Self-Cooling Solar Cells Boost Power, Last Longer
By adding a specially patterned layer of silica glass to the surface of ordinary solar cells, a team of researchers at Stanford University has found a way to let solar cells cool themselves by shepherding away unwanted thermal radiation.
Even the best solar cell designs operating at peak efficiency convert less than 30 percent of the energy they receive from the sun into usable electricity. Part of this loss is the unavoidable consequence of converting sunlight into electricity. A surprising amount, however, is due to solar cells overheating.
Under normal operating conditions, solar cells can easily reach temperatures of 130 degrees Fahrenheit or more. Such extreme temperatures quickly sap efficiency and shorten the lifespan of a solar cell. For every 1.8 degree Fahrenheit increase in temperature, the efficiency of a solar cell declines by about half a percent. In addition, for every increase of 18 degrees Fahrenheit, the rate at which a solar cell ages doubles.
Actively cooling solar cells, however—either by ventilation or coolants—would be prohibitively expensive and is at odds with the need to optimize exposure to the sun.
The new design avoids these problems by taking a passive approach to cooling. By embedding tiny pyramid- and cone-shaped structures on an incredibly thin layer of silica glass, the researchers found a way to redirect unwanted heat away from the surface of solar cells and back into space.
The researchers are currently fabricating these devices and performing experimental tests on their design. Their next step is to demonstrate radiative cooling of solar cells in an outdoor environment.
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