If you haven't seen already you might be interested in http://lightsailenergy.com/tech.html http://lightsailenergy.com/tech.html; they're working on compresse

If you haven't seen already you might be interested in http://lightsailenergy.com/tech.html http://lightsailenergy.com/tech.html; they're working on compressed-air-and-water-vapour storage (also DaniFong posts on HN sometimes)