Green Dreams: Life in the Year of the Rabbit
by Danielle Fong
I’ve lived a lifetime this year. It sometimes feels as if so much is happening that one can feel however one chooses. Yet, sometimes, life gives you so much to feel happy about you can’t help but be overwhelmed with a feeling of gratitude.
We’ve launched our new website, and finally revealed the technology that we’ve developed and we think is going to change the world — regenerative air energy storage!
LightSail set out to prove that the science of our regenerative air energy storage concept works, and we have answered that challenge with a triumphant yes!
We built an industrial scale machine by modifying a commercial natural gas compressor. We changed the cylinder head, added nozzles, replaced valves to allow reversibility, coated the surfaces to prevent corrosion, and threw our minds and hearts at the problem of showing that our approach could dramatically increase the efficiency of compressed air energy storage. Without water spray, and without burning natural gas, previous attempts at storing energy in compressed air topped out at less than 50% thermal efficiency — ok for a backup system, but not enough to change the world. This year, we aimed at greater than 80% thermal efficiency, at a high RPM (and therefore power), to show that unlike what people had assumed, high efficiency does not mean sacrificing performance.
We met or exceeded all our technical targets — demonstrating record breaking performance at the same time as record breaking thermodynamic efficiency — conclusively demonstrating our water spray heat transfer idea behind our regenerative air energy storage concept is effective at industrial scale.
We presented to Bill Gates, a limited partner in the fund that invested in us. He was super excited by the potential of our project — that if we hit our targets it would change the world.
We spoke before hundreds of policy makers and energy executives, and helped instate groundbreaking legislation supporting energy storage in California.
We have settled on our ultimate product architecture and design — a huge accomplishment. We’ve got a long way to go, but our models predict our experimental results within 5% RME accuracy, so we have some real confidence that it will hit all our hoped for technical specs.
We truly defined our market and value proposition. We’re aiming to make renewables plus energy storage a better and less expensive way to provide high value peak power than what the conventional sources — natural gas peakers, diesel gensets, and extra transmission wires — can muster.
This is an utterly enormous market; at least a trillion dollars in size over the next couple decades.

IEA Estimates of Energy Infrastructure Investment Over 2008-2030. More than 30% could be economically addressed by renewables + energy storage
We’ve found that we’re uniquely positioned to reach that target, providing the lowest levelized cost of dispatchable electricity of any source, way ahead of our competitors.
But most of all, we’re excited about changing the world. Not only does energy storage make a renewables based grid possible, it also makes it economical. That’s the key to changing the world!
We’ve been working hard to uncover the greatest, most urgent opportunities for energy storage worldwide, and the opportunities we’ve turned up are simply massive. Energy storage is just what’s needed in places as diverse as Hawaii, Texas, Ireland, California, Paris, Denmark, Iceland, Nova Scotia, New York City, Australia, Chile, Dubai, India, and Subsaharan Africa. The scale and diversity of opportunities were astonishing. The most amazing thing? The willingness of governments to put their feet forward and most towards a future that’s right. We have been cynical; we believed that only once we had a full product, a long history, and economic parity under the most conservative of assumptions would governments move. We were proven wrong. Governments are leading the world into a clean future of energy. It’s utilities that are pushing back!
Take Iceland — a country of stark beauty. More than 80% of the country’s electricity is exported in the form of aluminum — the processing of which is one of the most energy intensive for any widely used material in the modern world. This single industry represents 40% of the Icelandic economy.
Essentially 100% of their grid electricity comes from their amazing geothermal and hydroelectricity resources, and an enormous amount of their heating comes from geothermal cogeneration. Iceland is a land of abundant green energy.
There’s a catch, though. Transmitting power across the sparse, weatherbeaten land is an expensive, unreliable proposition, where remote locations risk being knock completely off-grid with each storm. This is worse than it seems — if power is cut to aluminum smelters, the aluminum freezes, severely damaging the equipment. To backup the geothermal and hydro plants, then, industries have had to co-locate with diesel gensets — hardly a solution in light of the self reliance and environmental commitment of the Icelanders. We intend to replace these gensets completely. But we can do a lot more.
Low-temperature geothermal heat is available nearly everywhere in Iceland, and we can harness it. By expanding air at a higher temperature (and therefore pressure and volume) than when it was compressed, we get more mechanical energy out than we needed to compress it. This allows us to convert heat energy into mechanical energy, and from there, electricity. So instead of sitting idly like backup diesel gensets, our machines can be producing clean, geothermal energy, constantly; leaving the compressed air available for bursts of power when the grid fails.
So, we met with Iceland’s Minister of Energy — a former thermodynamics professor at Lund University, who bemoaned parliament’s inability to understand the concept of exergy.
We have therefore ‘rebranded’ our efforts. From now on, we have an initiative in ‘energy quality management.’ This they understand.
He understood the implications of an economical energy storage and geothermal electric generator immediately, and urged us to consider a project in Iceland. This is exactly the sort of progressive movement that governments are making and utilities resist. But we will overcome their skepticism! Stay tuned.
