Concentrating Solar Photovoltaic Power (CSPP) is one of the most efficient and cost effective forms of solar energy, with costs expected to be reduced to $2,50-$3.00 per watt in a few years. Flat plastic fresnel lens between the sun and a cell focus and concentrate the sunlight many times (up to 500 times) onto a small cell area thus reducing the cell area required to an amount approximately equal to the concentration ratio. The concentration decreases the required cell area while also increasing the cell efficiency. One supplier, Amonix, Inc. of Torrance, Calif. is using multijunction cells with an efficiency of about 38%. The main idea is to use very little of the expensive semiconducting PV material while collecting as much sunlight as possible.
CSPP's have both advantages and disadvantages compared with flat-plate PV arrays. The main idea is to use very little of the expensive semiconducting PV material while collecting as much sunlight as possible. But because the lenses must be pointed at the sun, the use of concentrating collectors is limited to the sunniest parts of the country. Tracking of the sun is required to maintain the efficiency. Some concentrating collectors are designed to be mounted on simple tracking devices, but most require sophisticated tracking devices, which limit their use to electric utilities, industries, and large buildings.
The ultra-high efficiency solar cell technology, initially discovered at NREL and successfully developed for space satellites in the 1990s by Boeing-Spectrolab Inc provided the technology that enables the low-cost terrestrial systems. Boeing-Spectrolab and NREL have demonstrated over 37 percent efficient concentrator solar cells and field testing of Spectrolab's cells for over one year with no degradation promise a bright future. We expect concentrator solar cell performance to reach or exceed 40 percent by 2006 and anticipate continued enhancement in performance and reliability," said Dr. Nasser Karam, vice president of Advanced Technology Products at Spectrolab Inc.
An Entech 100 kW system near Ft. Davis, Texas, provided power to CSW's West Texas Utility (WTU) electrical grid for several years. Another Entech four-row, 100 kW system at the TU Electric (Texas Utilities) Energy Park near Dallas, Texas, provided power to the TU grid for several years. They are currently developing a 440X concentration system that they anticipate selling at $2.50 per watt. Entech appears to be focusing their efforts on NASA space applications rather than commercial terestial applications.
Amonix Inc. announced the formation of a joint venture with Spain's Guascor which will build a 10-megawatt per year assembly plant in Spain by the end of 2005. Amonix also plans to install 3 megawatts of PV concentrator systems in the southwestern U.S. while Guascor plans to install 10 megawatts of concentrator PV systems in Spain in 2006. Arizona Public Service Company (APS), a major Arizona utility, has installed a number of Amonix's systems.
Solar Systems of Australia announced plans to install more than 5 megawatts of PV concentrator systems in 2006.
Entech,Inc was rececently awarded three contracts, worht $17.5 million, by NASA for development of solar power arrays for moon/mars exploration.
Module sizes of 20 kw to 35 kw each are being built by the two companies. The modules are most suitable for utility installations and can be installed in multiples to provide any amount of power.
Resources:
NREL Newsroom, July 13, 2005
Amonix, Inc
NREL Concentrating Potovoltaic Research
NREL, Introduction to photovoltaic (solar cell) systems
Wire, Entech Inc
Entech, Inc
Source : The Energy Blog