Tk05 Report Assignment 1 Fix

UNIVERSITAS INDONESIA

PRELIMINARY DESIGN OF SOLAR THERMAL ENERGY POWER

PLANT WITH HEAT TRANSPORTATION BY MOLTEN SALT

REPORT ASSIGNMENT 1

GROUP 5

GROUP PERSONNEL:

Emmanuella Deassy E. (1206248924)

Kevin S. Sembiring (1206244075)

Osman Abhimata (1206202002)

Pandu Ervan N. (1206240726)

Shofiyyah Taqqiyah (1206250090)

CHEMICAL ENGINEERING DEPARTMENT

FACULTY OF ENGINEERING

UNIVERSITAS INDONESIA

DEPOK

2015

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EXECUTIVE SUMMARY

The energy crises include the energy crisis of petroleum, natural gas, fossil

fuels, and electrical energy. Electrical energy is an essential requirement to support

economic growth and social development. Based on data from population growth

of Indonesia, export-import scenario, predicted in 1990 the growth rate of the

electrical energy needs of Indonesia reached 8.2 percent on average per year. One

of the sources of energy that can be exploited is solar energy. Indonesia is located

on the equator which is sunlit 10-12 hours a day. The total intensity of solar

radiation in Indonesia is on average 4.5 kWh per square meter per day. Solar energy

utilization can be done through the thermal and electrical energy. Thermal

utilization can be done directly by letting the object in the solar radiation or using a

tool collectors and solar concentrators. One of the area that has good specification

to build a solar thermal power plant is Pontianak, West Borneo. The city is passed

by the equator and thus receive high intensity of solar radiation. The city is

currently in need of more electricity and planning to buy electricity from Malaysia.

After doing market analysis, it is decided that bulding a solar power plant in

Pontianak is feasible. Then we choose a suitable process and listed some possible

alternative process. Most solar powerplants work directly by using steam to move

generator. But here we use molten salt as a heat collector because it can store more

thermal energy than water. In collecting the solar thermal energy, we use the

Parabolic Through Solar Collector which will concentrate the thermal radiation into

the receiver and then transfer it into the molten salt. Molten salt will then enter a

heat exchanger and convert steam into superheated state with high temperature and

pressure. Next it will enter turbine and expand. The energy is converted into

mechanical work that moves the shaft that is connected to a generator that will

convert mechanical work into electricity.

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LIST OF CONTENTS

EXECUTIVE SUMMARY ..................................................................................... ii

LIST OF CONTENTS ........................................................................................... iii

LIST OF FIGURE ................................................................................................... v

LIST OF TABLE ................................................................................................... vi

CHAPTER I ............................................................................................................ 1

INTRODUCTION .................................................................................................. 1

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

1.2. Literature Review ..................................................................................... 3

1.2.1. Solar Thermal Power......................................................................... 3

1.2.2. Concentrating and Nonconcentrating Solar Thermal Power Plants

the Advantages of Heat Storage....................................................................... 3

1.2.3. Concentrating Solar Colle ctor .......................................................... 4

1.2.4. Parabolic Through System ................................................................ 4

1.2.5. Power Tower System ........................................................................ 6

1.2.6. Parabolic Dish System ...................................................................... 6

1.3. Raw Material Analysis ............................................................................. 7

CHAPTER II ......................................................................................................... 18

2.1. General Process ...................................................................................... 18

2.2. Alternative Process ................................................................................. 19

2.2.2. Central Receiver Solar Thermal Power Plants ................................ 19

2.2.3. Solar Air Preheating System for Combustion Turbines .................. 26

2.2.4. Dish/Engine Solar Thermal Power Plants ....................................... 27

2.3. Process Selection .................................................................................... 28

2.4. Process Description ................................................................................ 32

CHAPTER III ....................................................................................................... 42

MASS & ENERGY BALANCE ........................................................................... 42

3.1. Mass Balance for Equipment ..................................................................... 42

3.2. Energy Balance for Equipment .................................................................. 45

3.3. Overall Mass Balance ................................................................................. 46

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3.4. Overall Energy Balance .............................................................................. 46

3.5. Mass Efficiency .......................................................................................... 46

3.6. Energy Efficiency ....................................................................................... 47

CHAPTER IV ....................................................................................................... 49

CONCLUSION ..................................................................................................... 49

REFERENCES ...................................................................................................... 56

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LIST OF FIGURE

Figure 1. 1 Parabolic Through Solar Collector ....................................................... 5

Figure 1. 2 Power Tower System ............................................................................ 6

Figure 1. 3 Parabolic Dish System .......................................................................... 7

Figure 1. 4 Transmission Network West Borneo .................................................. 17

Figure 2. 1 Black Box for This Solar Thermal Power Plant ................................. 19

Figure 2. 2 Artist’s View of a Heliostat Field Focusing Sunlight onto a

Receiver/Tower System ........................................................................................ 26

Figure 2. 3 Different Configuration of Solar Receivers ........................................ 29

Figure 2. 4 Parabolic trough Solar Thermal Power Plant ..................................... 38

Figure 2. 5 Block Flow Diagram for This Plant ................................................... 39

Figure 2. 6 Process Flow Diagram for Gasification Unit..................................... 34

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LIST OF TABLE

Table 1. 1 Prediction of Energy Needs in Indonesia ............................................... 1

Table 1. 2 Prediction of Electrical Energy Supply in Indonesia ............................. 8

Table 1. 3 Electrification Ratio in West Borneo from 2010 to 2014 .................... 16

Table 1. 4 Demand of Electricity in West Borneo from 2010 to 2014 ................. 16

Table 1. 5 West Borneo Human Resources Availability ...................................... 18

Table 1. 6 Pontianak Human Resources Availability ........................................... 18

Table 1. 7 Electricity production by PT. PLN in West Borneo ............................ 20

Table 1. 8 Growth of Electricity in 2015-2024 ..................................................... 21

Table 1. 9 Supply-Demand West Borneo in 2010-2014 ....................................... 22

Table 2. 1 Characteristics of Central Receiver Solar Thermal Power Systems .... 26

Table 2. 2 Operating Temperature and Flux Ranges of Solar Tower Receivers .. 30

Table 2. 3 Summary of Operational Range for Tubular Water/Steam and Molten

Slat Receivers ........................................................................................................ 31

Table 2. 4 Comparison of Existing Solar Power Plant ......................................... 36

Table 2. 5 Scoring of The Types of Solar Power Plant ......................................... 36

Table 2. 6 Scoring of Types of Storage Medium .................................................. 37

Table 3. 1 Mass Balance On Pump P-100 ............................................................ 49

Table 3. 2 Mass Balance On Solar Collector ........................................................ 49

Table 3. 3 Mass Balance On Cold Tank ............................................................... 49

Table 3. 4 Mass Balance On Hot Tank ................................................................. 49

Table 3. 5 Mass Balance On HE E-100 ................................................................ 50



Table 3. 8 Mass Balance On Turbine K-100......................................................... 50

Table 3. 9 Mass Balance On Cooler E-103 ........................................................... 51

Table 3. 10 Mass Balance On Pump P-102........................................................... 51

Table 3. 11 Energy Balance for Equipment .......................................................... 51

Table 3. 12 Overall Mass Balance ........................................................................ 52

Table 3. 13 Overall Energy Balance ..................................................................... 52

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CHAPTER I

INTRODUCTION

1.1.Background

The growth of Indonesian community is effect on increasing the energy

needs. Meanwhile, the energy crisis is happening to the world community. The

energy crises include the energy crisis of petroleum, natural gas, fossil fuels, and

electrical energy. Electrical energy is an essential requirement to support economic

growth and social development. Based on data from population growth of

Indonesia, export-import scenario, predicted in 1990 the growth rate of the

electrical energy needs of Indonesia reached 8.2 percent on average per year. The

table below shows electrical energy needs in Indonesia,

Table 1. 1 Prediction of Energy Needs in Indonesia

Sector 1990 2000 2010

GWh percent GWh percent GWh percent

Industry 35.305 68,0 84.822 69,0 183.389 70,0

Household 9.865 19.00 22.2392 18.0 40.789 16.0

Public Facilities 3.634 7,0 6.731 6.0 12.703 5.5

Commercial 3.115 6.0 8.811 7,0 21.869 8.5

Total 51.919 100.0 122.603 100.0 258.747 100.0

(Source: Djojonegoro, 1992)

Electricity demand in Indonesia grew from 90 terawatt-hours (TWh) in

2003 to 190 TWh in 2013. However, the numbers of electricity demand are not

comparable with the availability of energy. Around 13 percent of Indonesia's

electricity still comes from fossil fuels. The cost to produce electricity from fuel oil

is about $0.18 cents/kWh and from coal is about $0.05 cents/kWh. A source of

electrical energy can be derived from petroleum, gas, coal, geothermal, hydro,

biomass, solar, etc. The table below shows the prediction of electrical energy supply

in Indonesia,

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Universitas Indonesia

Table 1. 2 Prediction of Electrical Energy Supply in Indonesia

Energy Sources 1990 2000 2010

MW percent MW Percent MW percent

Car coal

Gas

Oil

Solar Oil

Geothermal

Water

Biomass

Others

(Solar, wind)

1.930

3.530

2.210

11.020

170

2.850

270

20

8.8

16.0

10.0

50.1

0.8

13.0

1.2

0.1

10.750

7.080

1.950

9.410

500

7.720

290

160

28.4

18.7

5.2

24.8

1.3

20.4

0.8

0.4

28.050

14.760

320

4.060

430

10.310

460

370

35.3

21.5

0.5

5.9

0.6

15.0

0.7

0.5

Total 22.000 100.0 37.860 100.0 68.760 100.0

(Source: Djojonegoro, 1992)

The potential of geothermal energy, solar energy, ocean currents, wind, and

others still have not been used optimally. To fulfill the availability of electrical

energy in Indonesia, need to diversify their energy. One of the sources of energy

that can be exploited is solar energy. Indonesia is located on the equator which is

sunlit 10-12 hours a day. The total intensity of solar radiation in Indonesia is on

average 4.5 kWh per square meter per day. In 2001, the Director General of the

ministry of electricity and energy utilization of ESDM stated that the potential for

solar energy in Indonesia amounted to 156 487 MW.

