A New Hampshire startup called SustainX that wants to use compressed air to store power - a promising alternative to batteries - has gotten $5.3 million in Energy Department “energy storage” stimulus funding to pursue the research. Check this list for various winners.

Using compressed air to store energy is being pursued by a number of companies, because large-scale storage is necessary for intermittent alternative energy to be a big part of the grid. The idea is that on a sunny afternoon a solar farm uses excess electricity to power pumps that store the air; then at night, the air comes out to spin electrical turbines and generate what you might call indirect solar power.

SustainX’s s Web site says it uses “isothermal” compression and expansion of air to store energy. Isothermal mean no change in temperature. The company says this produces “efficiencies in excess of 90 percent” (at least experimentally) compared to roughly 50 percent for traditional expansion, presumably because of energy loss by changing temperature. How they do compression and expansion without changing temperature, which I’ve always thought is a basic component of compression, is beyond me.

(About that company name: I thought we were past the time that companies put an “X” in their logo to seem cutting edge. Oh, well - at least they’re not called iSustain.)

Tags: compressed air