(Tech Xplore)—An international team of researchers has found a way to increase solar cell efficiency in areas where there is small degree of cloudiness. In their paper published in Proceedings of the National Academy of Sciences, the team describes how they combined two solar technologies to produce a product that was more efficient than either alone in certain geographical areas.
Solar engineers have found that using concentrated photovoltaic modules is the most efficient way to produce solar energy in very sunny locales—in such modules, lenses are used to direct sunlight onto photovoltaic cells. Such modules work very well when exposed to near constant sunlight, but suffer dramatically if even thin clouds disperse the sunlight periodically. In other regions where there are more clouds, solar energy is typically produced using flat panel solar cells because they can produce energy from dispersed sunlight. In this new effort, the researchers combined the qualities of both technologies to provide the most efficient means of producing solar energy in places that get a small degree of cloudiness.
The new design has two variations; the first was built by simply cutting flat panel cells into strips and placing them onto the concentrator module back-panels. The second involved taking the opposite approach, putting the multi-junction cells on top of traditional flat panels. Both approaches allowed for producing energy under ideal sunny conditions and also when the skies were partially clouded—when unobstructed sunlight hits either of the two designs, it is directed by the lenses to a photovoltaic cell, but when it is diffused, the light strikes the flat panels. This approach offers the best of both worlds in a single collector. The sunnier it is, the more efficient the design works.
The researchers report that testing (at three sites at latitude between 35.9º to 40.2º north) showed efficiency improvements of between 1.0 and 8.4 percent over traditional flat panels depending on weather conditions. They also note that such hybrids would cost approximately 7.5 percent more to make than traditional panels. They suggest their hybrid module/panels would provide the best option for users in areas that are partly to mostly sunny for most of the year.