Marzan A. Iskandar (Head of BPPT) said despite the potential of solar

energy in Indonesia is very large, but its contribution through the solar cells in the

national energy supply is still very low. Until the year 2011, there were a total of

new applications reached around 17 MWp. When compared with the installed

capacity of power plants in Indonesia amounted to 33.7 GW, the contribution of

solar power for electricity generation only around 0.05 percent.

Solar energy utilization can be done through the thermal and electrical

energy. Thermal utilization can be done directly by letting the object in the solar

radiation or using a tool collectors and solar concentrators. In the use of solar

thermal energy collector takes a steam generator. Brine can be used as one of the

steam power generation in the solar thermal energy production and heat

transportation.

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1.2. Literature Review

1.2.1. Solar Thermal Power

Solar thermal power is a relatively new technology which has already shown

enormous promise. With few environmental impacts and a massive resource, it

offers an opportunity to the sunniest countries of the world comparable to the

breakthrough offshore wind farms is currently offering European nations with the

windiest shorelines. In many regions of the world, one square kilometre of land is

enough to generate as much as 100-200 Gigawatt hours (GWh) of electricity per

year using solar thermal. This is equivalent to the annual production of a 50 MW

conventional coal or gas-fired power plant. Worldwide, the exploitation of less than

1% of the total solar thermal potential would be enough to stabilise the world

climate through massive CO2 reductions.

Producing electricity from the energy in the sun’s rays is a relatively

straightforward process. Direct solar radiation can be concentrated and collected by

a range of Concentrating Solar Power (CSP) technologies to provide medium to

high temperature heat. This heat is then used to operate a conventional power cycle,

for example through a steam or gas turbine or a Stirling engine. Solar heat collected

during the day can also be stored in liquid, solid or phase changing media like

molten salts, ceramics, concrete, or in the future, phase changing salt mixtures. At

night, it can be extracted from the storage medium to run the steam turbine. Solar

thermal power plants can be designed for solar-only generation, ideally to satisfy

demand during daylight hours, but with future storage systems their operation can

be extended to almost base load requirements.

1.2.2. Concentrating and Nonconcentrating Solar Thermal Power Plants the

Advantages of Heat Storage

There are two fundamentally different types of solar thermal power plants.

First, the direct solar irradiation is concentrated by systems of mirrors, and with the

resulting high-temperature heat (the usable temperature range, depending on the

technology applied, is 300-1200°C), one generates electrical energy by means of

heat engines and electrical generators. These (optically) concentrating solar thermal

systems are often subsumed under the term “concentrating solar power” (CSP).

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(Sometimes, however, the term CSP is also used as a generic name for

concentrating thermal and concentrating photovoltaic systems). Under a large area,

glass roof at a height of a few meters, with a diameter of several kilometers, the

direct and the diffuse solar irradiation (i.e., the global insolation) is used to heat the

ground and thereby indirectly the air. This air, whose temperature is raised by ca.

30 K, rises in a central tower of 1000-1300 m height due to the chimney effect,

while cooler air from the surroundings flows in through the open sides of the

structure. This air flow drives turbines at the base of the tower. One refers to an

updraft power plant.

The use of solar energy as heat for generating electrical energy has the

advantage in principle that thermal energy storage is possible and can be

implemented at a relatively low cost. In contrast, for direct conversion using

photovoltaic cells, chemical energy storage using batteries or hydrogen technology

would be required. This, in turn, is very expensive, owing to the high investment

costs and the high loss rate (20-50%). Storage is, however, a decisive precondition

for a regenerative energy source to compete seriously with conventional energy

production sources (fossil and nuclear power), which themselves represent

chemical or nuclear chemical storage media.

1.2.3. Concentrating Solar Collector

Solar collectors are used to produce heat from solar radiation. High

temperature solar energy collectors are basically of three types;

a. Parabolic trough system: at the receiver can reach 400° C and produce steam

for generating electricity.

b. Power tower system: The reflected rays of the sun are always aimed at the

receiver where temperatures well above 1000° C can be reached.

c. Parabolic dish systems: Parabolic dish systems can reach 1000° C at the

receiver, and achieve the highest efficiencies for converting solar energy to

electricity.

1.2.4. Parabolic Through System

Parabolic trough power plant system is the oldest commercially available

concentrated solar technology in the market. The first commercially installed power

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plants are located in the Mojave Desert in California, United States of America.

They have now produced clean energy on a commercial scale for over 20 years

(NREL 2010).

Figure 1. 1 Parabolic Through Solar Collector

(Source: http://www.solarmillennium.de/)

The picture above shows a parabolic through mirror after the SKALET

principle in Almeria, Spain. The basic structure of the parabolic trough power plants

are long rows situated in a North-South axis. These rows follow the sun from East

to West. The parabolic reflectors consist out extremely transparent silver coated

glass. These coated glasses give the reflectors the possibility to concentrate the solar

irradiation to 80-fold. Absorber pipes in the focal point of the parabolic reflectors

receive the concentrated solar energy and heat up. The absorber pipes are made of

steel which is in a vacuum and heats special fluid up to a temperature of 400°C. The

heated fluid is pumped to a central heat exchanger where water is transformed into

hot pressurized steam to drive a steam turbine. The steam turbine is then used like

conventional power generation system by producing electricity with a generator.

The overall efficiency of this technology is about 15 percent in average and 28

percent in optimal conditions (Solar Millenium AG 2010).

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1.2.5. Power Tower System

In power tower systems, heliostats (A Heliostat is a device that tracks the

movement of the sun which is used to orient a mirror of field of mirrors, throughout

the day, to reflect sunlight onto a target-receiver) reflect and concentrate sunlight

onto a central tower mounted receiver where the energy is transferred to a HTF.

This energy is then passed either to the storage or to power-conversion systems,

which convert the thermal energy into electricity. Heliostat field, the heliostat

controls, the receiver, the storage system, and the heat engine, which drives the

generator, are the major components of the system. For a large heliostat field a

cylindrical receiver has advantages when used with Rankine cycle engines,

particularly for radiation from heliostats at the far edges of the field. Cavity

receivers with larger tower height to heliostat field area ratios are used for higher

temperatures required for the operation of Brayton cycle turbines.

Figure 1. 2 Power Tower System

(Source: http://www.firstsolarind.com/ )

1.2.6. Parabolic Dish System

The parabolic dish system uses a parabolic dish shaped mirror or a modular

mirror system that approximates a parabola and incorporates two-axis tracking to

focus the sunlight onto receivers located at the focal point of the dish, which absorbs

the energy and converts it into thermal energy. This can be used directly as heat for

thermal application or for power generation. The thermal energy can either be

transported to a central generator for conversion, or it can be converted directly into

electricity at a local generator coupled to the receiver.

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Figure 1. 3 Parabolic Dish System

(Source: http://www.firstsolarind.com/)

The mirror system typically is made from a number of mirror facets, either glass or

polymer mirror, or can consist of a single stretched membrane using a polymer

mirror of thin metal stretched membrane.

The PDCs (parabolic dish collector) track the sun on two axes, and thus they

are the most efficient collector systems. Their concentration ratios usually range

from 600 to 2000, and they can achieve temperatures in excess of 15000C. Rankine-

cycle engines, Brayton-cycle engines, and sodium-heat engines have been

considered for systems using dish-mounted engines the greatest attention though

was given to Stirling-engine systems.

1.3. Raw Material Analysis

1.3.1. Heat Transfer Fluid

Heat transfer fluid as liquid specifically manufactured for the purpose of

transmitting heat from one system to another. Solar collector will be receive from

solar radiation and will be used to heat fluid. Hot fluid is used to produce steam.

There are kinds of heat transfer fluid.

a. Synthetic Oil

Up to now, CSP plants commonly used synthetic oils with aromatic type as

heat transfer fluids. This fluid is organic or benzene based. This fluid typically

operate between 300-400oC. Synthetic oil cannot reach temperatures above 400oC

with acceptable performance due to its degradation into unusable components at

high temperatures so prevents solar thermal plants from running at maximum

efficiency. At temperatures higher than 400oC, fluid becomes inoperable. Synthetic

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oil has lower freezing point. Synthetic oil cannot act as thermal energy storage so

plant needs other fluid to store energy. Synthetic oil is flammable so safety for the

plant will be complex.

b. Molten salt

Molten salt is eutectic mixtures of inorganic salts. Composition of molten

salt consist of sodium nitrates 60%wt and potassium nitrates 40%wt. This fluid can

operate up to 550oC so molten salt will be produce more maximum efficiency than

synthetic oil. Molten salt can act as thermal energy storage. Molten salt has lower

vapor pressure and high evaporation point. Unlike oil, molten salt needs freeze

protection because molten salt has high freezing point. Melting point of molten salt

is about 223oC so the temperature must be keep above 220oC. To overcome these

disadvantage, research is being conducted by make alternative molten salt

formulation to decrease melting point of molten salt, for example by change the

concentration of components. Besides that, corrosion of molten salt and increased

process temperatures need to be considered because require selected materials.

In the world, only several plant use molten salt as heat transfer fluid. In the

near future, molten salt will be developed to be used as heat transfer fluid in

concentrated solar power (CSP) plant because molten salt has more advantages if

compared with synthetic oil.

