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CHAPTER - 4

Exergy Analysis of Solar Photovoltaic Systems

4.1 Introduction

Due to the growing concern and awareness of environmental issues among

the scientific community, power generation from renewable energy sources,

particularly solar energy has become significantly important for the last few decades.

Solar energy due to its intermittent nature is not available for a long time during the

day. Its durability varies from country to country and place to place. Solar energy

reaching to the surface of the earth can be utilised directly in two ways viz. directly

converting the solar radiation to the electricity for useful purposes by the means of

solar photovoltaic (SPV) modules or by heating the medium source for low

temperature heating applications. Photovoltaic module is not only an expensive but

also an essential component of any PV system and therefore its thermal assessment

based on the exergy analysis is very important.

Researchers from all over the world have been working for the last few

decades towards the enhancement of efficiency, low cost materials and fabrication of

solar cells using several approaches. One of the options might be the reduction in

the amount of material for the fabrication of solar cells. Wafer slicing technology

including kerf loss reduction for a thin having width less than 200 μm and the

manufacturing technology for the same are under investigation [1]. By using the thin

film technology for solar cells shortage of silicon material can be managed. Thinner

active layers having width less than 100 μm are the efforts in the direction of

achieving high-efficiency and low-cost solar cells [2], however before proceeding to

mass production there is need of further efforts to reduce the process cost. The

105

enhancement in the efficiency of solar cells means obtaining more power from the

same solar cells which in turn, reduces the amount of material required to fabricate

them and hence, reduced cost of cells. Recently, a lot of work all over the world has

been carried out in the direction for achieving the low cost and high efficiency solar

cells. So far, multi-crystalline silicon (mc-Si) has been found to be a good option as

compared to mono-crystalline silicon (c-Si).

However, as far as the efficiency is concerned, many problems has been

found in achieving the high efficiency ( around 20%) with a practical size. The

problems are crystal growth technology to control the grain quality uniformly,

passivation technology for surface, light-trapping technology, crystal grains itself and

grain boundary. These technologies have been systematically and actively

investigated at the laboratory level [3]. For obtaining both low cost and high efficient

solar cells, a different approach has been applied to develop a new a-Si/c-Si hetero-

junction structure, called hetero-junction with intrinsic thin layer (HIT) [4-8]. This

structure features a very thin intrinsic a-Si layer inserted between a doped a-Si layer

and a c-Si substrate. This structure has several advantages such as, an excellent

surface passivation and p–n junction which results in high efficiency, low-

temperature processes (<200 ºC) that can prevent any degradation of bulk quality

which happens with the high-temperature cycling processes in low-quality silicon

materials like Czochralski Si and compared with It has much better temperature

coefficient as compared to conventional diffused cells therefore high-Voc of the cells

can be obtained. Taguchi et al reported the high conversion efficiency of 21.5% in

HIT cells with a size of 100.3 cm2 [9].

In the present chapter, the performance evaluation and parametric study of

three different solar photovoltaic (SPV) modules viz. thin film, multi-crystalline and

106

HIT (hetero junction with intrinsic thin layer) have been carried out using the

energetic and exergetic analysis under typical climatic zone in North India for

different months of a year.

4.2 Materials and methods

In this experimental study, the comparative energetic and exergetic analysis

of different solar photovoltaic (SPV) modules has been carried out for a typical year

under the Indian climatic conditions for which following materials were used.

4.2.1 Weather Station

The weather station available at the site i.e. Solar Energy Centre, Gurgaon

(India) includes a meteorological measurement system and data acquisition system.

The meteorological measurement system composed of following equipments.

a) Pyranometers

The weather station has two pyranometers one at horizontal i.e. parallel to

earth’s surface and the second at the tilted positions equal to the latitude of the

experimental location for the measurement of global solar radiation having the

wavelength range of each pyranometer is 305 nm to 2800 nm. The photographic

view of pyranometres at horizontal and tilted positions has been shown in Figs.4.1

(c). As the silicon pyranometer is a very sensitive having the execution time a one

second. Also an UV pyranometer has been used for the measurement of ultraviolet

radiation only which is having the wavelength in the range of 280 nm to 400 nm.

107

b) Spectroradiometers

The Spectroradiometers for this particular system has been designed to

measure the spectral power distributions of illuminants. Also two different

Spectoradiometers such as visible Spectroradiometer (MS 710) and infrared

Spectroradiometer (MS 712) having the range of 350 -1100 nm and 900-1700 nm

respectively, have been used in this experimental study and the photographic view of

Spectroradiometers is shown in Fig. 4.1(d).

Figure.4.1(a)

Figure.4.1(b)

Figure.4.1(c)

Figure.4.1(d)

Fig.4.1: Photographic view of the weather monitoring system

108

c) Wind monitoring:

The wind monitoring is being done through a high performance wind sensor

which measures both the wind speed and the wind direction in the range 0-100 m/s

and 0°-360° respectively and photographic view of wind monitor is shown in Fig.

4.1(b).

d) Air Temperature and humidity sensor:

Finally the temperature and humidity were measured using air temperature and

humidity sensors, having the measurement range of -40 °C to 60°C for air

temperature and 0.8% to 100% RH for humidity, respectively and the photographic

view of the complete SPV power plant is shown in Fig. 4.2.

Fig. 4.2: Photographic view of the SPV power plant

4.2.2 Methods

The data was collected using data logger then this data loggers is connected

to a personal computer (PC) by using software LoggerNet. The daily data was

109

collected in a separate folder and the execution time for the data logger connected to

silicon pyranometer was set to be one second while for other two data loggers, it was

set to one minute and the data loggers were programmed to save the data in

separate folders in.

4.3 Energy and Exergy Analyses

After the data was recorded and collected in a PC on day to day basis, the

enrgy and exergy analysis was carried out separately, using the following

expressions:

The input energy i.e. energy of solar radiation is given by:

AIQ sin .

(4.1)

where sI is intensity of solar radiation and A is area of SPV module

The actual output of the SPV module may be defined as below:

FFIVQ scoco (4.2)

where ocV is open circuit voltage, scI is short circuit current and FF is fill factor. The

fill factor (FF) of the SPV system can be defined as the ratio of the product of voltage

corresponding to maximum power ( mV ) and the current corresponding to maximum

power ( mI ) to the product of open circuit voltage and short circuit current and can be

expressed as below:

scoc

mm

IV

IVFF

(4.3)

Using the above definition, Eq.(4.2) can also be expressed as below:

mmo IVQ

(4.4)

110

The input exergy i.e. exergy of solar radiation is given by:

AIT

TExEx s

s

ainsolar

1

..

(4.5)

where sT is the temperature of sun which is taken as 5777 K. The exergy output of

the SPV systems can be given as follows:

..

'IExExExExEx elecdthermelecout (4.6)

where thermdelectd ExExExI ,,

.

' which includes internal as well as external losses

Internal losses are electrical exergy destruction i.e electdEx ,

and external losses are

heat loss, thermdEx ,

which is numerically equal to thermEx.

for PV system. For the

calculation of electrical exergy of the PV system i.e. elecEx it has been assumed that

exergy content received by photovoltaic surface is fully utilized to generate maximum

electrical exergy ( scocIV ).

)('.

mmscocscocelecelec IVIVIVIEEx (4.7)

where, scocIV represents the electrical energy and )( mmscoc IVIV represents the

electrical exergy destruction. Therefore from the above equation we find the

electrical exergy as below:

mmelec IVEx .

(4.8)

The thermal exergy of the system (.

thermEx ) which is defined as the heat loss

from the photovoltaic surface to the ambient can be represented as below:

..

1 QT

TEx

cell

atherm

(4.9)

111

where acellca TTAhQ .

and vhca 8.37.5

where cah the convective (radiative) heat transfer coefficient and v is the wind

speed. Using the above equations exergy of SPV system can be written as below:

acellca

cell

ammPV TTAh

T

TIVEx

1

.

