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CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

Alternative energy sources or renewable energy sources have found

its way in the global energy market in a major way, thanks to the increasing

conventional fuel prices, environmental degradation caused by the burning of

fossil fuels. A system that can combine the benefits of power and hot water

system can be an interesting proposition in an energy starved country like

India. The environmentally clean and benign energy system like the

Combined Heat and Power System (CHAPS) based on photovoltaic linear

concentrators can be an interesting option in urban India. Cost effectiveness is

an important parameter in measuring the success of any new technology. High

capital costs are the major reason of the NIMBY (Not in My Backyard)

syndrome when renewable energy options are considered. Hence ways to

present an environmentally friendly technique like the CHAPS system in an

acceptable price to the customer is an important prerogative. A great deal of

research efforts had been taken towards the development of such technique.

However such system has a long way to go before being commercialized for

common man’s use. In an effort to futuristic ventures on commercialization of

CHAPS system, an effort is made in this research to conduct a techno

economic analysis and identification of suitable markets for diffusion. A

detailed literature survey is presented pertaining to the earlier works regarding

the optimized energy markets and scenarios, conceptual development and

techno economics of hybrid PV/T systems especially based on concentrator

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photovoltaics (CPV), estimation of the market potential and the diffusion of

renewable energy products into the markets based on optimization techniques

have been reviewed.

The literature review is carried out mainly on the following areas

Energy planning in the Indian perspective

CHAPS systems based on linear PV concentrators

Techno economics of renewable energy systems

Life Cycle analysis of PV systems

Carbon credit mechanism for renewable energy systems

Market potential estimation and diffusion of the technology

into the market

2.2 ENERGY PLANNING

Energy consumption is one of the most reliable indicators of

development and quality of line in a country. World Energy council defines

Energy planning as “that part of economics applied to energy problems,

taking into account the analysis of energy supply and demand, as well as

implementation of the means for ensuring coverage of energy needs in a

national or international context” (World Energy council 1992). Energy

planning considers three major aspects namely political, social and

environmental based on past data and previous energy models if any.

There are three categories of Energy planning namely

1. Planning by models

2. Planning by analogy and

3. Planning by inquiry

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The first method comprises of econometric and optimization

models, of which the econometric one relies upon mathematical and statistical

methods. In general the method stresses the empirical testing of theoretical

models as well as the derivation of quantitative statements about the operation

of economic aggregates. The optimization model is more or less a prescription

by a model than a description of the model. This is the key approach in this

study as the real time energy system of a regional level planning model

prescribes the levels up to which renewable energy especially photovoltaic

systems can contribute in the near future.

There are some standard Energy models that are described

1) BESOM – Brookhaven energy system optimization model that

attaches all costs to energy flows and minimizes their sum

over one year.

2) TESOM–Time stepped energy system optimization model

makes consecutive BESOM type optimizations for single year.

3) MARKAL – Market allocation model is a successor of

BESOM and is a large scale, technology oriented activity

analysis model which integrates the supply and demand side

sectors of an economy.

4) MENSA – Multiple Energy systems of Australia is an improved

and recognized version of MARKAL that chooses the

combination of demand side and supply side technologies which

delivers energy at a least cost, averaged over a specified time

period.

5) EFOM – Energy flow optimization model provides an

engineering oriented bottom up model of a national energy

system and has been developed under the approval of the

25

commission of the European communities. The EFOM

describes the energy system as a network of energy flows, by

combining the extraction of primary fuels, through a number

of conversion and transport technologies to the demand for

energy services or large energy consuming materials.

The second method of energy planning is by planning based on

analogy that allows the simulation of the same quantity, with a time lag, in a

less developed country, through the use of leading case as a reference and the

knowledge of the time behaviour of a quantity in a more developed country.

The third and the last method emphasizes on inquiry methods like delphi

questionnaires to expert members and evaluating their answers for an accurate

chart of the future (Cormio et al 2003).

Energy models can also classified as optimization models, resource

allocation models, models based on artificial intelligence techniques and

forecasting models. In addition to MATLAB various tools can be used to

formulate and run the models in computers like LINDO, LINGO, TORA and

GAMS which are primarily optimization packages. Energy models are

broadly classified into two types as Bottom up model and top down model.

The former model is an “engineering type model” that typically includes

description of given energy related tasks which are to be accomplished at

minimum costs given by a given menu of technologies and also finds out the

reasons about how emission reduction task be accomplished at minimum

costs. On the contrary the top down model considers energy demand in the

form of functions that depends upon sectoral economic product and on energy

prices (Leo 2005).

Privatization of the most important energy sectors have turned the

monopolies into free and open competition between participating companies,

in particular, in the vertical structure where the generation, transmission and

26

distribution activities of energy supply systems are split (like the trifurcation

of the activities of Tamilnadu Electricity board), in addition to this there is a

growing awareness among the general public over the environmental aspects

of large conventional power plants and distributed generation technologies

and in furtherance energy planning activity has moved to a regional level

rather than the cumbersome national level. The above reasons stated had

changed the facet of the energy systems in most of the growing economies.

The idea of shifting the border of the energy system to a smaller area where

new constraints of varying nature can be tried and the evolution of new

scenarios could be of an interesting one.

2.2.1 Distributed Generation

Energy planning is thus considered as a powerful tool for showing

the consequences of certain energy policies which helps decision makers

choose the most suitable strategies to promote the spread of what is called as

Distributed Generation (DG) technologies that takes into account

environmental impacts and costs to the community. Distributed generation

technologies include electrical generation units and co-generation units that

are as minimal as a few kilowatts to tens of Megawatts. They are designed to

pump in power to high or medium voltage levels or serve the purpose of

single customers in the low voltage levels.

DG technologies can be installed close to loads thus minimizing the

cost of energy transmission; safety operation margins increase and has lower

environmental impacts. In the very best interest of the environment the DG

technologies are least polluting when compared to their conventional fossil

fuel counterparts.

Renewable Energy technologies are emerging as potentially strong

incumbents for their widespread use. In spite of a good number of reasons to

27

be a key player the renewable energy technologies are not yet fully integrated

into the power sector of growing economies. Some of the renewable energy

technologies based on their availability had gained sufficient inroads but the

significance is largely case wise. Along with renewable energy sources,

energy efficiency measures and energy efficiency improvement methods in

the demand side management are implemented to reduce the consumption

thus reducing the imports and cuts down green house gases. (Dicorato et al

2008). DG penetration and adoption of energy efficiency improvement

measures have found strong advocacy by the energy systems planners and

strategists (Directive EC 2001).

A comprehensive energy system can be represented qualitatively

and quantitatively in a simulated environment wherein various scenarios can

be developed pertaining to the conditions that are specified.

2.2.2 Energy planning in the Indian perspective

The results of an energy planning study (Ramachandra 2008) with

the help of decision support systems for the Uttar Kannada region in

Karnataka state revealed that the energy requirements can be satisfied by

Renewable Energy Sources (RES). The investigations concluded that

effective implementation of energy planning cannot be achieved without

decentralization and community involvement. An analogous energy planning

study based on an econometric model was developed for the neighbouring

state of Kerala falling in the Southern Region Electricity Board (SREB). In

this study the future energy requirements in the form of coal, petroleum

products and electricity are forecasted based on socio economic

considerations (Sharma et al 2002). Econometric models are generally based

on statistics and do not cover the optimization aspects of energy planning.

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An energy planning procedure based on linear goal programming

approach for the western Indian state of Rajasthan. The analysis highlights the

importance of decentralized energy planning and reports that a micro level

energy planning approach reduces the dependence on electric grid, minimizes

environmental impact and offers new opportunities for employment

(Deshmukh et al 2008).

In the spirit of decentralization of power sector, RES can play a

remarkable role as shown by a model developed with constraints like social

acceptance and reliability based on Delphi technique, which revealed that

25% of the energy needs of India in the year 2020-21 will be met by

renewable energy technologies (Iniyan and Sumathy 2003).

Decentralized energy planning involves considerable private sector

participation. A case study for the state of Karnataka regarding the private

sector participation in decentralized energy planning was conducted and

various scenarios were developed by Balachandra (2006). Moulik et al

(1992) developed a macro level energy planning model for three states in

India namely Gujarat, Kerala and Rajasthan and analyzed various scenarios

based on a reference energy system with different input and output options

and disaggregated the energy sectors. The advisory board of energy for the

Government of India used the study to deeply investigate the peculiarities of

energy demand and supply sector.