Based on brief description above, we decide to choose molten salt as heat

transfer fluid. The reasons why we choose molten salt as our raw material are:

1. Molten salt is renewable material

2. Molten salts work as sole fluid for both heat absorption and storage

3. Heat exchanger for storage system can be eliminated since the fluid that

goes from the solar field to the storage system is the same

4. At higher temperatures, the molten salt volume for the storage system can

be reduced by 2/3 which also leads to a reduction in size of the storage tanks.

These savings represent an approximate 20% plant cost decrease when

compared with oil plants with storage.

5. Molten salt are cheaper, denser, and lower operating cost

6. Molten salt has lower vapor pressure so molten salt can be directly stored

and accessed at near ambient pressure

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7. Molten salt has high evaporation point so can retain more energy per volume

than oil based.

8. Unlike oil, molten salts are environmentally friendly, non-flammable, stable

fluid, pollute less, and no degradation of the receiving tube.

9. The higher temperatures reached by the molten salts enable the use of steam

turbines at the standard pressure or temperature parameters

10. Higher operating temperature can increase plant efficiency up to 6%.

We decide to import molten salt because no plant that produces molten salt in

Indonesia. We import from other country, such as China to get this raw material.

1.3.2. Water

In CSP plant, the steam that comes out of the turbines needs to be cooled so

that it condenses back to water. This is normally done by evaporation of water in

cooling towers. We get water from river or lake in West Borneo. Amount of lake

and river in this region is quite a lot so we can get water easily.

1.4. Plant Location Analysis

To select the location, we have to consider some important factors. The best

location of a plant is the location where the unit cost of production and distribution

process will be low and sales of products will be able to generate maximum profits

for the company. Plan site selection is one of the main factors that determine the

success of a plant.

We decide to build our plant in Pontianak, West Borneo. There are several

analysis why we choose Pontianak district in West Borneo as a plant location.

1. Inequality Construction of Power Plant

Currently, the construction of electric plant in Indonesia tend to focus on

Java-Bali and Sumatera region. This construction based on the electricity demand

in Java-Bali and Sumatera region is high. However, if equitable construction not be

done immediately, crisis of electricity will happen in East Indonesia, including

Borneo Island. In Borneo Island, PLN system interconnection is divided into two

system interconnection, West Borneo interconnection and East-Central-South-

North Borneo interconnection. We choose to build our plant in West Borneo

because construction of power plant in this region still less. Based on RUPTL

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(Rencana Usaha Penyediaan Tenaga Listrik) PLN 2015-2024, PLN West Borneo

has plans to construct new power plant. In 2015-2024, West Kalimantan is planning

additional new power plants with a total capacity of 1463 MW excluding the import

of the Sarawak, Malaysia to fulfill the demand. However, until now, there is no

plans that are entered construction stage. Therefore, construction of power plant in

this region is potential. Besides that, we also can help government to distribute

power plant construction in Indonesia.

2. Electricity Demand and Electrification Ratio

Electrification ratio is defined as the percentage of households with an

electricity connection. West Borneo is one of the provinces that has low

electrification ratio and the lowest in Borneo Island.

Table 1. 3 Electrification Ratio in West Borneo from 2010 to 2014

Year Electrification Ratio (%)

2010 52,61

2011 64,86

2012 63,40

2013 69,25

2014 74,2

(Source: Data Statistik PLN 2010, 2011, 2012, 2013, dan 2014)

In 2014, West Borneo has electrification ratio is 74,2%. This means that

there is 25,8% of households in West Borneo do not have electricity installation in

their home. As shown in the Table 1.3 above, from time to time, the electrification

ratio in West Borneo is increasing. Although the electrification ratio is increasing,

amount of demand of electricity, include electricity for industry also tend to

increase because of the growth of economy and population. In 2014, increase of

electricity demand is high. This shows that every year the electricity demand will

tend to increase.

Table 1. 4 Demand of Electricity in West Borneo from 2010 to 2014

Year Demand (MW)

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(Source: Data Statistik PLN 2010,2011,2012,2013, dan 2014)

If the total power generation plant in West Borneo is remain the same, crisis

of electricity will happen in West Borneo in future years. To cover it up, we decide

to build power generation plant in West Borneo.

3. Solar Intensity

Potential use of solar energy as an alternative to generate electrical energy

in Pontianak very supportive. Pontianak is a city that is passed by equator line so it

has high solar intensity. Average of solar intensity in Pontianak is about 5 kWh/m2

per day.

4. Electricity Strategic Network

Figure 1. 4 Transmission Network West Borneo

(Source: RUPTL PLN 2015-2024)

2010 238,79

2011 282,68

2012 295

2013 213

2014 424.39

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As we can see from the map above, Pontianak is near to the electric

transmission in West Borneo which can make the distribution of the electricity

easier and cheaper because transmission pipeline is needed can reduced. Besides

that, transmission locations that is close can decrease energy losses during

transmission process. Figure 1.4 is grand planning of PLN in distributing the

electricity in the West Borneo.

5. Transportation and Availability of Raw Material

Molten salt unavailable in Indonesia so we import from other country.

Molten salt will be delivered by ship. West Borneo has a lot of ports because the

location is close to the sea, one of them is Indonesia II Pontianak port. It is an

advantage because it will be easy to distribute molten salt to our plant location. We

get water for river or lake. Amount of river and lake in West Borneo is quite a lot

so water requirement will be fulfilled. We take water from the river or lake that is

closest to our plant. Water will be distributed by pipeline.

6. Topography

Topography in Pontianak is flat so that it can be easily be built and easily

get access from transportation so that the supply of raw material is not going to

disturb. This place is suitable for our plant so land area does not require

modification.

7. Labor

Table 1. 5 West Borneo Human Resources Availability

Year Total Labor Work Not Work

2012 2.182.524 2.106.514 76.010

2013 2.140.166 2.053.823 86.343

2014 2.320.229 2.226.510 93.719

(Source: BPS West Borneo, 2014)

Table 1. 6 Pontianak Human Resources Availability

Year Total Labor Work Not Work

2012 356.087 337791 18.296

2013 350.084 329.119 20.685

2014 376.824 351.953 24.781

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(Source: BPS West Borneo, 2014)

From the table above we can conclude that the human resource for labor

opportunity is high. The labor is ready for any job. The number of jobless people in

West Borneo, especially in Pontianak is high and increase every year. So, if our

plant is built, we can give job field for them and help West Borneo government to

develop their area.

8. Government Policy / Land Acquisition

Regarding government policy, as long as the location of the power

generation is not under protection or is national park, the government will be

approved quickly because the place of the power generation plant will be placed in

developing and even distributing area. The only problem is the time of the land

acquisition regarding the land of nearby civilization.

1.5. Market Analysis

In planning the construction of a plant, market analysis is the most

fundamental. This analysis need to determine the potential product market that we

made. Results of market analysis will determine the capacity of the plant the factory

will be built. Consequently, the market analysis should be done thoroughly.

Market analysis based on supply and demand of product for several years

ago. Market analysis also based on prediction of product requirement in the future.

The main market of this power plant is PT. PLN in West Borneo where the

electricity generated will be used to fulfill the electricity needs at the location. PT.

PLN cannot fulfill demand of electricity in West Borneo so PT. PLN must buy

electricity or rent generator from other plant.

Electricity demand in the region is driven by three main factors are:

1. Economic Growth

Economic growth in simple terms is the process of increasing the output of

goods and services. The process requires electrical power as one of the inputs

supporting. Economic growth is an increase in public revenue which boosted

demand for electrical equipment so electricity demand increase.

2. Electrification Programs

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Electrification ratio is defined as the percentage of households with an

electricity connection. In 2014, West Borneo has electrification ratio is 74.2%. This

means that there is 25.8% of households in West Borneo do not have electricity

installation in their home. Every year, PLN try to increase electrification ratio.

However, in every year, the number of people who need electricity also increased

so PLN will tend to need more electricity every year.

3. Transfer of Captive Power to the PLN Grid

Captive power is arising as a result of the inability of PLN to fulfill customer

demand in the region, especially the industrial and business customers. If ability of

PLN to serve electricity in the region has increased, the captive power will be turned

into PLN customers. The transfer of captive power to PLN is also driven by the

high price of fuel to generate electricity owned industrial or business consumers

while the selling price of the electricity is relatively cheaper.

Table 1. 7 Electricity production by PT. PLN in West Borneo


Based on Table 1.7 above, electricity supply from PT.PLN has decreased

every year. This is because adequacy and reliability of supply is still relatively low

because of the age of some diesel engines are old and generation reserve inadequate.

Electricity in West Kalimantan over 95% comes from fuel oil. Electricity shortage

in West Borneo over 50% are covered from diesel power plant (PLTD) are leased

by PLN so PLN must spend more money to lease this PLTD. Electricity demand in

the province of West Borneo in the last five years growth an average of 10.2% per

year where electricity demand is dominated by household customers.

Based on RUPTL (Rencana Usaha Penyediaan Tenaga Listrik) PLN 2015-

2024, sales growth in the last 5 years in West Kalimantan have averaged 10.23%

Year Supply from PLN Demand (MW) Costumers

2010 305,98 238.79 577.830

2011 174,45 282.68 653.383

2012 173,67 295 737.444

2013 156,47 213 806.035

2014 130,42 424.39 870.687

21


per year. Sales of electric power absorbed by household consumers (64.07%),

commercial consumers (21.68%), industry consumers (5.23%) and public

consumers (9.02%).

From electricity sales last five years and consider the tendency of

economic growth, population growth, and a target of increasing electrification

ratio in the future, demand for electricity in 2015-2024 based on RUPTL PLN

2015-2024 shows in Table 1.9 below.

