Simultaneously, advancements in companies developing high-efficiency multi-junction cells, which may be used in conjunction with CPV, are another boost to the field
Concentrated photovoltaics (CPV) is still a relatively new branch of solar technology, but its recent progress has elevated its position in the market for providing clean renewable energy. In general, CPV uses lenses or mirrors and tracking systems to focus a large region of sunlight into a narrow beam, where the concentrated light is utilized as a heat source for a conventional power plant or is concentrated onto solar cells or photovoltaic surfaces. In the last several years, the number of companies developing CPV systems has increased to over 30. Simultaneously, advancements in companies developing high-efficiency multi-junction cells, which may be used in conjunction with CPV, are another boost to the field.
Commercial deployments have increased from a few kilowatts at demonstration facilities to approximately 5–8 megawatts (MW) in 2008, according to Photovoltaics World magazine. In comparison, between 30 and 50 MW of CPV installations are expected this year. Moreover, in areas where the solar exposure and intensity is high, CPV systems are ideal, including geographic regions of the world such as southern Europe, southwestern U.S., Africa, Australia, parts of Latin America and Asia. The CPV Consortium estimates that CPV is particularly well-suited to about one-third of the world’s land regions, which represent about 40% of the world’s population. In these regions, CPV technology is poised to provide the highest level of energy production and the lowest cost of electricity. In any case, a country’s power grid system will likely require enhancement for an overhaul of new renewable energy or solar power resources.
CPV also helped contribute to achieving the world record for overall solar cell efficiency of 43% via a composite structure of five stacked cells developed by a research team at the University of New South Wales in Sydney, Australia.
In southern California’s Antelope Valley, 24,000 silver-bright mirrors were recently setup to reflect light on two 50-meter-tall towers. This concentrated light heated steam in the towers to turn a turbine as the first “power towers” in the U.S. to convert the sun’s heat into electricity for commercial use in this fashion. The facility is known as the Sierra SunTower, which is now a power plant that can produce 5 MW, enough to serve approximately 4,000 local homes at full capacity. Thus, this facility is serving as a pilot test plant for larger plants in California and New Mexico, according to eSolar, the Pasadena, CA start-up behind the endeavor. A 46 MW commercial design will incorporate 16 of these towers, as well as more than 200,000 mirrors that are capable of generating at least 90 gigawatt-hours of electricity per year.
The key element of eSolar’s design are the mirrors; however, they may be its biggest downfall due to the potential large-scale maintenance that may be involved. By precisely calibrating the mirrors with computer algorithms that guide tote-bag sized motors, eSolar can construct its sunlight-harvesting power plants with many more simply-manufactured small, flat mirrors, roughly one square meter in size, as opposed to the large, complex, parabolic-shaped specialty mirrors employed in more commonly-used competitive technology at companies such as Phoenix, AZ area-based Stirling Energy Systems (SES). Bill Gross, CEO of eSolar, estimates that the entire state of California’s peak electricity demand could be generated from an eSolar farm of 65 square kilometers. Furthermore, he has stated that the electricity would be competitive with conventional power sources at a cost of 13 cents per kilowatt-hour or less.
Improvements in solar tracking systems will elevate the performance of many types of CPV technology by efficiently directing sunlight to the most critical areas on related devices. OPEL International Inc., a leading global developer and supplier of high concentration photovoltaic and other solar products, including ground-based and rooftop tracker systems, recently announced it will be manufacturing two of its utility-scale high performance solar trackers- in the U.S. The major benefit of the new trackers in the OPEL product line is the possibility of increasing the amount of kilowatt-hours that can be produced per unit of area. This is particularly attractive when dealing with limited real state availability such as roof top applications for green building design. In addition, companies such as SolFocus, who are leaders in providing CPV mirrors are also expanding their U.S. manufacturing base, namely in Mesa, AZ, offering green jobs to help revitalize the economy.
In an upcoming follow-up article, a review of CPV market share will be presented in comparison to the overall solar energy agenda across the spectrum of leading U.S. power utility providers.