Science Buddies: "Ask an Expert"

I am doing the project of how temperature affects a solar cell output power, and i need to know if I need a load resistor, and if I do, how do i set it up and use it?

Hello rehmedy,yours was nice project.This project was done by Linnea L.Motts in 2003 California state science fair.
Project Title:The Effect of Temperature regulation on the power output of solar cell
Objectives/Goals
How does temperature regulation affect the power output of various solar cells (photovoltaic cells) in a
concentrator system? The six photovoltaic cells - single-crystal silicon, polycrystalline silicon, gallium
arsenide, thin film amorphous on steel, thin film amorphous on glass, and thin film amorphous silicon -
were tested at 20°C, 25°C, 30°C, and 35°C. It was hypothesized that in a concentrator module the gallium
arsenide solar cell at 20°C would produce the greatest power output of the cells tested.
Methods/Materials
1 IR (infrared) temperature probe
4 digital multi-meters
2 DC power supplies
1 Fresnel magnifying lens
75-watt halogen spotlight
6 various solar cells
A solar cell module was constructed, consisting mainly of a solar cell, heat sink, thermoelectric module,
and a DC brushless fan. At each temperature voltage, current, and resistance were recorded, and overall
power output was calculated for each individual cell. Furthermore, voltage and current were recorded for
the power supplies of the thermoelectric module and fan.
Results
Although each solar cell varied in individual measurements for voltage, current, power output, and
resistance; the solar cells generally had a negative temperature coefficient, meaning that as temperature
increased resistance decreased. However, power output decreased as temperature rose.
Conclusions/Discussion
The data supports earlier findings that as temperature rises, cell materials overall lose efficiency.
Additionally, the initial hypothesis supported the data in that solar cells perform more efficiently at lower
temperatures. In the hypothesis, gallium arsenide at 20°C was predicted to have the highest power output;
however, the thin film amorphous on glass cell at 20°C had the greatest power output.

Good luck,with ur project

Hi,

I presume you are doing the project described here:
https://www.sciencebuddies.org/science- ... #procedure

In this procedure, in step 4, ist says " measure a constant voltage across the resistor". So, yes, you need some kind of load resistor. Actually, the meter you use to measure voltage should be able to provide the load you need. Here is a schematic that shows you how you can set up your experiment:

http://www.makeitsolar.com/images/schem ... l_amps.jpg

Good luck with your experiment, and HAVE FUN!

The internal resistance of most DC volt meters and DVMs (digital volt meters) is designed to be high so that it doesn't load the circuit. In order to better characterize the ability of the solar cell to deliver power, you should choose a load resistance appropriate to the maximum amount of power that the cell is designed to deliver. For example, if your cell is designed to deliver 480 mW at 12 volts with maximum illumination, using Ohms law calculations make that 30 mA of current (480/12) and a 400 ohm resistor (12/0.030) rated at 1/2 watt would be an appropriate load resistor. Inexpensive volt meters that are 1Kohms/volt would present a 20K ohm load which is only 2 percent of the ideal load. More expensive meters that are 10K to 100K per volt would be even less of a load.