While compressed air energy storage is by no means a new technology, the intermittency of wind and solar power are driving a renewed interest (and investment) in the new technology. Perhaps the biggest recent news was the $37 million that LightSail Energy nabbed from big name investors, including Peter Thiel, Bill Gates and Vinod Khosla.

Compressed air storage works by converting excess electricity output from a generation source into highly pressurized air. The problem with doing this has been that the process produces enormous amounts of heat, with the air temperature rising to nearly 1000 celcius. Startups like LightSail spray water into the air during compression to absorb heat. Later the water has to be separated out of the mix so that you store dry air. Running the process in reverse releases the stored energy.

Most of the energy storage technologies around, including batteries, are very expensive right now. But it’s looking like there’s no alternative to dealing with supply side problems on the electrical grid so stepwise improvements in energy storage costs could find themselves competitive in the market.

For more on battery storage, see “Opportunities in next generation battery technologies.”