The amount of solar photovoltaics harnessing electricity from sunshine in the U.S. will more than double by 2013, thanks to plans to build 800 megawatts (MW) worth in California. The two vast solar farms—covering more than 12 square miles—will be among the largest ever built in the world and dwarf the current U.S. record holder: Nellis Air Force Base in Nevada with 14 MW. In fact, the total amount of solar photovoltaics connected to the grid in the entire U.S. is just 473 MW at present.

"These landmark agreements signal the arrival of utility-scale PV solar power that may be cost-competitive with solar thermal and wind energy," said Jack Keenan, chief operating officer and senior vice president for utility PG&E, which made the deal, in an announcement yesterday.

Once fully operational in 2013, the two farms would provide 1.65 billion kilowatt-hours of electricity per year—peaking in the afternoon on the sunniest days just when electricity demand is at its highest—enough to power 239,000 California homes or 800 Wal-Marts. Optisolar will employ 550 MW of its amorphous silicon thin-film solar panels at its Topaz Solar Farm project in San Luis Obispo while SunPower will install mechanical tracking for its more expensive 250 MW of crystalline silicon photovoltaics at High Plans Ranch II in a bid to boost their efficiency by 30 percent by following the sun across the sky.

Scientists at the U.S. National Renewable Energy Laboratory recently boosted the efficiency record of such photovoltaics to a full 40.8 percent, by using three layers of special photovoltaic material and the equivalent of the amount of light put out by 326 suns.

These plants won't have that luxury, though SunPower boasts the highest commercial efficiency at more than 22 percent. And although the two massive solar farms will help utility PG&E meet the California mandate of sourcing 20 percent of public utilities power from renewable resources, they may suffer financially if the federal government does not extend an investment tax credit program that rewards the development of such projects.

As Rhone Resch, president of the Solar Energy Industry Association told me earlier this year: "If the investment tax credit is not renewed, it will disrupt this high-growth sector, impact tens of thousands of U.S. jobs and undermine advances in clean energy production."

Photo © 2008 David Lena