(4.10)

The solar cell power conversion efficiency (pce ) can be defined as the ratio of actual

electrical output to the input solar radiation ( AI s ) on the PV surface and can be given

as below:

AI

IV

s

mmpce

(4.11)

The power conversion efficiency can also be written in the terms of FF using

the above equation as follows:

AI

IFFV

s

scocpce

(4.12)

In general the exergy efficiency ( ) is defined as the ratio of output exergy to

that of the input exergy and given as follows;

ExergyInput

ExergyOutput

(4.13)

Using the above equations, the exergy efficiency ( ) can be expressed as

follows:

AIT

T

TTAhT

TIV

s

s

a

acellca

cell

amm

1

1

(4.14)

However, the exergy efficiency can also be calculated using photonic energy

as given by Markwart et al. [10] and Joshi et al. [11], due to the fact that the solar

112

energy reaching on the surface of the earth can also be explained in the term of

photonic energy which travels in the form of packets ( h ) called ‘photons’ [12]. The

energy of a photon ( )(phE ) can be calculated as:

hchEph )(

(4.15)

The chemical potential or chemical exergy for the PV system can be given

[13] as below:

.

chemE

s

cellph

T

TE 1)(

s

cellph

T

TAN

hc1

(4.16)

where A is the surface area of PV module, phN is the number of photons falling on

the surface of PV module. Exergy is given by:

..

chempcechem EEx (4.17)

where pce is the power conversion efficiency. In the present thesis, two different

approaches have been presented for the performance analysis of different SPV

modules based on exergy analysis. The first method is based on the thermodynamic

fundamentals and second is based on the chemical potential of the solar radiation.

Either method can be used for the performance evaluation of the SPV module as

both are realistic.

113

4.4 Results and Discussion

The experimental study of SPV modules has been carried out for around 10

months at the typical climatic zone in North India which is located at 28º 26’ 24’’

latitude and 77 º 1’ 16’’ longitudes. The experiments have been carried out for each

sunny day of the different months of a year in the real outdoor conditions from 9 AM

to 5 PM. The calculations were made for clear sky days of each month of the year

except the month March and November because data of these two months could not

be collected due to technical problem and maintenance in the system. The

measured parameters includes, the wind speed, solar radiation, open circuit voltage,

short circuit current, maximum voltage, maximum current, fill factor (FF), ambient

temperature, average temperatures at the top, middle and the bottom of the module,

minimum temperature at the top, middle and bottom of the module, maximum

temperature at the top, middle and bottom of the module. The specifications of SPV

modules as given by the manufacturer at standard test conditions (STC) viz. solar

radiation of 1000 W/m2, air mass of 1.5 and ambient temperature of 25 ºC, are as

below:

Table 4.1: Parameters of SPV modules at standard test conditions (STC) as given

by manufactures.

Type of SPV module Pmax Voc (V) Isc (A) Vm (V) Im (A)

Thin Film 75 91.8 1.4 67 1.12

Multicrystalline 160 25.60 8.42 21.28 7.52

HIT 210 73.60 3.79 59.7 3.52

114

The specifications of the SPV modules at STC as obtained through the sun simulator

in the laboratory are given as below:

Table 4.2: Specifications of SPV modules at standard test conditions (STC) as

tested in the laboratory.

Type of SPV

module

Pmax Voc (V) Isc (A) Vm (V) Im (A) ηcell (%) ηmodule (%)

Thin Film 93.6 96.5 1.47 76.2 1.12 8.10 7.61

Multi-crystalline 170.6 26.08 8.80 20.84 8.19 16.9 15.80

HIT 209 68.7 3.82 56.8 3.67 19.9 17.4

Based on the experimental data recorded through the data loggers and

weather monitoring system as mentioned earlier, at the site, the energy, power

conversion and exergy efficiencies have been calculated and plotted against the

operating time from 9 AM to 5 PM for a typical set of operations at a particular

climate in North India and the discussion of results for different SPV modules is

given below:

4.4.1 Thin film SPV module

Figures 4.3 and 4.4 shows the variations of solar radiation, energy and power

conversion efficiencies against time for the month of January and February

respectively at a typical set of operating and designed conditioned as mentioned

above. It is seen from Fig.4.3 that the solar radiation first increases, attains its peak

near the middle of the day and goes down sharply towards the end of the day, while

115

fluctuating throughout the entire day which is an obvious case in practice. It is also

observed that all the efficiencies viz. energy, power conversion and exergy

efficiencies fluctuate with time which may be due to the fact that solar radiation also

fluctuates. Initially, all the three efficiencies are high and as the time increases they

decrease slowly then remain almost constant for over a long time period i.e.

approximately between 10 AM to 4 PM, and finally decreases which can be

explained in terms of lower input i.e. solar radiation. The fluctuation in the exergy

efficiency is found to be more than that of energy and power conversion efficiencies

which is may be due to the fact that the exergy efficiency is strongly dependent on

the wind speed, ambient and module temperatures which are also fluctuating in

nature throughout the day.

Fig.4.3. Efficiencies and Solar Radiation vs Time for thin film SPV module during the month of January

0

205

410

615

820

0

3.2

6.4

9.6

12.8

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

I (W/m2)

116

Fig.4.4. Efficiencies and Solar Radiation vs Time for thin film SPV module during the month of February

It is also found that the energy efficiency is always higher than that of exergy

efficiency throughout the day. This is due to the fact that the former is based on the

first law of thermodynamics and represents the quantity of energy while the later

based on the second law of thermodynamics and represents the quality of energy

which incorporates the losses/irreversibilities due to various parameters. Similarly,

energy efficiency is also found to be higher than that of the power conversion

efficiency which is the real measure of a module in terms of conversion ratio from

solar radiation to electrical output. Therefore output for power conversion efficiency

is less than that of energy efficiency and hence, the energy efficiency being a

theoretical ratio based on the measured parameters is always higher than that of

power conversion efficiency as well as the exergy efficiency. It is also found that the

0

230

460

690

920

0

3

6

9

12

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η

I (W/m2)

117

average energy, power conversion and exergy efficiencies are found to be 9.63%,

5.61% and 2.97% respectively in the month of January.

It is seen from Fig.4.4 that there is almost the same pattern of variation in all

the parameters i.e. energy, power conversion and exergy efficiencies and solar

radiation against time as that of Fig.4.3. From Fig. 4.4 it is found that for the month of

February, the fluctuation in the exergy efficiency is less than that of month of

January. This can be explained in terms of variation in wind speed, which varies

month to month and day to day. Also average energy, power conversion and exergy

efficiencies for the month of February are found to be 9.94%, 5.85% and 4.81%

respectively. Also from Figs. 4.3 and 4.4, it can be seen that the average exergetic

efficiency for the month of February is found to be higher than that of month of

January.

Variation of efficiencies and solar radiation against time of thin film SPV

module in the months of April and May can be seen from Figs.4.5 and 4.6.

Fig.4.5 Efficiencies and Solar Radiation vs Time for thin film SPV module during the month of April

0

220

440

660

880

0

3

6

9

12

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%) ηpce(%) η(%) I (W/m2)

118

Fig.4.6. Efficiencies and Solar Radiation vs Time for thin film SPV module during the month of May

From Fig.4.5 it is seen that the energy and power conversion efficiencies are

almost constant in nature throughout the day which may be due to the fact that the

fluctuation in solar radiation is not much for this particular data. However, the exergy

efficiency fluctuates due to the fact that it depends on various parameters other than

input solar radiation. The average energy, power conversion and exergy efficiencies

are found to be 9.75%, 5.91% and 4.26% respectively, for the month of April. Fig.4.6

also shows almost the same pattern of variation as that of figures 4.3-4.5 and due to

the same reason as explained above. The average energy, power conversion and

exergy efficiencies are found to be 8.64%, 5.28% and 3.24% respectively for the

month of May.

The energy, power conversion and exergy efficiencies and the solar radiation

are plotted against time for the months of June and July as can be seen in Figs.4.7

0

235

470

705

940

0

2.5

5

7.5

10

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

I (W/m2)

119

and 4.8 respectively. From Fig. 4.7, it is found that there is a sharp dip in all the three

efficiencies at around 11.20 AM.

Fig.4.7. Efficiencies and Solar Radiation vs Time for thin film SPV module during the

month of June

Fig.4.8. Efficiencies and Solar Radiation vs Time for thin film SPV module during the month of July

0

235

470

705

940

0

2.7

5.4

8.1

10.8

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

0

220

440

660

880

0

5

10

15

20

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

I (W/m2)

120

This dip in the efficiencies are due to sharp fall in the solar radiation at that

particular instant and therefore, the output to input ratio decreases sharply as a

result we got the lower instantaneous efficiency. The average energy, power

conversion and exergy efficiencies are found to be 9.48%, 5.68% and 4.77%

respectively for the month of June.