Of course, it wasn’t all business. If your mission call upon you to travel, it is your duty to truly experience the place. So I took the time harness some of nature’s forces myself. After I visited the grid operator and wind farms of Hawaii, I learned to surf!
We have continued to hire and improve our utterly world class team. We’re almost 30 people now, but I can tell you I have never before seen or even imagined such a diversity interests or depth of talent in a group. I work with the most amazing people I’ve met in my life! It is amazing to see how rapidly people are growing, but even more amazing to see how much more we can accomplish as a team. There are things that we literally couldn’t do on our own given all the time in the world — we have such a diverse set of skills in the company that we can make amazing things happen.
It was our first Burning Man. Our minds were blown. It is more than a festival, more than an amazing city. It is the most spiritually profound, unashamedly sensual, and maniacally creative place I’ve ever been.
We travelled as the chefs of the Airship Victoria last year; an airship project that eventually intends to hoist a Tesla-coil based lightning musical instrument. The camp, directly on esplanade, next to the flaming lotus girls, the sonic cannon, the flamethrower organ, and a 24 hour bar, was a surreal experience.
It felt like… the future! It turns out, in the future, there are lots of lights, people float around on bikes, and jellyfish hover and flow.
Wonderful. But the main thing about the future is that people can’t help but be caught in the moment.
Our camp featured tesla-coil concerts, and there, was, admittedly, high drama before the balloons were successfully fully deployed. Despite some initial setbacks, eventually the camp lifted their payload high into the air. In a city confined to a flat lakebed, the balloons added a third dimension to the playascape.
It’s impossible to describe the sense of flow one achieves in such a dizzying storm of self expression. We danced in drum circles in the nude, rode art cars and floated glowing jelly-fish, windsurfed and found inner peace. But what was most dazzling of all was the temple.
A strikingly elegant wooden structure, built in just 10 weeks by inspired volunteers, the temple was a deeply spiritual place of reckoning. The visitors, pilgrims of every creed, came and prayed, and made offerings for their loved ones, those who that had left them, those who they had left behind. Poems, and pictures, incense and chants, old clothes or talismans, and cherished items of every description, laid respectfully to rest, ultimately fated to return to the atmosphere aflame.
Steve was so overcome that he bent down on one knee and made an offering to his mother, a brilliant opera singer, who left the world when far too young.
As the temple’s towers, lean and graceful, slowly surrendered to the flames, glowing sparks rose deep from the inferno, and like wisps were carried up towards the heavens. The temple of transition, once a place of cool respite, now glowed brighter than the noonday sun. The crowd gasped as a shower of blue leapt out from the flames. Someone, days before, hid fireworks that launched streams of blue from the middle of the swirling firestorm, but in that splendid moment, it was impossible not to see those glowing blue apparitions, lifted high into the glowing sky, as souls, let finally free.
Upon our return, it seemed as if the whole of LightSail met us with faces silently asking us to bring them next year! We will.
This year, we’re starting a camp — tentatively named “Cleantech”. A solar powered shower and water recovery/purification system of our own design. It will be beautiful and efficient and environmentally friendly. Our kind of project!
At the end of the year, having wrapped up our work at our firehouse lab, having shown all we can with our current industrial scale prototype, we moved into our new facility — the former Scharfenberger chocolate factory, in which we will design, test , and manufacture our first product line. It is an amazing space. We will do outstanding work there, and we will be happy and proud.
As the move in completed, the holidays arrived, giving us the occasion to throw a lab-warming party for our friends and family. It was absolutely amazing. I felt as if the party unfolded as a microcosm of the entire project. It began with a simple idea: “let’s have a holiday party,” which lead to the conclusion “we clearly must have it at our new space,” and from that point, it took on a life of its own, spearheaded by people of admirable competence and outstanding creativity.
We were blown away by it all. The founders had no idea! Everywhere you looked there was perfectly executed brilliance.
Enter the space, we’re greeted with placards describing what all of the work is, what each of the rooms are, how each of the items work. There were demonstrations of our tank technology, our electronics and controls, our machineshop and quality assurance, our water spray lab, and even our original prototype (built in Ed’s garage using scrap parts and ebay!) We had no idea it would be there, and were blown away to see it!

Humble Beginnings: The Original LightSail Prototype, hydraulic, quirky, built of scrap, sweat, and parts ordered off ebay.
The original machine used a hydraulic approach — slower, with less power per unit mass or cost, and with higher inefficiencies, but we conclusively proved we could control the temperature of the air during operation, and control the valves to let only an amount of air in that would expand down to 1 atmosphere — yielding the very highest efficiencies. It was a cheap, quick way to show that some of our main ideas worked, and that we could build something. We sure have come a long way from that!
Travis O’Guin and his band played an incredible set of dixieland Jazz of some of the past century’s greatest compositions (ever wonder how “hit me baby one more time” is in dixieland jazz? Amazing.) Ed broke out into dance with a series of dancers, and the LightSail toddlers couldn’t resist the beat!
The machineshop was running — demonstrations included a CNC lathe disco ball, a hula dancer shaking it to an earthquake powered by the CNC mill, and just-in-time manufacturing of LightSail Branded Bottle Openers!

