California utility PG&E will buy 106.8 megawatts of electricity from a hybrid biofuel solar power plant to be built by a Portuguese firm in the state’s Central Valley.
The hybrid technology will allow two 53.4 megawatt plants to tap the sun and agricultural waste produced in surrounding Fresno County to generate green energy around the clock, according to San Joaquin Solar, a subsidiary of Portugal’s Martifer Renewables. For PG&E (PCG), 107 megawatts is just enough to keep the air conditioners running for some 75,000 homes. But if the biofuel solar hybrid performs as billed and can be scaled up, it’s a win-win – recycling ag waste – a huge and expensive problem in California – into electricity.
The percentage of electricity to be produced by solar versus biofuel and other details of the project’s design are sketchy. Andrew Byrnes, an executive with Spinnaker Energy – the San Diego company developing the project for Martifer – told Fortune that such information is “confidential” as are images of what the hybrid plant will look like and the identities of the company’s U.S. investors.
Here’s what we do know: San Joaquin Solar 1 and 2 will be built on private land outside the farming town of Coalinga. They will use long arrays of curved mirrors called solar troughs to focus the sun on liquid-filled tubes to produce steam that will drive electricity-generating turbines. That’s a standard solar technology currently operating in California and elsewhere. The biomass component of the plant will use agricultural waste, green waste and livestock manure to create heat that will generate steam.
It appears the biofuel will be used to keep the plant running at night or on overcast days. “The technologies can run simultaneously,” said Byrnes in an e-mail. “And when a cloud passes overhead (and after the sun sets) the solar facility can still generate energy, since the generation process is dependent on heat rather than direct solar radiation.”
While there is a natural gas-solar hybrid power plant under development in Southern California – see Green Wombat’s “The Prius of power plants” – San Joaquin Solar 1 and 2 will apparently be the world’s first biofuel solar hybrid.
Each power plant will each need 250,000 pounds of biomass a year to operate. Finding that fuel shouldn’t be a problem: Byrnes says a study shows that Fresno County alone produces nearly 2 million tons of ag waste annually.