Table 1. 8 Growth of Electricity in 2015-2024

Year Economic Growth

(%) Demand (MW) Costumers

2015 7,2 432 892.813

2016 7,5 486 939.891

2017 8 541 988.575

2018 8,2 600 1.072.188

2019 8,4 665 1.149.487

2020 8,1 737 1.211.441

2021 8,1 816 1.268.359

2022 8,1 901 1.318.956

2023 8,1 999 1.353.251

2024 8,1 1106 1.389.695

Growth (%) 8% 11% 5,1%

(Source: RUPTL PLN 2015-2024)

Based on Table 1.8 above, electricity demand increase approximately 5,1%

every year. This increase want covered by PLN with construct new power plant.

However, until now, there is no plans that are entered construction stage. Based on

RUPTL PLN 2015-2024, West Borneo plans to import electricity from Sarawak,

Malaysia to fulfill electricity. PLN West Borneo also plans to import from Sarawak

to fulfill base load of 50 MW in the future years to anticipate uncertainty supplying

base load power plant in West Borneo.

Based market analysis already described, construction of power plant in

West Borneo is very potential. Electricity demand will tend to always increase due

22


to economic growth, population growth, and target of increasing electrification ratio

so our plant can help PT.PLN to fulfill demand in West Borneo. Although PT.PLN

has a plans to increase the capacity, but there is no plans that are entered

construction stage. PT.PLN will still need Independent Power Producer to cover

power shortage. Besides that, increasing the power plant that does not use fuel oil

as main raw material can decrease usage of fuel oil for electrical fulfillment in West

Borneo. The type of our plant commonly is base load so we can supply electricity

continuously and can fulfill needs of base load power plant in West Borneo.

1.6. Plant Capacity Analysis

Market analysis for electricity in West Borneo become an important part for

determining the capacity of our plant. Here are the result s of the calculation for

supply demand analysis.

Table 1. 9 Supply-Demand West Borneo in 2010-2014


Based on Table 1.9 above, electricity supply from PT.PLN has decreased

every year. In 2014, PLN can fulfill all demand electricity in West Borneo.

However, in subsequent years, PT.PLN cannot fulfill the demand. In 2014, deficit

in West Borneo is large. PT. PLN must buy electricity and rent power plant from

other plant to fulfill it. In the previous section, electricity demand will always

increase every year approximately 5,1%. Growth of electricity is not accompanied

by construction of new power plant.

Based on consideration above and market analysis in the previous section,

production capacity from our plant is 30 MW. There are several other reasons why

we choose 30 MW as our production capacity.

Year Supply from PLN

(MW) Demand (MW)

Supply - Demand

(MW)

2010 305,98 238.79 67,19

2011 174,45 282.68 -108.23

2012 173,67 295 -121,33

2013 156,47 213 -56.53

2014 130,42 424.39 -293.97

23


1. Concentrated Solar Power (CSP) plant is plant that is relatively new and has

never existed in Indonesia so that the capacity that we choose is not too

large. This plant is still need of further review study to identify potential

capacity. This plant is very different from the solar power plant even though

both use solar energy as a primary energy source.

2. CSP plant needs large land area to construct the plant. CSP plant with 30

MW capacity needs land area about 70 ha. In this aspect, we consider the

difficulty of obtaining land with a large area.

3. Capital investment to construct CSP plant is very high. Capital investment

required for 30 MW capacity is about more than one trillion. Increase of

production capacity make capital investment will be higher.

24

CHAPTER II

PROCESS DESCRIPTION

2.1. General Process

Solar energy has a high exergetic value because it comes from processes

occuring at the sun’s surface at a blackbody equivalent temperature of

approximately 5777 K. Due to this high exergetic value, more than 93% of the

energy may be theoritically converted to mechanical work by thermodynamic

cycles (Winter, Sizmann, and Vant-Hull, 1991), or to Gibbs free energy of

chemicals by solarized chemical reactions (Kodama, 2003), including promising

hydrogen production processes (Seinfeld, 2005). According to themodynamics and

Plank’s equation, the conversion of solar heat to mechanical work or Gibbs free

energy is limited by the Carnott efficiency, and therefore to achieve maximum

conversion rates, the energy should be transferred to a thermal fluid or reactants at

temperatures close to that of the sun.

The optimum Concentrating Solar Thermal (CST) system design

combines a relatively large, efficient optical surface (e.g., a field of high-reflectivity

mirrirs), harvesting the incoming solar radiation and concentrating it onto a solar

receiver with a small aperture area. The solar receiver is a high-absorptance and

transmittance, low reflectance, radiative/convective heat exchanger that emulates

as close as possible the performance of a radiative black body. An ideal solar

receiver would thus have negligible convection and cunduction losses. In the case

of a solar thermal power plant, the solar energy is transferred to a thermal fluid at

an outlet temperature high enough to feed a heat engine or a turbine that produces

electricity by using steam. The solar thermal element can be a parabolic trough

field, a linear Fresnel reflector field, a central receiver system or a field of a

parabolic dishes, commonly designed for a normal incident radiation 0f 800-900

W/m2. The flow diagram for a black box of the plant can be seen in Figure 2.1.

Annual nirmal incident radiation varies from 1600 to 2800 kWh/m2 depending on

the available radiation at the particular size. This rate assumes 2000-3500 annual

full-load operating hours with the solar element.

25


Figure 2. 1 Black Box for This Solar Thermal Power Plant

(Source : Author’s Personal Data)

2.2. Alternative Process

There are some alternative processes to produce electricity from solar

thermal power. The differences come from their design technology to receive the

solar radiation. This design technology is made to maximize the heat solar radiation

directly from the sun to the receiver for producing great amount of electricity. The

alternative processes can be seen below.

2.2.1. Parabolic Trough Collector (PTC) Solar Thermal Power Plants

Parabolic Trough Collector (PTC) Solar Thermal Power Plants are linear

focus concentrating solar devices suitable for working in the 150-400oC

temperature range (Price et al., 2002). A PTC is basically made up of a parabolic

trough-shaped mirror that reflects direct solar radiation, concentrating it onto a

receiver tube located in the focal line of the parabola. Concentration of the direct

solar radiation reduces the absorber surface area with respect to the collector

aperture area and thus significantly reduces the overall thermal losses. The

concentrated radiation heats the fluid that circulates through the receiver tube, thus

transforming the solar radiation into thermal energy in the form of the sensible heat

of the fluid.

2.2.2. Central Receiver Solar Thermal Power Plants

This technology use power towers in the middle of mirrors. The receiver

is on the top of the tower. Incident sunrays are tracked by large mirrored collector

(heliostats), which the solar thermal energy is transferred to a thermal fluid inside

the receiver. After the energy collection by the solar subsystem, the thermal energy

conversion to electricity by turbine, so it is similar to fossil-fueled thermal power

plants.

The reflective solar concentrator are employed to reach the temperatures

required for thermodynamic cycle (Mancini, Kolb, and Prairie, 1997). In the power

tower or Central Receiver Solar (CRS) the solar receiver is mounted on top of a

Direct Solar Radiation Electricity Black Box

26


tower and sunlight is concentrated by means of a large paraboloid that is discretized

into a field of heliostats in Figure 2.2.

Figure 2. 2 Artist’s View of a Heliostat Field Focusing Sunlight onto a Receiver/Tower System

(Source : Manuel and Zarza, 2007)

CRS have a high potential for midterm cost reduction of electricity to

produce since there are many intermediate steps between their integration in a

conventional Rankine cycle up to the higher exergy cycle using gas turbines at

temperatures above 1300oC, leading to higher efficiencies and thoughputs. With

storage, CRS plants are able to operate over 4500 h per year at nominal power

(Kolb, 1998). The summary of characteristics of CRS can be seen in Table 2.1.

Table 2. 1 Characteristics of Central Receiver Solar Thermal Power Systems

Typical Size 10-200 MWa

Operating Temperature

Rankine 565oC

Brayton 800oC

Annual Capacity Factor 20-77%a

Peak Efficiency 16-23%a

Annual Net Efficiency 12-20%a

Commercial Status Scale-up Demonstration (10-30 MW)

Technology Development Risk Medium

Storage Available Nitrate Salt for Molten Salt Receiver

Ceramic Bed for Air Receivers

Hybrid Designs Yes

Invest Cost

$.W-1 4.4 - 2.5a

$.Wp-1b 2.4 – 0.9a

a Figure indicated expected progress from present to 2030.

b $/Wp removes the effect of energy storage or solar multiple, as in PV.

(Source : Adapted From DeMeo, E. A. and Galdo, J. F. 1997. TR-109496 Topical Report. U.S.

Department of Energy, Washington, DC)

27


A solar thermal, or central receiver system, plant may be described in terms

of the following subsytems:

Collector system, or heliostat field, created with a large number of two-axis

tracking units distributed in rows

Solar receiver, where the concentrated flux is absorbed. It is the key element

of the plant and serves as the interface between the solar portion of the plant

and the more conventional power block.

Heat exchanger system, where a heat transfer fluid may be used to carry the

thermal energy from the receiver to the turbine

Heat storage system, with which system dispatchability is ensured during

events like cloud passages, and can adapt to demand curves

Fossil fuel backup for hybrid systems with a more stable output

Power block, including steam generator and turbine-alternator

Master control, UPS, and heat rejection system

2.2.2.1. Heliostat and Collector Field

The collector field consists of a large number of tracking mirrors, called

heliostats, and a tracking control system to continuosly focus direct solar radiation

onto the receiver aperture area. During cloud passages and transients the control

system must defocus the field and react to prevent damage to the receiver and tower

structure.

This heliostats fields are characterized by their off-axis optics. The solar

receiver is located in a fixed position upside the heliostats, the entire collector field

must track the sun in the real time and every heliostat individually places its surface

normal to the solar receiver.