The environmental impact of the energy sector has to be taken into

account in an energy planning activity. A study conducted by Srivatsava et al

(2003) which lists that the emissions of CO2, SOx, NOx for the Tamil Nadu

state in the southern grid as 46.657 million tonnes, 0.364 million tonnes and

0.130 million tonnes per year.

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It is evident that electrical energy systems planning in India can

move further towards the goal of decentralization by increased private sector

participation and use of renewable based DG technologies. A model

comprising of the key participants in the regional energy grid is thus essential

to justify the cause of the distributed energy generation systems like solar

photovoltaic system in particular and their economics in the local market

conditions will be helpful in facilitating the penetration of the local market. A

bottom up energy flow optimization model by considering the demand and

supply options are helpful in determining the real time photovoltaic energy

requirements and other renewable energy requirements in a futuristic mode of

a region under consideration.

2.3 INTRODUCTION TO PV/T TECHNOLOGY

Photovoltaic thermal technology or photovoltaic/thermal (PV/T)

hybrid system is a combination of photovoltaic and thermal system

components which produces both electricity and thermal energy (hot water)

from one integrated component or system. Photovoltaic thermal technology

research is being carried out for the past 25 years with the aim to generate

photovoltaic and thermal energy simultaneously. It essentially has a

photovoltaic module in the front end and a plate/tube attached in the rear side

to remove the heat which is used for low temperature applications like water

heating, air heating . The heat removal indeed cools the PV cell which ensures

better PV performance. While it is proved by Zondag et al (1999) that the

individual performance of separate PV panels and thermal collectors is higher

than PV/T collector it is very much evident that two PV/T collectors together

produce more energy per unit surface area than one PV panel and thermal

collectors especially in applications when surface area availability is

significant which is a typical characteristic of PV/T systems.

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Figure 2.1 Classifications of PV/T systems

Figure 2.1 shows the alternative approaches to the PV/T systems.

PV/T systems are also referred as Combined Heat and Power systems

(CHAPS) systems. The diagram shows the various ways by which a CHAPS

or PV/T system can be realized based on the collector type, flow patterns,

nature of the solar cells, optics.

2.3.1 The Basics of PV/T Systems

The solar cell has a threshold photon energy corresponding to a

particular band gap which restricts the electricity conversion. The photon of

longer wavelengths striking the solar cells generates a lot of heat than that of

electron-hole pairs. More than 50% of the incident solar energy is converted

into heat which raises the cell temperature to at least 50oC above the ambient.

This can cause undesirable effects in the energy production of the solar cells

and results in the drop in cell efficiency (typically 0.4%/oC for crystalline

silicon cells) and permanent structural damage to the module if the thermal

stress remains for a longer period. It is evident from the above fact that, if the

PV/TSystems

AirWaterEvaporative Collectors

Monocrystalline

Polycrystalline

Amorphous

Thin film Solar cells

Flat Plate

ConcentratorSystems

Natural Flow

Forced CirculationSystems

Glazed

Unglazed panels

PV/TSystems

AirWaterEvaporative Collectors

Monocrystalline

Polycrystalline

Amorphous

Thin film Solar cells

Flat Plate

ConcentratorSystems

Natural Flow

Forced CirculationSystems

Glazed

Unglazed panels

Stand aloneBuildingIntegratedfeatures

PV/TSystems

AirWaterEvaporative Collectors

Monocrystalline

Polycrystalline

Amorphous

Thin film Solar cells

Flat Plate

ConcentratorSystems

Natural Flow

Forced CirculationSystems

Glazed

Unglazed panels

PV/TSystems

AirWaterEvaporative Collectors

Monocrystalline

Polycrystalline

Amorphous

Thin film Solar cells

Flat Plate

ConcentratorSystems

Natural Flow

Forced CirculationSystems

Glazed

Unglazed panels

Stand aloneBuildingIntegratedfeatures

31

cells are cooled the electrical efficiency would increase significantly. An

additional thermal energy as a result of the heat removal from the PV cells is

thus available for further use which leads to the development of PV/T Hybrid

technology.

Photovoltaics Thermal technology or thermo photovoltaics falls

into two broad categories as

a) Flat plate PV/T collectors

b) Concentrating PV/T collectors

While Flat plate collector appears like the normal thermal collector

with a PV panel attached to an absorber plate with tubes, the concentrator PV

(CPV) collectors aims at increasing the irradiance on a high performance PV

cell. The primary aim of using concentrator photovoltaics is to decrease the

area of solar cell. Besides using less area for the PV cells the concentrators

has an added advantage increased cell efficiency under concentrated light.

While having an advantage in terms of efficiency, CPV cells however have to

be tracked continuously for getting the direct beam radiation. This adds to the

cost and complexity to the overall system. As the cells are heated

continuously the increase in cell temperature causes a fall in the cell

efficiency and therefore has to be kept cool. The heat thus recovered from the

cells through cooling channels can be used as hot water for domestic

applications.

PV/T collectors can be classified on the basis of the cooling

mediums used.

a) Air cooled PV/T collectors

b) Water cooled PV/T collectors.

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Air cooled collector can be further distinguished based on air flow

pattern such as flow of air above the absorber, below the absorber and both

sides of the absorber in either single or double pass. Water cooled collector is

differentiated based on flow pattern such as sheet and tube, channel, free flow

and two absorber types (Charalambous et al 2007).

2.3.2 Concentrator Photovoltaic Thermal Technology

The main obstacle towards commercializing photovoltaic

technology is the high price of photovoltaic modules. This is due to high

material cost of the PV cells. In order to have a wider utility in the market the

price per kWh has to be reduced significantly, this is achieved by increasing

the system efficiency or reducing the total system price. If the system

efficiency is increased, the size of the system can be reduced; this is an

interesting proposition in highly populated urban areas where space is a

matter of concern.

Light concentration towards photovoltaic cells seems to be an

interesting option to increase the output from the Photovoltaic cells. Since the

PV module is the expensive component, the use of concentrated light

increases the electrical output of the cells and makes them function more

effectively provided that the price of the CPV cells are less than that of the

substituted PV cells. Concentrating Photovoltaic systems are also based on

the bending of light as Fresnel refracting type and parabolic reflectors. Most

of the concentrating systems use direct beam radiation and hence has to be

tracked.

Solar concentrators are divided into three broad categories namely

high concentrating systems have concentration ratios of 100 to 1000 which

could be achieved by two axis tracking. High temperatures obtained could be

used for generating electricity. Concentrated light can be used to irradiate

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extremely small PV cells which could prove cost effective. Medium levels of

concentrations (10 to 100 times) can be achieved by one axis tracking. The

heat generated due to this concentration levels are removed in the form of hot

water. The last form is low concentrator technology in which concentration

ratios of 1 to 10 is achieved. These concentrating systems can be stationary.

One interesting feature is that PV cells suitable for non concentrating

applications can also be used for these systems; this however needs cooling

for better cell performance. The commonly used geometry for these stationary

concentrating systems is the Compound Parabolic Collector geometry

(CPC’s). The cooling media used for most of the systems are either water or

air which is used for domestic hot water utilities, space heating applications or

powering absorption chillers.

2.3.3 Concentrating PV Cells

Silicon, the most commonly used material for concentrating solar

cells is generally designed to have low internal series resistance which is

largely due to the metal contacts and ohmic resistance in the semiconductor

material which in turn affects the fill factor of the cell. The other form of

defects is due to the shunt resistance which arises due to the defects in the PN

junction and also due to the current leakage along the edges of the solar cells.

Apart from silicon other materials like Gallium Arsenide (Ga As) too is used

for making concentrator PV cells. The Concentrating PV cell made at

Australian National University for the CHAPS system has an efficiency of

20-22% for 30x concentration. High efficiency cells are made by various labs

and research groups using multi junction cells. A peak efficiency of 37.4% is

obtained for 200x concentration by Takamoto on 2003 (Coventry 2004).

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Table 2.1 Various efficiencies attained by crystalline cells

Material Organisation Area(cm2) EfficiencyFZ UNSW(Australia) 4 24.7CZ ISE (Germany) 4 22CZ IMEC (Belgium) 95 16.7CZ BP Solar (Spain) 143 16.7CZ Several 100-140 13-15.5

mc-Si UNSW(Australia) 1 19.8mc-Si Sharp, Kyocera (Japan) 100,225 17.2mc-Si Several 100,225 11-13

The above Table 2.1 shows the various efficiencies attainable using

silicon crystalline solar cells. The Solar cells are made with different qualities

of crystalline silicon like Float zone, Czochralski (CZ) and multicrystalline

silicon. The highest efficiency of 24.7 was obtained by University of NewSouth Wales, Australia (Markavart 2000)

2.3.4 CHAPS based on PV/T Technology- Detailed Literature Survey

Combined Heat and Power Systems (CHAPS) refers to units that

can generate heat and power from a single input source of energy. They are

beneficial in many ways as the need of two such separate systems is avoided.

