Inexpensive Below Air Temperature Passive Cooling of Photovoltaic Modules

Approximately 80% of the solar energy collected by a photovoltaic (PV) device is converted to low grade heat throughout the day. As the temperature of the PV device increases, the recombination rate of photogenerated carriers also increases and the devices’ band gap decreases. These effects significantly reduce the modules’ open-circuit voltage (V_OC), conversion efficiency, and power collected, where the average annual loss in PV power due to high temperature is about 10%.

If the temperature of the PV device can be reduced by 20 degrees C on average, the absolute power output of the device can improve by 10%.While aluminum cooling fins have been added to the back of PV modules to decrease the temperature differential between the air and the device, these cooling fins are typically cost prohibitive (i.e. costing $20 to $40 per m²), add significant weight, and only decrease the module temperature by 5 degrees C to 10 degrees C. Furthermore, combined heating and PV generation products are expensive and are not useful for large PV plants as they need to be co-located with a thermal load (e.g. a building). To improve upon these limitations, NREL scientists have developed a passive cooling system to reduce the temperature differential between a PV device and the air.