From Fig.4.8, it is found that the initially all the three efficiencies are very high

then decreases sharply. This is due to the fact that the initially solar radiation is very

low and then increases sharply and also in the morning time module is cool and as

the time increases module gets heated and the corresponding temperature

increases. Therefore in the morning time corresponding voltage is high and as the

time increases voltage of the module decreases and we got the higher efficiencies in

the morning time. Average energy, power conversion and exergy efficiencies are

found to be 10.33%, 6.19% and 5.85% respectively for the month of July. Sample

calculation for the month July has been given in Table 4.3.

Figures 4.9 and 4.10 show the variations of solar radiation, energy and power

conversion efficiencies against time of SPV module for the month of August and

September respectively. From Fig.4.9, it is found that the solar radiation for the

month August is found to be more fluctuating in nature due to cloudy season in this

part of the country therefore, the corresponding efficiencies also found to be

fluctuating. The average energy, power conversion and exergy efficiencies are found

to be 10.23%, 6.09% and 3.96% respectively, for the month of August. Similarly,

from Fig.4.10 it is found that the solar radiation for the month September is very

good as compared to the month of August and the average solar intensity is found to

be 500 W/m2 besides, the wind speed is not very much varying in this particular

month.

121

Table 4.3: Sample calculation for typical set of operating conditions for thin film SPV module

Time (hrs)

Is (W/m2)

v (m/sec.)

Ta (ºC)

Tcell (ºC)

Pmax (W)

Voc (V)

Isc (A)

Vm

(V) Im

(A) FF ψ

(%) ηpce

(%) η

(%)

09:00AM 270.93 3.36 30 39.54 38 82.8 0.75 62.42 0.61 0.61 9.99 11.38 18.65

09:10AM 496.61 2.21 30.88 40.8 42 82.7 0.83 65.01 0.65 0.61 6.32 6.84 11.22

09:20AM 573.93 1.84 31.13 40.03 41 82.1 0.82 66.35 0.62 0.61 5.60 5.85 9.59

09:30AM 676.98 2.10 31.55 42.05 45 85.5 0.89 61.85 0.73 0.59 4.99 5.41 9.17

09:40 AM 637.74 2.20 31.46 42.66 45 84.9 0.90 63.33 0.72 0.59 5.18 5.78 9.79

09:50 AM 653.13 2.03 31.94 43.56 49 82.4 0.96 63.75 0.76 0.62 5.46 6.13 9.89

10:00 AM 662.58 1.12 32.28 44.98 51 82.8 1.03 62.59 0.82 0.6 5.82 6.26 10.43

10:10 AM 671.88 2.11 32.28 43.7 49 82.5 0.98 63.28 0.78 0.6 5.39 5.90 9.83

10:20 AM 719.81 2.50 32.48 46.12 52 84.3 1.05 63.7 0.82 0.59 4.93 5.92 10.03

10:30 AM 746.03 2.19 32.66 45.48 57 82.5 1.10 59.93 0.94 0.63 5.49 6.23 9.90

10:40 AM 764.11 2.93 33.16 46.79 57 84.9 1.15 62.38 0.91 0.58 5.06 6.02 10.39

10:50 AM 773.05 1.71 32.65 46.78 56 83.5 1.13 61.88 0.91 0.6 5.22 5.94 9.89

11:00 AM 699.69 2.67 33.36 46.33 48 82.4 0.97 62.07 0.78 0.6 4.67 5.55 9.25

11:10 AM 814.58 1.80 33 44.61 64 83.7 1.28 63.1 1.01 0.6 6.02 6.41 10.68

11:20 AM 719.19 2.04 33.33 47.31 46 80.8 0.93 60.69 0.77 0.61 4.35 5.18 8.49

11:30 AM 819.93 1.26 34.19 47.55 67 83.3 1.34 61.3 1.09 0.6 6.25 6.64 11.07

11:40 AM 837.93 0.48 33.65 46.46 66 83 1.33 61.67 1.07 0.6 6.25 6.42 10.70

11:50 AM 848.29 2.15 34.04 46.91 65 85.4 1.32 61.3 1.07 0.58 5.72 6.25 10.77

12:00 PM 837.73 1.86 34.39 47.59 66 82.7 1.34 61.69 1.08 0.59 5.93 6.36 10.79

12:10 PM 848.99 1.87 34.55 47.65 67 84.1 1.35 62.65 1.07 0.59 5.91 6.44 10.91

12:20 PM 866.48 0.95 34.26 47.7 67 83.1 1.35 61.9 1.08 0.6 5.98 6.32 10.53

12:30 PM 870.99 0.39 34.8 47.99 64 83.1 1.31 60.67 1.05 0.59 5.83 6.02 10.20

12:40 PM 864.43 1.31 34.91 48.07 67 83.6 1.35 61.8 1.09 0.59 5.96 6.29 10.65

12:50 PM 877.80 2.30 35.08 47.82 66 83.2 1.35 61.3 1.08 0.59 5.58 6.16 10.44

Cont...

122

01:00 PM 869.82 1.98 35.44 48.86 64 83.1 1.30 64.16 0.99 0.59 5.38 5.97 10.11

01:10 PM 859.65 2.07 35.83 48.77 64 83.1 1.29 62.58 1.02 0.6 5.51 6.09 10.15

01:20 PM 844.77 1.16 36.17 49.09 63 82.4 1.29 62.12 1.02 0.59 5.80 6.04 10.24

01:30 PM 830.69 0.33 36.26 48.45 61 82.7 1.26 62.64 0.98 0.59 5.95 6.00 10.16

01:40 PM 840.30 1.42 36.76 48.61 63 82.4 1.26 61.18 1.02 0.61 5.79 6.13 10.04

01:50 PM 837.01 2.11 36.64 48.45 58 82.2 1.18 59.58 0.98 0.6 5.24 5.68 9.46

02:00 PM 784.47 1.25 38.68 48.26 59 85.1 1.18 61.82 0.95 0.59 6.05 6.16 10.44

02:10 PM 775.84 1.70 40.01 47.49 60 82.9 1.19 63.38 0.94 0.61 6.32 6.33 10.38

02:20 PM 747.97 1.98 36.83 46.93 57 85.4 1.16 63.3 0.89 0.58 5.90 6.25 10.78

02:30 PM 739.75 0.74 37.18 48.4 54 82.4 1.08 60.81 0.88 0.61 5.74 5.98 9.80

02:40 PM 672.24 1.70 37.3 47.11 53 82.4 1.04 61.92 0.85 0.62 6.16 6.45 10.41

02:50 PM 672.66 0.26 36.89 46.56 46 81.3 0.94 60.94 0.76 0.61 5.57 5.61 9.19

03:00 PM 610.29 1.56 36.77 46.74 49 83.2 0.97 61.97 0.79 0.6 6.24 6.48 10.80

03:10 PM 601.87 1.24 37.18 46.9 47 81.8 0.94 60.84 0.77 0.61 6.15 6.31 10.35

03:20 PM 543.74 1.56 37.38 44.95 47 82.4 0.95 62.64 0.75 0.6 7.01 7.03 11.72

03:30 PM 497.85 2.39 37.4 44.28 41 83.5 0.84 59.91 0.68 0.58 6.60 6.66 11.49

03:40 PM 484.70 1.20 37.16 44 43 82.1 0.86 62.78 0.69 0.61 7.31 7.23 11.85

03:50 PM 478.70 1.08 37.43 43.89 35 83.1 0.70 61.61 0.57 0.61 5.98 5.99 9.82

04:00 PM 451.15 0.98 36.73 44.57 35 81.4 0.69 61.31 0.57 0.62 6.24 6.28 10.13

04:10 PM 431.08 0.81 37.11 43.37 32 81.8 0.65 61.03 0.53 0.6 6.17 5.99 9.99

04:20 PM 399.76 1.63 36.89 43.47 29 80.5 0.58 61.98 0.47 0.62 5.81 5.90 9.52

04:30 PM 364.00 1.36 37.38 42.61 28 82.4 0.61 59.75 0.47 0.56 6.39 6.28 11.22

04:40 PM 331.52 0.90 37.11 42.05 23 82.1 0.47 62.87 0.37 0.6 5.76 5.63 9.39

04:50 PM 304.38 1.30 36.93 42 21 79.98 0.43 60.08 0.35 0.61 5.69 5.61 9.19

05:00 PM 275.69 2.51 37.04 40.7 17 79.98 0.37 60.1 0.29 0.57 5.19 4.98 8.73

123

Therefore, the efficiencies were found to be less fluctuating during the month

of September. The average energy, power conversion and exergy efficiencies are

found to be 10.09%, 5.90% and 4.68% respectively for the month of September. The

exergy efficiency is found to be more fluctuating while the energy efficiency is the

least fluctuating followed by power conversion efficiency as can be seen from

Fig.4.10.

