Harnessing and Storing Renewable Energy using compressed air and water spray

An Entrepreneurial Technologists Vision...

Danielle Fong. Remember her name. Because this 26-year-old Canadian physicist is on course to irrevocably change the face of renewable energy forever. If her plans succeed, we may one day attribute mass accessibility to green energy to her and her start-up LightSail Energy.

Harnessing renewable energy

So what was her 'eureka' moment we hear you ask? Well, as we all know one of the major stumbling blocks to harnessing renewable energy is storage. When the wind blows, and the sun shines, we're in credit. But when neither is playing ball, we're left with a shortfall.

Fong's masterstroke was not merely to recognise the potential of storing energy by way of compressed air but rather how to find a way to overcome the medium's inefficiencies; namely the phenomenal levels of heat (nearly 1,000 degrees celsius) that is generated during compression.

Her solution? Water compression.

Writing on the LightSail blog, Danielle Fong says: “The problem is that when you compress the air, as anyone who pumps up a bicycle knows, the air gets hot. The basic idea is to spray water in during compression.

“Water has an incredibly high heat capacity, about 3300 times that of air at atmospheric pressures, so you don’t need a lot of it to hold the temperature of the mixture nearly constant during compression. And an atomized spray has an incredible amount of surface area.”

She continues, “That means it can transfer an incredible amount of heat. Essentially it’s like a heat exchanger that you can squish and regenerate inside the compressing volume.”

An economical solution

It's clever stuff indeed. It's also very economical. MIT Technology Review says, “Batteries are the current state of the art in storing excess wind and solar energy, but Fong says the LightSail system will cost less to purchase and will last for a decade or more.

“Over the long term, she says, the system could cost as little as one-tenth as much to own and operate as batteries do. A single system, which is about the size of a shipping container plus a car-size unit, will store the energy generated by a one-megawatt wind turbine running for three hours.”

Fong and her team developed a filter system to separate water from the highly compressed air, as well as a system that integrates both the compressing of the air and its expansion to drive a generator. If that wasn't enough, they've also sourced a top secret compound, that is more efficient than steel, to fabricate their storage tanks.

Little wonder that the Berkeley outfit has attracted funding from Khosla Ventures, Bill Gates and venture capitalist Peter Thiel to name but a few. Fong herself has been named amongst Time's '30 People Under 30 Changing the World' and 'CNN's 40 Under 40: Ones to Watch.'

Whole cities could be powered this way

The first test units should be rolled out sometime this year and eventually whole cities could be powered using LightSail Energy's low-cost technology.

LightSail say, “The expected cost of electric infrastructure upgrades worldwide over the next two decades is almost $14 trillion. More than 30% of this investment serves a need that could be economically met with energy storage at the right price.

“If it were less expensive to store and deliver low-cost, off-peak energy on demand than it is to make more of it with conventional peaker plants, the energy landscape would change dramatically.”

As for Fong, she is pragmatic about her role in bringing about that change. She says, “I knew that providing abundant clean energy would be one of the greatest challenges of my generation, and as a technologist, I knew it was something I could contribute most meaningfully towards.” Danielle, we believe you already have.

Watch this video on economically storing energy as compressed air.