Gas power plants are going solar.

A small, but growing number of utilities and power providers are trying to supplement natural gas power plants with solar thermal systems.

Think of it as risk mitigation. Utilities can supplement existing (or new) gas plants with solar technology, but without the onerous financial and logistical risks of building a massive solar plant. Unlike a standard solar thermal plant, a hybrid plant can provide power 24 hours a day. There is also far less need for a heat storage system. Solar thermal developers want to add molten salt systems to their plants to save heat harvested in the daytime to make power at night. Storage systems, however, add costs and are still under development (see Solar Thermal: Which Technology Is Best?).

Potentially, this also expands the range for solar thermal technology. Hybrid power plants likely won't require the same amount of desert real estate as those gigawatt-scale power plants planned for California and Nevada.

Technically, the existing solar thermal plants in California's Mojave Desert are already hybrids because they have small gas turbines.  However, these rarely are used: in a hybrid plant, power production between gas and solar are more evenly weighted.

Aora, a power provider in Israel, said today that it would open a hybrid power plant in Samar that consists of a field of 30 heliostats (i.e., mirrors) situated on half an acre of land. The power module is expected to supply 100 kilowatts of power to the national grid, enough to sustain approximately 70 households.

While Aora says its plant will be the first hybrid, it won't be the largest. Florida Power and Light is erecting a hybrid thermal-gas plant in that state that will provide 75 megawatts of solar power.

Abengoa, meanwhile, is erecting two 20-megawatt solar farms that will connect to larger gas plants in Morocco and Algeria, according to Fred Morse, of Morse and Associates. "You can buy $20 megawatts for $50 million," Morse said.

If the trend continues, it could benefit companies like Ausra and eSolar. Both solar thermal companies started out with plans to erect large solar thermal utility plants and sell water. Now, Ausra says it will sell solar thermal equipment to power providers while eSolar will continue with power plants and sell equipment.

Solar thermal, by the way, is living up to its claims. The two decades-old solar thermal plants in California's Mojave Desert "have not missed one hour of peak output in their lifetime," Morse said. "When Mt. Pinatubo blew ash into the sky, they just burned a little more gas."

Last year, California experienced six days of peak demand. The solar thermal plants produced at 110 percent capacity at that time. Wind turbines produced a measly 3 percent.


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Tags: abengoa, aora, ausra, esolar, fred morse, israel, mojave desert, solar thermal