Concentrated solar power experiment with a fresnel lens

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.

Fresnel lens concentrating light onto solar cell.
Fresnel lens concentrating light onto the solar cell.
Solar cell in a container filled with mineral oil.
Solar cell in a container filled with mineral oil for keeping
      the cell cool.

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.

How the solar cell was immersed in mineral oil for cooling.
How the solar cell was immersed in mineral oil for cooling to
      do concentrated photovoltaics.
Plastic container and cover.
Cutting hole in the cover.
Drilling holes for bolts.
Drilling holes for wires.
Cutting the metal plate.
Drilling holes for bolts.
Bolts in cover with silicone.
Bolting metal plate to cover.
Soldering positive to solar cell.
Soldering negative to solar cell.
Inserting the solar cell.
Attaching cell with silicone.
Scoring the glass.
Snapping the glass.
Attaching the glass using silicone.
Added protective aluminum tape.
Attaching remote temperature sensor.

The tests

The following four tests were done, as detailed below.

  • Test 1 - Normal sunlight/no cooling oil
  • Test 2 - Normal sunlight/cooling oil
  • Test 3 - Concentrated sunlight/cooling oil
  • Test 4 - Concentrated sunlight/no cooling oil

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.

Circuit and meters for measuring output.
Circuit diagram for measuring output from concentrated 
      photovoltaic test setup.
Normal sunlight, no cooling.
Concentrated solar power test 1 with normal sunlight and 
      no cooling.

Test 1 - Normal sunlight with no cooling oil

First a test was done essentially with the solar cell just sitting in normal sunlight with no mineral oil for cooling. The results were:

Voltage Current Temperature
234 mV 1.24 A 39C/102F

Test 2 - Normal sunlight with cooling oil

Next, mineral oil was added to the container and the test was repeated still with normal sunlight.

Voltage Current Temperature
276 mV 1.5 A 29C/84F

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.

Adding the mineral oil.
Adding the mineral oil coolant for the concentrated solar power
Normal sunlight, cooling oil.
Concentrated solar power test 2 with normal sunlight and 
      cooling oil.
Concentrated sunlight, cooling oil.
Concentrated solar power test 3 with concentrated sunlight and 
      cooling oil.

Test 3 - Concentrated sunlight with cooling oil

Finally the large fresnel lens was added to concentrate sunlight onto the solar cell. The solar cell was immersed in mineral oil, keeping it cool for the duration of the test.

Voltage Current Temperature
310 mV 1.4 A 32C/89F

Notice that the temperature was a little higher than test 2, likely due to the mineral oil slowly heating up due to the concentrated sunlight. However, it was still relatively cool. Interestingly, the voltage is much higher but the current is lower. The current is possibly lower compared to test 2's 1.5 amps due to the higher temperature. More on this in the results summary section below.

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.

Smoke out of top of container.
Smoke coming ouf of the top of the container.
Smoke pouring as container is opened.
Smoke pours out of the container as it is openned.
Fatally damaged solar cell.
The fatally dammaged solar cell from the concentrated sunlight.

Solar concentration tests results summary

The following is a summary of the test results.

Test Voltage Current Power Temperature
1 - Normal sunlight, no cooling oil 234 mV 1.24 A 290 mW 39C/102F
2 - Normal sunlight, cooling oil 276 mV 1.5 A 414 mW 29C/84F
3 - Concentrated sunlight, cooling oil 310 mV 1.4 A 434 mW 32C/89F

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.
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