Analysis of Impact of Variation of Parameters on the Power of Solar Module

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, Gurgaon-122017, 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

1. 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 12-18V. 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].

2. 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 I-V characteristics are to be studied. I-V 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].

   =0×0/ (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, I-Output current of cell

3. 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 I-V and P-V 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 I-V characteristics and P-V 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.

   1. 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 P-V and I-V characteristics curves are as shown in fig. 3.2 below:-

      Fig. 3.2: P-V and I-V curves, when constant values of parameters are taken

      The maximum power observed in this case is 55W.

   2. 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.

   3. 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 I-V and P-V 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: I-V and P-V curve when all the parameters are varied simultaneously except temperature and irradiance

      The maximum power in this case is 50 W.

   4. When all the parameters are varied,

   1. 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.

   2. 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

   1. 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 P-V 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.

4. 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

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

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

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

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

5. Second International Conference on Emerging Trends in Engineering and Technology, ICETET-09, MATLAB based Modeling to Study the Influence of Shading on Series Connected SPVA R.Ramaprabha**, Member, IEEE and B.L.Mathur.

6. Sheriff M. A., Babagana B. and Maina B. T., A Study of Silicon Solar Cells and Modules using PSPICE, World Journal of Applied Science and Technology, Vol. 3, pp. 124-130, No.1, 2011.

7. Source of Meteorological data of New Delhi: www.worldweatheronline.com/New-Delhi-weather- averages/Delhi/IN.aspx