Lightsail Energy, a Californian company, has secured funding from venture capitalists including Khosla Ventures, to trial grid-scale energy storage using compressed air.

The technology was developed by the company's founder, Danielle Fong.

In a compressed air storage system, an electric motor drives an air compressor. To deliver energy, the process is reversed – the air compressor becomes an expander and the electric motor becomes a generator.

During compression, waste heat can be supplied to nearby buldings. During expansion, buildings can be provided with air conditioning cooling.

Ms Fong's innovation was to greatly improve the efficiency of this type of system by spraying a mist of water into the air storage tanks. This acts to absorb and store the heat generated from the compression and release it on expansion. As a result, the LightSail system is able to achieve an overall efficiency of around 70%.

Lightsail also uses storage tanks made with a proprietary material which enables them to store the air at higher pressures.