Theoretical and Experimental studies of PV/T collectors were documented as

early as 1970’s. Either water or air was used as cooling medium for thecollectors. Flat plate systems were largely considered for the study.

2.3.4.1 Air type PV/T Systems

Garg and Adhikari (1997) worked on a steady state model and

pointed out that the increased transmission losses due to additional front cover

do not justify the heat loss reduction and beyond a certain limit the single glass

cover collects more heat than double glass cover. Garg and Adhikari (1998)

further conducted transient simulation studies based on the climate in New

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Delhi and concluded that in terms of overall energy performance the double

glass configuration is better than the single glass cover for PV/T air collectors.

Zondag et al (2007) reported that the efficiencies of PV and

Thermal systems if considered separately are higher than a combined system

but PV/T collectors produce more energy than a single PV and Thermal

collector next to each other which is an important thing to be considered in

situations where space area availability is much significant.

Sopian et al (1996) developed a steady state model for comparison

of the performance of single and double pass PV/T air collectors in which

they concluded that double pass collectors performed better for the reason that

it resulted in cooling of the solar cells and reduction of front cover

temperature. Bergene and Lovvik (1995) proposed a detailed physical model

of a flat plate PVT water collector and investigated the fin width to tube

diameter ratio and found that the total efficiency was in the range of 60-80%.

Using the Hottel-Whillier-Bliss model, De Vries (1998)

investigated the steady state long term performance of various PV/T

collectors in Netherlands and concluded that single cover design was much

efficient than the unglazed collector and the double glazed ones.

Fujisawa and Tani (1997) on conducting an exergy analysis on

uncovered and single covered design indicated that exergy output density of

unglazed collector was much higher than single cover design for the reason

that thermal energy contains much unavailable energy. Harbi et al (1998)

conducted experiments in Saudi Arabia and found that high ambient

temperatures in summer resulted in 30% drop in efficiency in spite of good

thermal efficiency, whereas in winter months the PV performance was better

when compared to the thermal performance which deteriorated.

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Tripanagnostopoulous et al (2002) conducted out door tests on

PV/T collectors of both air and water type with different collector

configurations for horizontal mounted applications. They found that the

manufacturing cost of PV/T air collectors are 5% higher than the PV modules

separately, PV/T water collectors with poly crystalline Silicon cells costs 8%

more than the conventional PV modules. It was also suggested that collectors

must be placed in parallel rows to avoid shading and low cost booster diffuse

reflectors can be kept to increase radiation received on collector surface.

These experiments gave efficiencies in the range of 55% to 80% for PV/T

water collectors and 38% to 75% for PV/T air collectors. Othman et al (2007)

stressed that using fins on the absorber surface and c-Si cells pasted to the

other side helped to obtain meaningful efficiencies for both thermal and

electrical output of the hybrid collector. Raman and Tiwari (2009) studied the

annual thermal and exergy efficiency of PV/T air collector for five different

climatic conditions in India. It is observed that the exergy efficiency is 40-

45% lesser than the thermal efficiency under strong solar radiation, it was also

found that double pass option showed better performance than the single pass

option. Dubey et al (2009) studied various glass to glass and glass to tedlar

PV modules in which they developed analytical expressions for efficiency in

terms of climatic and collector design parameters. An efficiency of with and

without duct was found to be 10.4% and 9.75% respectively whereas the

percentage difference with glass to glass and glass to tedlar were 0.24% and

0.086% respectively with duct and without duct respectively.

2.3.4.2 Liquid type PV/T system

Huang et al (2001) studied a PV/T collector based on water with a

Direct current (DC) circulating pump and a storage tank. The collector was

constructed with commercial PV modules attached on a polycarbonate

absorber plate with square shaped box channels and found that the

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characteristic daily thermal efficiency is 38% maximum, the primary energy

saving reaching 38% and PV efficiency at 9%. Kalogirou (2001) modeled a

pump operated domestic PV/T water based system with water storage unit

along with a differential temperature controller. The results showed an

optimum water flow rate of 25 liters per hour caused an increase in the mean

annual efficiency from 2.8% to 7.7% and covers 49% hot water needs of the

house thereby increasing the mean annual efficiency to 31.7%. Saitoh et al

(2003) experimentally studied the performance of a single glazed sheet and

tube PV/T collector with brine as the coolant for which at constant flow rate

the cell efficiency was found to be 10-13% and collector efficiency was 40-

50%. The exergy efficiency was higher than that of individual PV and thermal

systems. The payback periods were 2.1 years for energy, 0.9 for GHG

emissions and 35.2 years for cash flows.

Sandnes and Rekstad (2002) investigated the energy performance

of Crystalline Silicon (c-Si) solar cells with and without glass cover pasted on

a polymer thermal absorber. The absorber was filled with ceramic granules to

improve the heat transfer to the flowing water and found that the presence of

solar cells reduced the heat absorption by 10% of incident radiation and

reduces the optical efficiency by 5%.The application of such collector is a

promising prospect for low temperature applications

Zondag et al (2003) developed steady state dynamic simulation

models of a serpentine PV/T water collector and checked the accuracy with

the experimental data. All the simulation results were agreeable up to 5%

limit with the experimental results at Eindhoven Institute of technology.

Chow (2003) in his explicit dynamic model analyzed a single glazed sheet

and tube collector performance in which the influences of fluctuating radiance

were studied. The steady state energy flow analysis revealed the importance

of good contact between encapsulated solar cells and absorber plate and water

tubing.

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Zarachenko et al (2004) stressed the importance of good thermal

contact between the solar cells and thermal absorber and introduced a new

substrate material with a 2mm aluminium plate covered by an insulating film

and pointed out that solar cells must be smaller than the size of the absorber.

Kalogirou and Tripanagnostopoulos (2006) examined the

thermosyphon and forced circulation options in PV/T water based collectors

based on Polycrystalline Silicon (pc-Si) and amorphous Silicon (a-Si) solar

cells in three different cities (Nicosia, Athens and Madison) . The results

showed that the electricity generation was higher in case of pc-Si whereas the

thermal performance was better in case of a-Si cells. The cost benefit ratio too

was higher in case of a-Si systems due to lower initial costs. There was also

an economic advantage owing to better performance in case of Nicosia and

Athens than Madison due to high availability of solar radiation.

Dubey and Tiwari (2008) examined the performance of a self

sustained single glazed PV/T water collector with a partial coverage of PV

module in New Delhi. The electricity generated by the PV module at the

water inlet end was used to drive a Direct current (DC) circulation pump and

concluded that better system thermal efficiency could be attained which was

in confirmation with an analytical model developed with a thermal collector

(without PV) and PV/T water collector connected in series.

Erdil et al (2008) constructed and tested a hybrid PV/T system

based on open loop domestic water pre heating system which produced

thermal energy of 2.8 kWh/day and electrical output of 7 kWh/day. The

payback time was estimated to be 1.7 years.

Vokas et al (2006) performed a theoretical analysis of PV/T water

based collector for domestic heating and cooling in three different locations at

Athens, Heraklion and Thessaloniki respectively and found that the thermal

39

efficiency of PV/T water collector is 9% lower than that of the purely thermal

solar collector due to less effect played by the PV laminate. Dubey and Tiwari

(2009) analyzed the thermal energy, exergy and electrical energy yield of

PV/T water based sheet and tube collectors by varying the collectors in use,

their series and parallel connections and weather conditions, it was concluded

that collectors partially shaded with PV cells are beneficial for those who

preferred thermal energy and collectors fully shaded with PV cells are

beneficial for those who preferred electrical energy as a priority.

2.3.4.3 Concentrator PV/T technology

Salim and Nunilo (1980) reported the longest operating

photovoltaic concentrator with 350 kW capacity and proved that the long term

performance shows that this system makes it a reliable source of power with

minimum operation and maintenance requirements. The system was operated

with various modes including stand alone and cogeneration mode with a

diesel generator. Module failures were due to detachment of solar cells from

the substrates rather than separation of cell to cell interconnections.

Teoh et al (1983) measured the current voltage characteristics of

conventional photovoltaic modules at 25oC, 45oC and 60oC for illumination

levels varying from 50 to 350 mW/cm2 for determining the optimum

concentration factor which was found to be 2 for a temperature of 45oC.

