LightSail Energy: compressed air storage (closed)

LightSail Energy was a startup developing an energy storage system in the form of compressed air. Founded in 2008 with funding from leading innovation figures, the company fizzled out in 2017 and closed in 2018.

LightSail Energy’s technology

LightSail Energy was developing an isothermal compressed air storage system (CAES), also known asAdvanced Adiabatic Compressed Air Energy Storage(AA-CAES). The principle is to spray water during the compression/decompression stages, to absorb the heat changes in these two stages. The principle had already been published by Mike Coney et al. in 2002.

One innovation would have been the use of carbon fibers for the tank, which would be 2 to 3 times cheaper than steel for the same strength. They would also have reduced the number of cylinders and compression stages needed to compress to 200 bar.(source)

History and progress of LightSail Energy


LightSail Energy was co-founded in 2008 by Danielle Fong, Stephen Crane and Edwin P. Berlin Jr in Berkeley, California.

There was a lot of hype around Danielle Fong. She entered university at 12, graduated (Bachelor) of Science at 17, and co-founded the company at just 20, after dropping out of her PhD. She has been named one of Forbes’“30 under 30“, and in 2012 was named by MIT Technology Review as one of 35 innovators under 35.


The company has raised $46.9 million over 4 investment rounds:

  • july 5, 2009, $7.6 million from Khosla Ventures.
  • november 5, 2012, in the amount of $37.5M, notably from Innovacorp, Peter Thiel, Bill Gates and the TotalEnergies fund
  • february 9, 2013 (undisclosed)
  • april 20, 2015, in the amount of $2M.

It is frequently mentioned that, among the investors were Bill Gates and Peter Thiel, but I have no exact trace.


In May 2016, the company shed 75% of its payroll, down to 15 employees. On December 19, 2017, a press article reports that the CEO confirmed that the company was entering “hibernation”.

There seem to be several controversies surrounding the company and Danielle Fong. The latter responds on her blog. According to the latter, it was the choice of renting technology instead of manufacturing its own hardware that “essentially killed the company”.