LightSail Energy (LightSail) is a Berkeley, California, company that has developed compressed air energy storage technology which may be used for grid-scale storage.
The company’s central innovation is the injection of a mist of water spray into a compressed air system so the spray rapidly absorbs the heat energy of compression and provides the energy during expansion.
According to Cleantech PatentEdge™, LightSail owns at least 52 US, international, and European patents and published applications. U.S. Patent No. 8,240,142 (’142 Patent) is one of a family of patents relating to the company’s compressed air energy storage system.
The ’142 Patent is entitled “Compressed air energy storage system utilizing two-phase flow to facilitate heat exchange” and directed to a compressed air energy storage system (20) including a cylinder device (21) defining a chamber (22), a piston device (23) in the chamber, and a pressure cell (25). The cylinder (21) and pressure cell (25) together form a one stage reversible pressure compression/expansion mechanism (24).
Air enters the system (20) via pipe (10), passes through a filter (26) and enters the cylinder chamber (22) via pipe (30) where it is compressed by the action of the piston (23). Before compression begins, a liquid mist is introduced into the chamber (22) using an atomizing nozzle (44). The volume of mist injected into the chamber (22) is predetermined to be the volume required to absorb all the heat generated during that piston stroke.
As the mist condenses, it collects as a body of liquid (49e) in the cylinder chamber (22). The compressed air/liquid mixture is then transferred into the pressure cell (25) through outlet nozzle (11) via pipe (51).
According to the ’142 Patent, that is when the critical heat exchange occurs, followed by storage of the air:
In the pressure cell 25, the transferred mixture exchanges the captured heat generated by compression to a body of liquid (49f) contained in the cell. The air bubbles up through the liquid and on to the top of the pressure cell, and then proceeds to the air storage tank 32, via pipe 33.
According to this Greentech Media piece, LightSail’s system is more efficient because it captures and stores both the mechanical energy and the thermal energy used in compressing air. The article reports the company has received a recent funding round by some big name investors, including Bill Gates and Khosla Ventures.