 Open Access
 Total Downloads : 122
 Authors : Anu Khandelwal, Vandana Khanna
 Paper ID : IJERTV4IS041404
 Volume & Issue : Volume 04, Issue 04 (April 2015)
 DOI : http://dx.doi.org/10.17577/IJERTV4IS041404
 Published (First Online): 29042015
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Analysis of Impact of Variation of Parameters on the Power of Solar Module
Anu Khandelwal,
M.Tech student and Vandana Khanna, Senior Assistant Professor
ITM University, Gurgaon122017, India
Abstract A MATLAB based study of solar module has been presented in this paper. There are many parameters which can affect the power of solar cells such as solar irradiation, series and shunt resistances, saturation currents, temperature etc. The observations are taken by varying parameters with different patterns. To observe their effect with temperature and irradiance, the average values are varied according to the meteorological data of city New Delhi taken monthly from the year 2000 to 2012 and then accordingly power is observed for each case.
Keywords Solar cell, solar module, parameters, MATLAB, power

INTRODUCTION
With the problem of increasing energy crisis the experiments and research in the field of renewable energy has become the primary focus for all. The renewable energy consists of areas like wind energy, solar energy, water etc [1]. The solar energy is eco friendly and green. It is infinitely available to us and easy to access and use. In todays era of conventional energy sources, the solar energy is going to be a suitable substitute [2].
Due to these reasons, the photovoltaic cells came into existence. The photovoltaic cells convert solar energy into electrical energy for us to use. They work on the principle of photovoltaic effect [3]. A basic unit of solar cell can generate voltage up to 0.5V. But this small amount of voltage is not much of use for us. So, to get higher voltage these solar cells can be connected into series in the order of 24 or 36 cells [4]. This series connection is known as solar module. A solar module can give us voltage up to 1218V. By connecting no. of modules according to our need solar panels are made which can be mounted anywhere and can be used for domestic and commercial purpose [5].

SOLAR CELL MODEL
As a solar cell behaves differently in different conditions therefore an equivalent model of cell is used for simulation. A solar cell behaves as a current source in ideal case. To observe the variation in parameters of solar cell the IV characteristics are to be studied. IV characteristics can be obtained using two types of models: Single cell and Double cell model.
Fig. 2.1: Symbol of solar cell
The two diode model of solar cell is as shown below in fig. 2.2. It consists of two diodes D1 and D2. Two resistances are used, one series resistance Rs, taken as 0.001 ohm in ideal case and other shunt resistance Rsh, taken as 100 ohm in ideal case.
Iph is the photo generated current which can be represented as current source and it is proportional to light as input as shown in eq. (1).
Fig. 2.2 Two diode solar cell model
The practical experiments on solar cells are not an easy task. So, the simulations are done to test and observe the variations. There are many parameters which can affect the
.
The output current I is :
=01[+/a 1] [+/ 1](V+IRs/R )
efficiency of solar cells such as solar irradiation, series and shunt resistances, temperature etc. Various simulation software are available but MATLAB has been used in this work [6]. MATLAB consists of solar cell unit, power
Where,
1 1 02 2 2
p
(1)
sources and other models which are needed to design a solar cell module. The observations are taken by varying parameters with different patterns. To observe their effect with temperature and irradiance, the values are varied according to the meteorological data of city New Delhi and then accordingly power is observed for each case [7].
=0Ã—0/ (2)
k Boltzmann constant, q charge of an electron, Ir irradiance in W/m2,
T Measurement temperature value, N diode ideality factor,
V voltage across the electrical ports, Is diode reverse saturation current,
Ipho photo generated current for standard irradiance Iro, IOutput current of cell

SIMULATION AND RESULTS
The simulation for 36 cell solar module has been done in MATLAB. It consists of 36 solar cells, irradiance block for variation of irradiance, SPICE environmental parameters for variation of device temperature. The current sensor senses the current same as voltage sensor senses the voltage. The power is product of current and voltage therefore product block is used.
As a result, we get IV and PV curves.
Fig. 3.1: MATLAB model of 36 cell solar module
Fig.3.1 shows the complete MATLAB solar module for 36 cells, where 36 solar cells are shown using black box.
The fig. 3.2 shows the 36 solar cells connected in series to get a voltage of up to 18V. These solar cells can be connected into any form such as series or parallel according to the requirement.
Also, instead of 36 cells 24 solar cell modules are also being used for some applications.
The curve for IV characteristics and PV characteristics were obtained for this solar module by varying parameters one by one and together as well and the power for every simulation was observed.
Subsystem
Fig. 3.2: 36 solar cells connected in series
A single subsystem consists of 36 solar cells connected in series.

When constant values of parameters were taken
In this case, circuit temperature was taken as 25C and standard irradiance as 1000W/m2, according to STC. Other parameters values were taken constant such as series resistance 0.02 ohm, shunt resistance 98ohm, diode saturation current 1 as 1nA, diode saturation current 2 as 10nA and Ideality factor as 1.The PV and IV characteristics curves are as shown in fig. 3.2 below:
Fig. 3.2: PV and IV curves, when constant values of parameters are taken
The maximum power observed in this case is 55W.

