UNIVERSITY OF IDAHO ELECTRICAL AND COMPUTER ENGINEERING
Solar Cell Simulation Model Calculations and Results for Creating a Solar Cell Model Valerie Barry, Anthony Kanago, Benjamin Sprague 9/20/2011
VLSI Sensors Research Group
The goal of this procedure was to extract the parameters used to model the micro solar device. We used a standard one cell model and some typical approximations of the extraction formulas to make the procedure easier without losing too much accuracy. We successfully extracted variables for three different illuminations 1000 lux, 10,000 lux, and 30,000 lux.
Table of Contents A.
Abstract ........................................................................................................................................... 3
B.
Introduction ...................................................................................................................................... 3
C.
Calculations and Comments ............................................................................................................ 3
E.
Final Results .................................................................................... Error! Bookmark not defined.
F.
References ........................................................................................................................................... 4
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A. Abstract The goal of this procedure was to extract the parameters used to model the micro solar device. We used a standard one cell model and some typical approximations of the extraction formulas to make the procedure easier without losing too much accuracy. We successfully extracted variables for three different illuminations 1000 lux, 10,000 lux, and 30,000 lux.
B. Introduction It is extremely important to be able to model OSRAM SCPD micro solar cell devices for simulation purposes. For our project, we need an accurate representation on how our micro solar cell will behave in different illuminations and for different loads. There are many different models, but we chose to use a simple single-diode model, as seen in Figure 1.[1]
Figure 1: Single Diode Model Equations 1-4 below are the equations used to solve for the parameters in the Single Diode Model. They are non-linear and must be solved using the Newton-Raphson method, which is time-consuming and the success depends entirely and good first estimates. So it is clear that it would be useful to find a better way to approximate the parameters. Voc is the open circuit voltage, Isc is the short-circuit current, Vm is the voltage at the maximum power point, Im is the current maximum power point and Rso and Rsho can be calculated from Voc and Isc.[1] (
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of the equations the following equations can be used to solve for the parameters.[1]
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(5) ( (
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(6) (7)
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(8) (9)
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These equations were shown to have less than five percent error with typical values for solar cells [1].
C. Calculations and Comments The hardest part of these calculations was finding the slope/derivative at the open circuit and the short circuit. Instead of using the overall equation from the Excel graph or finding the sloped between the two points closest to the two intercepts, we discovered the best way to find the slope was to graph the first three to four points on around each intercept, discarding any data that did not fit well with the other data, and then using Excel to find the slope of these points. After this was done, the equations above were entered into Excel and used to calculate the values. The calculated values and the values used in the calculations are located in Table 1. Table 1: Parameters and Important Values
Illumination (lux) Voltage at Max Power (V) Current at Max Power (A) Short Circuit Current (A) Open Circuit Voltage (V) Rso (Ohms) Rsho (Ohms) Rsh (Ohms) n Is (Amps) Rs (Ohms) Iph (Amps)
1000 0.2795 0.000015573 1.76621E-05 0.3581 2540.8 932000 932000 1.102979687 6.21512E-11 887.403505 1.7679E-05
10000 0.342 0.000111 0.000129 0.439 408.58 555082 555082 1.766947 8.78E-09 52.97767 0.000129
30000 0.378 0.000342 0.000403 0.487 186.359 22145 22145 1.402414 5.73E-10 91.10892 0.000405
After calculations, we wanted to verify the accuracy of values. To do this we used Cadence Design tools to create a circuit with our values and used a variable resister to measure the output voltage and current with the same loads used to find the measured values. The results of the simulation indicated that our calculated values
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are accurate. The percent differences calculated for the output power, voltage, and current were mostly under a half a percent, with only a few over a percent. This is considered accurate enough for our purposes.
D. References [1] Phang, J.C.H.; Chan, D.S.H.; Phillips, J.R.; , "Accurate analytical method for the extraction of solar cell model parameters," Electronics Letters , vol.20, no.10, pp.406-408, May 10 1984. doi: 10.1049/el:19840281
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