Fig.4.9. Efficiencies and Solar Radiation vs Time for thin film SPV module during the

month of August

Fig.4.10. Efficiencies and Solar Radiation vs Time for thin film SPV module during

the month of September

0

270

540

810

1080

0

3.5

7

10.5

14

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%) ηpce(%) η(%)

0

245

490

735

980

0

3

6

9

12

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%) ηpce(%) η(%) I (W/m2)

124

The energy, power conversion and exergy efficiencies along with the solar

radiation are plotted against time for the months of October and December

respectively as can be seen in Figs.4.11 and 4.12.

Fig.4.11. Efficiencies and Solar Radiation vs Time for thin film SPV module during the month of October

Fig.4.12. Efficiencies and Solar Radiation vs Time for thin film SPV module during the month of December

0

245

490

735

980

0

3

6

9

12

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%) ηpce(%) η(%) I (W/m2)

0

225

450

675

900

0

2.5

5

7.5

10

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%) ηpce(%) η(%) I (W/m2)

125

From Figs. 4.11-4.12, it is found that the average intensity of solar radiation is

high enough and therefore, the efficiencies were found to be less fluctuating in

nature during months. The average energy, power conversion and exergy

efficiencies are found to be 10.26%, 6.0% and 4.83% respectively, for the month of

October while they are found to be 8.32%, 4.67% and 3.91% respectively, for the

month of December.

4.4.2 Multi-crystalline SPV Module

The variation of energy, power conversion and exergy efficiencies of multi-

crystalline SPV module along with solar radiation against hourly day light time is

shown in Figs. 4.13-4.14 for the month of January and February respectively, at a

given set of operating and designed conditions mentioned above. It is observed from

these figures that the solar radiation is increasing initially, attains its peak near the

middle of the day and goes down sharply towards the end of the day. It is also found

that the solar radiation fluctuates throughout the entire day which is an obvious case

in practice and so as the efficiencies of the multi-crystalline SPV module as can be

seen from these figures. Also all the efficiencies are more fluctuating in nature with

sharp peaks during the morning hours which may be explained in the terms of the

fluctuations in the solar radiation and temperature of module in the morning time

which can be seen from Fig. 4.13. It also seen from Fig.4.13, that all the three

efficiencies viz. energy, power conversion and exergy are initially increase and attain

sharp peaks and then as the time increases decrease slowly and remains almost in

limited range while fluctuating for over a long time period and again increases

towards the end of the day. This can be explained in terms of variation in solar

radiation, module and ambient air temperatures.

126

Fig. 4.13: Variation of different efficiencies and solar radiation against time for multi-crystalline SPV module during the month of January.

Fig. 4.14: Variation of different efficiencies and solar radiation against time for multi-crystalline SPV module during the month of February.

0

205

410

615

820

0

6.5

13

19.5

26

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce (%)

η

Is (W/m2)

0

230

460

690

920

0

5.5

11

16.5

22

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

127

In other words, the solar radiation, module and ambient air temperatures are

higher during the noon time as compared to those of the morning and evening times.

In fact the module temperature is lesser during the morning and evening times as

compared to the noon time, as a result the losses enhances due to the higher

module and ambient air temperatures and hence, we get the results shown in Figs.

(4.13-4.14). Also, all the efficiencies, in general are found to be decreasing function

for the month of February while solar radiation is found to be in the general trend as

can be seen from Fig, 4.14. The average energy, power conversion and exergy

efficiencies are found to be 17.93 %, 13.20 % and 10.87 % respectively, in the

month of January while for the month of February they are found to be 18.79 %,

13.48 % and 12.74 % respectively.

The physical significance of these results can be explained in different ways.

For example, during noon hours, as the temperature of the module increases, the

voltage decreases due to negative temperature coefficient of module and also

current increases but not in the comparative ratio as that of the voltage, thus the net

product of the voltage and the corresponding current decreases. However, during

the morning and evening hours the module and ambient air temperatures are lower

as compared to noon hours, thus the voltage is high therefore, the output to input

ratio is high leading to a better efficiency during morning and evening hours.

Similarly, the energy efficiency is found to be higher than that of the exergy efficiency

throughout the day. This is due to the fact that the former represents the quantity of

energy while the later deals with the quality of energy. Sample calculation for the

month of February has been given in Table 4.4 as below:

128

Table 4.4: Sample calculation for typical set of design parameters for multi-crystalline SPV module

Time (hrs) Is (W/m2) v (m/sec.) Ta (ºC) Tcell (ºC) Pmax (W) Voc (V) Isc (A) Vm (V) Im (A) FF ψ (%) ηpce(%) η(%)

09:00AM 339.65 1.12 12.61 17.60 58.00 25.24 3.00 20.57 2.83 0.77 16.46 15.87 20.61

09:10AM 389.33 1.26 13.10 17.87 65.00 25.78 3.38 20.80 3.14 0.75 16.15 15.52 20.70

09:20AM 433.91 0.99 13.87 19.24 72.00 24.66 3.74 20.35 3.52 0.78 15.85 15.34 19.67

09:30AM 471.26 1.17 14.65 24.37 78.00 24.27 4.19 20.01 3.92 0.77 15.51 15.37 19.96

09:40 AM 499.31 1.69 15.51 26.35 81.00 24.17 4.39 19.79 4.07 0.76 14.74 14.94 19.66

09:50 AM 537.65 1.72 16.05 28.11 87.00 24.17 4.77 19.26 4.50 0.76 14.55 15.07 19.83

10:00 AM 558.38 2.36 16.52 28.62 89.00 24.17 4.91 19.00 4.66 0.75 14.13 14.74 19.65

10:10 AM 608.07 2.79 17.17 29.57 95.00 25.73 5.37 19.22 4.96 0.69 13.85 14.52 21.04

10:20 AM 639.57 2.18 17.50 29.54 97.00 24.95 5.48 18.90 5.13 0.71 13.67 14.06 19.80

10:30 AM 663.34 1.73 17.59 31.29 100.00 24.41 5.72 18.70 5.36 0.72 13.54 14.03 19.49

10:40 AM 707.93 2.14 18.04 32.46 106.00 25.20 6.07 18.78 5.63 0.69 13.16 13.80 20.00

10:50 AM 730.21 3.18 18.43 32.11 109.00 25.34 6.33 18.59 5.88 0.68 13.02 13.83 20.33

11:00 AM 742.32 2.69 18.80 33.67 108.00 24.17 6.34 18.11 5.99 0.71 12.62 13.56 19.10

11:10 AM 749.71 2.31 19.28 35.57 113.00 24.22 6.66 18.06 6.23 0.70 12.90 13.95 19.92

11:20 AM 804.75 3.23 19.42 35.98 116.00 24.41 6.87 18.10 6.42 0.69 12.01 13.30 19.28

11:30 AM 815.36 1.33 19.99 36.12 116.00 23.93 6.98 17.88 6.47 0.69 12.68 13.08 18.95

11:40 AM 785.50 1.43 20.14 37.25 113.00 24.22 6.77 17.68 6.38 0.69 12.60 13.34 19.33

11:50 AM 871.80 2.08 20.24 37.67 121.00 25.39 7.37 17.42 6.94 0.65 11.94 12.92 19.87

12:00 PM 859.69 3.31 20.30 38.05 118.00 24.61 7.26 17.66 6.70 0.66 11.17 12.69 19.23

12:10 PM 848.18 2.83 20.51 39.24 118.00 24.22 7.20 18.07 6.51 0.68 11.23 12.93 19.02

12:20 PM 905.36 3.12 20.71 39.81 125.00 24.81 7.75 17.28 7.24 0.65 11.10 12.77 19.65

12:30 PM 872.13 2.42 20.96 39.92 120.00 23.73 7.47 17.31 6.94 0.68 11.39 12.79 18.80

12:40 PM 877.81 4.20 20.92 38.62 122.00 24.22 7.43 17.42 6.99 0.68 10.93 12.90 18.97

12:50 PM 882.87 2.40 20.75 38.64 120.00 23.58 7.48 16.98 7.06 0.68 11.43 12.58 20.86

01:00 PM 872.29 2.23 21.48 39.89 120.00 24.12 7.45 17.31 6.94 0.67 11.58 12.77 18.50

129

Cont...