When all the parameters are varied one by one except irradiance and temperature
In this case, the circuit temperature and irradiance are kept constant according to STC while other parameters such as series and shunt resistance, saturation current etc are varied with a variation of 10%, give or take, one by one. The values of parameters are taken randomly. For each parameter 20 simulations are done and the average value of all the simulations is shown as result.
The power value for each parameter variation is tabulated in table 3.1 below:
Variation of parameters
Power (W)
Variation in series resistance
53
Variation in shunt resistance
55
Variation in saturation current(IO1)
48
Variation in saturation current(IO2)
57
Table 3.1: Power values with variation of parameters by 10% and simulated at STC
It can be observed from the above values that the variation of even a single parameter affect the power of solar module.

When all the parameters are varied simultaneously except temperature and irradiance
In this case, all the parameters are varied simultaneously while temperature and irradiance are kept constant.
The IV and PV characteristics curves are as shown in fig.
3.3 below:
The values are as shown below in Fig 3.4:
60
50
Power(W)
40
30
20
10
Jan
Feb Mar Apr
M Ju
July Aug
Se Oct Nov Dec
0
Months
Temp(h) Temp(l)
Fig.3.3: IV and PV curve when all the parameters are varied simultaneously except temperature and irradiance
The maximum power in this case is 50 W.

When all the parameters are varied,

With variation in temperature,
In this case, all the parameters mentioned in last case are varied with variation in temperature but irradiance is kept constant. The temperature values are taken from meteorological data of city New Delhi i.e. monthly lowest and highest temperature of the city and the corresponding values of power are observed [7].
Fig. 3.4: Power values with variation in temperature, when all the parameters are varied
As it can be seen from the Fig.3.4 above, that as the temperature increases the power decreases. It happens because as the temperature increases, the current increases but voltage decreases. This decrement in voltage is faster than increment in current and so the overall power of the cell decreases.

With variation in irradiance,
In this case, all the parameters with irradiance are varied except temperature. The irradiance values are taken from meteorological data of city New Delhi i.e. monthly irradiance value of the city and corresponding power is observed [7].
The observations are tabulated in table 3.3 as below:
Table 3.2: Power values with variation of irradiance, when all the parameters are varied too
Month
Irradiance
(W/ m2)
Power(W)
January
344
35
February
466
50
March
605
60
April
686
67
May
704
70
June
631
62
July
537
53
August
525
52
September
533
53
October
496
51
November
390
40
December
326
33

When all parameters are varied simultaneously with temperature and irradiance
In this case, all the parameters such as series and shunt resistance, saturation currents are varied and also temperature and irradiance monthly values were varied according to the data of city New Delhi [7].The power observed are as tabulated below:
Table 3.3: Power values with variation of both temperature and irradiance, when all the parameters are varied
Month
Irradiance
(W/ m2)
Low Temp
(C)
Power
(W)
January
344
8
29
February
466
11
53
March
605
16
66
April
686
21
72.5
May
704
26
72.5
June
631
28
64
July
537
27
55.5
August
525
27
54
September
533
25
55.5
October
496
19
53.5
November
390
13
44
December
326
8
37.5
Month
Irradiance (W/ m2)
High
Temp (C)
Power (W)
January
344
20
34
February
466
50
43
March
605
30
61
April
686
37
66
May
704
40
65
June
631
38
61
July
537
35
53
August
525
34
52
September
533
34
53
October
496
33
50
November
390
28
40
December
326
23
35
Two graphs shown in Fig. 3.4 are for example and depicts (a) for the month of February (b) for the month of May.
(a)
(b)
Fig. 3.5: The PV curves show power of (a) 53W (b) 72.5 W
If we look at fig. 3.5, we see that in above curve (a), irradiance is 466W/m2 while temperature is 11C and power is 53W. In curve (b), with 704W/m2 irradiance and 26C temperature, power is 72.5W.
If we compare it with fig. 3.1, we can observe that even with slight variation in irradiance and temperature, there is large variation in power.


CONCLUSION
The solar module with 36 cells has been simulated in MATLAB. It can be observed from the results that the variation in parameters of solar cell with environmental factors such as irradiance and power shows high variation in power as well. So, it can be concluded that to increase the power of the module, these parameters should be taken care of. They can behave differently in different environmental conditions.
REFERENCES

Skoplaki E, Palyvos JA. Operating temperature of photovoltaic modules: a survey of pertinent correlations. Renew Energy 2009; 34:239.

Hadj Bourdoucen , Adel Gastli, Tuning of PV Array Layout Configurations for Maximum Power Delivery, World Academy of Science, Engineering and Technology, Vol:2, 2008.

M.A. Green , Photovoltaics: technology overview, Centre for Photovoltaic Engineering, University of New South Wales, Sydney, NSW 2052, Australia , 24 May 2000.

Marcelo Gradella Villalva, Jonas Rafael Gazoli, Ernesto Ruppert Filho ,MODELING AND CIRCUITBASED SIMULATION OF PHOTOVOLTAIC ARRAYS University of Campinas (UNICAMP), Brazil, IEEE conference 2009.

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Source of Meteorological data of New Delhi: www.worldweatheronline.com/NewDelhiweather averages/Delhi/IN.aspx