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$1 billion solar-thermal plant near Gila Bend to supply APS customers

Arizona’s solar-power supply is about to get a lot bigger.

A solar-energy plant planned near Gila Bend would be among the world’s largest when it opens in 2011, Arizona Public Service Co. said Wednesday.

APS would buy all the electricity from the solar-thermal plant – which would be built and operated by a Spanish company – to supply some of its 1.1 million customers.

As environmental concerns and rising costs affect traditional fuel sources, solar likely will be a bigger part of the mix of power supplies that feed the state’s energy needs.

At 280 megawatts, enough to power at least 70,000 households, the plant would make even more energy than a similar facility announced in December.

The two proposed plants represent a departure from small research projects in favor of full-blown power generation.

“This is a turning point for APS and the future of the state of Arizona as we move to become the solar capital of the world,” APS President Don Brandt said, estimating the Solana plant will cost more than $1 billion and cover 3 square miles.

“It will be the dawn of the Solar Age in Arizona.”

Solar-thermal plants use mirrors to focus sunlight and heat up liquids. They make steam that spins turbines just like coal or other power plants, but without pollution.

Officials say they plan to tap the state’s abundant sunshine because it is becoming more likely that global climate-change fears will increase the costs of making electricity the old-fashioned way with coal.

Solar-thermal plants work best in hot places, unlike the more common black solar panels that use a chemical reaction to turn light into electricity whether it is hot or cold.

APS, Salt River Project, Tucson Electric Power and other utilities announced in December that they would share the power from a 250-megawatt solar-thermal plant.

Unlike that partnership, APS will buy all the power from Solana – $4 billion worth over 30 years – making it a much bigger commitment from the utility.

“We will provide more solar capacity per customer than any utility in the United States,” Brandt said.

Meeting peak demand
Abengoa Solar Inc., a Spanish technology company that has several smaller solar-thermal projects in Spain, North Africa and the United States, will build and run the Solana Generating Station.

Solana will use 2,700 “troughs” of mirrors lined up across former alfalfa farmland, focusing sunlight on tubes in the middle of the troughs.

The tubes will be filled with a petroleum-based chemical that will heat up to 735 degrees, and transfer their heat to water, making steam and spinning turbines in two 140-megawatt generators. The petroleum liquid is reused in the tubes, not burned.

The plant also will use molten salt to store heat and continue generating electricity for as long as six hours after the sun sets. That’s key in Arizona, where residents use the most electricity between 5 and 6 p.m., when the sun is low in the sky and common solar panels struggle to generate electricity.

To meet peak demand, utilities buy expensive energy from natural-gas plants.

“This will displace our most expensive form of generation,” Brandt said.

However, solar plants cost more than coal, nuclear or even the most efficient natural-gas plants for the amount of electricity they generate.

APS will pay about 14 cents per kilowatt-hour, compared with about 10 cents per kilowatt-hour from natural-gas plants at peak demand.

The premium is worth it because coal and natural-gas prices are unpredictable, and emissions from those plants likely someday will be taxed for their contributions to global climate change, Brandt said. That makes predictable solar prices attractive.

New nuclear plants are being proposed around the country, but will take years to be given permits and to be built.

The extra cost will be blended into existing APS rates, which are kept at about 9 cents per kilowatt-hour because of inexpensive energy from Palo Verde Nuclear Generating Station. Brandt said that as the utility signs more solar contracts, he expects the price to keep falling.

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