 8 to10

kW) during the night as well as in the daytime in addition the night cooling load in

Aswan-TSFH higher than Aqaba-TSFH.

26

4. Solar Air-Conditioning Technologies

The aim of this chapter is to give a brief description of the available solar air-

conditioning technology. Solar air-conditioning systems can be divided into two groups

of systems:‘‘ solar autonomous systems and solar-assisted systems. In a solar

autonomous system “all” energy used by the air-conditioning system is solar energy. In

a solar assisted system the solar energy covers a certain fraction of the energy used by

the air-conditioning system and the rest of the energy is provided through an auxiliary

or backup system’’ [2]. Only the solar-assisted systems are considered in this study.

Solar air-conditioning technologies are any air-conditioning system that use solar

radiation as source of power to drive the cooling process in order to produce cold air for

buildings. This can be achieved through solar thermal conversion or solar photovoltaic

(PV) conversion. In PV air-conditioning systems, PV cells arranged in modules convert

solar radiation to electric power which then drives a traditional compression chiller.

Solar thermal air-conditioning technology converts solar radiation to heat power

(through thermal collector) which is fed into a thermal cooling process or into a direct

air-conditioning system.

4.1 Solar Photovoltaic Air-Conditioning Technology

Figure 4.1 :Basic structure of PV air-conditioning systems, [2].

27

Figure 4.1 shows the main components of PV air-conditioning systems available. This

system consists of three main parts: solar energy collection (includes PV cells) which

converts solar radiation into electric power in order to drive the electric machine heat

pump. This machine is any electric traditional air-conditioning system which converts

the electric power to cooling power. The cooling power is distributed for space cooling

either directly in a decentralized system or by a cooling coil and sometimes by a

hidronic system [2]. The PV air-conditioning system can include a storage system

(battery system) or it can be without a battery system.

4.2 Solar Thermal Air-conditioning Technology

Figure 4.2 :Basic structure of heat driven and desiccant air-conditioning systems,

[2].

Figure 4.2 shows the basic components and structure of a thermal air-conditioning

systems available. This technology can be divided in two groups [2]: a solar heat driven

air-conditioning system which consists of a solar thermal collectors (high temperature

or medium temperature hot water) where typically flat plate collectors, evacuated tube

collectors or concentrated parabolic collectors are used. This converts the solar

28

radiation to heat power. Then this power is provided to drive another system in order

to produce cooling power for buildings.

This system can be either an electrical air-conditioning (such as traditional air-

conditioning) or thermal air-conditioning (such as absorption/adsorption chillers) or

both. The other type is a desiccant cooling system which uses water as refrigerant in

direct contact with air and the desiccant dehumidification is combined with an

additional cooling system which may be a conventional cooling coil or evaporative

cooling.

Most thermally driven cooling systems and solar assisted air-conditioning systems

installed today are based on absorption chillers [34], [35]. According to [34], [36], [35],

[2], [37] and [9], the most commonly used thermal air-conditioning system with the

cooling power capacity below 30 kW is a single effect Lithium Bromide-water (LiBr-

H2O) absorption chiller with flat-plate collectors. Under normal operation conditions

such machines need a typical temperature of the driving heat of 80 oC – 100 oC and

achieve a COP of about 0.7. In addition, this system is the most economical option since

it requires a comparatively lower temperature heat input than a double effect chiller

because the additional evacuated tube collectors providing high temperature heat is

very costly. This system will be explained in detail later in Chapter 6.

29

5. Solar Air-Conditioning Scenarios Design and Simulation

The main objective of this thesis is to analyse and compare the performance of solar

thermal air-conditioning technology and solar photovoltaic (PV) air-conditioning

technology under the MENA region´s climate conditions and cooling load profiles .

Additionally, to compensate the cooling power production by these technology to TSFH

load demands for each case (Aswan-TSFH, Aqaba-TSFH).

In order to investigate the above stated objective, the following three scenarios are

designed and simulated for each building: Aswan-TSFH and Aqaba-TSFH, as:

Solar photovoltaic air-conditioning without storage

Solar photovoltaic air-conditioning with storage

Solar thermal air-conditioning with storage (absorption chiller)

In this chapter the design procedure, simulation and methodology for each scenario are

explained. Where the simulation of cooling production by each scenario is carried out

by Matlab-Simulink, where the solar radiation on tilted surface has been calculated by

using TRNSYS software. That based on the TSFH cooling demand profile which

simulated by TRNSYS software for each case as in chapter 3.

5.1 Matlab-Simulink Simulation Environments

Simulations are powerful tools for process design, for study of new processes, and for

understanding how existing systems function and might be improved [36]. Numerical

simulation offers the possibility to virtually study physical solar air-conditioning

systems. Simulation is then the most adapted method to investigate the performance of

the cooling profile of the system’s output. There are different dynamic simulation

software’s available for simulating the air-conditioning system and calculating it’s

cooling products. To mention, SPARK, Energy Plus, EES, Easy Cool, TRNSYS and INSE,

MATLAB [38].

30

In this study, for the Matlab-Simulink simulation in order to calculate the cooling

production by each scenario for each case (Aswan-TSFH and Aqaba-TSFH). Two time

series of data with 15 minute time steps are required as input data, in almost every

simulation of cooling production for each scenario: the first type of the time series

contains the global solar radiation on a tilted surface and the outside ambient air

temperature. The second type of the time series contains the cooling load demand of a

TSFH which is obtained from the TRNSYS simulation results of Chapter3. However, the

Aswan and Aqaba weather data files which received in this study include the solar

radiation data on horizontal surface. Additionally, Aswan data file is in TMYE format

which is unreadable by this program. Thus the solar radiation on tilted surface has been

calculated by using TRNSYS 16 before starting with the cooling production simulation in

Matlab-Simulink. Where the tilt angle is considered to be equal to the latitude of the

location (23°54'N for Aswan-TSFH and 29°31'N for Aqaba-TSFH).

5.2 Solar PV Air -Conditioning Scenarios

As per the objective of this study, two scenarios of the PV air-conditioning systems have

been investigated: PV air-conditioning without storage (see Figure 5.1) and PV air-

conditioning with storage (see Figure 5.2). These scenarios are designed for each case,

Aswan-TSFH and Aqaba-TSFH. This section discusses the system components and

designs followed by the system simulations and methodology.

5.2.1 System Components and Design Figure 5.1 and Figure 5.2 show the two scenarios based on a PV-driven compressed

chiller. The PV air-conditioning without a storage scenario consists of a PV–module,

inverter, a compressed chiller and a system distribution. The system set up of a PV air-

conditioning with storage is similar to the first scenario, but it additionally has a storage

(battery) system and a charge controller.

The PV module converts solar radiation into electric power as direct current (DC ). The

solar charge controller regulates the voltage and the current which comes from the PV

module into the battery. This prevents from the overcharging of the battery and

increases the battery life.

31

The inverter converts DC into alternating current (AC ) which is needed to drive the

compressed chiller. The battery stores the excess energy for supplying the compressed

chiller when there is no enough solar radiation to cover the cooling demand. The

compressed chiller converts the AC power to the cold air. The compressed chiller is

supplied as a back-up with an electric AC power from the grid, when there is not enough

DC power from the PV-array and the battery bank, especially at night, evening and

morning of the day when there is no enough solar radiation to drive the compressed

chiller.

Figure 5.1: Schematic flow diagram for solar PV air-conditioning without storage.

Figure 5.2: Schematic flow diagram for solar PV air-conditioning with storage.

Inverter

Compressed chiller

cold air

PV Module Back-up From grid

Inverter

Compressed

chiller Charge controller

Battery system

cold air

PV Module Back-up from grid

32

Compressed Chiller Design

The vapour compression system is the dominant system today for cooling and

refrigeration and is being used in almost all kind of applications [2]. It is available for a

wide range of sizes from 50 W up to 50 MW [2], [39].

Because of its dominance especially in MENA regions and due to its simplicity it was

selected for the design of these PV air-conditioning scenarios. A schematic flow diagram

of the vapour compressor system and its components are listed in Appendix A. For more

details about the system, the process cycles and concepts, see the detail in [2].

A useful parameter to compare the performance of air-conditioning is the coefficient of

performance (COP), which is defined as the useful cooling capacity per input power [2]:

........................................(5.1)

The COP value of a vapour compression systems for an air-conditioning seems to be

around 3 for a smaller to medium size units and up to 4-5 for larger systems [2], [40],

[41], [42]. The COP value of the system in this study is assumed to be equal to 3. The

cold air is distributed throughout the building by a ductwork.

PV array Sizing and Design

The first step in designing a solar PV air-conditioning system is to find out the cooling

power and energy consumption that need to be supplied by the PV-array . As discussed

in chapter 3, the maximum cooling power demands were 13.9 kW in Aswan-TSFH and

15 kW in Aqaba-TSFH .In this study, the maximum cooling power demands were 15 kW

assumed for both Aswan-TSFH and Aqaba-TSFH in order to simplify the comparison

between the two cases . This means the cooling peak of 15 kW must be delivered by the

solar air-conditioning scenarios in this study. Given the coefficient of the performance

as 3 for the selected compressed chiller (see Section 5.2.1.1), the AC peak power is

required to reach up to 5 kW (calculated by employing equation 5.1).

33

To compensate the power losses in the inverter and the battery system 20 % of power

is added to this value. Thus, the required peak DC power equals:

..................................................(5.2)

Different sizes of PV modules produce different amounts of power. The power produced

depends on the size of the PV system and the radiation at the site. The polycrystalline

solar module (SCHOTT PERFORMTM POLY) 225 watt peak (Wp), is produced by SCHOTT

solar company in Germany where the Module’s efficiency is 13.4 %.It was selected for

all PV air-conditioning scenarios. The data sheet of the PV module is attached in

Appendix B. The number of PV modules required is calculated by Equation 5.3. The air-

conditioning system should be powered by at least 27 PV-modules with 225 Wp each:

.......................................(5.3)

The total PV array’s area required is calculated by using equation 5.4 where the PV

module area equals 1.6732m2 as stated in Appendix B:

...............................................................(5.4)

The modules in a PV-array must be connected in combined connection, i.e 14 modules

in parallel and two in series, in order to deliver an output voltage of 44 V-64 V which is

the DC input voltage range for the inverter and battery system.

34

As shown in Figure 5.3, the TSFH roof is flat with an area of 224 m2. The area is large

enough for the installment of 27 PV modules with ( )and additional, other

applications . This is one of the building advantages in the MENA region. The PV-array

was installed on the surface area (1) on the TSFH-roof which covers the

three rooms(see Figure 5.3). The area equals 81 m2 which is enough by assuming that

there are no shading effects on the collectors and enough free space for maintenance.

The optimum PV-array orientation will depend on the latitude of the site, prevailing

weather conditions and the load to be met. As a rule of thumb, for low latitudes (as in

MENA-regions) the maximum annual power output is obtained when the array tilt angle

roughly equals the latitude and the array faces due south (in the northern hemisphere)

or due north (in the southern hemisphere) [43].

The PV-array orientation for the two PV air-conditioning scenarios is designed facing

south. The tilt angle equals the latitude which is 23 °54' N and 29°31'N, for each case

study: Aswan-TSFH and Aqaba-TSFH respectively.

Figure 5.3: The dimensions of a typical single family house (TSFH) - roof area (1) for

PV-array installation.

Aria (1) =81.0525 m2

16.05 m

5.05

m

17.05 m

6.05

m

Area (2)

8.7

m

13.9 m

35

Inverter Sizing and Design

‘‘An inverter is used in the system where AC power output is needed. The input rating

of the inverter should never be lower than the total watt of appliances. The inverter

must have the same nominal voltage as the battery. The inverter size should be 25-30 %

bigger than the total power of appliances’’ [44]. The maximum DC power demand is

calculated and equals 6 kW in Section 5.2.1.2 .

Stand-alone inverters are used to convert (DC )current from PV-array and battery to

(AC) in order to run the compressed chiller. For the suggested PV system , in this study

the required inverter should supply 230 V AC, 50 Hz, 6 kW. The chosen inverter is the

Outback Inverter XW6048-230-50, 6 kW ,( 44-64) V DC , 230 V AC/50 Hz with a peak

efficiency of 95.4 %. This inverter is produced by the Xantrex Technology Inc. Company

and the data sheet is attached in Appendix (c) [45].

Storage (battery) System Design

Energy produced by the PV array is accumulated and stored in batteries for use on

demand. The battery system is designed for a PV air-conditioning with storage. In this

scenario, when the electric DC power is higher than the electric power needed by the

compression chiller. The battery accumulated and stored the excess DC power as

electric energy.