Heliostat filed performance is calculated by the optical efficiency, which

is equal to the ratio of net power absorbed by the receiver to the product of the direct

insolation and the total mirror area. Complex optimization algorthms are used to

optimize the annual energy produced by unit of land, and the heliostat must be

installed as close as possible to the receiver to minimize the space and maximize

high concentration of radiation.

28


2.2.2.2. Solar Receiver

In a solar thermal tower plant, the receiver is the heat exchanger where the

concentrated sunlight is intercepted and transformed into thermal energy useful in

thermodynamic cycles. Radiant flux and temperature are substantially higher than

in parabolic troughs, and therefore, high technology is involved in the design, and

high-performance materials should be chosen. The solar receiver should mimic a

blackbody by minimizing radiation losses. To do so cavities, black-painted tube

panels or porous absorbers able to trap incident photons are used. In most design,

the solar receiver is a single unit that centralized all the energy collected by the large

mirror field, and therefore high availabilities and durability are a must. Just as cost

reduction is the priority for further development in the collector field, in a solar

receivers, the priorities are thermal efficiency and durability. Typical receiver-

absorber operating temperatures are between 500oC and 1200oC and incident flux

covers a wide range between 300 and over 1000 kW/m2.

There are different solar receiver clasiffication criteria depending on the

construction solution, the use of intermediate absorber materials, the kind if thermal

fluid used, or heat transfer mechanism. According to the geometrical configuration,

there are basically two design options, external and cavity-type receivers. In a cavity

receiver, the radiation reflected from the heliostats passes through an aperture into

a box-like structure before implinging on the heat transfer surface. Cavities are

constrained angularly and subsequently used in north field (or south field) layouts.

External receivers can be designed with a flat-plate tubular panel or a cylindrically

shaped. Cylindrical external receivers are the typical solution adopted for surround

heliostat fields. Figure 2.3 shows examples of cylindrical external, billboard

external, and cavity receivers.

29


Figure 2. 3 Different Configuration of Solar Receivers

From left to right and top to bottom: (a) External Tubular Cylindrical, (b)

Cavity Tubular, (c) Billboard Tubular, and (d) Volumetric.


Receivers can be directed or indirectly irradiated depending on the

absorber materials used to transfer the energy to the working fluid (Becker and

Vant-Hull, 1991). Directly irradiated receivers make use of fluids or particle

streams are able to efficiently absorb the concentrated flux. Particle receiver designs

make use of falling curtains or fluidized beds. Darkened liquid fluids can use falling

film. In many applications, and to avoid leaks to the atmosphere, direct receivers

should have a transparent window. Windowed receivers are excellent solutions for

chemical applications as well, but they are strongly limited by the size of a single

window, and therefore clusters of receivers are necessary.

The key design element if indirectly heated receivers is the

radiative/convective heat exchanger surface or mechanism. Basically, two heat

transfer options are used, tubular panels and volumetric surfaces. In tubular panels,

the cooling thermal fluid flows inside the tube and removes the heat collected by

the external black panel surface by convection. It is therefore operating as a

recuperative heat exchanger. Depending on the heat transfer fluid properties and

incident solar flux, the tube might undergo thermomechanical stress.

2.2.2.3. Tubular Receivers

30


The most common systems used in the past have been tubular receivers

where concentrated radiation is transferred to the cooling fluid through a metal or

ceramic wall. Conventional panels with darkened metal tubes have been used with

steam, sodium and molten salts for temperatures up to 500-600oC. Much less

experience is available on tubular receivers with gas, through temperatures in the

range of 800-900oC are possible. Operating temperature and flux ranges of solar

tower receivers can be seen on Table 2.2.

Table 2. 2 Operating Temperature and Flux Ranges of Solar Tower Receivers

Fluid Water/

Steam

Liquid

Sodium

Molten Salt

(nitrates)

Volumetric

Air

Flux (MW/m2)

Average 0.1-0.3 0.4-0.5 0.4-0.5 0.5-0.6

Peak 0.4-0.6 1.4-2.5 0.7-0.8 0.8-1.0

Fluid Outlet

Temperature (oC) 490-525 540 540-565

700-800

(>800)


Molten salt tubular receivers are represented by the Themis system

(cavity) and Solar Two (cylindrical external). In a molten salt system, cold salt at

about 290oC is pumped from tank at ground level to the receiver mounted atop a

tower where it is heated by concentrated sunlight to 565oC. Using molten salt as

receiver coolant provides a number of benefit because there is no phase change and

it is possible to heat up to 565oC without the problems associated in tubes with

superheating sections. Mixtures of 60% sodium nitrate and 40% potassium nitrate

have been extensively tested with satisfactory result in France and USA.

Molten nitrate provides good thermal conductivity (0.52 W/mK) and heat

capacity (1.6 kJ/kgK) at relatively low prices. Molten nitrate salt, through an

excellent thermal storage medium, can be a troublesome fluid to deal with because

of its relatively high freezing point (220oC). To keep the salt molten, a fairly

complex heat trace system must be employed. (Heat tracing is composed of electric

wires attached to the outside surface of pipe. Pipes are kept warm by way of

resistance heating.) Problems were experienced during the start-up of Solar Two

31


due to the improper installation of the heat trace. Through this problem has been

addressed and corrected, research is needed to reduce the reliance on heat tracing

in these plants. Also, valves can be troublesome in molten salt service. Special

packings must be used, oftentimes with extended bonnets, and leaks are not

uncommon. Furthermore, freezing in valves or packing can prevent it from

operating correctly. While today’s valve technology is adequate for molten salt

power towers, design improvements and standarization wolud reduce risk and

ultimately reduce O&M costs (DeMeo and Galdo, 1997).

2.2.2.4. Volumetric Receivers

As already mentioned, volumetric receivers use highly porous structures

for the absorption of the concentrated solar radiation deep inside (in the “volume”)

of the structure. Volumetric receivers can work open to the ambient or enclosed by

a transparent window. With metal absorbers, it is possible to achieve air oulet

temperatures up to 850oC, and with ceramic fibres, fams, or monoliths (SiC), the

temperature can suprass 1000oC.

The main advantages of an air-cooled volumteric receiver are:

The air is free and fully available at the site

No risk of freezing

Higher temperatures are possible and therefore the integration of solar thermal

energy into more efficient thermodynamic cycle looks achievable

No phase change

Simpler system

Fast response to transients or changes in incident flux

No special safety requisities

No environmental impact

The summary of operating range for tubular water and molten salt receivers can be

seen on Table 2.3.

Table 2. 3 Summary of Operational Range for Tubular Water/Steam and Molten Slat Receivers

32


Receivers Water/Steam Molten Salt Receivers

Temperature fluid outlet 250/525oC Temperature outlet 566oC

Incident flux 350 kW/m2 Incident flux 550 kW/m2

Peak flux 700 kW/m2 Peak flux 800 kW/m2

Pressure 100-135 bar Efficiency 85-90%

Efficiency 80-93%


2.2.3. Solar Air Preheating System for Combustion Turbines

Solar air preheating offers superior performance, as the solar energy

absorbed in the heated air is directly converted with the high CC plant efficiency.

For a certain annual solar share, this results in reduced heliostat field size and thus

lower overall investment cost for the solar part compared to solar steam generation.

Solar air preheating has a high potential for cost reducton of solar thermal power.

In addition, this concept can be applied to a wide range of power ouput level (1-100

MWe). At lower power levels, high efficient heat recovery gas turbine cycles can

be used instead of CC. The slar share can be chosen quite flexibility by the receiver

outlet temperature, which could be significantly higher than with other hybrid

concepts (2.g., ISCC with parabolic trough).

Air can be preheated by molten salt solar receiver (up to 560oC)(Price,

Whitney, and Beebe, 1996) or with pressurized volumetric receivers (Kribus, et al.,

1997; Buck, Lupfert and Tellez, 2000), in which, due to the limited size of the

quartz window, a number of receiver modules are placed on the tower. Each module

consists of a pressurized receiver unit with a secondy concentrator in front. The

secondary concentrator with a hexagonal aperture (located in the focal plane of the

heliostat field) reconcentrates the solar radiation onto the apperture of the pressure

vessel which is enclosed by a domed quartz window to maintain pressure. After

passing through the window, the radiation is absorben in volumetric absorber which

transfers the heat by forced convection to the airstream flowing through it. Power

is upscaled by installing many modules in a honeycomb formation to cover the

entire focal spot. The modules are then interconnected in the parallel and to a serial

connection.

33


For high temperatures, a highly porous SiC ceramic foam absorber with a

pore size of 20 ppi was used. The pressure resistant, domed quartz window was

cooled on the atmospheric side by air jets. For the low-temperature receiver the aim

was to achieve an overall cost reduction at the first, low-temperature stage of the

receiver cluster by employing simple, less expensive modules. The concept selected

was s multiptube coil attached to a hexagonal secondary concentrator, in which the

air was heated convectively while flowing through the tubes. The coiled tubes were

flexible and thus reduced mechanical stresses from thermal expansion of the tube

material.

2.2.4. Dish/Engine Solar Thermal Power Plants

Solar thermal power plants can also be applied to distibuted generation

through parabolic dishes in which a PCU is attached by an arm directly to the

concentrator.

2.2.4.1. Concentrator

This device is a key element of any dish/Stirling system. The curved

rellective surface can be manufactured by attached segments, by individual facets

or by a stretched membranes shaped by a continuous plenum. In all cases, the

curved surface should be coated or covered by aluminium or silver reflectors.

Second-surface glass mirrors, front surface thin glass mirrors or polymer films have

been used in various different prototypes.

