Greener Solar Plants Turn to Biofuels By Night

How do you make those solar thermal power plants, which are being built in California’s desert, even greener? Add biofuels to the mix. At least that’s what San Joaquin Solar (a subsidiary of power gear company Martifer Renewables) is doing. The company is building solar plants, which when the sun goes down, switch over to power its steam turbines via biofuels. How cool is that? And the company got a big customer this morning: Northern utility PG&E says it has entered into two contracts that will deliver 106.8 MW of solar thermal-biofuel hybrid power.

San Joaquin Solar will build these solar-biofuel projects, expected to begin operation in 2011, near Coalinga, Calif., which is smack dab in California’s Central Valley, between Los Angeles and the Bay Area. The plants are expected to deliver a total of 700 gigawatt-hours per year of renewable electricity for PG&E’s California customers. PG&E says that each hybrid project will require 250,000 tons of biofuel per year, which will come from local wastes, both from agriculture and livestock.

How do these things work? During the peak times of available sunlight, San Joaquin Solar’s projects will function the same way other solar thermal plant are supposed to — using the suns rays to heat liquid to run turbines that generate electricity. But at night, or when there’s little sun, the steam turbines will kick over to run off of biomass, solving one of the key problems of solar generation.

While it sounds like a good idea, we’re not sure how much output the biofuels-run turbines will add to the plants (we have a call to Martifer and are waiting to hear back). The added biofuels generation also sounds like a system that can be easily copied. If it works, those 11 solar thermal companies building plants in the desert should follow suit.

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