The battery’s capacity for storing energy is rated in amp-hours. The battery capacity is

listed in amp-hours at a given voltage. Batteries are sensitive to climate,

charge/discharge cycle history, temperature and age [46].

The battery system should be sized to be able to store excess power for 2 days. The

following calculations can be performed to select the suitable size of batteries for PV air-

conditioning with storage:

The excess energy is calculated based on simulation results of a PV air-conditioning

without storage scenario. This calculation is discussed later in more details in Chapter

6.2.2, where the results of this scenario: in April and October, the excess cooling

production is almost equal to the External back-up cooling load for both cases. Thus ten

days of an excess cooling power in April is taken. Then the average daily excess cooling

36

energy in Aswan-TSFH is calculated which is equal to 18.32 kWh/ day. The average

daily electric DC excess energy is 6.4 kWh/day which should be stored. This

value is close to the value which is calculated in Aqaba-TSFH. The battery system size is

thus, the same for both cases. Given the compressed chiller COP of 3, the inverter

efficiency of 95.4% and the daily excess cooling energy of 18.32 kWh, the resulting

DC energy is 6.4 kWh (see Equation 5.5):

………...…………………….…..…….(5.5)

The required nominal battery capacity (Cnom,Batt) in amp-hour for the daily power is

calculated by using Equation5.6 [47]. The required output voltage (VBtt) is 48 V. The

required autonomy factor (AF) for the scenario locations which are close to the equator

is 2. It is defined as the duration of time during which the nominal battery capacity

,starting from full charging conditions, can cover the energy demand of the consumer.

The minimum allowable depth of discharging (DOD) is 50–80 %. Deep-cycle batteries

are capable of many repeated deep cycles and are best suited for PV power systems

[46]. In the case study, the battery safety requires that the discharge of batteries should

not exceed 80 % of its capacity. The battery efficiency is 85 %. :

...........................................................................................(5.6)

According to the above calculations, the battery system which is required for this

scenario needs to produce about 392 Ah. Thus 8 batteries of 12 V each are required and

each 4 batteries are connected in series. Sun extender batteries PVX2120L are selected

for this scenario [46].

37

Controller

The solar charge controller regulates the voltage and the current which comes from the

PV module into battery. According to the previous calculations 27 PV modules are

required; each module producing 29.8 V and 225Wp (7.55 A). PV panels are connected

in parallel to supply 106 A. A controller is needed to hold at least 105.7 A. A controller

that carries a current of 105.7 A, 48 V DC has been chosen for the PV air-conditioning

with storage scenario.

Back-up System

When there is no enough electric power coming from the PV-array and the battery

system to cover the cooling power demands, the back-up system is designed to deliver

the remaining needed AC power. The back-up system is assumed to have a direct

connection to the electricity grid and to the compressed chillers. This connection is

considered and designed for both PV air-conditioning scenarios without and with

storage.

5.2.2 Systems Simulation and Methodology There are different simulation tools which are available to estimate the cooling

production of the PV air-conditioning system. A model based on Matlab-Simulink has

been carried out to perform the cooling power gain and its influence to cover the

cooling demands.

The simulation process is conducted for one year with a time step of 15 min using the

two time of series as an input data in Matlab-Simulink: the first data set is the time

series of meteorological data, solar radiation on a tilted surface and the ambient

temperature.

As discussed in Section 5.1, the solar radiation on a tilted surface Gtilt in W/m2 and is

calculated by using TRNSYS software. The second time series contains the cooling load

demand. The cooling load demand is simulated by using TRNSYS program in Chapter 3.

38

5.2.2.1 PV air-conditioning Without Storage Scenario

PV-array Electric Power Output

The DC power production of a PV-array is calculated by using Equations (5.7, 5.8,5.9)

where the selected PV module efficiency is 14.3 % (See Appendix B), the PV-array

area is 45. 176 m2 as discussed before:

…………………………………………………………………………………………(5.7)

Module’s operation temperature is a parameter that has a great influence on the

behaviour of a PV system as it influences its system efficiency and energy output. ‘‘It

depends on the module encapsulating material, its thermal dissipation and absorption

properties, the working point of the module, the atmospheric parameters such as

irradiance level, ambient temperature and wind speed’’ [48].

There are many empirical relations expressing Tc , the PV cell temperature, as a function

of weather variables such as the ambient temperature Tamb , and the local wind speed, as

well as the solar radiation, Gtilt [49]. In this study, the scenario simulations take the PV-

module operating temperature and associated effects on the power output into account.

Equation 5.8 represents the traditional linear expression for the PV electric efficiency

[49]. The module efficiency at the standard test condition (STC) is 14.3 % and

module’s temperature coefficient is 47.2 oC (both are given by the PV manufacturer

and listed in Appendix B).

…………………................................................................(5.8)

‘‘The Operation cell temperature TNOCT is employed in Equation 5.9. It is common to use

it as an indicator of module temperature, in fact, manufacturers usually include this

parameter in their module data sheets. It is defined as a mean solar cell junction

temperature within an open-rack mounted module in a standard reference

environment (SRE): tilt angle at a normal incidence to the direct solar beam at local

solar noon; total irradiance of 800 W/m2; ambient temperature of 20 0C; wind speed of

39

1 m/s and nil electrical load. It is an important parameter in module characterisation

since it is a reference of how the module will work when operating in real conditions.

Furthermore, in PV system design and simulation programs, many calculations are

based on the determination of module temperature from ambient temperature and

NOCT’’ [48].

........................................................................................(5.9)

Inverter Electric Power Output

After designing the PV-array, the DC power output is calculated. The inverter converts

the DC power to AC power by Equation 5.10. The inverter’s efficiency is 95.4 % (see

the data sheet in Appendix C):

……………………….………..……………………………………..……….….…(5.10)

Compressed Chiller Cooling Power Output

The compressed chiller converts the AC power into cooling power. This calculation is

the final step in each scenarios simulation and is represented by Equation 5.11 (where

COP is 3):

Pc coolling OP P In electric.................................................................................................(5.11)

Excess and Back-up Cooling Power

The excess and back-up cooling power are calculated by subtracting the output cooling

power of the PV air-conditioning system from the cooling power demand (Equation

5.12). If the value is positive, then the excess cooling power PE cess1 is available. If it is

negative, back-up cooling power P ack up cooling1 is necessary. The latter is compensated

by the back-up system connected to the grid:

PE cess1 ack up cooling1 Pc coolling P demand ..............................................................(5.12)

40

5.2.2.2 PV Air-conditioning with Storage Scenario In this scenario, the direct cooling power produced from the system is calculated. The

same calculation procedure as in the first scenario (without storage) is followed

(Equation 5.7 to Equation 5.12).Then the excess produced cooling power is converted to

DC by Equations 5.11 and 5.10. The electric power charged in the battery system

is calculated by Equation 5.13 where the battery efficiency is assumed to be

85 %. It is taken into account that the battery capacity is limited (see Equation 5.13),

where the maximum battery capacity of the system is 6.4kWh as discussed before:

......................(5.13)

Then, the cooling power produced by the contribution of the battery system

discharging is calculated by using Equation 5.14, where the DOD is

considered to be 80% and the chiller COP 3:

………………….……………………………..……….....……...(5.14)

There is a balance between excess power and the required back-up power. Excess

energy is usually available at noon while back-up power is needed during the morning,

evening and night. The back-up cooling energy which should be provided by the grid

E ack up cooling is calculated by Equation 5.15 :

E ack up cooling P ack up cooling1 t

0dt P att cooling

t

0dt...…………………………….…...(5.15)

41

5.3 Solar Thermal Air-conditioning Scenario (absorption chiller)

The thermally driven air-conditioning process is the heart of every solar cooling system.

Thermally driven air-conditioning systems are available on the market which

commonly utilize sorption processes. For air-conditioning applications, mainly

absorption chillers using the sorption pair Lithium bromide-water (LiBr-H2O) are

applied [9] since they require a comparatively low temperature as heat input. Most of

the thermally driven cooling system and solar assisted air-conditioning systems

installed today are based on absorption chillers [34], [35].

A Lithium bromide-water (LiBr-H2O)absorption chiller is selected for the two cases,

Aswan-TSFH and Aqaba-TSFH, in order to compensate the cooling demands for each

building. This section discusses the system components, design and; thereafter the

system simulation and methodology.

5.3.1 System Components and Design As shown in Figure 5.4, an absorption chiller coupled with a solar heating system and an

auxiliary energy supply as back-up electric heater is analyzed. In the assumed case, the

collector converts the solar radiation into heat and then the pump delivers it to the

storage tank. The storage tank then supplies the absorption chiller with thermal energy

to produce cold water. The coil and the fan system transfer the cooling power from cold

water to the inside air of the building. A duct system distributes it in the building. If

solar heat is insufficient e.g. at night or during cloudy days, the conventional back-up

electric heater is connected directly with the storage tank can provide heat. The system

components and design can be described as follows:

42

Figure 5.4: Solar thermal air-conditioning system scenario, coupling of an

absorption chiller with a solar heating system.

5.3.1.1 Solar Thermal Heating System The basic elements in the solar thermal heating system (see Figure 5.4) includes a

collector, a stratified hot water storage tank, and a back-up electric heater. All

components are described in the following.

Solar Collector

A solar collector is a special kind of heat exchanger converting the solar radiation into

thermal heat which is carried by a working fluid, e.g. water which is flowing through the

collector. There are three types of solar collectors which are typically used in a solar

thermal air-conditioning systems: flat plate collectors, evacuated tube collectors and

concentrated parabolic collector.

In the solar thermal air-conditioning system, the temperature level that should be

supplied by the solar thermal collector depends on the cooling technology used. Flat

plate collectors can be designed for applications requiring energy delivery at moderate

temperatures, up to perhaps 100 0C above the ambient temperature. The operation of

absorption air-conditioning with energy from flat plate collectors and storage systems

is the most common approach to solar cooling [36].

Solar heating system Absorption chiller

B C

A E

G

CT

HST

SC

ABCH

FC

ABCH absorption chillers

A absorber

C condenser

E evaporator

G generator

B thermal backup

FC Fan coil

SC solar collector

HST hot storage tank

CT cooling tower

43

The solar flat plate collector industry is available in the MENA regions especially in

Jordan and Egypt which are the selected locations in this study. To model this scenario,

a high quality flat plate collector from Schüco company is used. The collector

parameters are summarized in Table 5.1.

According to [50], a very simple assessment (rule of thumb) of the collector dimensions

in a solar-assisted air–conditioning system10 can be made using a single design point.

The specific collector area, defined as the collector area per nominal cooling capacity

can be roughly chosen according to the following Equation 5.16 [35]:

.......................................................................................................(5.16)

Where :

G: is the global radiation [w/m2 ]

coll

: is the collector’s efficiency in design condition

OP : coefficient of performance

For our case, G=800 W/m2 coll

=50%, OP=0.7 and the specific design collector’s area

resulted is Acoll,Spec =3.5 m2 for a 1kW of cooling capacity.

According to this rule of thumb, the solar collector area for the solar thermal air-

conditioning scenario is designed. The solar radiation for the two locations, Aqaba city

and Aswan city is approximately G=1000 W/m2 in summer (see Figure 2.1). This means

a specific collector’s area is Acoll,Spec = 3.5 m2 for 1kW cooling capacity which is needed

for this scenario.

As discussed in chapter 3, the maximum cooling load demand is 13.9 kW and 15.3 kW

for Aswan–TSFH and Aqaba-TSFH respectively. The assumption is made for both cases

that the maximum cooling load demand is 15 kW in each case. So, the area of the

collector needed for the system is 42 m2.

10 A solar air-conditioning system can be either a standalone autonomous system where all energy input is from solar or a solar-assisted air-conditioning system where partial energy input is supplied from solar.

44

In order to simplify the comparison between the PV air-conditioning scenarios and

thermal air-conditioning scenarios which is a major objective of this study, the solar flat

plate collector is designed for 45m2 which is equal to the PV-array area in the PV air-

conditioning scenarios.

Flat plate collectors are fixed and there is no tracking system. The collectors should be

oriented directly towards the equator. The collector’s location in the northern

hemisphere should be facing the south and vice-versa in order to maximize the amount

of daily and seasonal solar energy received by the collector. The optimal tilt angle of the

collector is an angle equal to latitude of its location [51]. However, in summer the tilt

angle should be smaller than the latitude to receive more solar radiation.

Table 5.1 : Parameters of the flat plate collector, [52].

Parameter Flat plate collector Unit

78.4 [%]

C1 4.28 [W/m2K]

C2 0.014 [W/m2K2]

Surface area 2.69 [m2]

45

Storage Tank

The solar photovoltaic air-conditioning system stores the excess DC in batteries.

