Turn a glass upside down and plunge it into a sink filled with water.
You’ve just demonstrated the operative principle behind a compressed air storage system being developed by startup Bright Energy Storage Technologies that — conceivably — could deliver large amounts of power for 2.5 cents to 6 cents per kilowatt hour.
The company’s core technology consists of a long, flexiblepolymer/glass bag shaped like a giant sea cucumber. One end of the bagis attached to an air hose on the surface. The other end is open to thesea. Sand from the sea floor anchors the open end of the tube to a sandflat 140 meters below the surface.
To store energy, generators on shore will compress air and funnel it to the bag. While some air can bubble out the open end if overfilled, themajority of it stays inside, in the same way air stays in the upsidedown glass or when you blow into a straw.
When needed, the air can be quickly dispatched. Sea water (or waterfrom a large lake) fills the void until more air gets sent down.
The potential low cost of the technology derives from the fact thatBright doesn’t need high pressure storage tanks or lots of activemechanical equipment. The body of water does most of the work.
“We design for no moving parts and no metal,” says chief technologyofficer Brian Von Herzen. “Sand at the sea floor is 100 times lessexpensive than steel. It is free at the bottom of the ocean. The mainexpenses for the ballast are the permit and installation.”