01:10 PM 912.51 2.00 21.59 40.34 124.00 24.61 7.64 17.60 7.03 0.66 11.51 12.59 19.08

01:20 PM 884.14 2.23 21.56 40.22 118.00 23.39 7.33 17.44 6.78 0.69 11.18 12.39 17.95

01:30 PM 864.82 2.60 22.05 41.18 117.00 25.39 7.17 17.49 6.67 0.64 10.96 12.47 19.48

01:40 PM 861.09 2.48 21.90 39.22 116.00 24.81 7.04 17.73 6.55 0.66 11.40 12.39 18.78

01:50 PM 829.01 1.84 22.23 38.63 116.00 24.41 7.01 17.84 6.49 0.68 12.25 12.99 19.11

02:00 PM 874.65 1.85 21.95 40.66 116.00 26.51 7.13 17.47 6.65 0.61 11.26 12.21 20.01

02:10 PM 819.09 3.75 22.19 39.32 112.00 24.22 6.75 17.76 6.28 0.69 10.89 12.74 18.47

02:20 PM 773.36 2.18 21.89 37.35 104.00 23.78 6.15 18.30 5.67 0.71 11.63 12.43 17.51

02:30 PM 756.66 3.05 22.05 37.34 105.00 23.58 6.16 18.18 5.77 0.72 11.73 12.80 17.78

02:40 PM 713.36 2.18 22.42 37.64 99.00 23.68 5.84 18.13 5.47 0.72 12.03 12.92 17.95

02:50 PM 671.41 2.55 22.11 36.72 97.00 23.49 5.67 18.22 5.35 0.73 12.50 13.41 18.37

03:00 PM 676.57 2.96 22.30 38.06 97.00 23.78 5.62 18.11 5.34 0.73 11.85 13.35 18.29

03:10 PM 661.84 3.29 22.26 36.27 91.00 24.76 5.25 18.53 4.93 0.70 11.64 12.73 18.18

03:20 PM 533.78 2.25 21.99 33.90 77.00 23.58 4.31 18.60 4.11 0.76 12.69 13.39 17.62

03:30 PM 530.57 2.70 22.06 32.42 79.00 23.78 4.40 18.72 4.20 0.76 13.35 13.86 18.24

03:40 PM 519.88 2.13 22.16 33.20 77.00 24.41 4.31 18.90 4.05 0.73 13.27 13.67 18.72

03:50 PM 486.90 2.46 22.10 33.46 71.00 25.54 3.95 18.92 3.75 0.70 12.86 13.41 19.16

04:00 PM 429.57 2.76 21.89 32.13 63.00 23.58 3.43 19.41 3.25 0.78 12.97 13.58 17.41

04:10 PM 412.79 2.96 21.89 30.89 61.00 24.85 3.32 19.20 3.16 0.74 13.21 13.70 18.51

04:20 PM 345.10 2.70 21.89 29.87 51.00 23.39 2.75 19.35 2.63 0.79 13.36 13.64 17.27

04:30 PM 348.23 1.60 21.77 29.21 51.00 23.98 2.77 19.32 2.65 0.77 13.70 13.60 17.66

04:40 PM 297.15 1.37 21.65 28.73 42.00 24.02 2.26 19.64 2.12 0.78 13.04 13.17 16.88

04:50 PM 256.77 3.00 21.49 26.79 37.00 23.83 1.98 19.62 1.88 0.78 13.37 13.27 17.02

05:00 PM 214.83 2.48 21.31 25.64 31.00 23.83 1.66 20.09 1.54 0.78 13.63 13.32 17.08

130

The energy, power conversion and exergy efficiencies and the solar radiation

for multi-crystalline module are plotted against time for the months of April and May

as can be seen in Figs. 4.15 and 4.16 respectively. It is seen from these figures that

the energy and power conversion efficiencies are almost constant in nature

throughout the day which is due to the fact that the fluctuations in solar radiation are

lesser as compared to the months of January and February. However, the exergy

efficiency fluctuates due to the fact that the fluctuation in the wind speed and

increasing of module temperature during the day time which has been explained in

the previous section also.

Fig. 4.15: Variation of different efficiencies and solar radiation against time for multi-crystalline SPV module during the month of April.

Again the energy and power conversion efficiencies for the month April are

found to be higher than those of the month of May, however, the exergy efficiency for

the month of May is found to be higher than that of month of April so as the solar

radiation. Also the fluctuation in the exergy efficiency as well as the energy efficiency

0

220

440

660

880

0

5

10

15

20

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

131

during 10:30-3:00 hrs are found to be more as compared during 11:30-01:30 hrs

during the month of may which can be explained in terms of ambient air temperature,

module temperature and wind speed as given earlier. The average energy, power

conversion and exergy efficiencies are found to be 17.07 %, 11.47 % and 10.02 %

respectively, for the month of April, while they are found to be 16.54 %, 11.11 % and

10.13 % respectively, for the month of May.

Fig. 4.16: Variation of different efficiencies and solar radiation against time for multi-crystalline SPV module during the month of May.

The variation of efficiencies and solar radiation against time for multi-

crystalline SPV module during the months of June and July are shown in Figs.4.17

and 4.18 respectively. From these figures it is observed that there is a sharp dip in all

the three efficiencies at 11.20 AM for the month of June and at around 9.30 AM for

the month of July and again at around 3.00 PM. This dip in the efficiencies are due to

the sharp fall in the solar radiation at that particular instant therefore, the output to

input ratios decrease sharply, as a result we got the lower instantaneous efficiencies

0

235

470

705

940

0

5

10

15

20

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

132

as can be seen from Figs. 4.17-4.18. The average energy, power conversion and

exergy efficiencies are found to be 16.22%, 11.31% and 10.70% respectively, for the

month of June while, they are found to be 16.30%, 11.12% and 9.03% respectively,

for the month of July.

Fig. 4.17: Variation of different efficiencies and solar radiation against time for multi-crystalline SPV module during the month of June.

Fig. 4.18: Variation of different efficiencies and solar radiation against time for multi-crystalline SPV module during the month of July.

0

235

470

705

940

0

5

10

15

20

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

0

220

440

660

880

0

5

10

15

20

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%) ηpce(%) η(%) Is (W/m2)

133

The solar radiation, energy and power conversion efficiencies are plotted

against time in Figs. 4.19 and 4.20 for the multi-crystalline SPV module during the

month of August and September, respectively. It is seen from these figures that all

the efficiencies for the month of August is fluctuating very frequently which is due to

the fact that the corresponding solar radiation also fluctuates during this particular

month which is an obvious case in this part of country. The average energy, power

conversion and exergy efficiencies are found to be 17.41%, 12.00% and 9.68%

respectively, for the month of August. Since, the solar intensity is much higher, days

are more shining and the variation in wind speed is lesser during the month of

September as a result, the better performance was observed with lesser fluctuations

as can be seen from Fig. 4.20. Also the average energy, power conversion and

exergy efficiencies are found to be 17.80%, 12.06% and 10.91% respectively, for the

month of September which is higher than the month of August, mentioned above.

Fig.4.19: Variation of different efficiencies and solar radiation against time for multi-crystalline SPV module during the month of August.

0

270

540

810

1080

0

6.5

13

19.5

26

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

134

From the above results it is concluded that the all the efficiencies in the month

of September is higher than that of month August however, it is also seen that there

is not much variation in energy and power conversion and exergy efficiencies. This is

due to the fact that during the month of September, the insolation is high, the day is

clear with higher sun shining and at the same time the wind speed is not varying

much therefore, the losses are also less and hence, we got the better in the month of

September than those for the month of August.

