Barbara Haislip for the Wall Street Journal:  Few industries are more daunting for entrepreneurs these days than clean energy.

Developing the technology and hardware is expensive, and setbacks are common. Even if all goes well, getting a product to market can take a decade or more. Most venture-fund investors, meanwhile, want a quicker payout.

Danielle Fong, co-founder and chief scientist of LightSail Energy, is trying to keep investors happy while working toward some ambitious clean-energy goals. Her company’s aim, she says, “is to produce the world’s cleanest and most economical energy-storage system” through a technology that uses compressed air to store energy from the grid. LightSail’s technology will do this more efficiently than other solutions, Ms. Fong says, by capturing some of the excess heat that comes when compressing air.  “Until now, this was wasted, reducing efficiency,” she says.

Founded in 2009, Berkeley, Calif.-based LightSail has raised $70 million from several investors, including Bill Gates, Peter Thiel,Khosla Ventures and the French energy giant Total.  Cont'd...