Entire cities could run on compressed air by Tina Casey

CleanTechnica

The company LightSail Energy started out a few years ago with a student’s modest idea for a compressed air scooter, and now it has just raised $37.3 million in private funding to bring utility scale, compressed air energy storage to the market. That’s a big leap not only for the company but for compressed air technology itself, which has long been eyed for its clean energy potential. The problem has been to make the process efficient enough to deliver power at a commercial scale, so let’s take a look and see how LightSail solved the problem.

The Compressed Air Conundrum

As aptly described by writer Rachel Metz over at the MIT Technology Review, half of the compressed-air equation is simple enough from a clean energy perspective. You can use any form of alternative energy such as solar or wind to generate electricity, which in turn powers a motor that compresses air in a tank.

The  hard part kicks in when you try to store large quantities of compressed air. Compression adds energy in the form of heat (almost 1,000 degrees centigrade, according to Metz) and that leads to enormous complications.

The Indian car manufacturer Tata Motors has apparently found at least a partial solution for small scale compressed air, but LightSail is going down an entirely different road.

LightSail’s Compressed Air Solution

Danielle Fong, Chief Scientist and co-founder of LightSail, is the former student who dreamed of a compressed-air scooter. She solved part of the problem by designing two related features into the system. One involves using mist to cool the air, and the other involves recapturing energy from the spent mist, in the form of heat.

According to Metz, Fong and her partners also identified a compound that could be used to manufacture tanks strong enough to store bulk quantities of compressed air above ground, in relatively inexpensive facilities, leading to the conclusion that “there are no technical barriers to building units large enough to power entire cities.”