The Clean Venture spherical solar cells are an example of how additional gains in conversion of light to energy can be achieved with low cost concentrating optics. Non-imaging optics increase the efficiency of photo voltaic systems with a low incremental materials cost. Such panels are particularly well suited for regions where insolation is diffuse.
Treehugger Lloyd Alter provides some history about spherical solar cells: “Texas Instruments evidently first made them in the ’80s but efficiency was only about 10% and the costs were high.” In the 1980s the United States was the leader in photo voltaic development, but Germany and Japan subsequently have been the countries to watch in terms of solar energy.
Japan’s Clean Venture 21 has developed a new spin on solar with their Spherical Silicon Solar Array… Clean Ventures puts each little 1mm ball into a little reflector. It still is only 12% efficient, but they claim that it has only one fifth the amount of silicon and should only cost one fifth as much to make, using half as much energy as conventional solar cell manufacture. Evidently silicon balls are made by dripping rather than cutting, so little raw material is needed, there is no cutting, and the optical properties are good.
The impetus for a concentrating photo voltaic technology is to reduce cost. As previously noted, there are two main ways that non-imaging optics can concentrate light, either with mirrors or lens. An additional way to increase the efficiency of photo voltaic systems is with use of a tracking system. Whereas optics add cost, tracking systems, a.k.a., heliostats, add another trade-off; does the increase in efficiency exceed the decrease in efficiency from using energy to gain energy?