Mbewe et al (1985) presented semi empirical expressions for open

circuit voltage, short circuit current, fill factor and conversion efficiency of

silicon solar cells as explicit functions of optical concentration and

temperature. The agreement of the model was found to be 10% with the

experimental data.

40

Sharan et al (1986) made a theoretical analysis of an actively

cooled photovoltaic thermal solar concentrator, receiver system and studied

the variation of overall electrical output, thermal output, temperature of the

solar cells and coolant with the length of the absorber and found that the

overall electrical and thermal out put increase rapidly in the beginning along

the length of the absorber but after a certain distance the electrical and thermal

outputs are relatively small. This is due to the low coolant temperatures at the

early stages of the entry where much heat is removed from the absorber tubes.

Moreover the electrical power output is higher and thermal output is lower for

mass flow rate of 0.05 kg/s because at higher coolant mass flow rates the solar

cells operate at lower temperatures. Cooling is one of the key parameters of

concentrator photovoltaics since cells may experience short term efficiency

loss and long term irreversible degradation due to excessive temperatures.

Gee and Hansen (1986) emphasized the testing procedures used in

Sandia National Laboratories especially with single pulse flash tester which

has several advantages for testing the concentrator cells. The errors that occur

while testing cells at high irradiances or current densities and the assumption

of linearity for determining the irradiance were also discussed.

Maish (1986) discussed the procedures used to measure the

concentrator module and array performance at Sandia National Laboratories,

the method describes the method used to characterize efficiency as a function

of Direct normal radiation and heat sink temperature and also investigates the

uncertainties in the measured efficiency due to the independent variables by a

range of 5-8%, independent of instrument accuracy.

Hamdy et al (1988) presented a mathematical model in which

spectral beam splitters are used to extract the spectrum on which the PV

converter operates with peak efficiency and use the remaining spectrum for ahigh temperature collector loop that is thermally decoupled from the PV.

41

A comparison is made with a purely PV system and it is proved that the PV

converters with spectral beam splitters have high electrical efficiency than thepure PV systems under same concentrations.

Bhatnagar and Joshi (1990) carried out the field performance of

concentrating modules based on Silicon cells at 40X concentration for a

period of 3 years and had collected the module power output, temperature and

solar radiation data and found that such concentrating modules are not

suitable for the Indian conditions as the panels are prone to degradation of

2-3% from the average initial efficiency of 7% mainly due to reduction in

photo generation current and increase in series resistance.

Hein et al (2003) developed a solar concentrator system with one

axis tracking up to 300 suns using a parabolic trough mirror and a three

dimensional second stage consisting of compound parabolic concentrators and

characterized the second stage.

Coventry and Lovegrove (2003) developed a ratio between the

electrical and thermal energy output from a domestic style PV/T system.

Various methods like exergy, open market approach, renewable energy

market approach and environmental analysis were used and ratios were

developed for each approach using real time data and a ratio of 4.24 based on

renewable energy market approach was suggested. There existed a critical

energy value ratio below which a collector with amorphous silicon cells is

more effective than the one with crystalline silicon cell.

Segal et al (2004) used beam down optics using a hyperboloid shaped

beam splitter in a solar tower system for a large scale grid connected PV system

to split the solar spectrum. In this set up they used silicon solar cells at 55-60%

efficiency to produce electricity and the remaining spectrum is used to produce

thermal energy, the PV array produced 6.5 MWe of electricity and 11.1 MW of

thermal energy for a total solar heat input of 55.6 MW.

42

Coventry (2004) proposed a concentrating PV/T solar collector

operated at 37 suns (37x) concentration which yielded a thermal efficiency of

58% and electrical efficiency of 11% thereby resulting a combined efficiency

of 69%. The effect of non uniform flux was measured by moving a calibrated

solar cell (named as skywalker module) along the line of the receiver and it

was found that receiver support post shading, shape errors and gaps between

mirrors had a significant effect on the overall electrical performance.

Royne et al (2005) presented a review on various cooling

techniques especially those methods which are used in other industries like

nuclear reactors, Gas turbines and electronics industry. They stressed that

optimum cooling requirements differ between single cell arrangements, linear

concentrators and densely packed solar cells. Single cells typically need

passive cooling whereas densely packed cells under high concentrations needs

active cooling system.

Rosell et al (2005) combined the advantages of Photovoltaic

thermal collectors and low concentration technologies to develop a 11x

concentration dual axis tracking system based on linear fresnel concentrator.

Besides this an analytical model to simulate the thermal performance was

proposed and validated. The measured thermal performance was 60% and the

theoretical analysis confirms that the thermal conduction between the PV cells

and the absorber plate is a critical parameter to be considered.

The use of concentrator collectors instead of flat plate ones is to

increase the radiation intensity onto a smaller area since the PV cells are able

to handle higher currents thereby reducing material requirements and costs

but complex tracking mechanisms are to be addressed for reaping the benefits.

Segal et al (2004).

43

Kribus et al (2006) analyzed a novel miniature PV system (MCPV)

which produced 140-180 W of electricity and 400-500 Wth of heat. The

system can operate over a wide range of temperatures and provides thermal

energy not only for water heating but also for cooling, desalination and

industrial process heat. Current cost estimates show that the MCPV systems

can be produced at low, competitive cost and the net savings to the customer

can be better than the conventional Flat plate Photovoltaic (FPPV) systems.

Moreover the payback time is also shorter.

Vorobiev et al (2006) presented a theoretical study on a two stage

hybrid device that working with an energy flux concentrators and explored

two systems, one with the separation of thermal solar radiation and the other

without solar spectrum division and solar cells operating at high temperatures.

The former operates at low temperature and a concentration level of 1500

suns but requires a new solar cell that does not absorb or dissipate solar

radiation at infra red level and has a conversion efficiency of 35-40%. The

other type has a Ga As based single junction cell having room temperature

efficiency at 24% and concentrated at 50x which has a conversion efficiency

of 25-30%.

Sangani and Solanki (2007) developed a V-Trough concentrator

system for conventional one sun PV module to assess PV electricity cost

reduction and the resulting V trough concentrator (2 sun) system is tested for

seasonal, one axis tracking mode and two axes tracking. The output power for

a V-Trough concentrator system was increased by 44% when compared to a

flat plate PV system and the cost per unit watt of electricity generated is

reduced by 24% for the V trough system when compared to the same flat

plate PV system.

44

Mittelman et al (2007) suggested simultaneous production of

electricity and high grade thermal energy with concentrating photovoltaic

thermal collectors (CPVT). These collectors can operate at temperatures of

around 100oC. A single absorption cooling system operating with CPVT

collectors is investigated in technical and economic terms. The results showed

that under a wide range of economic conditions, the combined solar cooling

and power generation plant can be better than the conventional alternative.

Nilsson et al (2007) carried out tests on asymmetric compound

parabolic reflector system with two truncated parabolic reflectors made of

anodized aluminium and aluminium laminated steel respectively and the output

is calculated using MINSUN simulation program. The front reflector collects

most of the irradiation during summer and the back reflector collects the

irradiation during spring and fall. Both back reflectors deliver 168 kWh/m2 of

electricity compared to 136 kWh/m2 electricity for cells without reflectors

whereas the cells facing front reflectors deliver 205 kWh/m2 of electricity and the

estimated thermal output was 145 kWh/m2 glazed area at 50oC.

Castro et al (2008) proved the feasibility of industrializing silicon

concentrator cells manufacturing by setting up a pilot line capable of

manufacturing significant number of cells at 100x. The efficiency obtained

was 18.5% at 100X with 70% of cells having efficiency more than 18% and

costs ranged from 0.31 to 0.41 Euros/W.

Reis et al (2010) developed a theoretical model to describe the

response of V-Trough systems in terms of module temperature, power output

and energy yield wherein the module was adjusted to Double sun technology

which integrates dual axis tracker and mono crystalline Silicon modules. The

double sun technology increases the output to 86% the yearly energy yield of

fixed flat plate systems.

