Concentrating Solar Gearing Up for Home-Brewed Power

February 8, 2007 – Vol.11 No.46

CONCENTRATING SOLAR GEARING UP FOR HOME-BREWED POWER.

On December 5, 2006, the US Department of Energy confirmed that state-of-the-art solar cell maker Spectrolab, of Sylmar, California had achieved a new world record in concentrator solar cell electric conversion efficiency: an eye popping 40.7 percent.

At 40 percent, DOE says, solar concentrating power plants could be built at an installed cost of $3 per watt: Solar power from the grid would be 8 -10 cents per kilowatt hour. Pretty cheap for renewable energy. Really cheap for solar. Concentrating solar power could be a regular part of the electric mix on the grid, DOE said.

But was this exciting news for homeowners yearning for solar power? Only if you want to buy solar power from the grid, not generate it from your rooftop.

The cells developed by Spectrolab were used in a concentrating system that focused sunlight to 400 Suns or so, not solar cells mounted in a frame and screwed to a roof. They were heat-protected and possibly cooled. These high power cells were specifically designed for solar concentrating, grid-connected solar power plants, not the kind of solar system you’d stick on a carport roof.

However, somewhat less intense solar concentrating systems for residential use could be the next big thing in solar. New technologies coming to the marketplace share the same traits of the megawatt-class solar power plants: fewer solar cells for a given output ( meaning less system cost) and cells that grab Sunlight from more angles (meaning more total solar power output throughout the day.)

Two companies are making significant headway in bringing concentrating solar to homes, businesses and other applications.

Practical Instruments, of Pasadena, California has developed Heliotube which puts rows of solar cells at the bottom of reflective troughs. Aligned in parallel, the troughs are packaged within a panel of the same footprint as a typical flat solar module. The troughs swivel and follow the Sun across the sky for more uniform power throughout the day than fixed flat panels.

The opportunity for more uniform solar electric output has attracted three new installers to the company. The installers agree that performanced-based incentives, in which solar owners get credit for the amount of solar power their system actually produces, are becoming the norm. Steadier solar power output during the day increases the credit homeowners would receive.

Heliotubes use 88 percent fewer cells than flat panels of the same output and will be available to customers in 2008, according to the company website.

Silicon Valley Solar (SV Solar), of Santa Clara, California has a slightly different twist on small scale concentrating solar, The company uses a non-tracking, nonmoving system to reflect as much sunlight as possible on rows of solar cells. Their Sol-X2 product is also the size of a conventional flat module, though thicker, and uses about 50 percent of the cells needed for the same size and output.

SV Solar has signed a contract with Gebaude-Solarsysteme (GSS) of Germany to produce Sol-X2 in large quantities. SV Solar secured a 10 megawatt purchase order for Sol-X2 panels from Pacific Power Management in December, 2006 for delivery beginning in 2008.

Visit Spectrolab at http://www.spectrolab.com/ , Practical Instruments at http://www.practical-instruments.com/ and Silicon Valley Solar at http://www.sv-solar.com/