Similarly, It is necessary to use a thermal energy storage tank, either heat or cold

storage in thermal air-conditioning system.

According to [36], the thermal energy from the collector can be stored to be used when

needed by the air-conditioning (heat storage). Alternatively, the cooling product by the

air-conditioning can be stored in a low temperature (below ambient) thermal storage

unit (cold storage). That’s to provide cold energy for a few hours in the afternoon when

solar radiation already decreases but internal cooling load demand is still high.

These two alternatives are not equivalent in capacity, costs or effect on the overall

system design and performance. The required capacity of a cold storage tank is less than

that required of a heat storage tank because the heat storage has a higher conversion

efficiency than the cold storage tank [36]. In addition, heat storage tanks can be used for

other applications for example domestic hot water or space heating.

There are two technologies for hot water storage tanks which can be used. Either with

thermal stratification or without. Stratification means moving the thermal heat from

layers of cold water at the bottom of the tank to the hot water at the top of the tank.

That will increase the performance efficiency of the system.

According to [6], in order to achieve a solar fraction of 80 % for the given cooling load

profile, a collector aperture area of 48.5 m2 and a storage tank volume of 2 m3 is

required if the generator is always operated at an inlet temperature of 85 0C.

This study analyzes a solar thermal air-conditioning system (Lithum-Bromide water

absorption chiller with a COP of 0.7 and a nominal cooling capacity of 15 kW ) in

Madrid. Madrid has a Mediterranean climate similar to the selected locations in this

study ,where the solar radiation reaches 1000 W/m2 in summer.

In this study the stratification of a hot water storage tank volume is 2m3. The tank is

produced by KWB company in Germany (see Table 5.3) [53]. The tank parameters are

listed in Table 5.3.

According to [50]and [35], high temperature differences between the inlet and outlet of

a collector are not recommended in a solar air-conditioning systems. The basic reason is

46

that thermally driven chillers in general work at comparatively low temperature

differences between inlet and outlet, e.g. 10 0C. Therefore, in this study 20 0C

temperature difference in the storage tank is assumed.The storage tank has 20 0C

temperature nodes to simulate stratification with minimum temperature equal to the

chiller outlet hot water temperature of 75 0C and the maximum temperature of 95 0C.

Back-up System

When there is no enough solar radiation (e.g. at evening, night or on cloudy days), it will

be a necessary to have a back-up system for the cold production or to allow the solar

air-conditioning system to continue.

Two different back-up approaches can be used to achieve this objective, either back-up

heating or cooling systems. The back-up heating system usually uses burners (oil, gas or

pellet) or electric heater connected directly to the heat storage tank. The back-up

cooling system usually uses conventional vapour pressure cooling devices.

In this study, a back-up electric heater supplies the storage tank with heat whenever the

storage tank temperature drops below the set point temperature required for driving

the sorption chiller (85 0C). This gives stability for the cooling production of the chiller

especially in the afternoon(see Table 5.3).This choice (back-up heater)and not back-up

cooling system has been built based on two arguments. Firstly compared with back-up

cooling system, the back-up heater support the absorption chiller to going on even if the

hot water which delivered by the collectors is lower than the minimum operation

temperature of the absorption chiller, this leads to increase the absorption chiller

operation time during the presence of solar radiation. which means higher solar gain

and benefit . The second argument the price of back-up heater system is much less than

the back-up cooling system.

47

5.3.1.2 Absorption Chiller

Most of the thermally driven cooling system and solar assisted air-conditioning systems

installed today are based on absorption chillers [34], [35].

The absorption chillers are used to produce chilled (cold) water which can be used for

any type of air-conditioning equipment to cover the cooling load demand in the

building.

Physical Description

Figure 5.5: Schematic diagram for an absorption chiller for chilled water

production, [37].

Figure 5.5 depicts the schematic diagram for the working principle of absorption chiller

systems. ‘‘They are similar to a mechanical compression cooling system with respect to

the system components evaporator and condenser. In a mechanical compression

cooling system, a mechanical compressor is employed in order to produce the pressure

differences and to circulate the refrigerant. Whereas the absorption chiller uses a heat

source. The absorption chiller consists of an absorber, a pump, a heat exchanger, a

generator and a throttle valve instead of a mechanical compressor.The steps description

of the absorption cycle as following’’ [37]:

Heating rejection (cooling tower ) Driving heat (e.g. Solar collector )

Throttle valve solution heat exchanger

Throttle valve

pump

Pressure

Useful cold (Qcooling) Heat rejection (cooling tower)

Temperature

Condenser

Evaporator

Generator

Absorber

48

In the evaporator: the refrigerant (water) converts from liquid to vapour by

extracting heat from a low temperature heat source like building to be cold. The

results from this process is a useful cold.

The refrigerant vapour moves to the absorber: where a concentrated hygroscopic

solution (Lithium-Bromide) absorbs the refrigerant vapour. This process generates

latent heat which should be removed to keep the process going usually by using a

cooling tower.

The mixture of the two fluids is pumped to the generator which is connected to the

driving heat source, e.g. the solar collector. In the generator, the mixture is

separated again by increasing temperature and partial pressure by the heat supply.

The refrigerant vapour is released at high pressure and moves to the condenser and

the concentrated hygroscopic solution flows back to the absorber.

In the condenser: the refrigerant vapour is condensed, heat is rejected to a heat sink

and usually removed by using a cooling tower.

In this step, the pressure of the refrigerant condensate is reduced by streaming

through an expansion valve, afterwards it flows back to the evaporator.

Coefficient Of Performance (COP)

The efficiency of a thermal absorption chillers is determined by the coefficient of

performance COP. Looking to the absorption chiller as shown in Figure 5.5, the position

of the components represents the pressure and temperature levels.

The COP depends on three external temperature levels: hot water inlet temperature

(heating) which comes from the collectors, the required temperature of the chilled

water (chilled) which needs to cover the cooling demand in the building and the

temperature of the re-cooled water(re-cooling) which circulates through the cooling

tower. According to the first and the second laws of thermodynamics, the ideal

coefficient of performance, COPideal , can be expressed as follows [55], [35]:

49

……………………………………………………………..…..….….(5.17)

Where :

: inlet temperature of the generator (heating ), [ 0 K]

: outlet temperature of evaporator (chilled), [ 0 K ]

: inlet temperature of condenser (re-cooling), [ 0 K]

Equation 5.17 shows how the COP is affected by the three temperature levels depending

on the external technical operational side: for heating (flat plate or evacuated tube

collectors, waste heat source), re-cooling (cooling tower) and cooling application

(sensible and /or dehumidification, fan coils etc). Finally, when making the choice of the

product, the boundary conditions should be taken into consideration as done in this

study.

Absorption Chiller Selection and Design

Absorption chillers are available on the market in a wide range of capacities and design

for different application. For air-conditioning applications, mainly absorption chillers

using the sorption pair Lithium Bromide-water (LiBr-H2O) are applied [9].

There are two types of absorption chiller technologies. Single-effect or double-effect

absorption chillers. ‘‘The term single-effect refers to the fact that the supplied heat is

used once by a single generator. A double-effect absorption chiller can be viewed as two

single-effect cycles stacked on top of each other. The top cycle requires heat at a higher

temperature level compared to a single-effect machine. Double-effect cycles have a

higher COP than single-effect cycles’’ [37].

‘‘For solar-assisted air-conditioning systems with common solar collectors, single-effect

LiBr absorption chillers are the most commonly used systems since they require a

comparatively low temperature heat input’’ [37].

50

According to the simulation results of the thermal cooling load demands for the Aswan-

TSFH and Aqaba-TSFH, the maximum cooling load demand are 13.9 kW and 15.3 kW

respectively. Based on this results the absorption chiller has been selected in this study.

WEGRACAL SE 15ACS15 is a water /Lithium Bromide single effect absorption chiller11

with a nominal capacity of 15 kW and a COP of 0.71 . This absorption chiller is selected

for the solar thermal air-conditioning scenario as shown in Figure 5.4. In this study, the

system is designed to work under the device parameters from the manufacturer in all

cases (see Table 5.2).

Table5.2: Lithium Bromide-water (WEGRACAL SE 15ACS15) absorption chiller

parameters, compiled from [56[, [37] and [10].

Parameter Absorption chiller LiBr-Water Unit

Manufacturer EAW [-]

Designation Wegracal SE 15ACS15 [-]

Technology Absorption [-]

Sorbent refrigerant LiBr/H2O [-]

Cooling capacity 15 [kW]

COP 0.71 [-]

Heating temperature 90/80 [0C]

Re cooling temperature 30/35 [0C]

Cold water temperature 17/11 [0C]

Electricity demand 30 [W]

Hot water 2 [m3/h]

Cold water 5 [m3/h]

11 It is designed by the company EAW, Westenfeld and the Institute of Air Conditioning and Refrigeration in Dresden (ILK-Dresden) [35].

51

5.3.1.3 Cooling Tower

A cooling tower is a special heat exchanger where re-cooling water is brought into

contact with ambient air to transfer rejected heat from the coolant. ‘‘Heat rejection

greatly affects the performance and efficiency of the chiller. In most systems the waste

heat is released into the environment by dry coolers or wet cooling towers. The wet

cooling tower is suitable for moderate climate zones that only occasionally have high

outside temperatures (>30 °C)’’ [56]. However, the dry cooling tower generally shows

less efficient operation, increased electricity consumption due to larger fans and at least

double the investment costs in comparison to wet cooling towers [37]. In this study, a

wet cooling tower is assumed 12(see Table 5.3).

5.3.1.4 Cold distribution System

The type of cold distribution system in the building is assumed to be fan coils with a

working temperature of 11 oC / 17 °C . The chilled water circuit consists of a pump and a

water/air heat exchanger (fan coil) which refrigerates the building zones through a duct

system. The fan coil is located inside the building.

Table5.3: Technical parameters of the back-up heater, storage and cooling tower,

[37]and [10].

Parameter Back-up

heater

Cooling

tower

Storage

tank

Unit

0.95 [-]

KhLlosses 0.8 [W/(m2K)]

TmaxSTH 98 [°C]

Volume 2 [m3]

Electricity Consumption 6-10 [W/kWof cooling power]

12 For more details about the wet cooling tower system see the schematic diagram and the description of this system in according to [37] in Appendix D.

52

5.3.3 System Simulation and Methodology The simulation provides useful information about the long-term performance of a solar

thermal air-conditioning system. This section describes the simulation steps for the

solar thermal air-conditioning scenario by the using Matlab-Simulink for both cases of

Aswan-TSFH and Aqaba-TSFH.

Simplifications are made by keeping the coefficient of performance of the absorption

chiller (COPABCH) constant at 0.71, by assuming a constant heating water temperature of

85 oC re-cooling water temperature (30 oC) and a cold water temperature (11 oC) as

indicated by the manufacturer (see Table 5.2).

The simulation process is done step by step for each case, starting with the loads that

have to be compensated by the chiller depending on the cooling load demands. In the

first step, the hot water and the power consumption of the chiller together with the

cooling tower is calculated by assuming the cooling power demands Pcool- load c and the

coefficient of performance for the absorption chiller COPABCH . The heat power supply

required by the absorption chiller P hABCH h is calculated by using the following equation

(5.18) [36] :

...................................................................................................(5.18)

In the second step, the heat power production Pcollh from the collector is calculated by

using Equation (5.19). The collector’s efficiency is calculated by Equation (5.20)

[57].

The collector’s efficiency is defined as the ratio of the usable thermal energy and the

received solar energy. It could also be obtained for each time step if the optical and the

thermal loss coefficients of the collector, C1 and C2, are known. The optical

efficiency indicates the percentage of the solar rays penetrating the transparent

cover of the collector (transmission) and the percentages being absorbed. Basically, it is

the product of the rate of transmission of the cover and the absorption rate of the

absorber [58]. For more details about the collector parameters see Table 5.1.

53

…………………………………………………………………………………….….....(5.19)

..................................................................(5.20)

Where :

: Collector optical efficiency; [-]

C1 : linear heat transfer coefficient; [W/m2K]

C2: quadratic heat transfer coefficient; [W/m2K2]

T coll: average fluid temperature in the collector; [K]

G tilt : solar radiation on a tilted surface; [W/m2]

At the storage tank, based on the first and second steps, the heat power product by the

solar collector Pcoll h and the heat losses from the storage PhABHh by the demand of

cooling system are known. In addition to that, the heat losses PST;loss h to the surrounding

from the surface of the storage tank due to non-ideal insulation is determined by

Equation 5.22.

