PG&E links with Ausra for 177 megawatts of solar thermal power

Pacific Gas and Electric has entered into a contract to buy 177 megawatts of power from a solar thermal power plant that will be built by Ausra.

The power plant will be located in San Luis Obispo county in central California and provide, roughly, enough power for 60,000 homes. Ausra has filed applications to build the plant with the California Energy Commission and hopes to have the plant up and generating power in 2010.

This won't be the last solar thermal contract PG&E will sign. PG&E says it plans to get a gigawatt worth of power from solar thermal systems in five years. Another likely partner is Brightsource Energy. The company, a reincarnation of an Israeli company, also plans on building plants in California. PG&E already has an agreement to buy 533 megawatts from Solel, which has a solar thermal plant in the Mojave Desert.

The utility is shooting to get 20 percent or more of its electricity from renewable sources, not including traditional hydroelectric power, by 2010. It currently gets 12 percent of its electricity now from renewables and has contracts that push it up to 18 percent. Most of its renewable energy so far comes from wind and biomass: PG&E right now gets only a little of its power from solar.

Another day at the solar thermal plant

(Credit: Ausra )

In solar thermal plants, mirrors to collect heat from the sun. The heat turns a liquid into a gas, and the pressure from the gas cranks a turbine. Excess heat can be stored in molten salt to generate electricity when the sun goes down. Heat, salt, water, mirrors: technically, these are components that have been used by engineers since Tacitus. The plants, though, are quite complex: typically, solar thermal plants take up hundreds of acres, cost millions to erect, and take years to build.

Despite the complexity and scale, many scientists and energy experts say that large solar thermal plants can generate power at a cost that's comparable with some types of traditional fossil fuel plants, a significant milestone.

Ausra, from Australia, says it can dramatically cut the costs of building solar thermal plants. Rather than employ parabolic mirrors, Ausra's system uses cheaper flat mirrors. The liquid is water too, rather than oil. Real estate is additionally economized. The San Luis Obispo plant will only occupy a square mile, or 640 acres.

Less land means that the plants can be built closer to population centers. Connecting these plants to the grid costs about $1.5 million a mile in transmission lines. Ausra, which recently raised $40 million in a venture funding round, signed a deal for a 300 megawatt plant in Florida earlier this year.