45

2.3.5 Techno Economics of Solar Energy Systems

Solar energy is one of the abundant sources of energy that drives

the various other energy forms of our planet and available almost every where

in varying amount Earth receives about 4000 trillion kWh of energy every day

in the form of electromagnetic radiation which is hundred times the energy

consumption of world in a year. The utilizable form of solar energy is either

as electricity or thermal energy form. Electricity is by direct conversion

through photovoltaic or by thermal-electric conversion by solar thermal

power plants. Thermal energy from solar collectors like flat plate and

concentrating systems are used for cooking, distillation and drying. Solar

energy is an abundant yet dilute form of energy widely used for power

generation in the PV and thermal route, water heating, drying, cooking,

heating and cooling of living spaces and refrigeration. Another major area of

usage is the hybrid systems where hot water and electricity are simultaneously

produced. One such earliest attempt was made in the eighties to derive the

formulas for determining the unit cost of energy of a concentrator

photovoltaic system. In such a system studies showed that the cost of useful

energy went on decreasing when both the electrical and thermal output of the

system are collected for useful purposes. (Sharan et al 1985).

Solar energy systems are not designed to meet the complete energy

demand of the application that is specified, such a systems if designed are

generally over sized systems resulting in claims that cannot be justified

economically. For this simple reason, solar energy systems are designed with

a storage system or an auxiliary system. Various cost components involved in

solar energy systems are initial cost of the system inclusive of installation

cost, land procurement costs, costs of sensors, control equipments, cost of

storage systems, collectors, balance of system costs etc, Annual cost of the

system that includes costs of fuel or electricity consumed by auxiliary energy

46

source, parasitic costs including electricity costs for pumps especially in

forced circulation systems, electricity costs for tracking systems in

concentrators.

Savings on fuel/electricity due to the usage of solar energy systems

is yet another factor in the solar energy economics, savings on fuel/electricity

results the annual savings which arises after deducting repayment of loan,

maintenance charges, local taxes. Savings accrued over the number of years

cumulatively over the entire life time of the device too can be calculated from

the savings of fuel mentioned above. One of the major figures of merit in the

economic analysis is the payback period which calculated the time frame

within which the initial investment is retrieved back. Economic analysis of

solar energy systems are important especially while one has to consider the

financing schemes as the initial cost of the systems are very high. This has a

significant influence in the customers even though such renewable energy

system promises low operating costs. Economic analysis is needed to justify

the best and the most economic route of energy supply among many other

options and to allocate scarce funds for the deserving option.

Emission reduction targets fixed under Kyoto protocol too compels

the developed countries to participate in local energy saving measures and

emission reduction projects in developing countries thus taking credits. Clean

Development Mechanism (CDM) facilitates such transactions making carbon

as a tradable commodity. Solar energy systems both thermal and photovoltaic

system thus has a bright and promising prospect in such international carbon

trading schemes as it has the potential to mitigate harmful emission and the

revenue generated under CDM would be a part of the financial benefits of the

system and can be included in the calculation of annual savings.

47

2.3.5.1 Solar photovoltaics

An attempt to obtain the minimum achievable electrical generating

cost from Photovoltaic system showed that a cost of 2.8 cents per kWh in a

plant at south west US for a module price of 22 cents per Wp. It is also evident

that the capital cost dominates PV system cost. (Sabisky 1996). An earliest

initiative for the financial evaluation of Solar lanterns for rural lighting in

India was done by comparing SPV lanterns with kerosene lamps and it was

evidently seen that using SPV lanterns for four hours a day for 300 days a

year would save about 60 liters of kerosene and the Net Present Value (NPV)

of the investment is positive as the kerosene price is more than Rs 5.12/litre

(Seemin and Kandpal 1996).

The economics of a standalone PV system was studied in

Bangladesh especially in remote and rural areas using NPV for which the life

cycle cost of the PV system is Tk 43.40/kWh for a family whereas this cost

becomes Tk 124/kWh for a village that is one kilometer from the grid thus

proving the economic viability of stand alone PV plants. (Bhuiyan et al 2000).

A model for economic evaluation of electrical energy production from PV

systems which takes into account the operational incomes and expenses for

implementation, operation and maintenance costs is suggested by Stampolidis

et al (2006) in which the value of discount rate was found to have a

significant effect on the PV performance. Production costs and energy costs

for 21 different reverse osmosis (RO) plants are compared and an equation is

proposed to estimate the unit production costs of RO desalination plants as a

function of plant capacity using both photovoltaic and thermal energy. Solar

generated electricity for desalination can be cost competitive from 1 US$/Wp

for electricity price of 0.06 US$/kWh in Egypt which faces acute water

shortage problem (Lamei et al 2008). Economics of Solar Photovoltaic

systems in Sagardeep Island (India) was studied by Moharill (2009) proved

48

that for a demand within 25 kW at a load factor of 30%, SPV will be a

competitive option when compared to conventional electricity.

Assessing a SPV pump for irrigation as a CDM measure revealed

that maximum potential could be achieved only with supportive policies by

the government (Purohit and Michaelowa, 2008). Energy pay back analysis

was studied for a stand alone PV system based on an optimum sizing

methodology for two different insolation areas and different PV options.

The study revealed that best sustainable energy solutions should use CdTe

or mc-Si panels for which CdTe systems had an Energy Pay back period

(EPBP) of 15 years and the battery component of the stand alone system plays

a significant part in the system life cycle energy requirements (Kaldellis et al

2009). A photovoltaic powered domestic refrigerator of 165 liters was tested

and simulated with RET Screen software and a Coefficient of Performance

(COP) of 2.102 was observed at 7am, the system can be economically viable

only if carbon trading, initial subsidy or reduction in component cost is

considered. (Anish et al 2009). Several dissemination models including the

ownership and free for service/rental model based on centralized solar

charging station concept for CFL and LED based designs of solar lanterns

available in India are analyzed. It was found that Central charging station is

not viable even with 100% subsidies as the people felt that owning the solar

lantern to be a better option than paying rent which was not more effective

than the daily cost of owning the system.(Chaurey and Kandpal , 2009).

2.3.5.2 Solar thermal systems

Drastically increasing electricity demand and availability of

abundant land area with sunshine makes India an ideal country for solar

thermal power generation and a techno economic analysis revealed that solar

thermal electricity as an economically viable option with high insolation

levels and the capital is available at low interest rates. The Levelized

49

Electricity cost (LEC) for a centralized energy generation is 4.6 to 15.8

cents/kWh and 11.7 to 39.9 cents/kWh for decentralized power generation.

(Beerbaum and Weinrebe 2000).

Monte Carlo method was used for reading solar radiation data and

further simulations on a linear parabolic concentrating systems produced

electrical energy 2501 kWe and thermal energy of 13000 kWhth annually and

a present worth of savings amounts to US$ 5787 and a payback of 12 years is

estimated compared to a natural gas based system (Bakos and Tsagas 2002)

An economic analysis of solar water heating systems with flat plate

technique showed that for up to 20% interest rate, solar energy systems are

preferable over its alternatives but not preferable in case of a highly

inflationary market (Ismail 1995).

Cost benefit analysis for solar water heating systems in comparison

with the conventional water heating systems is done in Greece which revealed

that the use of solar collectors resulted in a significant net social benefit if

substituted for electricity or diesel but not for natural gas (Diakoulaki et al 2001).

A similar study was made for the country of Jordan where a Gas

geyser system is compared with solar hot water systems. Solar hot water

systems are more economical as long as electricity is used to heat water for

less than 120 days. (Kablan 2004) Potential number of Indian households

capable of investing in DSHWS (domestic solar hot water systems) is found

out to be 45 million and it is based upon various factors like income

distribution of the country, capital cost of the systems and interest rate

charged on loan provided for the purchase. Seasonal and diurnal variations of

ambient temperatures are also identified. (Chandrasekhar and Kandpal 2004).

50

With the emergence of solar desalination as a promising renewable energy

powered technology, combining the principle of humidification and

dehumidification with solar desalination results in an overall increase in the

efficiency of the desalination plant (Said et al 2006).

A comparison between open sun drying and techno economic

evaluation of hybrid PV/Diesel/Battery power systems in desert environment

was analyzed using NREL’s HOMER software, for a 80kWp PV system with

175 kW diesel system and a battery storage yielded a PV penetration of 26%

and the cost of energy was found to be 0.149 $/kWh for Saudi Arabia.

(Shaahid and Elhadidy 2007). Dissemination of Solar water heaters will not

reach its maximum potential in another 25 years. However Clean

development mechanism (CDM) would help achieve this target quickly when

compared to the current diffusion if supportive policies are introduced.

(Purohit and Michaelowa 2008).

In the Life cycle cost analysis (LCA) for a FRP based solar

parabolic trough concentrator systems, the present worth of life cycle solar

savings for the PTC hot water generation system when it replaces the

conventional electric water heating system in a restaurant attains a value of

Rs 23,171 after 15 years.(Valanarasu and Sornakumar 2008).

