Solar World: PG&E makes another solar move

JERUSALEM, Aug. 17 (UPI) -- California utility Pacific Gas and Electric continues to support solar energy, this time by signing a deal to buy at least 500 megawatts from solar thermal firm Luz II starting in 2010.

"This new project has the potential to be a tremendous additional resource and to help further solidify our leadership when it comes to providing customers with clean, climate-friendly energy," PG&E's vice president of energy procurement, Fong Wan, said in a company statement.

"More than 50 percent of the power we (already) deliver comes from zero-carbon emission sources (including solar, hydroelectric, geothermal and wind). We look forward to expanding that."

The deal with Luz II, announced last week, is another step in this process, the company said.

"(PG&E) is aggressively adding renewable electric power resources to its supply at a planned rate of 300 megawatts per year," the statement said.

Solar thermal energy works much like conventional power. Electricity is generated by boilers and turbines. In solar thermal, however, the source of the heat is the sun and not fossil fuels.

Solar thermal facilities use mirrors of various shapes to concentrate sunlight on a receptor. In the early 1980s, Luz I pioneered a parabolic trough-shaped mirror to aim sunlight on a receptor rod in the middle. Luz I plants with this design, built in the 1980s, are still contributing 354 megawatts in California's Mojave Desert.

The company was bought out in the early 1990s by Beit Shemesh, Israel-based Solel, which still uses the trough model. Luz II is based in Jerusalem and Towson, Md.

Luz's president for Israeli operations, Israel Kroizer, said told United Press International he was convinced the second incarnation of the company would also go back to troughs because that was what the company was already good at.

But he emphasized that the company sees its competitors as conventional electric utilities, not other solar companies -- and in order to be competitive with fossil-fuel produced electricity, Luz facilities would have to be more efficient.

"A higher temperature means more efficiency," Kroizer said. And for that, the company needed to think outside the trough.

Luz II's solar thermal tower stands between 200-feet and 262-feet high, with an array of flat mirrors fanned out in front of it like an audience. It reaches temperatures of 1022 degrees F, whereas trough technology generally tops out around 752 degrees.

The area needed for mirrors around the tower depends on how much sun is available on the site, but in general, the DPT 550 -- "distributed power tower" that reaches 550 degrees Celsius (1022 degrees F) -- needs half a million square meters of area for mirrors to produce 100 megawatts, Kroizer said.

The next step will be the DPT 1200, which will reach even higher efficiency at a temperature of 1200 degrees Celsius (2192 degrees F). The higher-temperature towers will need about 400,000 square meters of space for mirrors.

Like the Luz I trough technology, Luz II's DPT 550 plants work on a hybrid of solar and gas. "There are only between 2,500 and 3,000 hours of sunlight a year," Kroizer said. "You have to design for everything ... (the technology) needs some kind of backup," he said.

"Qualified facilities" in California normally run on 25 percent gas and 75 percent solar, Walter Drimer, the executive vice president of Luz II, told UPI, and the company expects that the proportions for the new plants for this deal will be around the same.

News of the deal comes to California on the heels of the passage of bill SB-1, popularly known as the Million Solar Roofs Initiative. The law deals with solar power generated by photovoltaic panels, which lay flat on rooftops, collect sunlight and convert it to electricity via a chemical reaction.

PG&E also plays a significant role in this initiative by buying electricity generated by its customers who have solar panels. Instead of buying the electricity at the at-cost price, PG&E pays customers the retail price of around 11 cents per kilowatt hour, according to a company spokesman.

The upper limit, by law, of power the utility had to buy this way was quickly approaching, industry experts said, but SB-1 raises the cap.

"PG&E has more than 12,000 customers with photovoltaic (systems)," Noah Kaye, the spokesman for the Washington-based Solar Energy Industries Association, told UPI.

The deal with Luz II doesn't have a direct effect on the photovoltaic market.

"I would submit that concentrated solar (thermal) power is a utility-scale operation, while photovoltaic is more for retail electricity market generation," Kaye said.

However, any good news in the solar industry is good news for everyone.

"There is a role for each of these technologies," Kaye said. "The large-scale plants can raise awareness (of solar energy) and be a benefit to the retail photovoltaic market, and vice versa. They're somewhat symbiotic."