concentrating photovoltaic: coming of age?
A recent edition of Barron’s Online featured
an article on Emcore and its Concentrating Photovoltaic (CPV) technology. On August 13th OPEL International announced that its CPV technology received a strong reception at Canaccord Adams’ 28th Annual Growth Conference. This latter release went on to say that while CPV technology is not new it is now coming into its own in the marketplace. Finally, a CPV technology primer on Solfocus’ website indicates that concentrating photovoltaics have been an established science since the 1970’s but are only now reaching commercial viability.
Two questions: Why has CPV technology apparently been around for so long yet only now being commercialized? and How are the various entrants in this market space defining themselves technologically?
The fundamental concept behind CPV systems is the use of a system to reflect or focus incoming solar energy down to a much smaller area than the original incident light, such that a much smaller area of photovoltaic (PV) material is required. A concentrating factor of 500 is common. Along with the concentrated solar energy comes elevated temperatures. In fact the temperature is elevated to the point where traditional Si-based PV systems are not appropriate. The answer to the first question is likely related to the development of multi-junction PV materials that can operate at “CPV” temperatures.
Some thoughts on the second question.
Emcore appears to be designing the entire system from the multi-junction material to the Imaging optics to the structure for supporting the entire system. United States published application 2008/0245409 is but one example of Emcore’s work on the PV material, while issued patent 7,381,886 describes a terrestrial solar array and its components.
Solfocus appears to be concentrating its efforts on the cell optics, integrating technology licensed from Palo Alto Research Center (PARC) and purchased tracking technology. Recently published United States patent application 2008/01233313 describes a semiconductor mount for the PV cell, within the overall cell array. It is noted in paragraph  that suitable triple junction cells may be provided by Sharp, Emcore or Spectrolab.
Developments associated with work at PARC are outlined in various patent documents including published United States patent application 2006/0231133.