The temperature of the storage differs from one time step to the next due to the heat

consumption by the adsorption chiller from the storage tank, heat losses and the heat

supply by the collector to the storage tank. The temperature difference (∆TS) of the

storage between the two time steps is calculated by using Equations (5.21) [36]:

................................................................................(5.21)

Where:

w : density of water; [kg/m3]

54

V storage: Volume of the storage; [m3]

Cw : specific heat capacity of water; [4.2kJ/kg .K]

: storage temperature deference; [k]

.....................................................................(5.22)

Where :

U : storage heat losses coefficient in [W/m2K]

As: storage surface area [m2]

For the heat losses of the storage tank due to non-ideal insulation, it was assumed that

the temperature difference between the storage Tstorage and its surrounding is constant

throughout the year for all location with 65 oK (Tstorage =85 oC and the room temperature

≌ 20 oC).

The fourth step refers to Equation 5. 1. If the ∆Ts (TSTHset – TSTHnew) is negative, the

heating power from the back-up heater is required. The heat which has to be supplied

by the back-up heater and is calculated by Equation 5.23 where the back-up heater

efficiency is 0.95 (see Table 5.3) [10] as:

–

.............................................................(5.23)

From Equation (5. 1), if the value for the ∆Ts (TSTHset – TSTHnew) is positive, there is

excess heat available from the collector which is not required according to the cooling

load demands. So the amount of heat power which has to be stored PSh in the tank as a

thermal energy is calculated by using Equation 5.24 [36]:

..........................................................................................(5.24)

55

The daily heat capacity limit for the storage tank is taken into account by using Equation

5.23. The maximum daily heat capacity in (kWh) of the storage water is calculated for

the given storage size of 2 m3 by using Equation 5.25 as:

.................................................................................(5.25)

where the is the storage tank difference in (K). As discussed before the maximum

was 20 k in this study. The direct heat power(under assumption: the system without

storage) which is driving the chiller to produce the direct cooling power was calculated

by using Equation 5.26 :

..........................................................................................(5.26)

The

powers are converted from heat power to the cooling

powers:

and , where the is 0.71. as in the subsequent

Equations:

..................................................................................(5.27)

..............................................................................................(5.28)

...................................................................................(5.29)

56

.....................................................................................(5.30)

A simplification is made in this study by neglecting the power consumption of the

pumps. For the technical parameters of the back-up heater and storage tank see Table

5.3.

The back-up cooling power is calculated by using Equation 5.29 without

subtracting the cooling power which is compensated by the storage since there is a

mismatching between the charging heat power in storage tank and the back-up heat

power needed; where the charging heat power happened at noon of the day while the

back-up heat power is needed in the morning, evening and night. So in this scenario, the

back-up cooling energy which should be covered by the grid is calculated by

using Equation 5.31 as:

=

..............................................................................(5.31)

where the cooling energy which is compensated by the storage and the direct

cooling energy compensation is calculated by using Equation 5.32 and

Equation 5.33 respectively. The total cooling energy demand is calculated by employing

Equation 5.34 :

......................................................(5.32)

................................................................................................(5.33)

…………………………………………………………………………………..…..….……(5.34)

57

5.3.3.1 Solar Fraction

The solar fraction is the fraction of the total load which is covered by the solar energy

which is usually expressed as percentage [50]. The solar fraction of a particular system

depends on many factors such as the collector and storage size, the operation and the

weather. Therefore, it is a key indicator for sizing the solar thermal system [35].

The annual solar cooling fraction (SF) is calculated by employing Equation 5.35:

….......................................................................................................(5.35)

where the is the annual back-up heat energy for driving the chiller process which

is calculated by using Equation 5.36 :

…......................................................................................................(5.36)

.

Where t=35041 is the number of time steps (15 min) per year and the annual

required heat energy for driving the chiller process which is calculated by using

Equation 5.37:

………………………………………………………………....……….……………....(5.37)

58

6. Simulation Results and Analysis for Solar Air-Conditioning

Scenarios

This chapter includes the simulation system scenarios results. The results are analysed

for each scenario. Then, the comparison between the solar thermal air-conditioning

with storage scenario and a solar PV- air-conditioning scenarios with and without

storage scenarios is done. Eventually, conclusions and the further work are delineated.

So in this study the e pressions, ‘Cooling production energy/power’ means the cooling

energy/power which is produced by any air-conditioning system scenario as without

storage. ‘Direct cooling compensation energy/power’ means the cooling energy/power

which compensate part from the cooling demand by the air-conditioning system

scenario as without storage. ‘Storage compensation’ means the cooling energy which

compensates part from the cooling demand by the contribution of the storage system in

the air-conditioning system scenario. ‘External back-up cooling energy/power’ means

the cooling energy/power which produced by the contribution of the backup system of

the solar air-conditioning system from the grid electricity in each scenario, in order

compensate the residual cooling demand, (the electric back-up heater in thermal air-

conditioning scenario, direct grid connection with the compressed chiller in PV air-

conditioning scenarios).

6.1 Solar Photovoltaic (PV) Air-conditioning Scenarios

The simulation results and analysis of the results for the two PV air-conditioning system

scenarios, without and with storage (battery) has been discussed for the Aswan-TSFH

and Aqaba-TSFH cases. The battery was designed to compensate the cooling load

demands. Firstly, the influence of the cooling production load by the solar PV air-

conditioning system without (battery) scenario is diagrammed. Then it is followed by

the excess of cooling production and the external back-up cooling load results analysis,

in order to explain the storage which is designed for the solar air-conditioning system

with battery scenario. Finally, analysis of the results is made for annual cooling energy

products to compensate the cooling energy demands of the two cases, Aqaba-TSFH and

Aswan-TSFH. That’s for each scenario, PV solar air-conditioning system without battery

and PV solar air- conditioning with battery.

59

6.1.1The Influence of a Direct Cooling production

Yearly Analysis:

Figure 6.1: PV air-conditioning cooling production along the year for Aswan-TSFH.

Figure 6.2: PV air-conditioning cooling production along the year for Aqaba-TSFH.

The cooling production covers almost entirely the maximum peak of the cooling load

demand for Aswan-TSFH especially in the summer. On the contrary, for the case

of Aqaba-TSFH, the cooling production is lower than the maximum peak of the cooling

load consumption by 3 to 4 kW for the reason that there is a higher solar radiation in

Aswan than in Aqaba. Besides, Aqaba-TSFH has higher peak load demand in summer

than Aswan.

60

For both cases, the cooling production in winter is higher than in summer. This in turn

means, operation module is more efficient in winter than in summer. That’s due to the

PV module’s operation temperature being lowered in winter than in summer. As a

result, it leads to enhancing the PV module efficiency and increasing the electric power

outputs from the PV array.

On the other hand, the ambient air temperature in winter is lower than in summer for

both cases (see Figure 2.2 ). This reduces the thermal effect on the PV module by

improving the heat transfer rate from the PV module to the ambient air with the help

of the temperature difference between the module and the air which is higher in winter

than in summer. This leads to increase the module efficiency and electric power output.

In winter, the cooling production reaches 17 kW and 15 kW in Aqaba-TSFH and Aswan-

TSFH respectively, due to a lower thermal effect on the module as discussed before. In

addition, there could be a higher diffused solar radiation and a higher reflected

radiation by the ground in Aqaba than in Aswan where the PV module is tilted at angle

of 29°31' in Aqaba and is higher than Aswan’s 23°54'.

Weekly Analysis:

Figure 6.3 to Figure 6.6 illustrates the weekly distribution of cooling production in

summer and in winter for the two cases by PV air-conditioning system without storage .

Figure 6.3: Solar-PV air-conditioning cooling production in Summer week for

Aswan-TSFH.

61

Figure 6.4: Solar-PV air-conditioning cooling production in Summer week for

Aqaba-TSFH.

Figure 6.5: Solar PV air-conditioning cooling production in winter week for Aswan-

TSFH.

Figure 6.6: Solar PV air-conditioning cooling production in winter week for Aqaba-

TSFH.

62

In summer (see Figure 6.3 and Figure 6.4), in general, Aswan-TSFH has excess cooling

production than the cooling demands compared with the case of Aqaba-TSFH by which

there is a little of excess cooling production. This due to a bigger solar radiation in

Aswan city than in Aqaba city and vice versa of cooling demand. There is a bigger

cooling demand in Aqaba than in Aswan especially in summer; June ,July and August; as

discussed before.

As shown in Figure 6.3 and Figure 6.4, most of the external back-up cooling load is

needed during the evening, the night and in the morning due to a high cooling load

demand in these periods of the day.

The shape of the daily cooling production curves are diagrammed in Figure 6.3 and

Figure 6.4. As can be seen in the figures, there are several differences between the two

cases. In Aqaba-TSFH case, the curve starts increasing in the morning with a high slope

and reaches its peak at noon and in turn it decreases to reach zero in the evening,

compared with the Aswan-TSFH case. The reason is the increment in the solar radiation

which is higher than Aqaba during the day time and this increases the thermal heat

effect on the PV module’s efficiency and reduces the module electric power output. In

addition, the presence of a higher ground solar reflection and diffusion in Aqaba city

than in Aswan city could lead to an increment in power output from the PV module.

In winter as shown in Figure 6.5 and Figure 6.6, there is an excess cooling production

than cooling load demands due to a low cooling consumption in winter. This in turn

means a high wastage of power during this season. In addition, the percentage of the

daily cooling demand which is covered by the production reaches approximately 50 %

to 70 %.The wastage power in winter, it can be a benefit power if it has been stored in

the grid network. This leads increase the aver all efficiency of PV air-conditioning

system, so it is one of the PV air conditioning technology advantages compared with the

solar thermal air-conditioning technology.

63

6.1.2 Excess of Cooling Production and External Back-up Cooling for a

Battery Design After the discussion of the cooling production load by the solar PV air-conditioning

without battery, we deducted the ‘direct cooling compensation’ by this scenario which

covers apart from the cooling load demand .

This section discusses and analyses the excess cooling production and the residual

cooling load demands which should be covered by external back-up system. The

external back-up system as discussed in Chapter 5 is designed to have a direct

connection of electric compressed chiller in the solar PV-air-conditioning system with

the grid electricity and hence it covers the residual cooling load demand.

As shown in Figure 6.7 and Figure 6.8 there are excess cooling production and external

back-up cooling power from the first scenario, without battery. So to increase the solar

power gain as cooling compensation and to reduce the external back-up cooling power.

Hence, that is the main reason for the selection of the second scenario: solar PV air-

conditioning with battery for both cases.

The storage battery is designed for the second scenario, based on the results of the first

scenario as illustrated in Figure 6.7 and Figure 6.8.

Figure 6.7: PV air-conditioning without storage scenario, Excess cooling production

and external back-up cooling loads for Aswan-TSFH.

64

Figure 6.8: PV air-conditioning without storage scenario, Excess cooling production

and external back-up cooling loads for Aqaba-TSFH.

As shown in Figure 6.7 and 6.8, Aswan-TSFH has an excess of cooling production along

the year but in Aqaba–TSFH case, there is a little excess of cooling production in

summer season especially in June, July and August. That’s due to a higher solar radiation

in Aswan and a higher cooling demand in Aqaba-TSFH in these periods as discussed in

section 6.1.1.1. Aswan-TSFH has a higher external back-up cooling than Aqaba-TSFH.

Approximately there is no external back-up cooling load needed in January ,February

and December and there is a significant excess cooling production load. In April and

October, the excess cooling production is almost equal to the external back-up cooling

load for both cases. So based on the design optimization and by taking into account the

battery, it benefits as much as possible for both cases. Ten days in April having excess

cooling production load is selected to calculate the nominal battery capacity in order to

design the battery system in the second scenario. The calculation results show as

discussed in chapter 5, The battery system should participate in compensating the

cooling demands with a maximum cooling capacity equals to18.32 kWh/ day, as cooling

energy in Aswan-TSFH. This value is close to the value which was calculated in Aqaba-

TSFH. This value equals to 6.4 kWh/ day as DC electric energy.

According to the batteries’ system design, which was done in chapter 5, the battery

system which is required for the solar PV air-conditioning with storage scenario is

designed to produce about 392 Ah. Eight batteries of 12 V each are required and each of

4 batteries are connected in series.

65

6.1.3 Annual Cooling Energy Compensation Analysis This section discusses the annual cooling energy compensation using two scenarios:

solar PV air-conditioning without battery and Solar PV air-conditioning with battery.

Figure 6.9 and Figure 6.10 show the total yearly and monthly cooling energy

compensation for each scenario, where the ‘direct cooling compensation’ in each figure

means the cooling that is covered by the first scenario (PV air -conditioning without

storage scenario) without storage and the remaining quantity means the external back-

up cooling of the first scenario which is covered by the grid electricity .

