SAN FRANCISCO (KCBS)- Earlier this week came word that Southern California Edison would be buying electricity from seven solar power plants that will be built by two Bay Area companies.

This is becoming a trend now that the technology is more affordable. It's a change that has come about in the last five to seven years.

"Many solar plants that were built previously were using a technology called solar-thermal, where sunlight is concentrated down to heat and water, and then basically makes a steam turbine," said Paul Alivisatos, director of the Lawrence Berkeley National Laboratory.

KCBS' Susan Leigh Taylor Reports:

He said that in the new solar power plants, photovoltaic technology will be used.

"That is where the sunlight is used to create a current inside a semi-conductor," said Alivisatos. "It's really a more advanced technology in some ways."

Photovoltaic has been around for a while, but was a very expensive way to produce energy, but the cost has now dropped dramatically. In the area of crystal and silicon, there are a whole slew of new manufacturers who've driven costs down.

"Also in the thin-film solar industry new manufacturing techniques have developed as the volume of the photovoltaics has increased," said Alivisatos.

With a cost of only 10 to 15 cents per kilowatt hour, Alivisatos expects this to become a significant source for energy. After that, the issue of storage will take center stage.

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