This is an experiment I did concentrating sunlight onto a single silicon solar cell using a 2 foot by 4 foot fresnel lens which I'd taken from a rear projection TV. To keep the solar cell cool I put it inside a container filled with transparent mineral oil (see photos below.) Mineral oil was chosen because it's not electrically conductive. The container has a glass window on top for light to enter.
How the solar cell is cooled with mineral oil
The solar cell needs to be kept cool otherwise it would quickly be damaged by the heat generated by the concentrated sunlight, as was demonstrated in test 4 below. This was achieved by immersing it in a container of transparent mineral oil, which is an electrical insulator. The mineral oil would heat up eventually too but it would take longer than the test was run for.
The following diagram and photos show how a container was made that would withstand the heat and yet allow cooling.
The following four tests were done, as detailed below.
The diagram below shows how the voltage and current were measured for the solar cell output. It was necessary to measure both at the same time as the tests were being filmed for the video below.
Test 2 - Normal sunlight with cooling oil
Next, mineral oil was added to the container and the test was repeated still with normal sunlight.
Notice that the voltage and current are both higher than in test 1 above. This is likely because the temperature was cooler in the container due to the cooler mineral oil. A cooler solar cell runs more efficiently than a hotter solar cell.
Test 4 - Concentrated sunlight with no cooling oil
The final test was expected to be descructive to the solar cell. Sure enough the solar cell was fatally damaged. Before the test enough mineral oil was removed from the container to expose the solar cell to air. Soon after the test began, and as the photos below show, the container filled with smoke.
Solar concentration tests results summary
The following is a summary of the test results.
As pointed out above, test 2's output is likely higher than test 1's due to the cooler temperatute. A cooler solar cell runs more efficiently than a hotter solar cell.
Interestingly, the current for test 3, 1.4 amps, with the concentrated sunlight is less than the current for test 2, 1.5 amps, without the concentrated sunlight. This could be due to the higher temperature in test 3. Doing the calculations, there is a 0.03 amps per degree celcius difference between tests 1 and 2. There is the same 0.03 amps per degrees celcius difference between tests 2 and 3 as well. This consistency supports that conclusion.
The voltage is significantly higher for test 3, however, and the power is slightly higher. This means that the concentrated sunlight resulted in higher power output despite a temperature increase.
Video - Concentrated Solar Cell Test with Fresnel Lens
The following is the video I made including the construction of the container, the tests and the analysis.