Transparent coating keeps solar cells cool and efficient throughout the day
Gizmag, September 23, 2015. Image credit: Theen Moy
Stanford engineers have developed a transparent silicon overlay that can increase the efficiency of solar cells by keeping them cool. The cover collects and then radiates heat directly into space, without interfering with incoming photons. If mass-produced, the development could be used to cool down any device in the open air – for instance, to complement air conditioning in cars.
After a full day in the sun, solar cells in California can approach temperatures of 80° C (175° F), even in winter months. Excessive heat can pose problems because, while the cells need sunlight to harvest energy, they also lose efficiency as they heat up. A standard silicon cell, for example, will drop from 20 to 19 percent efficiency by heating up just 10° C (18° F) or so.
The silica (SiO2) solar panel cover devised by Prof. Shanhui Fan and colleagues at Stanford is successfully making use of space as the largest of heat sinks. It does so by collecting and then radiating heat as infrared electromagnetic waves, which can easily travel through the atmosphere, out into space. The coating is transparent, so it won’t interfere with the solar cell’s light collecting ability, and improves on the heat dissipation of the silicon found in most cells.
According to the study results, the overlay allowed visible light to pass through to the solar cells while cooling the underlying absorber by as much as 23° F (13° C). This translates to an absolute efficiency gain of over one percentage point which, although it may not sound like much, would add up to something substantial over the life of the cell.