Techno economics of Solar water heaters with electrical back up in

Malaysia affirmed that the annual cost of electric heaters is more than that of

annual costs of SWHS and hence it is advantageous for a family to use solar

water heater after 4 years. An economic study on solar powered desalination

revealed that the cost per m3 of potable drinking water was $15/m3 for small

systems and $18/m3 for larger systems based on membrane distillation. The

life time of the membrane is a key factor in determining the water production

cost (Banat et al 2008).

51

Performance of an indirect solar cabinet type dryer is studied for

drying bitter gourd to a moisture content of 5%, the drying time reduced to 6

hours from the conventional open sun drying which takes about 11 hours. The

drying cost is Rs 17.52 per kg instead of Rs 41.35 in case of electric heating,

the cumulative annual savings turns out to be Rs 31,659 which is much higher

than the capital cost of the dryer and the payback is found to be 3.26 years

(Sreekumar et al 2008)

An economic feasibility study conducted in Cyprus regarding the

use of parabolic trough collectors in which a parametric cost benefit analysis

is carried out by varying parameters like plant capacity, capital investment,

availability and emission trading system price. The size of the solar thermal

plant if increases, makes the investment more attractive and economically

feasible in the Mediterranean region. (Poullikas 2009)

Organic Rankine Cycles (ORC’s) are a novel idea used for the

utilization of low grade heat. The typical application ranges from power

production to fresh water production. Systems based on solar energy are

typically suited for Organic Rankine cycles. An economic analysis of a two

staged solar operated rankine cycle for reverse osmosis desalination was

conducted in Greece where the developed system was briefly analyzed and

the specific fresh water cost was 7.48 Euros/m3 and cost of energy was found

to be 2.74 Euros/kWh. A comparison was also made with PV based RO

system. (Kosmadakis et al 2009).

2.3.5.3 Solar PV/T systems

Deriving both thermal energy in the form of hot water and

electricity from a single system, is an attractive option which can be effective

for conserving space, especially in urban areas. In the past decade many

researchers have contributed towards the development of such systems using

52

high performance PV cells up to 40x concentration ratio cooled either by

water or air. The recovered low grade heat is utilized for domestic purposes.

A techno economic analysis taking into consideration various system

parameters is essential to justify this novel aspect for potential market

penetration in a developing country like India. Moreover, the fossil fuel saved

would ensure monetary benefits to the user and environment. Similar studies

have been conducted in recent years, regarding the techno economics of solar

hot water systems and PV systems separately.

The foremost barrier of any renewable energy technique like the

CHAPS system is the high capital cost of the system along with accessories

like the Balance of System components (BOS). The availability of

subsidies for certain categories of solar energy systems proves the point in

pushing forward new and innovative energy delivery systems like CHAPS

for commercialization and market penetration. The availability of 40%

subsidy with an upper limit of Rs. 40,000 in the case of solar generators and

Rs.10,000 subsidy for 74 W modules in the case of solar home systems

proves the point in pushing forward new and innovative energy delivery systems

like CHAPS for commercialization and market penetration (IREDA 2011).

With growing concerns about the emissions due to electricity

generation, cutting edge technology like the CHAPS system that meets both

the PV and Thermal energy needs is necessary to reduce emissions. An

Economic analysis of solar energy system like the CHAPS is important,

especially when one has to consider the financing schemes as the initial cost

of the systems are very high. This has a significant influence on the customers

even though such renewable energy system promises low operating costs. The

CHAPS system as a new prospective candidate for carbon credits and its

wider market diffusion would save the emission of Green House Gases and

help in further cost reductions.

53

The techno-economic analysis of a combined PV and Thermal

system is first reported in the literature by Gibart (1981), in which

technologies for cell bonding, cell interconnections and mirrors were

developed and it was reported that the peak photovoltaic efficiency reaches

71% of a flat PV collector and thermal efficiency bettering the efficiency of a

flat thermal collector, due to the fact that the efficiency calculations used

direct beam radiation values for a combined photovoltaic and thermal system.

Gibart (1981) further demonstrated that hybrid PV/T collectors will

be competitive with separate PV and Thermal systems only when the ratio of

the concentrator cell cost to the usual cell cost decreases to a reasonable

value. The unit cost of energy produced in a combined heat and power system

based on concentrating solar power and its variation with respect to the

concentration ratio was studied by Sharan et al (1985). The authors concluded

that the unit cost of energy was low in the case of an actively cooled system,

when compared with that of a passively cooled system and the appropriate

utilization of the electrical and thermal output resulted in a decrease in the

unit cost of energy with an increase in the concentration ratios.

Sharan et al (1985) compared a flat photovoltaic array with a

concentrator photovoltaic system, and they found out that, to make the latter

more cost effective than the former, a good quality solar concentrator at

reasonably low cost and cheaper concentrating type solar cells are needed.

Highly efficient solar cells even at lower concentration ratios can generate

electricity better than simple photovoltaic arrays.

The balance between PV and thermal outputs from the CHAPS

system is to be considered while analyzing the techno economics. A suitable

energy value ratio must be used to divide the thermal output to make it

equivalent to the electrical output of the system. This is due to the fact that

54

electrical and thermal energy are not equally useful, electricity being the

superior form of energy in a given system. A wide range of electrical to

thermal energy ratios were determined. It takes the lowest value of 1 when

both outputs are considered as equally important, whereas a value of 2.5 is

assumed for a coal station efficiency of 40%, and 4.2 is assumed for the

renewable energy market approach. Thus, the assumption of the energy value

ratio, is case specific for any particular application (Coventry 2004).

The seasonal variation in the use of hot water systems is another

important factor while analyzing the techno economics of a hot water system.

Effective capacity utilization thus plays a major role in its techno economics.

(Chandrasekhar and Kandpal 2004).

2.4 LIFE CYCLE ANALYSIS

Life cycle costing or Life cycle analysis (LCA) is the investigation

and evaluation of the environmental impacts of a given product or service

caused or necessitated by its existence. It gives a holistic approach towards

the assessment of raw material production, manufacture, distribution, disposal

of wastes and transportation. Moreover life cycle analysis helps in optimizing

the environmental performance of a single product or the company as a

whole. Life cycle analysis is a technique for assessing various aspects

associated with development of a product and its potential impact throughout

the products life time. Carbon dioxide payback time is an important outcome

of the life cycle analysis to understand the impact of the electricity generation

on the environment by the device whether a new and novel one or which are

already in service. This will also help in manufacturers to reduce the energy

requirements for the production processes.

55

Life cycle analysis enables one to understand the system

performance under various criteria’s including emissions, energy use, costs

and decision making and would aid the government in setting up regulations

and tax benefits for worthy projects (Gaines and Stodolsky 1997).

Even though termed as the sunrise industry, the photovoltaic industry

had been in the infancy for a quite long time and had teething problems

regarding the failure of cost reductions and grossly over estimated market size.

Moreover the industry is fed with a lot of subsidies and grants. It is high time

that the industry is subjected to rigorous economic analysis, on par with other

industries to identify the financial and economic barriers. In this way the gap

between actual and potential deployment can be a starting point for innovative

policies. (Guru 2002, Oliver and Jackson 1999, Bradley 1997)

New and emerging technologies like solar cells based on Quantum

Dots are analyzed based on life cycle analysis. An initial estimate based on

10% efficiency and a life time of 25 years for the fact that new and emerging

techniques initially tend to have low efficiencies and lifetime. It is found

that Net Energy ratio, Energy Pay back time (EPBT) and CO2 generated for

Quantum Dot cells are less than that of conventional PV modules

(Azzopardi and Mutale 2010).

A comparison of a single slope passive and hybrid photovoltaic

active solar cells based on their annual performance is estimated by

considering various parameters like interest rate, maintenance cost and life of

the system. It was found that the comparative cost of distilled water produced

from passive solar still (Rs. 0.70/kg) is found to be less than hybrid (PV/T)

active solar still (Rs. 1.93/kg) for 30 years life time of the systems. The

payback periods of the passive and hybrid (PV/T) active solar still are

estimated to be in the range of 1.1–6.2 years and 3.3–23.9 years respectively,

56

based on selling price of distilled water in the range of Rs. 10/kg to Rs.2/kg.

The energy payback time (EPBT) has been estimated as 2.9 and 4.7 years

respectively for the passive system and the PV/T system. (Shivkumar and

Tiwari 2009).

