WEST LEBANON, New Hampshire, March 22, 2011 /PRNewswire/ -- A fourth patent has been awarded by the US government to SustainX, a fast-growing technology venture in Lebanon, New Hampshire. SustainX has developed a transformational technology for utility-scale energy storage using compressed air. The new patent covers methods for controlling the way air is expanded and compressed in such systems.

Energy storage is essential to making the electrical grid more efficient, according to the US Department of Energy, but affordable storage technologies have so far been lacking. To meet this need, SustainX compresses air by using electricity to drive pistons inside cylinders. The resulting high-pressure air is stored in above-ground vessels. To release energy at a later time, the system uses stored air to drive the same pistons, which in turn drive an electric generator.

The company's new patent, No. 7,900,444, covers the use of measurements of conditions inside the cylinders, such as temperature or pressure, to keep the air at a nearly constant temperature during compression and expansion. One method for controlling the air's temperature is to spray water through it. By maintaining near-constant ("isothermal") air temperature, SustainX significantly improves the efficiency of compressed-air energy storage.

"This patent, along with the three others awarded to SustainX during the last year, further establishes the company as the world leader in isothermal compressed-air energy storage," says President and CEO Thomas Zarrella.

This new patent, combined with previously issued patents on staged compression and expansion and on heat exchange with a thermal well or the environment, strengthens SustainX's IP position in the field of compressed-air energy storage. The issued patents are general enough to cover a wide range of isothermal systems, including both existing SustainX systems and those in development.