The DOE considers energy storage a crucial technology for the smart grid, the modernized version of the electrical grid that will be built over the next decade or two. The goals of the smart grid are higher efficiency, lower pollution, and lower cost.
SustainX said that, when demand rises suddenly, the peaking turbines fired by natural gas must rapidly come on-line. Since such plants are idle most of the time, they are an expensive source of power. With storage units scattered at strategic points throughout a smart grid, however, shifts in demand could be met more flexibly, lowering transmission and generation costs.
Energy storage will also enable the grid to support integration of renewable energy sources. The SustainX energy storage system addresses the need by storing energy in the form of compressed air. Electrically-driven hydraulic pumps are used to compress air to high pressure (up to 3,000 psi) for storage above-ground in standard industrial pressure vessels. This air is later expanded, powering a hydraulic motor that drives an electric generator. The technology uses isothermal cycling – that is, the air is kept at a constant temperature – coupled with staged hydraulic compression and expansion to deliver efficient energy storage.
Each SustainX energy-storage unit acts like a large storage battery. No fuel is needed to run the unit. A cluster of such units will produce megawatts of electricity for hours on end.
The DOE award is funded under the American Recovery and Reinvestment Act of 2009. Previously, SustainX has received a Small Business Innovation Research grant from the National Science Foundation and venture-capital funding from Polaris Venture Partners and Rockport Capital Partners.