The accumulated primary energy consumption for the construction

of a photovoltaic power plant ranges from 13,000 to 21,000 kWh/kWp and

would be between 7,000 to 12,000 kWh/kWp in the next five years as

technology improves. Moreover a specific emission factor of

0.62 kg-CO2/kWh is considered. The CO2 emissions are 3.360 kg-CO2/kWp

and 5.020 kg-CO2/kWp for amorphous and crystalline silicon respectively

(Schaefer and Hagedorn 1992). The energy payback period of mono

crystalline wafers of p-type silicon which were largely imported, is

approximately 4 years. The results were obtained by an energy analysis of

solar PV production in India (Prakash and Bansal 1995).

Off grade silicon supplied from semiconductor industries were used

for single crystalline silicon (c-Si) PV cells and residential PV systems to

constitute a 3 kW residential PV system on a roof top connected to the utility

grid. An annual energy generation of 3.47 MWh/year was realized and an

indirect CO2 emissions of the PV systems using the c-Si photovoltaic cells made

up of the off grade Si cells was estimated as 91 g-CO2/kWh (Kato et al 1997).

A gradual reduction of the CO2 emissions from 50-60g/kWh to 20-

30g/kWh could be realized in the future for an investigation of energy

requirements and CO2 emissions for the production of c-Si and thin film

modules along with the BOS components. The energy payback period was 2.5

to 3 years for roof mounted system and 3-4 years for multi megawatt ground

mounted system. (Alsema 2000).

57

A life cycle analysis of the Balance of System components (BOS) of

the 3.5 MWp multi crystalline PV installations at Tucson Electric Power (TEP)

Arizona, USA, using both mc-Si and thin film PV technologies showed that the

total primary energy in the BOS life cycle is 542 MJ/m2 of installed PV modules

and the energy payback period is 0.21 year whereas the GHG emissions during

the life cycle of the BOS are 29-31 kg-CO2/m2. (Mason et al 2005).

A comparison of a distributed 2.7 kWp solar PV system in

Singapore revealed that, based on the functional unit of 1 kWh of electricity,

the life cycle energy use would reduce to 2.2 MJ/kWh and Energy payback

time would be 4.5 years and the GHG emissions would be about 165 g-

CO2/kWh. (Kannan et al 2006).

Two different payback times namely energy payback time and

carbon dioxide payback times are determined based on the life cycle analysis

for a Photovoltaic system and a Photovoltaic/Thermal system (PV/T) using

SimaPro 5.1 software of which, a PV/T system with glazing, operating at the

lowest temperature yielded a payback time of 0.8 years (Tripanagnostopoulous

et al 2005).

A life cycle analysis of the Indian photovoltaic industry was

analyzed in a three segments namely the government, commercial and

consumer segments which were likely to grow in different proportions in the

future. Government procurement will remain steady and shall be dictated by

political convenience whereas the consumer segment will enjoy a support in

the form of integrated delivery chains from cell to the utility at home, service

provision would continue to be the revenue earner as the margins from the

sale of module would dwindle. The solar PV market would grow on support

from the commercial finance from rural and co-operative banks rather than on

subsidy programs. It is moreover stressed that subjecting the photovoltaic

industry to rigorous economic analysis alongside the mainstream industry

58

marks a turning point and to look in a different perspective to reduce the

subsidies thus making the Indian solar photovoltaic market a truly competitive

one. (Srinivasan 2007).

2.5 COMMERCIALIZATION OF CONCENTRATOR

PHOTOVOLTAICS

The research on concentrator photovoltaics began as early as the

1970’s during the oil crisis, Sandia national laboratories managed the research

through the funding from US department of Energy and various options

including reflective, refractive and luminescent concentrators were tried.

Large companies like Motorola, RCA, GE, Martin Marietta, Entech, Boeing,

Accurex, Spectrolab were involved in developing these systems. The

fundamental research was supported by Stanford, Arizona state university and

Purdue University.

Coming out of the research laboratories, several successful large

scale demonstration plants were installed, the notable ones were 350 kW

Solares project in Saudi Arabia and 300 kW Entech system at Austin, Texas.

With the end of oil crisis, as the price of oil and natural gas plummeted and

governmental funding became scarce, the concentrator photovoltaic

programmes were shelved till 1990 when US Department of Energy(DoE)

created a concentrator initiative by bringing cell and module manufacturers

together till 1992. About 40 million US dollars were spent towards the

research which is infinitesimally minimal when compared to the research

funding for flat PV technologies.

Alpha Solarco, in collaboration with its chinese partners developed

glass Fresnel lens to replace acrylic lens using the 3M ‘Lens film’ process.

Point focus Fresnel lens up to 20 kW capacity was developed by Amonix Inc

at Stanford University. Ben gurion University in Israel has developed a large

59

water cooled dish PV system. A 480 kW trough based concentrating PV

system was built at Canary Islands called as the EUCLIDES project which is

a joint venture between BP solar and Polytechnic University of Madrid. The

system uses passive cooling by heat sinks and the generation costs are

projected to drop to 13 cents/kWh. Entech projects a levelized electricity cost

of 7-15 cents/kWh at a production rate of 30MW/year based on line focus

Fresnel lens PV systems with their newest fourth generation modules at 15%

efficiency. Franhoufer Institute in Germany had demonstrated an efficiency of

24% with GaAs cells and Fresnel module efficiency of 19%.

Ioffe physical-Technical institute is working towards GaSb and

AlGaAs cells for multijunction applications. NREL has developed 30%

efficient GaInP/GaAs cells at 150x concentrations suitable for space industry.

Unit costs projected as low as 4-6 cents/kWh at 100MW/yr by one sun cells at

10X concentrations are tried by Photovoltaics international, LLC. A single

close packed silicon array developed by Solar Research Corporation produced

more than 200W with 22% efficiency at 239 suns and Ga As module

produced 85W at 18% efficiency at 381 suns. Peak efficiencies as high as

27% for 100X concentration and 26% for 250X concentrations is attainable

for concentrator silicon solar cells for point focus Fresnel lens applications

built by Sun Power Corporation. Innovative grooved back reflectors are used

for enhancing reflection in a static concentrator for rooftop applications are

developed by the University of New South Wales. Tokyo A & T university

has been researching two (1.65x) and three dimensional (2x) refractive static

concentrators which are capable of accepting diffuse light. (Swanson 2000)

The Australian National University has developed low cost Sliver

Cells which reduces 50% cost of silicon wafers and 25% cost of wafer

processing to minimal values which leaves just the 25% costs involved in

packing and forwarding. This makes the Sliver cells more economical and

60

compatible to the ordinary PV cells. The efficiency of mature sliver cells is

likely to be 20 % (Blakers 2009).

Castro et al (2008) have proved an industrial process for a 100x

concentration solar cells which can attain 21% efficiency by modifying anti

reflection coating, annealing process and back contact. Dicing and manual lift

off process can be automated which are reported to be the weakest link in the

production line. This yielded an average efficiency of 18.5% at 100x

concentration with 70% of the cells having an efficiency greater than 18%.

2.6 FINANCING OF RENEWABLE ENERGY TECHNOLOGIES

High capital costs of renewable energy systems when compared to

their conventional counterparts are the foremost and important barrier towards

its dissemination and acceptance among the general public and also forbids

the potential commercial and industrial users from considering the usage of

renewable energy systems for meeting their energy requirements. Some major

disadvantages like higher risks and the difficulty in establishing the extent of

the risk by the financing institution, smaller project size, smaller size of the

renewable energy industry when compared to their conventional counterparts

and somewhat uncertain policies of the government cumulatively creates a lot

of difficulty in obtaining the financing at reasonable costs.

2.6.1 Key Elements of Financing and Potential Parties to Financing

Kandpal and Garg (2003) elaborated some key elements of

financing that includes equities which has the provision of money in return of

partial ownership of the project which grants the right to receive payments for

the usage of money for financing the project and also the ownership control,

debts by which a borrowed money is repaid with the pledged interest amount,

grants which provides money, goods and services without any expectation in

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return and by this means the party providing the grant aims for public good

than the private gain, insurance by which some value of money is given for

specified circumstances which also covers the risk undertaken in

implementing the project, tax incentives by which reduces the liability of

payable tax for the investor and regulations like statutes, orders and

administrative regulations which aids in the development and dissemination

of renewable energy systems. Potential parties that can finance renewable

energy technologies include banks, financing companies, individual investors,

limited partnerships, R&D partnerships, manufacturers of Renewable energy

systems, Energy management companies, organizations involved in power

generation, transmission and distribution, Insurance companies, venture

capital firms and leasing companies.