The direct cooling compensation plus the storage compensation means the total cooling

compensation by the second scenario: solar PV-air-conditioning system with battery

.The back-up cooling in the figures means the external back-up cooling energy needed

for this scenario.

Figure 6.9: yearly cooling energy compensation by the solar PV air-conditioning

system with and without storage scenarios for the Aswan-TSFH and Aqaba-TSFH.

0 3000 6000 9000

12000 15000 18000 21000 24000 27000 30000 33000 36000 39000 42000 45000

Aswan Aqaba Direct compensation Compensation by storage Back-up cooling energy

Co

olin

g En

ergy

66

Table6.1: Yearly cooling energy compensation by the solar PV air-conditioning

system with and without storage scenarios for Aswan-TSFH and Aqaba-TSFH.

Compensation [kWh] PV air-conditioning Without storage

PV air-conditioning With storage

Aswan-TSFH Direct cooling compensation 17447.23911 17447.23911

Cooling compensation by storage 0 4729.541232

External back-up Cooling energy 26883.92848 22154.38725

Total compensation 17447.23911 22176.78035

Aqaba-TSFH Direct cooling compensation 15571.9346 15571.9346

Cooling compensation by storage 0 3176.484789

External back-up Cooling energy 27921.75655 24745.27176

Total compensation 15571.9346 18748.41938

Figure 6.10: Monthly cooling energy compensation by solar PV air-conditioning

system with and without storage scenarios for Aswan-TSFH and Aqaba-TSFH.

6.1.3.1 PV Air-conditioning Without Storage Scenario

Figure 6.9 shows the yearly cooling energy production to compensate the cooling

demand in each case: PV air-conditioning with and without storage. The yearly direct

cooling energy compensated in Aswan-TSFH case is higher than the Aqaba-TSFH case

by 1876 kWh due to a higher solar radiation in Aswan city than in Aqaba city and due to

a lower yearly cooling energy demand in Aqaba-TSFH than in Aswan-TSFH .The yearly

external back-up cooling energy which is covered by the grid electricity, it is higher in

Aswan-TSFH than Aqaba-TSFH in by 1038 kWh. This leads to a conclusion that the PV

air-conditioning without storage scenario in Aswan-TSFH is more efficient than Aqaba-

TSFH.

0 500

1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000

JAN

FEB

MA

R

AP

R

MA

Y

JUN

JUL

AU

G

SEP

OC

T

NO

V

DEC

JAN

FEB

MA

R

AP

R

MA

Y

JUN

JUL

AU

G

SEP

OC

T

NO

V

DEC

Back-up cooling energy Cooling compensation by storage Direct cooling compensation

Aqaba Aswan

Co

olin

g En

ergy

[K

Wh

]

67

Figure 6.9 displays the direct cooling energy in May, June, July, August, October and

November in Aswan-TSFH is higher than in Aqaba-TSFH. This in turn means the yearly

direct cooling energy compensation difference between the two cases comes from these

months of the year for the presence of a higher solar radiation in Aswan than in Aqaba

(see Figure 2.1).

In addition, the tilted PV modules’ angle is designed at 9.31o and 23o for the Aswan and

Aqaba cases respectively. Consequently, in summer the solar radiation declination angle

is more normal to the horizontal surface. This in turn means a higher tilted angle PV will

result in a lower efficiency.

6.1.3.2 PV Air-conditioning With Storage Scenario

Figure 6.9 shows that the Aswan case has a higher total cooling compensation (direct

cooling compensation energy plus cooling compensation by the storage) than the

Aqaba-TSFH case by 3428 kWh in one year as shown in Table 6.1.

Figure 6.10 shows that the Aswan-TSFH case has a higher monthly cooling energy

compensation (direct cooling compensation energy plus cooling compensation by the

storage) which is produced by the Solar PV air-conditioning with batteries scenario

than the Aqaba-TSFH in each month. The reason for this is, the Aswan-TSFH case has a

higher monthly direct cooling energy compensation than the Aqaba-TSFH case.

Furthermore, there is a compensation by the storage in Aswan-TSFH, where there is no

cooling energy compensation by storage in June, July and somehow in August in Aqaba-

TSFH case . That’s due to the presence of a higher solar radiation in Aswan city.

Figure 6.10 and Figure 6.9 could help in taking a technical decision for the Solar PV air-

conditioning with storage scenario for both cases. The storage system is more efficient

in Aswan case than in Aqaba case because of a higher excess solar radiation in Aswan

especially in summer season.

For both cases, in January, in February and in December, the battery system has a small

contribution to the compensation of a cooling energy demand which is useless in

December and January due to a lower cooling energy consumption in these months.

This in turn means the stored energy by the battery system will be a waste energy.

68

Full cooling demand is covered in November for both cases. This means the battery

system contributes for the compensation with the best efficiency by reducing the

mismatch between the excess energy and the external back-up cooling energy which is

needed at night. In February , the battery system in Aqaba-TSFH is more efficient than

in Aswan-TSFH ,due to a higher cooling energy demand in Aqaba especially at night.

As shown in Figure 6.9, the contribution of the battery system in the Aswan-TSFH case

for the cooling energy compensation almost doubles the contribution of the battery

system in Aqaba-TSFH. In Figure 6.10, the monthly battery system contribution with full

capacity is distributed along 9 months in one year in Aswan-TSFH case. On the other

hand, in Aqaba-TSFH case it was only 6 months long. That’s due to a higher solar

radiation in Aswan city than in Aqaba city especially in these months. This leads to a

technical decision that the design of a battery system is more efficient for Aswan-TSFH

case than for Aqaba-TSFH case.

To design a battery system for the PV-air-conditioning with storage system, it should be

based on the influence of the excess cooling power curve and a external back-up cooling

power curve along the year as it is done in this study. Besides, it is also based on the

total energy consumption of a cooling energy demand.

69

6.2 Results and Analysis for Solar Thermal Air-conditioning Scenario

The solar thermal air-conditioning system (absorption chiller) cannot be realized

without a storage tank . But in the first part of this section, the system assumed as

without storage, for the sake of several reasons . Namely, in order to understand and

investigate the influence of the cooling production under assumption as the system

without storage, to understand and investigate the storage contribution in the cooling

compensation, to make a comparison between the two case studies for the solar thermal

air-conditioning system simulation results and to clarify the results of the a whole

system with storage. So the e pression ‘cooling production’ means the cooling load

which is produced by any air-conditioning system scenario as without storage.

This section is divided in to two parts. The first part discusses the influence of cooling

production. This includes a yearly and a weekly cooling production where the system as

without storage. The second one discusses the annual compensation cooling energy

analysis for the howl of system with storage.

6.2.1 The Influence of Cooling Production

Yearly Analysis:


Aswan-TSFH.

70


Aqaba-TSFH.

Figure 6.11 and Figure 6.12 give an overview of the cooling production throughout the

year by the solar thermal air-conditioning systems as without storage for Aswan-TSFH

and Aqaba-TSFH respectively. These graphs show that in Aswan-TSFH case, there is a

higher cooling production along the year than the cooling load demand in Aqaba-TSFH.

In addition to that, it is beyond the maximum peak cooling demand in summer season.

In the case of Aqaba, the situation is different in the summer season. The cooling

production rises up to near the maximum peak cooling load demand. In other words,

there is a little excess of cooling production . Both cases have a high overloaded cooling

production in winter season as a waste of energy especially in January and December

because there is no cooling demand.

Generally, the results due to the summer solar radiation in Aswan city is higher than in

Aqaba city(see Figure 2.1). And the change in the solar inclination angle during the year

leads to a lower solar gain from the tilted collectors in summer season. That especially

when the collector is tilted by an angle 29.31 o C in Aqaba case which is higher than in

Aswan case which is designed at 23 o C. In addition, as discussed in chapter 3, in June,

July and August, the cooling demands of Aqaba-TSFH is higher than Aswan-TSFH’s.

Furthermore, Aqaba has a higher solar thermal losses from the flat plate collector to the

ambient air (see Figure 2.2) which shows the summer daily ambient air temperature in

Aqaba is lower than in Aswan city and a more daily fluctuation. This specially during

July and August .

71

The solar thermal air-conditioning system is designed to give the nominal capacity

equal to 15 kW as a peak cooling load. This amount is based on the simulation results of

the thermal cooling load demand for Aqaba-TSFH and Aswan-TSFH, where 45 m2 of a

flat-plate collectors area was installed. As discussed in hapter 5, the collectors’ tilt

angle is designed so as to be equal to the location latitude based on the rule of thumb

[51]. However, Figure 6.11 and Figure 6.12 help in taking a technical decision and the

design is correct for both cases. But in the case of Aqaba, to optimize the performance of

the compensation cooling load in the summer, the collector should be tilted at 15°

greater than the latitude.

Weekly Analysis :

This section includes a weekly result samples in summer and winter in order to zoom

in, analyse and evaluate the performance of the cooling production by the solar thermal

air-conditioning as without storage.


Aswan-TSFH.

72


Aqaba-TSFH.

Figure 6.15: Solar thermal air-conditioning cooling production in winter week for

Aswan-TSFH.

Figure 6.16: Solar thermal air-conditioning cooling production in Winter week for

Aqaba-TSFH.

73

In each plot, generally the cooling production load of the thermal air-conditioning

system starts to grow late in the morning and reaches the maximum peak compensation

cooling load around noon time at 12. And then, it begins to decline until it reaches zero

at the beginning of the evening due to the movement of the sun during the day.

In summer season, Figure 6.13 and Figure 6.14 in Aswan case display that there are

excess of cooling production than the cooling demand. On the contrary, for Aqaba-TSFH

case, there is a little excess of cooling production. In addition, it has a higher

mismatching with cooling load demand due to higher solar radiation in Aswan city than

Aqaba city. And it has a higher heat losses from the solar collector to the ambient air.

Most of the external back-up cooling needed for compensation is during evening and

night due to a bigger cooling load demand in both Aswan-TSFH and Aqaba-TSFH. This

shows the importance of a daily storage for a system in summer especially for Aswan-

TSFH case since it has a higher excess cooling production and night cooling demands

compared with Aqaba-TSFH, as discussed in chapter 3.

In winter Figure 6.15 and Figure 6.16 show, for both cases, that the cooling production

reaches approximately 40% or 50% of the daily cooling demand which in turn means

higher matching between the cooling load demands and the cooling production than in

the summer. Furthermore, in winter it has a huge excess cooling production than

demand where in some days for instance on Friday, there is no cooling load demand for

both cases. This leads to a generalization that all of the excess cooling production will be

a waste of power. In addition, less daily external back-up cooling is needed in winter

than in summer due to the lower cooling demands in this season. The excess of heat

power gain from the thermal collector in winter, it can be used for other applications

such as space heating or domestic hot water which leads to increase the aver all system

efficiency. This is one of the solar thermal air-conditioning technology compared with

PV air conditioning technology.

74

6.2.2 Annual Cooling Energy Compensation Analysis

Now this section dealing with cooling production of the air-conditioning scenario as

with storage .The hot water storage tank is one of the main components in the solar

thermal air-conditioning system which combines the solar heat source (solar collector)

and the absorption chiller. Hence, the solar thermal air-conditioning system cannot

work in the absence of the storage tank . As discussed in Chapter 5, the solar thermal

air-conditioning system scenario for each case includes the solar thermal heating

system (45 m2 of solar flat plat collector, 2m3 hot water storage tank and the external

back-up system) integrated with the absorption Lithium Bromide/water chiller where

the external back-up system is electric boiler.

This section discusses the annual cooling energy compensation by the solar thermal

cooling system with storage scenario for both cases. In addition ,it explains how the

contribution of the storage to reduce the external back-up cooling by the compensation

from the excess power for each case study.

6.2.2.1 Excess Cooling Production and External Back-up Cooling Loads


back-up cooling loads for Aswan-TSFH.

75


back-up cooling loads for Aswan-TSFH.

The Figure 6.17 and Figure 6.18 shows the excess of cooling production load and the

external back-up cooling load after deducting the direct cooling which covered part

from cooling demand . As shown by the weekly results analysis earlier, most of the

external back-up cooling is at night due to a higher cooling demand for both cases.

As can be seen in the above figures, for the Aswan-TSFH case there is a surplus in the

cooling production along year. On the contrary, there is no surplus in the

summer months, especially in June, July and August for the Aqaba-TSFH case. The

Aswan-TSFH case has a higher external back-up cooling than Aqaba-TSFH. There is

implies a mismatching between the excess of cooling production and the external back-

up cooling due to a huge night cooling demand.

