How A Young Physicist Is Making Solar Power Work, Even When The Sun Is Down

Danielle Fong might have dropped out of grade school, but that hasn’t stopped her and her company LightSail from finding a way to potentially drastically change how much power we can get from renewable energy.

It is not unreasonable to expect that the renewable energy collected by the world’s solar panels and wind farms is being stored somewhere, ready and waiting to power our microwaves and hairdryers at a moment’s notice. Bad news: mostly, it’s not. Sure, there are a few methods in practice—expensive batteries that degrade over time, a medieval-sounding technique that involves pumping water up and down a hill—but by and large, if there’s a lot of wind blowing but not enough lightbulbs to use it, that energy simply goes to waste.

Hopefully, that’s about to change. Danielle Fong is the chief scientist (and grade-school dropout) behind LightSail Energy, a Berkeley-based team that’s developing compressed-air technology to store the power we don’t use, and return it to the grid when needed. It’s a simple concept: Just use the electricity generated by your solar panel and/or windmill to power a compressor, pushing air into a tank. When you want your energy back, you release the air out of the tank, and use it to drive a generator, creating electricity. "That’s the basic idea," says Fong. Sadly, there’s more bad news again.

Compressed-air technology has long struggled with efficiency—the heat energy generated via compression has always gone to waste—and that’s the almost part where LightSail’s greatest innovation swoops in. Fong was researching compressor-powered vehicles when she had her eureka moment: "It became clear that what you wanted to do for maximum efficiency was keep the temperature as close to constant as possible in compression and expansion," she says. "It turned out nobody had figured out how to do that, and I read a Wikipedia article saying it was impossible to do it, and I said, ‘My god, that’s not true. You can just spray water in.’ And then I was like, ‘Wait. I could just spray water in.’ And thus the company and core idea was born."

What does spraying water in do? Best to let the genius explain: "Instead of wasting the heat, we collect it by spraying water into the air during the compression process," she says. "That keeps the temperature down, and it keeps the pressure down, so you have to put less energy in to compress the same amount of air. During expansion, spraying water sends heat back into the air, which keeps the pressure high, and increases the amount of energy you get back." Science aside, the numbers don’t lie: LightSail’s process recovers 70% of the energy it puts out, pretty much doubling the efficiency of the standard compression method. "Eventually, we’re going to replace all of the energy requirements of the world," says Fong. "Or so we plan. The world has a way of turning out with surprises."

Indeed, surprises abound in Fong’s story, starting with her decision to bail on middle school at the age of 12. Her precocious worldview was shaped via reading everything from astrophysics textbooks to A Confederacy of Dunces, as well as through video games like Sid Meier’s Civilization and Alpha Centauri, where, as she puts it, "I would take responsibility for the future of the world over and over again." A big influence was SimEarth: The Living Planet. "It is notably hard over eons to keep the climate of SimEarth stable," she explains. "My Earth kept dying. So I gained a visceral awareness of the interconnectedness of all these different life systems, and as a result, I think I questioned whether or not we were doing the right thing." By 17, she’d graduated from Dalhousie University in her native Halifax, Nova Scotia. From there, she was accepted to the PhD program at Princeton’s Plasma Physics Lab, where she decided the whole hot fusion thing was taking way too long, she had no interest in the academic model of writing (and being rejected from) grant applications, and she wanted to start changing the world now. "I don’t see why people should waste time," she shrugs.

Having set out to earn enough money to fund her independent research, Fong was working a brief stint at a video game company in 2008 when she met up with a PhD physicist named Steve Crane. Something clicked, and three months later, the two had founded LightSail; three years later, they had all the kinks worked out, and were ready to start the production phase of development. They plan to deliver their first shipping-container-sized units in late 2013. And after that? World domination, of course. "We’ve talked a lot about different defining visions for the company," Fong says, "and one that’s always risen to the fore is this idea of democratizing energy: Providing energy how people want it, where they want it, and when they want it, at affordable prices for everyone."

