Photovoltaic Panels at a PG&E's Dixon-Vacaville array. (Photo: Craig Miller)

Photovoltaic solar panels are becoming the new black for large-scale solar projects in California.

Developers of what’s billed as the world’s largest solar project, spanning 7,000 acres in Blythe, California, say the plant will get half of its 1,000 megawatts from photovoltaic panels. This recent announcement makes Solar Trust of America the fourth large-scale solar developer in California to switch from solar thermal to photovoltaic panels, which Solar Trust CEO Uwe Schmidt calls “the right technology at the right time.”

Brett Prior, Senior Analyst at Greentech Media, says that large-scale solar developers have preferred solar thermal but the plummeting cost of photovoltaic panels is changing that.

“Over the last couple of years PV [photovoltaic] panels have dropped significantly in price,” says Prior.

How’s 70% over the last two years for “significant?” Prior says that’s because China is emerging as a major player in panel manufacturing. “Just in the last five years, China has gone from sort of a minimal role to over 50% of all worldwide manufacturing of PV panels.” says Prior.

However, cost of technology isn’t the only factor affecting large-scale solar projects.

“One area where [solar thermal] players are making a lot of progress is incorporating thermal storage,” says Prior.

For some solar developers, thermal storage is a viable feature for solar thermal power and worth the extra cost. Since solar photovoltaic panels only work when the sun is shining, some solar-thermal plants incorporate a feature that uses molten salts, which can store heat throughout the day and be released to generate steam for turbines.

Prior says solar-thermal plants using storage features allow more flexibility to grid demand, which is consistent after the sun sets.

“They can store energy during the morning when it’s not really needed by the grid, deliver 100% output at one p.m. when it’s most needed, and continue to deliver 100% output at eight p.m. when electricity demand drops off,” says Prior.

Despite the emerging energy storage technology, three other large-scale solar plants (links to interactive map, below) have made the transition from solar thermal to solar photovoltaic panels for at least part of the project. Other developers like NextERA’s Beacon Solar, builder of a large project in Kern County, have suggested similar plans.

View Making the Swtich in a larger map