76

6.2.2.2 Annual Cooling Energy Compensation

Figure 6.19 and Figure 6.20 show how the yearly and monthly distribution of the

cooling energy compensation through the solar thermal air-conditioning system

scenario in order to fulfill the cooling energy demand for both cases, Aswan-TSFH and

Aqaba-TSFH. That are a direct cooling compensation , the cooling compensation by the

storage in addition to the external back-up cooling energy which is covered from the

grid electricity.

Figure 6.19: The cooling energy compensation by the solar thermal air-conditioning

system scenario for Aqaba-TSFH and Aswan-TSFH.

Figure 6.19 shows the highest annual cooling energy compensation by the system via

(direct plus storage) which occurs in Aswan-TSFH. The lowest compensation occurs in

Aqaba-TSFH .In Aswan-TSFH case ,the total annual cooling energy compensation by the

(direct plus storage) is higher than the Aqaba-TSFH case by 4348 kWh.

The other point seen from identical figure is, the cooling energy compensation by the

storage and by the direct cooling energy separately, in Aswan-TSFH case is higher than

in Aqaba-TSFH case. In addition, the external back-up cooling in Aqaba-TSFH is higher

than in Aswan-TSFH for a twofold reason. Firstly, there is a higher solar radiation in

Aswan city than in Aqaba city. Secondly, the Aswan-TSFH case has a higher cooling

energy demand than Aqaba-TSFH as discussed in Section 3.3.1.

0 3000 6000 9000

12000 15000 18000 21000 24000 27000 30000 33000 36000 39000 42000 45000

Aqaba Aswan

Back-up cooling Energy compensation by storage Direct compensation

Co

olin

g En

erg

y [k

W h

]

77

The contribution of the storage tank in the cooling energy compensation is to overcome

the cooling energy demand. In this regard, the Aswan-TSFH case almost doubles that of

the Aqaba-TSFH case per year due to the contribution of the storage tank which

improves the performance of the device. This in turn means a better solar gain stored

and it overcomes the cooling night demands, because there are higher solar radiation

and night cooling demand in Aswan-TSFH.

Figure 6.20: Monthly cooling energy compensation by the solar thermal air-

conditioning system scenario for Aswan-TSFH and Aqaba-TSFH.

Figure 6.20 shows the storage contribution in the cooling compensation

which extends over all months of the year in Aswan-TSFH case. On the other hand, the

Aqaba-TSFH case shows that there is no compensation by the storage during

the summer months.

In the summer season, especially in June, July and August for the case of Aswan-TSFH,

the total compensation (direct plus storage ) of the cooling energy is higher than the

Aqaba-TSFH case as shown in Figure 6.20. This is due to the contribution of the

hot water storage tank in the cooling compensation. This leads to the main reason as

shown in Figure 6.17 and Figure 6.18 , where there is no excess of cooling energy

produced in the summer season in the case of Aqaba-TSFH contrary to Aswan-TSFH.

This due to a higher of solar radiation in Aswan than in Aqaba. In addition, there is a

lower cooling demand in Aswan-TSFH. Furthermore, a higher heat losses from the solar

0 500

1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000

JAN

FEB

MA

R

AP

R

MA

Y

JUN

JUL

AU

G

SEP

OC

T

NO

V

DEC

JAN

FEB

MA

R

AP

R

MA

Y

JUN

JUL

AU

G

SEP

OC

T

NO

V

DEC

Direct compensation compensation by storage Back-up cooling Energy

Aqaba Aswan

Co

olin

g En

ergy

78

collector to the ambient air in Aqaba than in Aswan , where the collector temperature is

designed to work at 85 o C and the outside air temperature in the Aqaba is lower than in

Aswan during the summer and a more fluctuation (see Figure 2.2 ).

In winter for both cases the cooling energy demand is fully covered especially in

November, December, February and October. This in turn means the cooling demand at

the evening and at night happens by the storage participation without requiring a

external back-up cooling. That is due to the cooling demand in winter being less than

the summer’s .

The month of March fulfil cooling demands where the compensation by the storage is

higher than the direct. This in turn means a better overcoming of night demand in both

cases is obtained in this month of the year.

Generally, the Aswan-TSFH case has a higher external back-up cooling in April and

October than the Aqaba-TSFH case due to a higher night cooling demand in these

months.

In Aqaba-TSFH case, the month of October has a higher contribution by the storage to

compensate the cooling energy demand than in Aswan-TSFH case. This is because of a

higher night cooling in Aqaba-TSFH than in Aswan-TSFH. On the other hand, the storage

in this month reduces the mismatching between the cooling production and the demand

more efficiently in Aqaba-TSFH case.

79

6.2.2.3 Solar Fraction

As discussed in Chapter 5, solar fraction (SF) is a key factor in sizing the solar thermal

system which works as the source of energy to drive the absorption chiller. It is

dependent on many factors such as the load demand , the collector, the storage size ,the

operation ,and the climate and hence SF is calculated for the two cases.

Figure 6.21: Annual solar fraction for the solar thermal air-conditioning system

scenario in Aswan-TSFH and Aqaba-TSFH.

Figure 6.22: Monthly solar fraction for the solar thermal air-conditioning system

scenario in Aswan-TSFH and Aqaba-TSFH.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Aqaba Aswan

So

lar

frac

tio

n [

%]

0

0.2

0.4

0.6

0.8

1

Sola

r fr

acti

on

[%

]

JAN FEB

MAR APR

MAY JUN

JUL AUG

SEP OCT

NOV DEC

Aswan Aqaba

80

Figure 6.21 and Figure 6.22, give an overview of the monthly and yearly solar fraction

that can be obtained for the solar thermal system under a solar thermal air-conditioning

system with a storage scenario designed for both locations under the same storage size

of 2 m3 and a collector area of 45 m2. The graphs are valid for a TSFH in the two selected

locations, Aqaba and Aswan, and for the flat plate collector under the system design

boundary conditions of this study.

As shown in Figure 6.21, the yearly SF is 50% and 41% for Aswan and Aqaba cases

respectively. While comparing those SF values by which the Aswan case is higher than

Aqaba case. This is due to the high solar radiation. As a result, much of the heat

produced by the collector can be stored. Therefore, better overcoming of the solar gain

and load mismatching is obtained. In addition, we can achieve a better overcoming of a

night demand in Aswan-TSFH case. Further more in Aqaba-TSFH case has higher heat

losses from the collector and the storage tank than Aswan-TSFH, this due to low

ambient air temperature in Aqaba city.

In summer(see Figure 22), the higher SF is obtained in Aswan than in Aqaba case. As

already discussed, it is because the Aswan-TSFH case has higher solar gain and it means

better to overcome the night demand which is obtained by the contribution of the

storage (see Figure 6.20). The graph could help in taking a technical decision. The

storage tank size for the solar thermal air-conditioning system scenario in Aswan-TSFH

could play for the compensation of a cooling load better than in Aqaba-TSFH system

scenario.

In winter for both cases(see Figure 22), the solar fraction reaches 100% which in turn

means the cooling load demand has been covered fully 100% by the solar thermal air-

conditioning system without the need to external back-up cooling. This due to a low

cooling demand and a high solar energy gain by the collector in this period (see Figure

6.20 ). But it should be clear that the Cooling energy consumption is very little or

negligible in some months, such as November, January and February. As a result, most

of the heat produced from the collectors will be a waste energy.

81

6.3 Thermal Air-conditioning Scenario Versus PV Air-conditioning

Scenarios

6.3.1 The Direct Cooling Production Load Performance

This section discusses and analyzes the solar thermal air-conditioning scenario versus

solar PV air-conditioning scenarios based on the performance of the cooling production

on the weekly and daily bases(as the systems without storage).

Weekly Performance:

Figure 6.23 and Figure 6.24 illustrate the weekly cooling production load for the solar

PV air-conditioning scenarios versus thermal air-conditioning scenario where the

systems as without storage. Generally, these samples represent the weekly cooling

compensation especially in the summer where there are high cooling demands.


production performance in Summer Week for Aswan-TSFH.

82


production performance in Summer Week for Aqaba-TSFH.

Figure 6.23 and Figure 6.24 generally show the following for each day in the week for

both cases: Aswan-TSFH and Aqaba-TSFH.

The daily cooling production along the week by the thermal air-conditioning scenarios

has a higher peak curve than the PV air-conditioning scenarios. In addition, the excess

cooling production which is above the cooling load demand curve of the solar thermal

air-conditioning scenario is higher than the curve for the solar PV air-conditioning

scenario. That could lead us to say that the storage system for the thermal air-

conditioning scenario is more important and efficient than the PV scenarios especially

in summer for Aswan-TSFH.

The daily cooling production curve which is produced by the solar PV air- conditioning

starts in the morning before the curve of the solar thermal air-conditioning system

scenario and ends at the evening and vice versa. This leads to a conclusion that the daily

direct cooling compensation by the PV air-conditioning scenario is more efficient than

the thermal scenario. In another way, the daily direct cooling energy compensation

which is the area under the cooling production curve, under the cooling demand curve

in PV air-conditioning scenarios is higher than in the thermal air-conditioning scenario.

83

In addition, the daily external back-up cooling energy needed is the remaining area

under the cooling demand curve after deducted the area of direct cooling compensation

energy. This external back-up cooling energy is higher than the direct compensation

energy for both scenarios. That’s due to a higher night cooling demand. Furthermore,

the external back-up cooling needed for the PV-system is lower than for the thermal

system. which leads to say that the thermal system as without storage has a higher

mismatching with the cooling load demand than in the PV-system without storage.

Daily Performance:

After the weekly discussion and analysis, this Section discusses and analyzes the daily

performance of the cooling production in order to link the results with the main

technical and physical reasons. And this leads to clarify the weekly results in the whole

scenarios’ results.

Figure 6.25:PV air-conditioning versus solar thermal air-conditioning, cooling

production performance in Summer day for Aswan-TSFH.

84


production performance IN Summer day for Aqaba-TSFH.

Figure 6.23 to Figure 6.26, diagram that the PV air-conditioning scenarios have higher

direct cooling compensation than the one by the solar thermal air-conditioning

scenario, the cooling production curve by the PV air-conditioning scenario starts earlier

in the morning than the thermal air-conditioning scenario. Furthermore, at the evening

the curve of the PV air-conditioning scenarios ended at a zero value and late compared

with the curve of thermal air-conditioning scenario. In addition approximately, in

morning and at evening, the cooling compensation curve of the PV air-conditioning

scenario is higher than that of the thermal air-conditioning scenario in this period . The

reasons are summarized below.

The reasons are, firstly the thermal collector has higher efficient compared to PV

module where the solar collector efficiency is around 50% and PV module is around

14% . But not too much due to the COP of compressed chiller and Absorption chiller is

completely different. Where the COP is nearly 3 for the compressed chiller in the PV air-

conditioning scenario and it is around 0.7 for the absorption chiller in the thermal air-

conditioning scenario, this lead to say in the direct cooling compensation, the overall

system efficiency of PV air-conditioning scenarios is higher than the one by the solar

thermal air-conditioning scenario.

85

The second reason, the high thermal losses from the flat plate collector in thermal air-

conditioning scenario to the sounding outside air, where its temperature is lower in the

morning and at the evening compared with the noon. In addition, the thermal losses

from the hot water storage tank. As discussed in Chapter 5, where the solar thermal

collector is designed to work at a temperature as high as 85 0C in order to drive the

adsorption chiller. That leads the solar flat collector to start working late in the morning

and ended earlier in the evening especially when the thermal losses are higher than the

solar gain from the collector as designed in this study.

The third reason, in the morning and at the evening, the ambient air temperature is

lower than the noon’s. The PV module works with a high efficiency where the operation

temperature of the module is low due to a high thermal heat transferred to the ambient

air. And hence a low thermal effect on the PV module efficiency.

In addition, in the morning and at the evening there is a high reflection and diffused

radiation compared with a noon and in turn a higher electric power gain from the PV

module. On the contrary, the diffused and reflected radiation are not so sufficient to

produce heat by flat plate collector.

At noon of the day, the solar thermal air-conditioning scenario is more efficient to

produce a cooling load than the PV air-conditioning scenario. But most of the cooling

compensation by thermal air-conditioning scenario in this period exceeds the cooling

demand. As discussed before, the storage system is more important for thermal air-

conditioning scenario than the PV air-conditioning scenario.

The reason for this result is the flat plate collector works at noon with the highest

efficiency because of a higher solar radiation which increases the solar gain as hot water

in addition to a small thermal heat losses from the collector at this period, where the

ambient air temperature is higher compared with the morning and the evening. In

addition the peak cooling demand occurs at noon.