2.2.4.2. Receiver

The receiver absorbs the light and transfers the energy as heat to the

engine’s working gas, usually helium or hydrogen in central receivers and parabolic

trough absorbers. Thermal fluid working temperatures are between 650oC and

750oC. This temperature strongly influences the efFiciency of the engine. Because

of the high operating temperatures, radiation losses strongly influences the

efficiency of the engine. Because of the high operating temperatures, radiation

losses strongly penalized the efficiency of the receiver; therefore, a cavity design is

the optimum solution for this kind of system.

Two different heat transfer methods are commonly used in parabolic dish

receivers (Diver, 1987). In directly illuminated receivers, the same fluid used inside

the engine is externally heated in the receiver through a pipe bundle. Although this

34


is the most conventional method, a good high-pressure, high velocity heat transfer

gas like helium or hydrogen must be used. In indirect receivers, an intermediate

fluid is used to decouple solar flux and working temperature from the engine fluid.

One such method is heat pipes, which employ a metal capillay wick impregnated

with a liquid metal heated up through the receiver plate and vaporized. The vapor

then moves accros the receiver and condenses in a cooler section, transferring the

heat to the engine. The phase change guarantees good temperatue control, providing

uniform heating of the Stirling engine (Moreno et al., 2001).

2.2.4.3. Stirling Engine

Stirling engines solarized for parabolic dishes are externally heated gas-

phase engines in which the working gas is alternatively heated and cooled in

constant-temperature, constant-volume processes. This possibility of integrating

additional external heat in the engine is what makes it an ideal candidate for solar

applications. Because the Stirling cycle is vey similar to the Carnot cycle, the

theoritical efficiency is high. High reversibility is achieved since work is supplied

to and extracted from the engine at isothermal conditions. The clever use of a

regenerator that collects the eat during constant-volume cooling and heating

substantially enhances the final system efficiency. For most engine designs, power

is extracted kinematically by rotating a crankshaft conected to the piston by a

connecting rod. Through theoritically, Stirling engines may have a high life cycle

projection, the actual fact is that today their availability is still not satisfactory, as

an important percentage of operating failures and outages are caused by pistons and

moving mechanical components.

2.3. Process Selection

In the process of selection, there are many criteria to decide which one is

the most suitable project to be build in Indonesia. Several considerations are made

based on the data which have been published in many countries.

2.3.1. Type of Solar Thermal Power Plant

To determine the type of solar thermal power plant, there are seven points

to discuss which one is the best to be build here.

a. Capital Cost

35


Capital cost is one of the big issue for solar thermal power because every

project has to deal with big investment. The feasibility study plays important

role for technical and economical analysis. If the amount of capital investment

is great, it will be more aspects that we should be studied to reduce the

investment risk. From three existing solar thermal power plant, there is a

difference in their cost. For PTC the cost range is $3,000-3,500/kW, and for

central receiver the cost range is $3,500-4,000/kW. The last option is

dish/engine with the most expensive cost in range $6,500-7,500/kW.

b. Maintenance & Operational Cost

Maintenance dan operational cost is the cost that we need to opertate and

maintenance the solar thermal power plant to produce electricity. This cost is

calculated annually, for PTC the cost is in range $9,000-10,000, the solar

receiver is in range $14,000-15,000, and the dish/engine costs the most

expensive in range $15,000-16,000.

c. Efficiency

Efficiency of the plants also plays an important role in selection process.

The efficiency is how much heat energy can be converted into electricity. The

bigger the efficiency, the bigger the power produces. For PTC the efficiency is

in range 11-16%, 7-20% for central receiver, and 13% for dish/engine.

d. Life Time

Life time is the duration for plants to operate from the beginning to end.

Out of these three types, PTC is the longest life time up to 30 years, for central

receiver the duration length of operating plant is in range 25-30 years, whereas

the dish/engine power plant with the shortest duration of a life time, reaching

only 20 years.

e. Technology

Technology development also plays a role in the selection process.

Technology here is instrumental in increasing efficiency, decreasing the cost

per output power, efficiency of land, etc. For PTC, the technology development

risk is low, so that allowing more development processes to succed. For central

receiver, the risk of development in technology is higher than PTC, and so is

the dish/engine.

36


Table 2. 4 Comparison of Existing Solar Power Plant

Parabolic Trough

Collector

Central

Receiver Dish/Engine

Capital Cost ($/kW) 3,000-3,500 3,500-4,000 6,500-7,000

Annual Maintenance &

Operational Cost ($) 9,000-10,000 14,000-14,500 15,000-16,000

Efficiency 11-16 7-20 13

Life Time 30 years 25-30 years 20 years

Technology Development

Risk Low Medium Medium

Typical Capacity (MW) 10-300 10-200 0.01-0.025

Operating Temperature (oC) 350-550 250-565 550-750

Hybridization Yes and direct Yes Not planned

Storage with Molten Salt Commercially

available

Commercially

available

Possible, but not

proven

(Source : International Renewable Energy Agency, 2012)

Based on the summary in Table 2.4, we select which one is the most suitable

project in Indonesia by scoring three of them in Table 2.5 by six aspects.

Score range runs from 1 (poor) to 5 (excellent). The highest score in selecting

process will be the type of power plant to be constructed.

Table 2. 5 Scoring of The Types of Solar Power Plant

Parabolic

Trough

Collector

Central

Receiver Dish/Engine

Capital Cost ($/kW) 3 3 2

Annual Maintenance &

Operational Cost ($) 4 3 2

Efficiency 3 3 4

Life Time 5 4 3

Technology Development Risk 4 3 3

Typical Capacity (MW) 4 4 2

Total 23 20 16

(Source : Author’s Personal Data, 2015)

2.3.2. Types of Storage

37


There are two types of storage used in PTC, single-medium storage system

and two-medium storage system. The selection process is based on some aspects

below.

a. Efficiency

Based on the efficiency of fluid to storage, single-medium storage system

are those in which the storage medium is the same fluid circulating through the

collectors. The most common is molten salts as both the working fluid and the

storage medium. The efficiency of these systems is over 90%. In the other,

dual-medium storage system are those in which the heat is stored in a medium

other than the working fluid heated in the solar collector. Fluid working and

fluid medium is different, the efficiency of these system is in rang 85-90%.

b. Operational Cost

Based on the operational cost, single-medium storage has lower cost than

dual-medium storage. The usage of dual-medium storage need extra heat

exchanger to transfer heat from working fluid to the storage medium, because

both fluids have a different path of circulating systems. The usage of single-

system does not need extra heat exchanger because the working fluid and the

storage medium are the same path of circulating system.

c. Safety

Based on safety, single-medium storage has an advantage over dual-

medium storage tank. The usage of oil as the working fluid in dual-medium

storage, it is needed to keep the oil in the storage tank pressurized and in an

inert atmosphere. Thermal oil has to be kept pressurized above the vapor

pressure corresponding to the maximum temperature in the oil circuit to

prevent the oil from changing into gas. The inert atmosphere also avoids the

risk of explosion in the tank from pressurized mists which are explosive in air.

In the other hand, single-medium storage does not need extra safety procedure

for storage the medium because the working fluid and the storage medium are

molten salts.

The scoring of this process selection can be seen on Table 2.6 below.

Table 2. 6 Scoring of Types of Storage Medium

38


Parabolic Trough

Collector Central Receiver

Efficiency 4 4

Operational Cost 4 3

Safety 4 2

Total 12 9

(Source: Author’s Personal Data, 2015)

2.4. Process Description

Parabolic Trough Collector (PTC) Solar Thermal Power Plants are linear

focus concentrating solar devices suitable for working in the 150-400oC

temperature range (Price et al., 2002). A PTC is basically made up of a parabolic

trough-shaped mirror that reflects direct solar radiation, concentrating it onto a

receiver tube located in the focal line of the parabola. Concentration of the direct

solar radiation reduces the absorber surface area with respect to the collector

aperture area and thus significantly reduces the overall thermal losses. The

concentrated radiation heats the fluid that circulates through the receiver tube, thus

transforming the solar radiation into thermal energy in the form of the sensible heat

of the fluid. Figure 2.4 shows a typical PTC and its components.

Figure 2. 4 Parabolic trough Solar Thermal Power Plant

(Source : http://www.cnet.com/news/skyfuel-heats-up-solar-thermal-power-race/)

2.4.1. Block Flow Diagram

http://www.cnet.com/news/skyfuel-heats-up-solar-thermal-power-race/

39


The solar thermal energy to electricity conversion process used in this plant

which uses molten salt as the heat transport medium typically incorporates

the process concept as shown in Figure 2.5:

Figure 2. 5 Block Flow Diagram for This Plant


2.4.2. Process Flow Diagram

The processes from Figure 2.5 in detail can be seen in process flow diagram

in Figure 2.6 below:

40


Figure 2. 6 Process Flow Diagram for Gasification Unit.


41


2.4.3. Process Description

A. Process in PTC SolarReceiver

PTCs are dynamic devices because they have to rotate around an axis, the

so-called tracking axis, to follow apparent daily movement of the sun. Collector

rotation around its axis requires a drive unit. One drive unit is usually sufficient for

several parabolic trough modules connected in series and driven together as a single

collector. The type of drive unit assembly depends on the size and dimensions of

the collector (aperture area less than 100 m2), whereas powerful hydraulic drive

units are required to rotate large collectors. A drive unit placed on the central pylon

is comanded by a local control unit in order to track the sun.

Local control units currently available on the market can be grouped into

two categories: (1) control units based on sun sensors and (2) control units based

on astronomical algorithms.

Control units in group 1 use photocells to detect the sun position, whereas

those in group 2 calculate the sun vector using very accurate mathematical algoritms

that find the sun elevation and azimuth every second and measure the angular

position of the rotation axis by means of electronic devices (angular encoders or

magnetic coded tapes attached tp the rotation axis).