2.6.2 Initiatives by the Government of India

Chandrasekhar and Kandpal (2005) consolidated the Government

of India’s measures taken to promote solar energy technologies in the form

of fiscal and financial incentives. Soft loans are given through IREDA

(Indian Renewable Energy Development Agency) by interest subsidy

schemes. Along with IREDA nationalized banks and financial institutions

also are involved in the financing of solar energy (Renewable energy)

technologies. Fiscal incentives like income tax benefits (accelerated

depreciation claimed in the first year of installation of the renewable energy

systems) , exemption or reduction in excise duty (electricity generated from

renewable energy sources is not subject to central government’s excise tax),

income tax holidays (income generated during the establishment of new and

renewable energy facility in the first five year are not subject to the central

income tax) and central sales tax and customs duty exemption on import of

spare parts and related equipments. In addition to these potential incentives

like capital gain investment related income tax benefits and income tax

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benefits to the user on the amount of interest paid on the loan availed for

purchasing solar energy technologies are also provided. State governments are

urged by the Ministry of New and Renewable Energy (MNRE) to announce

general policies for the dissemination of renewable energy technologies. The

efficacy of these schemes of fiscal incentives and subsidies were aimed at

reducing the investment cost of the investor so that the availability of these

technologies is well within the customers reach.

The recent launch of the Jawaharlal Nehru National Solar Mission

(JNNSM) by the Government of India to meet the nation’s energy security

challenge aims at setting up a favorable environment for solar technology

penetration at centralized and decentralized levels which had to be worked out in

phases. The first phase, set to end by March 2013 will focus on off grid (stand

alone) systems and other hybrid systems to meet the supplement power heating

and cooling requirements. These systems still require interventions to bring down

the cost. Viable business models are essential to justify the cause. Various off

grid PV systems up to 100 kWp per site and off grid and decentralized solar

thermal applications to meet the supplementary power, heating and cooling

arrangements are covered under this scheme. The MNRE provides financial

support in the form of subsidies up to 30% and/or 5% interest bearing loans. The

benchmark price for photovoltaic systems with battery back up support is

considered as Rs 300/Wp. The boundary conditions for support to off grid solar

PV applications are Rs 90/Wp with battery storage and Rs 70/Wp without battery

storage. The JNNSM however had laid down guidelines for the minimum

requirements for off grid/stand alone solar power plants which include

standards description and numbers for modules, power conditioners, charge

controllers, batteries, switches/circuit breakers/ connectors, junction boxes,

cabling and installation practices. Further guidelines for roof top PV and

small solar power generation programme which connects them to low voltage

33 kV are also available under the JNNSM.

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2.7 A SURVEY BASED ESTIMATION OF TECHNICAL,

MARKET AND ECONOMICAL POTENTIAL OF

CONCENTRATOR PHOTOVOLTAIC BASED CHAPS

SYSTEM

Social acceptance of renewable energy systems are three

dimensional namely Socio political acceptance, Community acceptance and

Market acceptance. The concept of Market acceptance so far has received less

attention as compared to the other two dimensions. Socio political acceptance

and community acceptance had been widely used to understand the

contradictions between general public supports for renewable energy

innovations. (Wustenhagen et al 2007). Rogers technical adoption model

claims that adoption comes about through a decision making process

occurring in stages- knowledge, persuasion, implementation and confirmation

and that can be traced to a number of factors like relative advantage,

complexity and triability. (Alexandra 2007). About 80% of the commercial

energy needs in India comes from the fossil fuels and they account for about

64% of the total primary energy. Scarcity of fossil fuel reserves and ever

increasing energy demand and awareness in the climate change has pushed

the clean energy forms “Renewables” to the forefront. Renewable energy

technologies are set to play a key role in the future energy mix of the country

(Pillai and Banerjee 2009). Renewable Energy based installations make up a

mere 6% in the overall installed capacities of the country and India aims to

achieve a further 10% growth in renewables by 2012 (Daniel et al 2009).

There exists a large gap between the available maximum potentials for

renewable energy sources and the current levels of dissemination a thoughtful

study is therefore essential to find the possible causes of such

mismatch.(Chandrasekar and Kandpal 2007) Of all the Renewable energy

technologies in the country Solar Energy has a relatively mature market in the

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country as it has the capability to reach the consumers especially the common

man much easily than other renewables like wind energy and biomass energy.

The former needs specific sites with wind potential and the later needs a

continuous supply of raw materials. Solar energy systems are highly modular

in nature and can be easily installed. The average global radiation falling on

the country ranges from 1200-2300 kWh/m2 with most of the country has a

radiation greater than 1900 kWh/m2 with about 300 clear sunny days.(MNRE

Annual Report) makes solar energy a significant energy source in the

Renewable energy mix. In spite of having a promising prospect solar energy

systems are still on the back foot when compared to the other significant

energy resources like wind and biomass energy systems due to various

factors. A Study based on the Analytical Hierarchy Process in which key

determinants like cost, efficiency, environmental impact, installed capacity,

estimated potential, reliability and social acceptance are compared with

respect to wind, biomass and solar energy and the ranking showed that wind

and biomass energy edged out solar energy. Cost and efficiency were found to

be the most important criteria of decision making in India when it comes to

the point of selecting the renewable energy technologies. The study further

revealed that incentives and policies of the government play a key role in the

social acceptance factor of a particular energy system (Daniel et al 2009).

Australia and India Scientific Research Fund (AISRF) and

Department of Science and Technology (DST) had enabled a collaborative

research between both the countries for the estimation of the market potential

of Solar Linear Concentrators in India. Australian National University

(ANU), Canberra significantly contributed in the technology development of

a Solar Linear concentrator which generates both PV and Thermal energy

from a single system.

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This combined Heat and Power System (CHAPS) system is an

interesting option when there are limitations in the availability of installable

space especially in the densely populated urban areas in India. This study is

aimed at determining the level of acceptance of such system in the typical

Indian context. A detailed questionnaire based survey on an interview basis is

carried out to determine whether such innovative energy option is viable

among the Indian General public. The study is aimed at locating the causes of

NIMBY (Not in my Backyard) syndrome which are classically associated

with renewable energy products. NIMBY syndrome represents a social

dilemma or a game situation for the customers. A similar study was

conducted in Australia regarding the tourist’s perception about the wind

energy technologies targeting a candidate pool from four different tourist

accommodation resorts in Australia. (Dalton et al 2008).

2.8 SUMMARY OF THE LITERATURE REVIEW

In this chapter the works carried out by various researchers in the

area of Energy models, hybrid PV technologies and that of the specialization

in the concentrating PV technology are highlighted. A nascent technology like

concentrating PV technology needs to be analyzed in the technical and

economic perspective to justify its part in the renewable energy market

(scenario)

The following conclusions can be drawn from the literature survey

1) A regional level model to predict the futuristic PV installation

needs are required. Of the many energy models that were

described, the energy flow optimization model (EFOM)

provides a clear insight by considering the balance of supply

and demand side management through various conventional

and non conventional energy conversion routes.

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2) Photovoltaic systems and the innovativeness of employing the

PV/T systems are described and the way in which

concentrating photovoltaics could be a suitable candidate in

the PV market is analyzed by considering the technical and

operational aspects of the system. Participation of CPV in

domestic sector is not yet explored and it has to be justified

economically for possible commercialization.

3) Literature survey reveals that the techno economics of

photovoltaic systems had been dealt separately so far and the

techno economics on hybrid PV/T systems were limited to flat

PV/T systems. The techno economics of concentrating

photovoltaic systems in Indian market conditions needs to be

investigated.

4) A literature review on the Life cycle analysis is carried out

with respect to the solar based system which reveals the real

time costs of the system under consideration. The life cycle

analysis with respect to the combined heat and power system

based on concentrating photovoltaic systems had not been

investigated so far.

5) Commercialization of such a system needs financial support in

the form of subsidies and incentives for which a life cycle

analysis can provide a vital input, various support policies of

the government is highlighted.

6) Market survey is essential before a product launch to find the

acceptance of the product in a market; a market survey reveals

the general trend of the customer mindset and the way in

which the renewable energy is viewed by them in general.

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It is thus inferred from the literature review that a significant

amount of work related to techno economics is carried for photovoltaic

systems and solar thermal systems separately and even for PV/T hybrid

systems based on flat panel solar PV technologies but work related to techno

economics of concentrated photovoltaic technology are meager and thus

throw open interesting avenues for investigations. The present research work

is aimed at analyzing the techno economics of CHAPS based on

concentrating PV technology suitable for Indian market conditions.