On the contrary at noon, the PV module efficiency reduces and stops due to the thermal

effect, where the module operation temperature is high by time the ambient

temperature is high . This low driving temperature reduces the heat transfer from the

module to the ambient air.

86

Comparison Between Aqaba-TSFH Case and Aswan-TSFH Case:

As shown from Figure 6.23 to Figure 6.26, there are generally two major differences in

the performance of the cooling production by the thermal and PV scenarios as without

storage, for both the Aswan-TSFH case and Aqaba-TSFH case. These differences are

elaborated below.

The first difference in all scenarios , the Aswan –TSFH case has a higher extra cooling

production compared with Aqaba-TSFH due to a higher solar radiation in Aswan

especially in the summer season ( see Figure 2.1).

Secondly in all scenarios , the direct cooling production curve behaviour for the Aswan-

TSFH is more thin during the day than the Aqaba-TSFH. Besides, the Aswan-TSFH case

is mismatching a lot between the cooling compensation and the cooling load demand

than the Aqaba-TSFH case.

That’s due to the behaviour of the solar radiation in each city. In addition, a higher

diffusion and reflected solar radiation is observed in Aqaba city than in Aswan city

especially for this boundary condition of this study. Where an immense reflected solar

radiation in Aqaba city comes from the collector tilted angle, designed in this study,

29°31' which is higher than 23°54' for Aswan case. That in turn means a higher ground

reflected radiation which is collected by the collectors in Aqaba. In addition, the Aqaba

city is near the Red Sea and therefore has a higher air humidity compared with Aswan

(see Figure 2.3 ). This then leads to an increase in the diffused radiation in Aqaba city.

87

6.3.2 Annual Cooling Compensation Energy Percentage Figure 6.27 and Figure 6.28 illustrate the yearly percentage of the direct cooling energy

compensation, the compensation of the cooling energy by storage and the external

back-up cooling energy which is covered by the grid for each scenario. This percentage

is calculated based on daily energy yield compensation in order to calculate the yearly

cooling energy compensation for each case study, Aswan-TSFH and Aqaba-TSFH . SO as

to make a comparison between the scenarios.

Figure 6.27: Percentage of cooling Energy compensation by the three scenarios for

Aswan-TSFH.

30.8% Direct copensation

20.1% Compensation by

storage

50.1% Backup compensation

Solar Thermal air-conditioning system with storage

39.3% Direct

copensation

10.7% Compensation by storage

50% Backup

compensation

Solar PV air conditioning system with storage

39.3% Direct

copensation

60.7% Backupcompens

ation

Solar PV air conditioning System without storage

88

Figure 6.28: percentage of cooling Energy compensation by the three scenarios for

Aqaba-TSFH.

From Figure 6.27 and Figure 6.28, several observations are made below.

The yearly direct cooling compensation percentage of the PV air-conditioning scenarios

is 39.3% and 35.8% for the Aswan-TSFH and for the Aqaba-TSFH cases respectively.

The above mentioned percentages are higher than the direct cooling compensation

percentage by the thermal air-conditioning scenario, 30.8 % and 30.9 % for the Aswan-

TSFH and for the Aqaba-TSFH cases respectively. This in turn means a higher

mismatching between the direct cooling compensation and the cooling demand in the

thermal air-conditioning scenario.

30.9% Direct

copensation

11.9% Compensation by

storage

57.2% Backup compensation

Solar thermal air-conditioning system with storage

35.8% Direct

copensation

7.3% Compensation by storage

56.9% Backupcompensa

tion

Solar PVair-conditioning system with storage

35.8% Direct

copensation

64.2% Backup

compensation

Solar PV air-conditioning System without storage

89

As discussed before, the main reason is a higher daily direct cooling compensation in

the morning and at the evening by the PV air-conditioning scenarios than the thermal

air-conditioning scenario. That’s due to the COP of compressed chiller and Absorption

chiller is completely different where the COP of the compressed chiller is around 3 and

it is around 0.7 for the absorption chiller. That leads to enhanced the overall system

efficiency of the PV-air conditioning scenarios comparatively with thermal air-

conditioning scenario. In addition at the evening and in the morning, low ambient air

temperature makes the thermal losses be higher than the solar gain from the flat plate

collector in addition to the thermal losses storage tank. In addition, PV module works

early with a higher efficiency at low solar radiation in the morning and the evening time.

Yearly, the total percentage cooling energy compensation by direct and storage in solar

thermal air-conditioning system with storage scenario is 50.9 % and 42.8 % for Aswan-

TSFH case and for the Aqaba-TSFH case respectively. The total compensation by PV air-

conditioning with storage scenario, 50 % and 43.1 % are respectively for Aswan-TSFH

and for Aqaba-TSFH cases. From these results, the percentage difference between the

two scenarios does not exceed 1 % in both cases(Aswan-TSFH and Aqaba-TSFH)and in

turn there is no big difference between the two scenarios based on the cooling demand

and the boundary condition of this study. that due the same reason which mentioned

above, the COP effects on the overall system efficiency.

The percentage of the cooling energy compensation by the storage in the thermal air-

conditioning scenario is 20.1 % and 11.9 % for Aswan-TSFH and for Aqaba-TSFH

respectively. The aforementioned percentages are higher than the percentage

compensation by the storage in PV air-conditioning with storage scenario, 10.7 % and

7.3 % for Aswan-TSFH and Aqaba-TSFH respectively. That’s because of significantly

excess output power, from the thermal air-conditioning system with storage scenario

compared with the PV air-conditioning system with storage scenario, where the

contribution power which is produced by the flat plate collector is higher than the

output power of the PV module at noon. This contribute to compensate the night cooling

demand throughout the storage.

This helps to make a technical decision based on the study boundary condition. We can

deduct that the storage technology for thermal air-conditioning scenario is more

efficient to improve the whole system’s efficiency than a PV air-conditioning scenario.

90

7. Conclusions and Future Research

7.1 Conclusions

The traditional air-conditioning is one of the main consumers of electrical energy today

in the MENA region. However, this region has a huge solar energy potential with an

average DNI13 of 2,334 kWh/m2/year and with average daily sunlight exceeding 8.8

hours [4]. Solar air-conditioning technology is definitely a solution to cover the cooling

demand for this hot and sunny region. The present study analyzes and compares the

solar thermal air-conditioning technology and the photovoltaic air-conditioning

technology under two different locations in the MENA region (Aswan, Egypt and Aqaba,

Jordan). That is based on the cooling demand for the reference building (TSFH ) in these

regions.

Cooling load demands:

The thermal load demands for the reference building (TSFH) in each location were

determined by TRNSYS software. The following points can be concluded:

The maximum cooling load demand during the summer season are: 13.9 kW and 15.3

kW for Aswan-TSFH and Aqaba-TSFH respectively. For both cases, the cooling demand

occurs for ten months while the heating demand is only required in two months. The

annual cooling energy demands are: 44,330 kWh/year and 43,490 kWh/year for the

Aswan-TSFH and the Aqaba-TSFH respectively which represents 97.5 % and 96.3 % of

the total annual energy consumption (heating and cooling). That shows the importance

of cooling compared to heating in these locations.

The performance of the cooling load during a summer day shows a huge cooling

demand (approximately 8 to 10 kW) during the night. Therefore, it is necessary to cover

the night cooling demand as well as the day time in these regions.

13 Direct Normal Irradiance

91

Solar Thermal Air-conditioning Scenario and PV Air-conditioning Scenarios :

The cooling production and compensation of each scenario is determined by Matlab-

Simulink for three scenarios:

Solar thermal air-conditioning with storage scenario includes a single water/Lithium-

Bromide absorption chiller with 15 kW nominal capacity and requires 85 oC driving

temperature, 45 m2 flat plate collectors, a stratified storage tank with 2 m3 volume and

an electric heater as back-up system.

Two PV air-conditioning systems with and without storage scenarios were designed

with a 45 m2 of PV-array, a compressed chiller and the grid as a back-up system. The PV

air-conditioning system with storage includes additionally 8 batteries.

Form the analysis and comparison between the thermal and the PV scenarios the

following points can be concluded:

The total annual percentage of cooling energy compensation (direct14 plus storage15) by

the solar thermal air-conditioning system with storage scenario is 50.9 % and 42.8 %

for Aswan-TSFH and for Aqaba-TSFH respectively. The compensation by the PV air-

conditioning with storage scenario which is 50 % and 43.1 % respectively for Aswan-

TSFH and for Aqaba-TSFH. The percentage difference between the two scenarios does

not exceed 1 % in both cases. However, there are differences in the direct cooling

compensation and the compensation by the storage:

1. The yearly direct cooling compensation percentage of the PV air-conditioning

scenarios is 39.3 % and 35.8 % for the Aswan-TSFH and for the Aqaba-TSFH

respectively. The aforesaid percentages are higher than the direct cooling compensation

percentages by the thermal air-conditioning scenario, 30.8 % and 30.9 % for the Aswan-

TSFH and for the Aqaba-TSFH cases respectively.

2. The performance of the daily direct cooling compensation by the PV air-conditioning

scenarios is more efficient than in the thermal scenario although the flat plate collector

efficiency is around 50 % and the PV module is around 14 %, due to three reasons.

14 The cooling energy which covers the cooling demand when the air-conditioning system as without storage. 15 The cooling energy which covers the cooling demand only by the contribution of the storage in the air-conditioning system.

92

The first and the main reason, the COP of the compressed chiller and the absorption

chiller are completely different. It is nearly 3 for the compressed chiller in the PV air-

conditioning scenario and it is around 0.7 for the absorption chiller in the thermal air-

conditioning scenario. The second reason, the solar flat plate collector starting to work

late in the morning and ended earlier in the evening. That is due to a low ambient air

temperature in the evening and in the morning times and the collector works at a high

temperature as 85 0C in order to drive the adsorption chiller. This makes the thermal

losses be higher than the solar gain from the flat plate collector which leads to

shutdown the device in these duration. The third reason, in the morning and at the

evening, there is electric power gain from the PV modules due to a high share of diffused

radiation and the ambient air temperature is lower than the noon’s. Hence a low

thermal effect on the PV module efficiency in these duration.

3. The percentage of the cooling energy compensation by the storage in the thermal air-

conditioning scenario is 20.1 % and 11.9 % for the Aswan-TSFH and for the Aqaba-

TSFH cases respectively. These are higher compared to those of PV air-conditioning

with storage scenario, 10.7 % and 7.3 % for Aswan-TSFH and Aqaba-TSFH respectively.

That’s because of the contribution of the e cess power which is produced by the flat

plate collector is higher than the excess output power of the PV module at noon. It can

be concluded that the PV air-conditioning with storage scenario needs less storage to

cover the same amount of cooling load demand compared to solar thermally air-

conditioning with storage scenario. In addition, the storage system in PV air-

conditioning scenario is minor and the direct compensation is major. That is vice versa

in the thermal air-conditioning scenario.

4. In winter season, the excess solar power gain is more useful in the PV air-

conditioning scenarios than the thermal air-conditioning scenario due to, the electric

power is more universal conversion compared with the thermal power conversion. The

excess electric power can be used for many other electric applications such as building

lighting or space heating etc.. The excess of the thermal heat power can be used only for

space heating or domestic hot water. In addition the excess electric power gain can be

fed to the grid if there is a feed-in-tariff in this region.

93

Comparison Between Aqaba-TSFH and Aswan-TSFH

The cooling demand follows the outside solar radiation and ambient air temperature

along the year due to solar gain through the building’s envelope. The monthly cooling

demand in Aswan-TSFH is higher than Aqaba–TSFH’s throughout the year e cept in

June, July and August although the solar radiation and the ambient air temperature in

Aswan city are higher than in the Aqaba city. Therefore, it is due to a higher ambient

relative humidity in Aqaba than in Aswan. This means ventilation increases the

humidity inside the building and results in a higher cooling demand in Aqaba-TSFH.

The contribution of the storage system (storage tank or battery system) to the cooling

energy compensation in each technology is more efficient in Aswan-TSFH case than in

Aqaba-TSFH case and it is almost double, because there is a higher solar radiation in

Aswan especially in summer season. This in turn means a better solar gain is stored

which can cover the night cooling demands.

The direct cooling compensation curve behaviour during the day of the PV air-

conditioning scenarios for the Aqaba-TSFH is better than the Aswan-TSFH. That’s due to

a higher diffusion and a reflected solar radiation which is observed in Aqaba city than in

Aswan city.

In the summer season, the cooling production by all scenarios in Aswan-TSFH case has

an excess of cooling production power at noon. But in the case of Aqaba-TSFH, the

situation is different: the cooling production rises up close to the maximum peak cooling

load demand. It can be concluded that the performance of the compensation cooling

load in the summer is optimized if the collector is tilted at 15° greater than the latitude

in each scenario in Aqaba-TSFH case. Then, more energy can be stored and used at

night.