Flux line trackers and shadow band use photocells (group 1). Shadow band

trackers are mounted on the parabolic concentrator and face the sun when the

collector is in perfect tracking (i.e., the sun vector is within a plane that includes the

receiver tube and is perpendicular to the concentrator aperture plane). Two

photosensors, on on each side of a separating shadow wall, detect the sun’s position.

When the collector is correctly pointed, the shadow wall shades both sensor equally,

and their electric output signals are identical.

Flux line trakers are installed on the receiver tube. There are two sensor

which are placed on both sides of the absorber tube to detect the concentrated flux

reaching the tube. The collector is correctly pointed when both sensors are equally

illuminated and their electrical signals are the same magnitude. Now, all

commercial PTC designs use a single-axis-sun-tracking-system. Through PTC

designs with two-axis sun-tracking systems have been designed, manufactured, and

tested in the past, evaluation results show that they are less cost-effective. Through

42


the existence of a two-axis tracking systems allow the PTC to permanently track

the sun with an incident angel equal to 0o (and thus reducing optical losses while

increasing the amount of solar radiation available at the PTC aperture plane), the

length of passive piping and the associated themal losses are significantly higher

than in single-axis collector. Furtermore, their maintenance costs are higher and

their availability lower because they require a more complex mechanical design.

Thermal oils are commonly used as the working fluid in these collectors

fot temperatures above 200oC, because at these high operating temperatures normal

water would produce high pressures inside the receiver tube and piping. This high

pressure would require strong joints and piping, and thus raise the price of the

collectors and the entire solar field. However, the use of demineralized water for

high temperatures/pressures is currently under investigation at the PSA and the

feasibility of direct steam generation (DSG) at 100 bar/400oC in the receiver tubes

of PTC has already been proven in an experimental stage. For temperatures below

200oC, either a mixture of water/ethylene glycol or pressurized liquid water can be

used as the working fluids because the pressure required in the liquid phase is

moderate.

When choosing a thermal molten salts to act as working fluid, the main

limiting factor to be taken into consideration for stability is the maximum oil bulk

temperature.above this temperature, oil cracking and rapi degradation occur.

We can also use oil. The most oil widely used in the PTC for temperature

above 395oC is VP-1, which is a eutetic mixture of 73.5% diphenyl oxide and 26.5%

diphenyl. The main problem with this oil is its high solidification temperature

(12oC) that requires an auxiliary heating system when oil lines run the risk of

cooling below this temperature. Because the boiling temperature at 1013 mbar is

257oC, the oil circuit must be pressurized with nitrogen, argon, or some more inert

gas when oil is heated above this high temperatures because high pressure mists can

form an explosive mixture with air. Through there are other suitable thermal oils

for slightly higher working temperatures with lower solidification temperatures,

they are too expensive for large solar plants.

The typical PTC receiver tube is composed of an inner steel pipe

surrounded by a glass tube to reduce convective heat losses from the hot steel pipe.

43


The steel pipe has a selective high-absorptivity (>90%), low emissivity (<30% in

the infrared) coating that reduces radiative ther,al losses. Receiver tubes with glass

vacuum tubes and glass pipes with an antireflective coating achieve higher PTC

thermal efficiency and better annual performance, especially at higher operating

temperatures. Receiver tubes with no vacuum are usually for working temperatures

below 250oC, because thermal losses are not so critical at these temperatures. Due

to manufacturing constraints, the maximum length of single receiver pipes is less

than 6 m, so the complete receiver tube of a PTC is composed of a number of single

receiver pipes welded in series up to the total length of the PTC.

B. Steam Generating

The proper PTC temperature range and their good solar-to-thermal

efficiency up to 400oC make it possible to integrate a parabolic trough solar field in

a Rankine water/steam power cycle to produce electricity. Today, all the solar

thermal power plants with PTCs use the HTF technology because steam production

by flashing is not suitable for 100 bar steam pressure and commercial DSG has not

yet been proven.

Basically, there are three elements in a parabolic trough power plant, such

as: the solar system, the steam generator, and the power conversion system (PCS).

The solar system is composed of a parabolic trough solar collector field and the

molten salts circuit. The solar field collects the solar energy available in the form

of direct solar radiation in receivers and converts it into thermal energy as the

temperature of the molten salts circulating trough the receiver tubes of the collectors

increases. Once heated in the solar field, the molten salts goes to the steam

generator, which is an molten salts–water heat exchanger where the molten salts

transfers its thermal energy to the water that is used to generate the superheated

steam required by the turbine. The steam generator is, therefore, the interface

between the solar system (Solarfield Coil circuit) and the PCS itself.

Normally, the steam generator used in these solar power plants consists of

three stages:

a. Preheater: The process is water from the deaerator pumped into the preheater.

Then, water is preheated to a temperature close to evaporation by using molten

44


salts thermal energy from the sun’s radiation which is collected in solar field.

The operation condition is at 680oF and 74 bar.

b. Evaporator: The water from preheater is pumped to the evaporator. Using

molten salts from collector, the preheated water is evaporated and converted

into saturated steam. The operation condition is at 430oC and 74 bar.

c. Superheater: the saturated steam produced in the evaporator is heated in the

superheater to the temperature required by the steam turbine. 530oC and 74 bar.

The PCS transforms the thermal energy delivered by the solar field into electricity,

using the superheated steam delivered by the steam generator. This PCS is similar

to that of a conventional Rankine power plant, except for the heat source.

C. Process in Steam Turbine

The superheated steam produced by the steam generator is then delivered

and expanded in a steam turbine that drives an electricity generator. The thermal

power from superheated steam technically converted to the electricity with only

10% efficiency.

The steam turbine is usually composed of two consecutive stages, for high

and low pressure steam. High pressure steam passes along the machine axis through

multiple rows of moving and alternaltively fixed blades. From the steam inlet port

of the turbine towards the exhaust point, the turbine cavity and the blades are

progressively larger to allow for the expansion of the steam. The stationary blades

act as nozzles in which the steam expands and emerges at an increased speed but

lower pressure. As the steam impacts on the moving blades it impacts some of its

kinetic energy to moving the blades of turbine. Steam leaving the turbine high-

pressure stage goes to a reheater where its temperature rises before entering the low-

pressure turbine stage. The operation condition is at 530oC and 74 bar.

Though parabolic trough power plants usually have an auxiliary gas-fired

heater to produce electricity when direct solar radiation is not available, the amount

of electricity produced with natural gas is always limited to a reasonable level.

Parabolic trough power plants can play an important role in achieving sustainable

growth because they save about 2000 tn. of CO2 emissions per MW of installed

power yearly.

45


D. Condensation

After the stage from steam turbine, the steam is condensed and the

condensate goes to a water deaerator to remove oxygen and gases dissolved in the

water. The type of condenser used in this process is surface condenser.

The water flowing through the condenser may be once-through, or

single-pass, or it may be made to reverse one or more times before being discharged.

Surface condensers are basically shell and tube heat exchangers. The turbine

exhaust steam condenses on the shell side, and the cooling water flows through the

tubes in one or more passes depending on the condenser design

Expansion occurs between the turbine and condenser as a result of the

temperature difference between the two components. This expansion is

accommodated by an expansion joint located between them. Condenser

performance is very important to having an efficient and reliable power plant.

Leakage of air and cooling water can result in accelerated boiler corrosion and

deposits. In addition, poor condenser performance results in high backpressure,

which in turn results in lower electric output, lower efficiency, and therefore high

operating costs. The operation condition in this stage is at 300oC and 40 bar.

The steam leaving the turbine low-pressure stage can be condensed either

in a wet cooling system (evaporative cooling towers) or in a dry cooling system

(air-cooled condenser).

E. Process in Cooling Tower

The process in this stage is cooling the outflow water from condenser. But,

before entering te cooling tower, there are several processes to do pretreatment for

controling the quality of water. The properties are conductivity, pH, alkalinity, and

hardness. Conductivity is a measure of water’s ability to conduct the electricity. In

cooling water, it indicates the amount of dissolved minerals in water. conductivity

is measured in 𝜇S/cm (microSiemens/cm) and can vary from a few for distilled

water to over 30,000 𝜇S/cm for sea water. pH is a indicator of the relative acidity ir

basicity of water used in cooling water. The pH scale runs from 0 to 14, smaller

scale indicates increasing acidity. In cooling water, two forms of alkalinity play a

key role. These are carbonates ions (CO32-) and bicarbonate ions (HCO3

-). These

alkalinity acts as a buffer to charges acidity or basicity. Hardness refers to the aount

46


of magnesium and calcium ions present in water. These four parameters should be

controlled to prevent corrosion, scale, or fouling in piping and process system.

When designing a new system, choose corrosion-resistant materials to minimize the

effect of an agressive environment to prevent corrosion. What to do to prevent scale

forming is limiting the concentration of scale forming minerals by controlling

concentration ratio or by removing the minerals before they enter the system.

“concentration ratio” is the ratio dissolved solid in the blow-down to dissolved

solids in the make up. After several pretreatment process, then water is pumped to

cooling tower.

The temperature of water from condensor can exceed more than 50oC. The

operating condition for this stage is at 99.63oC and 1 bar. The temperature of water

will be decreased below 60oC before entering a deaerator. Cooling process use air

flow which is entering the side of tower. Hot water sprayed from the top of the

tower is contacted with the air flow. Heat transfer occur from water to air flow.

This condition cause evaporation of water to form vapor. The heat from water is

absorbed by the vapor so that water temperature is going down. The cool water then

pumped to deaerator to continue the process.