Fig.4.20: Variation of different efficiencies and solar radiation against time for multi-crystalline SPV module during the month of September.

The energy, power conversion and exergy efficiencies and solar radiation

against time are shown in Figs. 4.21-4.22 respectively, for the months of October

and December. From these figures, it is found that during these two months the

intensity of solar radiation is much better and the fluctuations are very less as

compared to other months of the year as can be seen from these figures, mentioned

0

245

490

735

980

0

5.1

10.2

15.3

20.4

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

135

above. Therefore, the efficiencies are found to be in better range with lesser

fluctuations especially, during the morning and evening times. However, due to

higher solar intensity, the module temperature rises and hence, the losses also

enhances, this has been explained earlier, as a result, all the efficiencies especially,

the exergy efficiency goes down significantly during the noon hours as can be seen

from these figures.

Fig. 4.21: Variation of different efficiencies and solar radiation against time for multi-crystalline SPV module during the month of October.

Also the average energy, power conversion and exergy efficiencies are found

to be 18.09%, 12.26% and 11.17% respectively, for the month of October while they

are found to be 15.15%, 11.03% and 10.50% respectively, for the month of

December. Also all the efficiencies are found to be less fluctuation and in higher

range for the month of October as compared to those for the month of December,

which can be explained in terms of solar radiation, module and ambient air

temperature as explained earlier.

0

245

490

735

980

0

5

10

15

20

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

136

Fig. 4.22: Variation of different efficiencies and solar radiation against time for multi-crystalline SPV module during the month of December.

4.4.3 Hetro-junction with Intrinsic Thin Layer (HIT) SPV Module

The variation in energy, power conversion, exergy efficiencies and solar

radiation against time of HIT SPV module for the month of January and February

respectively has been illustrated in Figs. 4.23 and 4.24 at a typical set of operating

and designed conditions as mentioned above. From Fig. 4.23 it is observed that the

solar radiation increases initially, attains its peak near the middle of the day and goes

down sharply towards the end of the day, while fluctuating throughout the entire day

which is an obvious case in practice. It has also been found that all the efficiencies

such as energy, power conversion and exergy fluctuate with time which is due to the

intermittent nature of solar radiation which also fluctuates with time as mentioned

above. Also all the efficiencies are fluctuating in nature which means that a small

change in radiation causes a sharp change in efficiencies which may be explained in

the terms of temperature of module in the morning and evening times. It is also

observed from Fig. 4.23 that all the three efficiencies are initially high and increases

0

225

450

675

900

0

4.5

9

13.5

18

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

137

as the time increases and then decreases slowly then remains almost constant for

over a long time period i.e. approximately between 10 AM to 4 PM, and again

increases. This variation in efficiencies is due to variation in solar radiation which is

also given in the figure and variation in temperature of module throughout the day.

Fig.4.23. Variation in efficiencies and solar radiation against time for HIT SPV module during the month of January

It can also be observed from the Fig. 4.23 that all the three efficiencies are

high in the morning and evening time as compared to noon time which is due to the

fact that during the morning time the module temperature is lower and as the time

increases temperature of the module also increases and finally during the evening

time the temperature of the module goes down as compared to that of the noon time.

As the temperature of the module increases the voltage decreases due to negative

temperature coefficient of module while the current increases but not in the ratio of

voltage so the product of voltage and current i.e. output energy decreases.

0

205

410

615

820

0

8

16

24

32

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η

Is (W/m2)

138

Fig.4.24. Variation in efficiencies and solar radiation w.r.t. time of HIT SPV module in the month of February

In other words, the product of voltage and current is high In the morning and

evening time as compared to noon time and hence, the output to input ratio i.e.

efficiencies are high in the morning and evening time as compared to the noon time.

The exergy efficiency fluctuates more frequently than that of energy efficiency which

is due to the variation in the wind speed throughout the day because exergy

efficiency is strongly dependent on the wind speed as well as the ambient and

module temperatures. The energy efficiency is found to be always higher than that

of the exergy efficiency which has been explained above. The average energy,

power conversion and exergy efficiencies are found to be 22.16 %, 17.65 % and

16.12 % respectively, during the month of January. The sample calculation for the

month of February has been given in Table 4.4 as below:

0

230

460

690

920

0

6.5

13

19.5

26

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η

Is (W/m2)

139

Table 4.4: Sample calculation for typical set of design parameters for HIT SPV module

Time (hrs) Is (W/m2) v (m/sec.) Ta (ºC) Tcell (ºC) Pmax (W) Voc (V) Isc (A) Vm (V) Im (A) FF ψ (%) ηpce(%) η(%)

09:00AM 339.65 1.12 12.61 14.72 80 74.45 1.316 64.83 1.236 0.82 20.68 19.74 24.07

09:10AM 389.33 1.26 13.10 16.48 93 73.14 1.527 64.15 1.445 0.83 20.81 19.87 23.94

09:20AM 433.91 0.99 13.87 16.6 100 74.37 1.647 63.32 1.576 0.82 20.15 19.32 23.56

09:30AM 471.26 1.17 14.65 20.17 110 75.37 1.843 63.59 1.728 0.79 20.26 19.43 24.60

09:40 AM 499.31 1.69 15.51 21.83 115 74.06 1.933 63.12 1.82 0.8 19.88 19.14 23.92

09:50 AM 537.65 1.72 16.05 23.96 126 74.98 2.094 63.06 2 0.8 20.12 19.49 24.37

10:00 AM 558.38 2.36 16.52 24.21 129 74.75 2.183 62.14 2.084 0.79 19.84 19.26 24.39

10:10 AM 608.07 2.79 17.17 25.01 140 74.98 2.383 62.4 2.249 0.78 19.71 19.13 24.52

10:20 AM 639.57 2.18 17.50 26.09 143 72.6 2.438 61.61 2.327 0.81 19.15 18.71 23.09

10:30 AM 663.34 1.73 17.59 26.34 150 72.52 2.529 62.31 2.4 0.82 19.33 18.92 23.07

10:40 AM 707.93 2.14 18.04 27.48 155 73.37 2.664 62.11 2.494 0.79 18.63 18.20 23.04

10:50 AM 730.21 3.18 18.43 27.28 164 74.91 2.812 61.41 2.667 0.78 19.06 18.78 24.07

11:00 AM 742.32 2.69 18.80 28.06 164 74.6 2.831 61.46 2.664 0.78 18.76 18.52 23.74

11:10 AM 749.71 2.31 19.28 30.6 168 72.6 2.924 60.64 2.768 0.79 18.84 18.67 23.63

11:20 AM 804.75 3.23 19.42 30.83 173 72.06 3.013 60.42 2.87 0.8 17.95 18.01 22.51

11:30 AM 815.36 1.33 19.99 31.1 177 73.22 3.092 60.43 2.93 0.78 18.54 18.07 23.17

11:40 AM 785.50 1.43 20.14 31.55 174 71.91 3.04 60.9 2.85 0.8 18.80 18.58 23.22

11:50 AM 871.80 2.08 20.24 31.91 186 71.75 3.257 59.95 3.098 0.8 18.01 17.89 22.37

12:00 PM 859.69 3.31 20.30 32.43 183 73.52 3.221 59.8 3.058 0.77 17.64 17.70 22.99

12:10 PM 848.18 2.83 20.51 32.83 182 72.52 3.201 60.2 3.017 0.78 17.83 17.81 22.84

12:20 PM 905.36 3.12 20.71 33.4 194 72.06 3.429 60.56 3.203 0.79 17.78 17.99 22.77

12:30 PM 872.13 2.42 20.96 33.11 185 73.75 3.277 60.6 3.058 0.77 17.83 17.81 23.12

12:40 PM 877.81 4.20 20.92 32.19 191 73.14 3.343 60.2 3.17 0.78 18.05 18.13 23.24

12:50 PM 882.87 2.40 20.75 32.76 187 71.83 3.32 59.14 3.169 0.78 17.85 17.58 22.54

01:00 PM 872.29 2.23 21.48 34.46 186 71.29 3.28 59.59 3.115 0.8 17.79 17.89 22.37

01:10 PM 912.51 2.00 21.59 34.34 191 73.37 3.401 59.26 3.22 0.77 17.59 17.57 Cont...