Sound impossible? Fong doesn’t see why that should stop her. "The message I would like to put forth is that there are great innovations in ways to do things that are sort of right under people’s noses," she concludes. "And if they opened their eyes and worked towards it, it might not take too long before we live in a much greater world. This is a neat trick: If you don’t feel confident enough to say something is possible, you can say, ‘Well, is it impossible?’ Try to prove that it is not impossible, and in so doing you can show the way."

This piece is part of Change Generation, our series on young, change-making entrepreneurs. Read the rest here.

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  • John

    Compressing air to store energy is a great idea , and the heat generated could be captured to boost refrigerant temperatures of heat pumps  both air sourced and hydronic systems  when in heat mode too!

  • Dan

    Interesting Stuff. Any heads up on the capacity and pricing this? We could undertake some trials to see how it adds up in 'live' conditions. drop me a line.

  • Danielle Fong

    Our pricing is extremely competitive. You're welcome to contact us at contact at lightsail dot  
    .com for more information; at present we have quite a waiting list for our sales but are searching for the right partners for entry into specific markets.
    -- Danielle

  • tphm

    Great work and best of luck, Danielle.
    I sincerely hope it work. I saw other way to store energy via transferring of gravels up and down hill, but we don't all live near or own a hill.
    If this device is compact enough and reasonably priced, it could really trigger our energy revolution through distributed and connected grid.
    It's great to see you are influenced by my favorite Civilization game also :)

  • Jerry

    Your attitude/philosophy is quite inspirational.  Curious how you deal with corrosion/oxidation issues?  Seems most people want to keep water out of their compressed air tank...

  • Danielle Fong

    We recycle the water using a separator. In most populated areas, at most times, the device actually condenses more energy from the atmosphere than we lose to evaporation. This is not true in inland Saudi Arabia (where a very small water addition in the very worst cases approximately .2 L per kWh, about 0.1% of the desalination energy cost ), but is otherwise quite a robust phenomenon. 

    -- Danielle

  • Jerry

    Not sure it's that simple ;-) Second question do you recapture & reuse the water? The tank will obviously separate it, or perhaps a centrifugal water separator. If my solar farm is in a hot dry area, what will my water requirements be?

  • Bill Nunley

    Danielle, I am very interested in this technology but I want to see this on an individual basis. Would you be willing to share exactly how this works?

  • Danielle Fong

    We have some patents and a website which you may read, but we can't share on an individual basis based on time constraints. Sorry.


  • Danielle Fong

    A couple comments:

    At Princeton I was largely working on hot forms of fusion, though occasionally interested in colder muon catalyzed forms. Cold fusion might be possible but I've done no real work in the area. Who knows at this point. 

    I graduated at 17 and entered Princeton before my 18th birthday.

    Most importantly, however, the message at the end is how I'd like to phrase it! 

    - Danielle Fong

  • NicholasTylerMiller

    Compressing air is just as 'midevil' as pumping water up and down a hill.  It's not a bad idea, but why slam hydraulic energy storage?  At 85% efficiency, it's actually more efficient than the technology you're reporting on and already in use around the country.

  • Danielle Fong

    To be clear, the efficiency of pumped hydro varies between 60 and 85%, depending on geography, temperature and humidity. Furthermore, our system is locatable in many more places, allowing one to avoid the cost of transmission and distribution upgrades -- one of the most important and prominent values of an energy storage system. You can't do that unless you're actually co-located with the varying supply or demand.

    Pumped hydro is a great technology, but limited in scope. And largely tapped out, unfortunately. Locations near a lake, river and mountain are often beautiful areas claimed for natural parks. Both landowners and environmentalists are reticent to dam and flood them in order to store energy, and they usually claim huge areas.

    We also believe that we'll end up besting the cost --both capital and levelized -- for pumped hydro, in the vast majority of locations and applications.

    - Danielle Fong

  • Dibbo

    Not sure about the rest of the country, but here in California the one major pumped hydraulic storage setup, Helms Creek, tied to Diablo Canyon Nuclear Power Plant, I do no believe is operating at 85% efficiency. Please see the following link.  Also Helms Creek cost over $ 1 Billion to build. While the cost for one of Ms. Fong's containers was not disclosed, the topic of return on investment, not just efficiency must be included.  Also Helms Creek has a 1600 foot difference in elevations between reservoirs, not a situation common in much of the country.