F. Process in Deaerator

The process in this device is removing oxygen and other dissolved gases

from the feedwater to steam generator. Oxygen existence in water can cause serious

problem of corrosion in steam systems by attaching in wall of piping and other

metallic equipments and forming oxides. Dissolved carbon dioxide in water can

form carbonic acid, this compund can also cause serious corrosion in piping and

process equipment. Most deaerator are designed to remove oxygen below 7 ppb by

weight as well as essentially eliminating carbon dioxide.

G. Storage Tank

The type of storage tank in the PTC solar thermal power plant is single-

medium systems. The single-medium storage systems are those in which the heat

is stored in a medium by the working fluid heated in the solar collectors. Iron plats,

ceramic materials, molten salts, or concrete can be used as the storage medium. In

47


these systems, the molten salts is commonly used as the heat transfer medium

between the solar field and the thermal storage in iron plates, the molten salts

circulates through channels between cast iron slabs placed inside a thermally

insulated vessel, transferring thermal energy to them (charging process) or taking it

from them (discharging process).

Molten salts (an eutetic mixture of sodium and pottasium nitrate) can also

be used for single-medium thermal storage systems in parabolic trough solar plants.

In this case, two tanks are needed; one for cold molten salt and another to store the

hot molten salt. Obviously, the lowest temperature is always above melting point

of the salt (approximately 250oC). This type of thermal storage system is claimed

to be the most cost-effective option for large commercial solar power plants with

large solar shares.

48

CHAPTER III

MASS & ENERGY BALANCE

From the process in chapter II, we can calculate mass and energy balance of

the plant. Mass balance will be evaluated each equipment. From this chapter, we

will know how much solar heat, molten salt and water needed to produce 30 MW

electricity. Then, we will know the energy needed. In this chapter, mass and energy

balance will be calculated each unit and then each equipment.

Mass and energy balance calculation are done by simulate the plant in a

process simulator. The process simulator used is UniSim®. The result of our plant

simulation in UniSim® is as shown below.

Figure 3. 1 Solar Thermal Power Plant (UniSim® Simulation)

(Source: Author’s Personal Data)

3.1. Mass Balance for Equipment

There are total of ten main equipments used in the solar thermal power plant

we proposed: Pump P-100, Solar Collector, Hot Tank, Cold Tank, E-100, E-101,

E-102, K-100, E-103, and P-102. In this section we will make a mass balance for

each equpment.

49


Pump P-100

Table 3. 1 Mass Balance On Pump P-100

Component Stream In (ton/h) Stream Out (ton/h)

5 1

NaNO3 32.298 32.298

KNO3 18.102 18.102

H2O 0 0

TOTAL 50.400 50.400 (Source :Author’s Personal Data)

Solar Collector

Table 3. 2 Mass Balance On Solar Collector


1 2

NaNO3 32.298 32.298

KNO3 18.102 18.102

H2O 0 0


“Cold” Salt Storage Tank

Table 3. 3 Mass Balance On Cold Tank


18 5 V1

NaNO3 32.298 32.298 0

KNO3 18.102 18.102 0

H2O 0 0 0


“Hot” Salt Storage Tank

Table 3. 4 Mass Balance On Hot Tank


7 8 V2

NaNO3 32.298 32.298 0

KNO3 18.102 18.102 0

H2O 0 0 0


50


Heat Exchanger E-100

Table 3. 5 Mass Balance On HE E-100


10 19 12 13

NaNO3 32.298 0 32.298 0

KNO3 18.102 0 18.102 0

H2O 0 218.877 0 218.877





12 16 17 19

NaNO3 32.298 0 32.298 0

KNO3 18.102 0 18.102 0

H2O 0 218.877 0 218.877





17 11 18 16

NaNO3 32.298 0 32.298 0

KNO3 18.102 0 18.102 0

H2O 0 218.877 0 218.877


Steam Turbine K-100

Table 3. 8 Mass Balance On Turbine K-100


13 14

NaNO3 0 0

KNO3 0 0

H2O 218.877 218.877


51


Cooler E-103

Table 3. 9 Mass Balance On Cooler E-103


14 15

NaNO3 0 0

KNO3 0 0

H2O 218.877 218.877


Pump P-102

Table 3. 10 Mass Balance On Pump P-102


15 11

NaNO3 0 0

KNO3 0 0

H2O 218.877 218.877


3.2. Energy Balance for Equipment

In this section we will make energy balance for each equipment in the plant.

All units are in kJ/h.

Table 3. 11 Energy Balance for Equipment

Equipment In (kJ/h) Out (kJ/h)

Duty

Required(+)/

Produced(-)

(kJ/h)

Qloss (kJ/h)

Pump P-

100 -1.201.E+08 -1.201.E+08 1.106.E+04 0

Sollar

Collector -1.201.E+08 -1.013.E+08 2.503.E+07 6.257.E+06

Hot Tank -1.013.E+08 -1.013.E+08 0 0

Cold Tank -1.201.E+08 -1.201.E+08 0 0

E-100 -3.489.E+09 -2.947.E+09 0 -5.419.E+08

E-101 -3.503.E+09 -3.503.E+09 0 0

E-102 -3.545.E+09 -3.513.E+09 0 -3.170.E+07

K-100 -2.837.E+09 -2.945.E+09 -1.080.E+08 0

E-103 -2.945.E+09 -3.431.E+09 -4.855.E+08 0

P-102 -3.431.E+09 -3.430.E+09 1.158.E+06 0 (Source :Author’s Personal Data)

52


3.3. Overall Mass Balance

After mass balance for each equipment is finished, we can then calculate the

overall mass balance. Overall mass balance is the mass balance for the entire plant

as one system. Meaning, the mass in is the mass stream that enter the plant, and

mass out is the mass stream that exit the plant. The overall mass balance is as shown

below.

Table 3. 12 Overall Mass Balance

Component Mass In (ton/h) Mass Out (ton/h)

NaNO3 0 0

KNO3 0 0

H2O 0 0

TOTAL 0 0 (Source :Author’s Personal Data)

As we can see above, there is no mass in our out into the plant, because our plant

can be considered a closed system. Both molten salts and water are circulated in the

system and none of them exits or enters the system.

3.4. Overall Energy Balance

Similar with overall mass balance, we will make overall energy balance for

our plant as shown below.

Table 3. 13 Overall Energy Balance

Stream Energy In (kJ/h) Energy Out (kJ/h)

NaNO3 0 0

KNO3 0 0

H2O 0 0

Qsolar 2.503.E+07 0

Q-100 1.106.E+04 0.000.E+00

W 0 1.080.E+08

Q-102 1.158.E+06 0.000.E+00

TOTAL 26197115.7 1.080.E+08 (Source :Author’s Personal Data)

3.5. Mass Efficiency

From mass balance calculation above, we can calculate mass efficiency. Mass

efficiency for power plant is defined as the main product needed for each energy

53


produced. The raw material used in out plant is molten salts and water. So there are

two mass efficiencies, one for molten salts and the other one for water, as shown

below.

Mass efficiency for water

Mass efficiency (water) =𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑖𝑡𝑦 𝑃𝑟𝑜𝑑𝑢𝑐𝑒𝑑

𝑊𝑎𝑡𝑒𝑟 𝑛𝑒𝑒𝑑𝑒𝑑

Mass efficiency (water) =1.080. 𝐸 + 08

𝑘𝐽ℎ

218.877𝑡𝑜𝑛ℎ

= 493,427𝑘𝐽

𝑡𝑜𝑛= 137 kWh/𝑡𝑜𝑛

Mass efficiency for molten salt

Mass efficiency (molten salt) =𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑖𝑡𝑦 𝑃𝑟𝑜𝑑𝑢𝑐𝑒𝑑

𝑀𝑜𝑙𝑡𝑒𝑛 𝑠𝑎𝑙𝑡𝑠 𝑛𝑒𝑒𝑑𝑒𝑑

Mass efficiency (molten salt) =1.080. 𝐸 + 08

𝑘𝐽ℎ

50.400𝑡𝑜𝑛

ℎ

= 214,286𝑘𝐽

𝑡𝑜𝑛

= 595 kWh/𝑡𝑜𝑛

As show in the calculation above, our mass efficiency is 137 kWh/ton water and

595 kWh/ton molten salts, meaning that for each ton of water needed, there will be

about 137 kWh energy (electricity) produced and for each ton of molten salts

needed, there will be about 595 kWh energy (electricity) produced, assuming that

100% work produced in steam turbine is converted into electricity in the generator.

3.6. Energy Efficiency

In this last section we can calculate the energy efficiency from the energy

balance calculation above. Energy efficiency is defined as the energy needed

divided by energy (electricity) produced.

𝐸𝑛𝑒𝑟𝑔𝑦𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 =𝐸𝑛𝑒𝑟𝑔𝑦 𝑃𝑟𝑜𝑑𝑢𝑐𝑒𝑑

(𝑆𝑜𝑙𝑎𝑟 𝐸𝑛𝑒𝑟𝑔𝑦 𝑛𝑒𝑒𝑑𝑒𝑑 + 𝑃𝑢𝑚𝑝 𝐷𝑢𝑡𝑦)= 4.123

54


From the calculation above the energy efficiency is 4.123. It means that for

each kWh solar energy plus pump duty needed, our plant can produce 4.123 kWh

electricity, again assuming that 100% energy produced from steam turbine is

converted into electricity energy.

55

CHAPTER IV

CONCLUSION

1. Indonesia has a lot of potential to use solar thermal energy as a renewable

energy source.

2. Raw materials that needed for the process are molten salt and water.

3. Based on criteria and considerations in selecting, we choose Pontianak,

West Borneo as our plant location.

4. Our plant capacity will produce 30 MW electricity

5. Parabolic Trough Collector is the most suitable type of solar thermal

power plant in Indoneisa based on some aspects, economically and

technically.

56

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