SustainX announced today it's received $14.4 million in funding from GE subsidiary GE Energy Financial Services, Cadent Energy Partners, Polaris Ventures, and Rockport Capital.

The New Hampshire-based company is a start-up that grew out of the Thayer School of Engineering at Dartmouth College in 2007, and has been developing a compressed-air energy storage unit intended for integration with smart grids.

Simply put, its innovative storage unit uses compressed air to store, then generate electricity. But unlike other compressed-air storage units, which use a compressor to store air underground, SustainX stores the air in a standard tank located above ground and uses a hydraulic piston system and hydraulic motor.

Electricity initially runs the hydraulic piston system to create and store high-pressure air in the tanks. Then, when electricity is needed, that high-pressure air is channeled to drive a hydraulic motor that powers an electric generator. The system uses isothermal compression and expansion to keep the air at a consistent temperature to maximize efficiency.