High concentration PV lets deserts ride a waterless solar wave

Around this time next year, energy customers in Colorado will be getting some of their electricity from a new type of solar-energy facility: the largest — and first utility-scale — high concentration solar photovoltaic (HCPV) plant in the world.

The Alamosa Solar Generating Project, which will be located near the south-central Colorado town of Alamosa, is expected to generate around 75,000 megawatt-hours of renewable energy each year: enough to power more than 6,500 homes. The source of clean energy will also help prevent more than 43,000 tonnes of carbon emissions every year.

The project comes a step closer to reality this week with an offer of a $90.6-million US Department of Energy loan guarantee to the facility’s developer, Cogentrix, a Charlotte, North Carolina-based subsidiary of The Goldman Sachs Group.

HCPV solar power is generated by focusing sunlight from a large area onto a smaller area with a photovoltaic panel on it, rather than just allowing direct sun to fall on a flat-panel solar cell. According to Cogentrix, the multi-junction Amonix solar cells to be used at Alamosa have an energy conversion efficiency of nearly 40 per cent. That’s about twice as much as the typical efficiency for standard flat-panel photovoltaics.

The technology can give solar power a big boost in regions that receive large amounts of direct sunlight. According to Amonix, HCPV also offers a great advantage over power tower or parabolic trough solar technologies, both of which require a significant amount of water for operations — water that is in scarce supply in the sunny American Southwest where Amonix has put its focus. By contrast, the small amount of water required to regularly clean the HCPV panels can easily be trucked in as needed.

In addition to its concentrating optics, the Alamosa plant will feature a dual-axis tracking system that keeps solar cells tilted at an optimal angle toward the sun. All of the electricity generated at the plant, scheduled for completion in the second quarter of 2012, will be sold to Public Service Company of Colorado, an Excel Energy company.

Being built on 225 acres of land at an elevation of 7,500 feet, the Alamosa plant will be 38 time larger than a similar HCPV facility built by the same general contractor — Mortenson Construction — in Aurora, Colarado.