22.82

140

01:20 PM 884.14 2.23 21.56 34.01 183 72.52 3.263 58.96 3.109 0.77 17.39 17.20 22.33

01:30 PM 864.82 2.60 22.05 34.11 181 73.75 3.213 60.21 3.014 0.76 17.57 17.38 22.86

01:40 PM 861.09 2.48 21.90 33.31 182 71.75 3.2 60.04 3.037 0.79 17.85 17.58 22.25

01:50 PM 829.01 1.84 22.23 33.64 176 73.52 3.098 60.1 2.923 0.77 17.97 17.65 22.93

02:00 PM 874.65 1.85 21.95 34.43 182 71.45 3.221 60.36 3.021 0.79 17.57 17.35 21.96

02:10 PM 819.09 3.75 22.19 33.51 171 71.6 3.009 60.31 2.83 0.79 17.27 17.34 21.95

02:20 PM 773.36 2.18 21.89 32.91 157 73.37 2.742 60.34 2.598 0.78 17.08 16.93 21.71

02:30 PM 756.66 3.05 22.05 31.68 158 71.29 2.741 60.78 2.6 0.81 17.65 17.45 21.55

02:40 PM 713.36 2.18 22.42 32.41 147 72.52 2.574 60.11 2.448 0.79 17.48 17.25 21.83

02:50 PM 671.41 2.55 22.11 31.65 143 72.14 2.495 60.78 2.36 0.79 18.08 17.67 22.37

03:00 PM 676.57 2.96 22.30 32.53 146 73.06 2.522 60.79 2.4 0.79 18.08 17.95 22.73

03:10 PM 661.84 3.29 22.26 31.5 137 73.68 2.36 62.36 2.2 0.79 17.43 17.32 21.92

03:20 PM 533.78 2.25 21.99 30.67 111 72.75 1.924 61.24 1.817 0.79 17.65 17.29 21.88

03:30 PM 530.57 2.70 22.06 29.93 113 71.98 1.951 61.85 1.83 0.8 18.13 17.67 22.09

03:40 PM 519.88 2.13 22.16 29.49 111 73.22 1.916 61.08 1.818 0.79 18.30 17.79 22.52

03:50 PM 486.90 2.46 22.10 29.89 103 73.37 1.736 60.84 1.7 0.81 18.04 17.68 21.83

04:00 PM 429.57 2.76 21.89 28.75 90 71.45 1.56 62.3 1.446 0.81 17.84 17.54 21.65

04:10 PM 412.79 2.96 21.89 28.04 87 73.22 1.476 62 1.397 0.81 17.92 17.70 21.85

04:20 PM 345.10 2.70 21.89 27.48 71 70.68 1.229 61.89 1.149 0.82 17.63 17.22 21.00

04:30 PM 348.23 1.60 21.77 27.26 73 72.91 1.259 62.19 1.178 0.8 18.16 17.60 22.00

04:40 PM 297.15 1.37 21.65 26.06 57 70.68 1 63.07 0.91 0.81 16.75 16.08 19.85

04:50 PM 256.77 3.00 21.49 25.21 52 73.14 0.898 62.3 0.828 0.79 17.36 16.86 21.34

05:00 PM 214.83 2.48 21.31 24.07 43 70.37 0.745 61.93 0.687 0.82 17.24 16.70 20.36

141

Fig. 4.24 shows almost the same pattern of variation in all the performance

parameters i.e. energy, power conversion and exergy efficiencies and solar radiation

against time as that of Fig.4.23. However, Fig. 4.24 shows that the average exergetic

efficiency is higher than that of power conversion or actual efficiency which is reverse

in the case of crystalline technology based modules. The higher exergy efficiency

than that of power conversion efficiency for HIT based modules shows that the

losses are less as compared to that of the crystalline based technology due to its

internal structure which combination of both amorphous silicon (a-Si) and crystalline

silicon (c-Si). It is also found that the fluctuation in all the three efficiencies for the

month of February are less than that of month of January which is due to the

variation in solar radiation, ambient air temperature and wind speed etc. All the

efficiencies have been found to be high in the morning and evening time as

compared to noon time same as in the month of January but all the efficiencies in the

morning time are higher than that of evening time. Also the average energy, power

conversion and exergy efficiencies for the month of February are found to be 22.53

%, 18.03 % and 18.35 % respectively. Also found that all the efficiencies for the

month of February are found to be higher than those of month of January.

The energy, power conversion and exergy efficiencies and the solar radiation

for HIT module are plotted against time for the months of April and May as can be

seen in Figs.4.25 and 4.26 respectively. From Fig. 4.25 it is seen that the energy and

power conversion efficiencies are almost constant in nature throughout the day this is

due to the fact that the fluctuation in solar radiation is not much. However the exergy

efficiency fluctuates due to the reason as explained above. The average energy,

power conversion and exergy efficiencies are found to be 20.52 %, 16.04 % and

15.77 % respectively for the month of April.

142

Fig.4.25. Variation in efficiencies and solar radiation against time for HIT SPV module during the month of April

Fig.4.26. Variation in efficiencies and solar radiation against time for HIT SPV module during the month of May

Again Fig. 4.26 shows almost the same pattern of variation of all performance

parameters as that of figures 4.23-4.5 which can be explained in similar way as

mentioned above. The average energy, power conversion and exergy efficiencies

0

220

440

660

880

0

6

12

18

24

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

0

235

470

705

940

0

5.5

11

16.5

22

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

143

are found to be 19.54 %, 15.40 % and 15.50 % respectively for the month of May.

From Figs. 4.25 and 4.26 it also found that the all the efficiencies for the month April

are found to be higher than that of month May, as can be seen from these figures.

The variation of efficiencies and solar radiation against time of HIT SPV

module in the months of June and July can be seen from Figs. 4.27 and 4.28, it is

found that there is a sharp dip in all the three efficiencies at 11.20 AM and sharp

increase at 11.30 AM. This dip in the efficiencies are due to sharp fall in the solar

radiation at that particular instant and therefore output to input ratio decreases

sharply as a result we got the lower instantaneous efficiency and increase in

efficiencies is due to corresponding increase in solar radiation. The average energy,

power conversion and exergy efficiencies are found to be 19.52%, 15.50% and

15.72% respectively for the month of June and 18.53%, 14.66% and 13.28%

respectively for the month of July. From Figs. 4.27 and 4.28 it also found that the all

the efficiencies for the month June are found to be higher than that of month July.

Fig.4.27. Variation in efficiencies and solar radiation against time for HIT SPV module during the month of June

0

235

470

705

940

0

8.5

17

25.5

34

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%) ηpce(%) η(%) Is (W/m2)

144

Fig.4.28. Variation in efficiencies and solar radiation against time for HIT SPV module during the month of July

Figures 4.29 and 4.30 show the variations of solar radiation, energy and

power conversion efficiencies against time of hetero-junction with intrinsic thin layer

(HIT) SPV module for the months of August and September, respectively. Figure

4.29 shows that all the efficiencies for the month of August are fluctuating which are

due to the fact that the corresponding solar radiation also fluctuates. The average

energy, power conversion and exergy efficiencies are found to be 21.16%, 16.18%

and 14.81% respectively, for the month of August. Again, Fig. 4.30 shows the month

of September is clear and shiny and therefore, we got the solar radiation most of the

time above 500 W/m2 also variation in wind speed is very less. Therefore all the

efficiencies also don’t fluctuate much. Average energy, power conversion and exergy

efficiencies are found to be 21.95%, 16.80% and 16.94% respectively for the month

0

220

440

660

880

0

6.5

13

19.5

26

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

145

of September. In view of the above, it is found that the all the efficiencies in the

month of September is higher than that of month August however, it is also seen that

change in energy and power conversion efficiencies is not much but exergy

efficiency changes approximately 2%.

Fig.4.29. Variation in efficiencies and solar radiation against time for HIT SPV module during the month of August

Fig.4.30. Variation in efficiencies and solar radiation against time for HIT SPV module during the month of September

0

270

540

810

1080

0

7.5

15

22.5

30

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%) ηpce(%) η(%) Is (W/m2)

0

245

490

735

980

0

6

12

18

24

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

146

This is due to the fact that in the month of September insolation is good and also

wind speed is not varying therefore losses are also less hence we got the better

exergy efficiency in the month of September than those of month August.

