Pacific Gas & Electricity has won one of the Obama Administration’s 16 advanced grid awards totaling $620 million in American Recovery and Reinvestment Act (ARRA) funds, aimed at making more renewable energy available to the grid. PG&E’s $25 million award will fund initial work to see if California can store its excess night time wind – in air.
The utility planned (previous story) to build 300 MW of compressed-air energy storage that will enable Californians to get more clean power out of the wind energy that is currently on their grid, but goes to waste in the wee hours while they sleep. To make that change happen, night wind storage is key.
PG&E’s Jonathan Marshall told me “There have been times that wind turbines at Tehachapi have actually had to be turned off at night, because power going into the grid causes damage if it’s not used.”
If the tests of this technology pan out, then air in porous rock in Kern County will be able to store and release 300 megawatts of wind every night that would otherwise go to waste, for a total cost of $365 million.
Underground compressed-air is the cheapest (per the EPRI ) of the excess storage options to pair with renewable energy, but it does require a certain sort of porous rock formation in the right place to be a viable option. There is a good chance that Kern County has the right geological formation to be a good site.
At night electricity generated by the excess wind would power air compressors to force air into underground caves. Then in the morning when power is needed, the air is released to power a turbine, which generates electricity. Compressed air cuts the small amount of gas used by the generator in half. CAES is a key ingredient in getting more renewable power on the grid cheaply as it could also release low-carbon bursts of power during times when the sun suddenly goes behind a cloud, normally a job for gas power plants.
Marshall told me that with the DOE award, PG&E hopes to get CPUC rate approval to raise a matching fund to begin the geological surveys and site work, and ultimately to build the remainder of the $356 million project.
The CAES project could save customers money in the long run by capturing and using low-cost, off-peak energy to avoid the need to build new power plants to serve peak demand. A similar plant under development through Sandia National Labs; the Iowa Stored Energy Park is expected to save $5 million a year with 268 MW of compressed-air energy storage.