94

7.2 Future Research

In terms of energy efficiency in buildings and the feed-in-tariff law in Germany and in

Europe of self-consumption which becomes more important in these days, the

calculations of the TSFH cooling demand calculation and the cooling compensation of

each scenario based on the meteorological data with less than one hour or a 15 minute

time interval is necessary. In addition, it should be based on the real-time compensation

especially for the storage contribution.

One of the main objectives of the solar air-conditioning systems is to save primary

energy consumption, therefore the study can be extended to analyse and compare the

solar thermal air-conditioning scenario and the solar PV air-conditioning scenarios

under MENA regions’ climates in terms of primary energy and economic analysis.

Moreover, the future cost reduction by learning curves of both technologies can

influence the economic feasibility.

Further work should compare and analyse between the two technological scenarios in

the case of heat pump system in order to compensate the heating demand as well as the

cooling demand. Also, a comparison between these two technologies is necessary if

there is feed-in-tariff in the MENA region and the PV air-conditioning scenarios can use

the grid as storage.

The determination of the reference building (TSFH) in this study for the two locations

(Aswan, Aqaba) was based on the Jordanian TSFH envelope construction for both cases

under the assumption that there is no big difference between the Jordanian TSFH and

the Egyptian TSFH. Therefore, the Egyptian TSFH’s envelop constructions should also be

considered. In addition, this research can be extended to include different building

types such as office buildings.

95

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102

Appendices

Appendix A: Schematic vapour compression cycle

Figure A: Schematic vapour compression cycle, [2].

Appendix B: Solar Photovoltaic module data sheet

Taken from SCHOTT solar COMPANY in Germany

103

Appendix C: Inverter data sheet, [45]

104

Appendix D: Description of Wet Cooling Tower, [37]

According [37]‘‘see (Fig .A1), The basic function of a cooling tower is to ensure a good

heat and mass transfer between the cooling water stream and ambient air. Thus, the hot

water enters the upper part of the cooling tower, where it is evenly distributed across

the tower by a spraying system. To increase the effective contact surface between water

and air, there is additional filling material installed inside the cooling tower. At the

bottom of the tower, the cooled water is collected again in a reservoir. To ensure

sufficient air-flow through the tower, a fan is installed that either forces entering air into

the tower or sucks discharge air at the outlet. Additional installations for water

treatment and blow-down are required for all cooling towers to replace the evaporated

cooling water and to prevent fouling.’’

Figure D: Schematic drawing of an open type wet cooling tower, [37].

105

Declaration

I, Younis Yousef Badran, declare that this master thesis is my own genuine work and has

not been submitted in any form for another degree or diploma at any university or

other institute of tertiary education. Information derived from the published and

unpublished work of others has been acknowledged in the text and a list of references is

given in the bibliography.

March 5, 2012

Kassel, Germany

Signature : .........................................................

صالملخ

إن الزيادة في الطلب على المكيفات الهوائية الكهربائية المستخدمة لتبريد المباني تؤدي إلى زيادة استهالك مصادر

حيث تعتبر منطقة الشرق األوسط وجنوب إفريقيا من أكثر مناطق العالم .ولية غير المتجددة بشكل كبيرالطاقة األ

في ةمن الطاقة الكهربائية المستهلك% ۰۳إن ما نسبته : فعلى سبيل المثال. اتللطاقة بواسطة هذه المكيف" استهالكا

جمهورية مصر العربية هي طاقة مستهلكة بواسطة هذه المكيفات وذلك بسبب ارتفاع درجات الحرارة وزيادة نسبة

ستخدام الطاقة الشمسية وبما أن هناك تكنولوجيا حديثة تقوم على إ. اإلشعاع الشمسي على مدار السنة في هذه المنطقة

إن . إلنتاج الهواء البارد لتكييف المباني فبالتالي تعتبر هذه التكنولوجيا الجديدة الحل الجذري لهذه المشكلة في تلك المناطق

هناك نوعان من هذه التكنولوجيا الجديدة، النوع األول يقوم على استخدام الطاقة الشمسية الحرارية لتسخين المياه بواسطة

لوا المجمعة لشأشعة الشمسية، ومن ثم تحويل هذه الطاقة الحرارية إلى طاقة تبريد وذالك باستخدام تكنولوجيا األ

أما النوع الثاني فهو تحويل الطاقة الشمسية الضوئية الى طاقة كهربائية بواسطة األلوا الشمسية الضوئية . اإلمتصاص

.مبانيلتشغيل المكيفات الهوائية المستخدمة لتبريد ال

إن هذه الرسالة تقدم دراسة تحليلية ومقارنة بين نظام التبريد بواسطة الطاقة الشمسية الحرارية ونظام الطاقة

حيث طبقت هذه الدراسة على نموذج للبيت العائلي الواحد . الشمسية الضوئية في منطقة الشرق األوسط وشمال إفريقيا

وقد تمت هذه الدراسة على ثالث مراحل . تي أسوان في مصر والعقبة في األردنالشائع في هذه المنطقة ضمن مناخ مدين

المرحلة األولى وقد تم فيها عمل محاكاة لحساب طاقة التبريد المستهلكة لهذا البيت على طول السنة في كل منطقه وذلك :

د الجوية خالل ساعات سطوع بواسطة إدخال بيانات سنوية لشأرصاTRNSYS) )بواسطة استخدام البرنامج الحاسوبي

الشمس التابعة لكل منطقة باإلضافة الى إدخال البيانات المعمارية واإلنشائية التفصيلية المتبعة لتصميم وبناء المنازل في

على مخرجات ونتائج الخطوة األولى والتي تتمثل في تصميم ثالث " أما المرحلة الثانية فتمت بناء. تلك المناطق

وهذه السيناريوهات ، . أنظمة التكييف بواسطة الطاقة الشمسية لتغطية طاقة التبريد المستهلكة للبيتسيناريوهات من

،أما النظام الثاني بنفس النظام ( البطاريات)األول نظام التبريد بواسطة الطاقة الشمسية الضوئية بدون نظام تخزين الطاقة

السيناريو الثالث فهو نظام تبريد بواسطة الطاقة الشمسيه الحرارية ، أما(البطاريات)األول ولكن مع نظام تخزين للطاقة

-Matlab)والمرحلة الثالثة تمثلت بعمل محاكاة بواسطة برنامج حاسوبي (. خزان مياه ساخنة)مع نظام تخزين

Simulink )ه المحاكاة وخالل عمل هذ. لحساب طاقة التبريد المزودة من قبل كل سيناريو من أجل تغطية استهالك البيت

.تم إدخال بيانات سنوية لشأرصاد الجوية خالل ساعات سطوع الشمس التابعه لكل منطقة

إن المحاكاة األولى أظهرت أن الكمية السنوية لطاقة التبريد المستهلكة في البيت لكل من منطقتي أسوان والعقبة على

ضافة لذلك فإن أقصى قدره يصل لها االستهالك في سنة باإل/كيلو وات ۰۹٤۳٤سنة ،/كيلو وات ۰۳۳٤٤ التوالي هي

حيث تشير هذه األرقام إلى أن النسبة المئوية . وات على التوالي كيلو٥۳. ۳ كيلو وات ،۹.۳۳ البيت في كل منطقه هي

. % ٦۹. ۳، % ٧۹. ٥على النحو التالي ( التدفئة والتبريد)لطاقة التبريد من مجمل الطاقة المستهلكة في البيت

المحصلة فإن هذه األرقام تثبت وتبين أن كمية االستهالك لطاقة التبريد المستهلكة كبيرة مقارنة مع طاقة التدفئة وب

.المستهلكة وأن نظام التبريد مهم لهذا النمط من البيوت في هذه المناطق

الثالث من ناحية المجموع السنوي إن نتائج المحاكاة الثانية أظهرت أنه ال يوجد فرق كبير بين السيناريو الثاني و

في كال ۳۱ الكلي للنسبة المؤيه المتمثلة في تغطية طاقة التبريد المستهلكة للبيت حيث أن فرق النسبه ال يتجاوز

لكن هناك فروقات تمثلت في أن األداء اليومي للتغطية المباشرة للتبريد المستهلك بواسطة السيناريوهين األول . المنطقتين

نظام التبريد بواسطة )أفضل مما هو عليه في السيناريو الثالث ( نظام التبريد بواسطة الطاقة الشمسية الضوئية) والثاني

ستهلك بشكل مباشر عندما يكون أي نظام بدون وأن النسبة المئوية السنوية لتغطية التبريد الم(. الطاقة الشمسية الحرارية

التبريد )بواسطة السيناريو األول أوالثاني % ۸.٥۳, % ۳ ۹ .۳مخزن لكل من بيت أسوان و العقبة على التوالي هي

التبريد بواسطة الطاقة الشمسية )بواسطة السيناريو االثالث ۹.۳۰۱، %۸.۰۳،و ( بواسطة الطاقة الشمسية الضوئية

كما أن النسبة المؤية السنوية لتغطية التبريد بواسطة مساهمة نظام التخزين لكل من حالة أسوان والعقبة على (. الحرارية

. في السيناريو الثالث %۹.۳۳، % ۳.۰۰ في السيناريو الثاني و % ۳.٧ ، %٧.۳۰ التوالي هي

( بواسطة الطاقة الشمسية الضوئية مع نظام التخزيننظام التبريد )إن خالصة هذه النتائج تظهر أن السيناريو الثاني

نظام التبريد بواسطة الطاقة الشمسيه )أفضل وذلك من ناحية تغطية التبريد المستهلك مقارنة مع السيناريو الثالث

أي . لكةإضافة إلى أنه أقل احتياجا لنظام التخزين لتغطية نفس الكمية من طاقة التبريد المسته( الحرارية مع نظام تخزين

أن نظام التخزين في نظام التبريد بواسطة الطاقة الشمسية الضوئية يعتبر من حيث األهمية والكفاءة في المرتبة الثانية

بينما في نظام التبريد بواسطة الطاقة الشمسية . بينما التغطية للتبريد المستهلك بشكل مباشر يعتبر في المرتبة األولى

. الحرارية يعتبر عكس ذلك

دراسة تحليل ومقارنه للتبريد بواسطة الطاقة الشمسية الحرارية والطاقة الشمسية

الضوئية في منطقة الشرق االوسط وشمال افريقيا

إعداد

يونس يوسف عبد ربه بدران

رسالة مقدمه إلى كلية الهندسة في جامعة القاهرة

ل و إلى كلية الهندسة وعلم الحاسوب في جامعة كاس

كجزء من متطلبات الحصول على درجة الماجستير

في الطاقة المتجددة وكفاءة الطاقة في منطقة الشرق االوسط وشمال افريقيا

تحت اشراف

كالودي ألبرت. د

أستاذ دكتور بقسم الهندسة الكهربائية

كلية الهندسة وعلم الحاسوب

جامعة كاسل

عادل خليل حسن خليل.د

سم هندسة القوى الميكانيكيةأستاذ دكتور بق

كلية الهندسة

جامعة القاهرة

كلية الهندسة وعلم الحاسوب، جامعة كاسل

كاسل، ألمانيا

كلية الهندسة، جامعة القاهر

الجيزة، جمهورية مصر العربية

آذار،۲۳۰۲

دراسة تحليل ومقارنه للتبريد بواسطة الطاقة الشمسية الحرارية والطاقة الشمسية

ئية في منطقة الشرق االوسط وشمال افريقياالضو

إعداد

يونس يوسف عبد ربه بدران

ةرسالة مقدمه إلى كلية الهندسة في جامعة القاهر

و إلى كلية الهندسة وعلم الحاسوب في جامعة كاسل

كجزء من متطلبات الحصول على درجة الماجستير

االوسط وشمال افريقيافي الطاقة المتجددة وكفاءة الطاقة في منطقة الشرق

:يعتمد من لجنة الممتحنين

سيد أحمد كاسب. د

عضو

أستاذ مساعد دكتور بقسم

هندسة القوى الميكانيكية



كالودي ألبرت. د

المشرف الرئيسي

أستاذ دكتور بقسم الهندسة

الكهربائية

كلية الهندسة وعلم الحاسوب

جامعة كاسل

عادل خليل حسن خليل.د

المشرف الرئيسيأستاذ دكتور بقسم هندسة

القوى الميكانيكية



كلية الهندسة وعلم الحاسوب، جامعة كاسل

كاسل، ألمانيا

القاهرةكلية الهندسة، جامعة

الجيزة، جمهورية مصر العربية

آذار،۲۳

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