The energy, power conversion and exergy efficiencies and the solar radiation

are plotted against time for the months of October and December as can be seen in

Figs. 4.31 and 4.32 respectively. From Figs. 4.31-4.32 it is found that the intensity of

solar radiation is very good as that of month September. Therefore efficiencies don’t

fluctuate much in these months also. Average energy, power conversion and exergy

efficiencies are found to be 22.37%, 17.09% and 17.31% respectively for the month

of October and 21.15%, 16.54% and 16.98% respectively for the month of

December. From Figs. 4.31 and 4.32 it also found that the all the efficiencies for the

month October are found to be higher than that of month December.

Fig.4.31. Variation in efficiencies and solar radiation against time for HIT SPV module during the month of October

0

245

490

735

980

0

6.5

13

19.5

26

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

147

Fig.4.32. Variation in efficiencies and solar radiation against time for HIT SPV module during the month of December

4.4.4 Year Round Comparison between the Three SPV Modules

The comparative of all efficiencies i.e. energy, power conversion and exergy

for the complete year (10 months) for thin film SPV module is shown in Fig. 4.33. The

data for the months of March and November was not available due to the repair and

maintenance works on the modules and is not taken into consideration in this study.

From Fig.4.33 it is found that the energy, power conversion and exergy efficiencies

for the month of July are highest among all the months analysed and presented in

the study. Analysis of the month March and November has not been taken into

consideration because of the unavailability of data in these months. Exergy efficiency

of the month June is found to be the second best however, as far as energy point of

view, August is found to be the second best month. Since exergy

0

225

450

675

900

0

6

12

18

24

09:00AM 11:00 AM 01:00 PM 03:00 PM 05:00 PM

Eff

icie

ncie

s (

%)

Time (hr)

ψ (%)

ηpce(%)

η(%)

Is (W/m2)

148

performance is the true measure of any system, therefore from the point of view of

thermodynamics and heat transfer, June is the second best month for the SPV

module followed by month October.

Fig.4.33. Monthly variations of energy, power conversion and exergy efficiencies of thin film SPV module

The comparative variation in the energy, power conversion and exergy

efficiencies for multi-crystalline module are plotted against time for the complete year

as shown in Fig. 4.34. From Fig. 4.34 it can be seen that the energy, power

conversion and exergy efficiencies for the month of February are the highest among

all the months analysed and presented in the study. All the efficiencies for the month

October are found to be the second best and less fluctuating which has been

explained above that the solar intensity is better and less fluctuating which is also in

the case of wind speed. But as the ambient temperature is higher than that of the

month of February, as a result we got less fluctuating but lower efficiencies in the

month of October than that for the month of February. The exergy efficiency for the

month December is found to be better as compared to other few hot and humid

months viz. April, May July and August as can be seen from Fig.4.34, which is due to

0

3

6

9

12 E

ffic

ien

cie

s (

%)

Months

ψ

ηpce

η

149

the fact that the ambient temperature is lesser during the month of December and

hence, the module temperature is also lesser as a result we got better performance,

while the energetic efficiency in the month of December is found to be the lowest of

all months analysed and presented in this study. However, as far as exergy is

concerned exergy efficiency for the month July is found to be the least, which can be

explained in terms of exergy losses due to wind speed, module and ambient air

temperatures, therefore from the point of view of thermodynamics and heat transfer,

performance of multi-crystalline module in the month of July is found to be the least.

Fig.4.34. Monthly variations of energy, power conversion and exergy efficiencies of multi-crystalline solar module

For other months, the performance of multi-crystalline module is found to be

somewhere between the two months mentioned above viz. lesser than the month of

February and higher than that of the month of July.

Comparative monthly variation of all the efficiencies i.e. energy, power

conversion and exergy for the complete year (10 months) is shown in Fig. 4.35.

0

5

10

15

20

Eff

icie

ncie

s (

%)

Months

ψ

ηpce

η

150

From Fig.4.35 it can be seen that the energy, power conversion and exergy

efficiencies for the month of February are highest among all the months analysed

and presented in the study. Energy efficiency has been found to be higher than those

of power conversion and exergy efficiencies in all the months analysed and

presented in this chapter. However, a mixed response has been found in the case of

exergy efficiency and power conversion efficiency i.e. in some month’s exergy

efficiency has been found to be higher than that of power conversion efficiency such

as in the months of February, May, June, September, October and December and in

rest of the months power conversion efficiency has been found to be higher than

those of exergy efficiency.

Fig.4.35. Monthly variations of energy, power conversion and exergy

efficiencies of HIT SPV module

This is unlike c-Si technology based SPV modules as mentioned above where

power conversion efficiency is always higher than those of exergy efficiency. This

variation is due to internal structure of HIT SPV module where both a-SI and c-Si has

been used for the HIT solar cell fabrication and therefore losses were found to be

lees in this type of SPV module. All the efficiencies of the month October is found to

0

6

12

18

24

Eff

icie

ncie

s (

%)

Months

ψ

ηpce

η

151

be the second best. However, all the efficiencies were found to be least in the month

of July. Therefore, performance of HIT module in the month of July has been found

to be the least and in the month of February best.

Figure 4.36 shows the year round average energy, power conversion and

exergy efficiencies of different SPV modules. From the figure it is found that HIT

based SPV module has the highest year round average efficiencies followed by

multicrystalline SPV module. Thin film based SPV module has the lowest year round

average efficiencies among the three SPV modules studied and analysed in this

chapter.

Fig.4.36: Year round average energy, power conversion and exergy efficiencies of

different SPV modules

0.00

5.50

11.00

16.50

22.00

Thin film Multicrystalline HIT

Eff

icie

nc

ies (

%)

Modules

ψ

ηpc

η

152

4.5 Conclusions

Present study deals with the year round comparative performance analysis of

different SPV modules viz. thin film, multicrystalline and HIT for the typical Indian

climatic condition based on exergetic and energetic analysis. Three different

efficiencies viz. energy, power conversion and exergy efficiencies have been

evaluated and based on the findings the comprehensive discussion has been made.

From the above discussion it is found that the all three efficiencies show the different

nature of variations in the efficiencies for different months of the year due to

intermittent nature of solar radiation. Based on the experimental study and the

discussions of results following conclusions have been drawn:

I. It is found that the energy, power conversion and exergy efficiencies for the

month of July are found to be the highest among all the months analysed and

presented in the study for thin film SPV module under the climatic condition of

North India.

II. The energy, power conversion and exergy efficiencies for the month of

February are found to be the highest among all the months analyzed and

presented in the study for multicrystalline and HIT SPV module.

III. All the efficiencies for all the modules studied in this chapter have been found

to be higher in the morning and evening hours as compared to noon time.

Also all the efficiencies in the morning time are higher than that of evening

time which is due to variations in the ambient and module temperatures

throughout the day.

IV. For thin film SPV module exergy efficiency of the month June is found to be

the second best however, as far as energy point of view, August is found to be

the second best month. Since exergy performance is the true measure of any

153

system, therefore from the point of view of thermodynamics and heat transfer,

June is the second best month for the SPV module followed by month

October.

V. Energy efficiency is found to be always higher than that of power conversion

and exergy efficiencies in case of thin film and multicrystalline based SPV

module. This is due to the fact that energy efficiency doesn’t consider the

losses in the system and based on the first law of thermodynamics. However,

exergy efficiency represents the quality of energy and takes account into the

thermal losses in the system.

VI. For HIT SPV module, energy efficiency is found to be always higher than that

of power conversion and exergy efficiencies. A mixed response has been

found in the case of exergy efficiency i.e. in some months like February, May,

June, September, October and December exergy efficiency has been found to

be higher than those of power conversion efficiency however, reverse is found

in rest of the months.

VII. From the study it is also found that the fill factor (FF) plays an important role in

improvement of exergy and power conversion efficiencies. Fill factor is directly

proportional to both the efficiencies, higher the FF, higher will be exergetic and

power conversion efficiency.

In this study, the concept of exergy analysis has been applied to different SPV

modules such as, muticrystalline, thin film and HIT first time and studied under

the typical climatic conditions of North India. Other researchers can also use this

study for the designing of different types of SPV modules and to minimise the

losses associated with these modules. Also this will work as a reference for

154

exergy evaluation in different months of year, which is rarely available in the

literature.

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