SustainX Inc., an energy storage technology company based in West Lebanon, N.H., has bumped its recent funding round up by an additional $5.6 million and added new backer General Catalyst Partners to the investor mix, the company reported in a release.

This new funding amount boosts the recent funding announced in March to $20 million. According to the release from SustainX, the new money will be used to further develop the company’s compressed air energy storage technology. The original $14.4 million funding amount in this round came from GE Energy Financial Services, a unit of GE (NYSE: GE) and other investors. Other backers include Rockport Capital, Polaris Venture Partners, Cadent Energy Partners and General Catalyst Partners. ...

SustainX, which was founded in 2007 by engineers at the Thayer School of Engineering at Dartmouth College, compresses air for energy storage by using electricity to drive pistons inside cylinders. The high-pressure air is stored in above-ground vessels. To release energy when needed, the system uses stored air to drive the same pistons, which in turn drive a generator.