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Solar Power Question: What is High concentration photovoltaics?

Answer: High concentration photovoltaics (HCPV) systems employ concentrating optics consisting of dish reflectors or fresnel lenses that concentrate sunlight to intensities of 200 suns or more. The solar cells require high-capacity heat sinks to prevent thermal destruction and to manage temperature related performance losses. Multijunction solar cells are currently favored over silicon as they are more efficient. The efficiency of both cell types rises with increased concentration; multijunction efficiency also rises faster. Multijunction solar cells, originally designed for non-concentrating space-based satellites, have been re-designed due to the high-current density encountered with CPV (typically 8 A/cm2 at 500 suns). Though the cost of multijunction solar cells is roughly 100x that of comparable silicon cells, the cell cost remains a small fraction of the cost of the overall concentrating PV system, so the system economics might still favor the multijunction cells.

Much of the original research into multijunction photovoltaics was sponsored by governments and the astronautics industry. More recently, the technical research and product development of CPV systems has grown due to investment in terrestrial electric generating systems. Recent technological advances in triple-junction solar cells by Fraunhofer Institute ISE have yielded 41.1% conversion efficiency.

In May 2008, IBM demonstrated a prototype CPV using computer chip cooling techniques to achieve an energy density of 2300 suns.

Recently, Concentrix (Germany) and Amonix (USA) have announced operating AC efficiencies of 23% and 25%, respectively. These numbers point to significantly higher annual energy generation with HCPV than with competing technologies.

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