Dave Sprinkle spent years in the racing industry, but it's cupcakes that bring this smile to his face...
But what really stole the party were the cupcake cars, brought in by the brilliant Keith Johnson and his merry friends Lisa Pongrace and Greg Solberg. Our partygoers insist they’re even more fun to drive than a Tesla.
It was an unbelievable way to ring-in the new year. This is going to be a great one. That everyone injected such creativity and excellence in such a gathering just shows how much people care about their work and their team and this company and how high a standard they have for themselves. It seems as if everything at LightSail is like that — our people perform at a higher level than us founders can even think to ask of them, or indeed, even to imagine.
To top it all off, we received coverage from none other than Forbes Magazine. I am honored to be highlighted as the standout in the field of energy in the Forbes 30 under 30 ranking! My extended family is finally less suspicious of my dropout ways. What a relief! I had a wonderful time at home with my brothers and little cousins and found to my amazement that my family had founded four businesses between us since we last visited. I guess it’s in the genes.
This year looks to be even better. It feels like we’re reaching escape velocity.
I am honored to have been elected a mentor for the Thiel 20 under 20 Fellowship. These kids aren’t waiting to change the world, they’re just going out and doing it — I am so excited to be working with them!
I have been tapped to judge the Nova Scotia Cleantech Open, remarkable not only for being in my home province, but also for its amazing quality, rigor, and prize money ($100k free money with $200k of seed investment available.) I’m joining Matthew Nordan, of Venrock and Lux Research, whose work and judgement I have always admired greatly. His “The State of Cleantech VC is already a classic in the field.
We’re working full-speed on our product and technology, and are rallying allies across the planet to realize a wonderful number of as yet unannounced projects and partnerships.
Last year was an amazing year, but I have a feeling this one will be even better.
I am so happy to be alive at this moment in history. Great things are afoot. The winds are changing.
Fantastic post, Danielle! I’m so happy for you and Lightsail! May 2012 burn even brighter ! Wait- maybe not- might set us all on fire! :)
Fantastic update Danielle! We’re so happy to have you at 2U2 :).
Wow, it’s so cool to see this development. I can’t wait to see what happens next. Wish I could help more. Good luck trying to make more headway US energy, that will be an interesting battle I’m sure.
Here’s to continued success in the year of the Dragon!
wow ! this is wonderful website.very good update.Good luck trying to make more headway US energy.
Hi Danielle, This is a well written blog and a very intriguing ‘economizer’ application to Regenerative air storage systems. 90% for storage and 70% for generation, so 63% net? How does this compare to the best case hydroelectric type ‘storage’ system?
Do you guys have any whitepaper explaining the workings in details (I am a thermal engineer) and assumptions on the graphs?
I work for a company/industry where there is a very interesting (and huge) application for this. Also there are ways to make the system even more efficient with waste heat available. I couldn’t find your email address here, but please send a note to me on the email address mentioned below.
Thanks
Ankit
It’s 70% net; or so we aim. Pumped hydro can be up to 80% efficient but in actuality 70% is more typical so we’re at parity.
We can’t share too much but if you’d like to talk more just write us at contact@lightsailenergy.com
Hello Danielle:
May 2013 greet the coterie / small band of people dedicated to conquering energy, not just with profit around the fringes, but success in their pursuit at paradigm changing enabling technolgy. We are on the cusp of introducing, RET (working name) our proprietary high efficiency, inexpensive, multifuel (albeit NG, methane are fuel of choice, it can use waste heat, geo/solar thermal as energy stock), scalable turbine. Its operational domain includes low pressure differentials. It can improve the net efficiency of your compressed air storage system. I would like to discuss this with you at mutual convenience. I look forward to your positive response
Jay Rosenberg CEO, Sannerprojects, Inc (SPI),
An Energy Technology, Sales and Strategic Marketing Company
301-520-9719 Sannerwind@gmail.com CONFIDENTIAL SKYPE:Sannerwind
Hi I came across the cooling to compress air with spray water idea and it made me think about our refrigerators. If we have microwaves to heat our food, why isn’t there an electromagnetic wave to cool our food? There is theoretical talk of using sound in refrigeration for years but I’m not sure if it will ever reach mass production. I say this because it seems like a lot of engineering to interface the two phases of water and gas in the tanks. I’m not a science kind of person so honestly have no idea what I’m talking about. But, it would be sweet if a light or sound of a particular frequency can cool the air for compression and another frequency to heat it for expansion. Is there a alternative to water spray? You are doing good work. All the best.
I congratulate you on ditching fusion (meh, neutrons!) and going after the single hardest problem in renewable energy, which is storage.
So rather than storing the energy in the compressed air, you are storing it in water which you have warmed by 20 C. Presumably the water is held in an insulated tank. If you want to store a kilowatt-hour, you’ll need to heat up 43 kilograms of water, or about 10 gallons. The tank to hold that is going to cost about a dollar a gallon, or $10/kWh. You could shrink the tank by increasing the temperature swing… ah but that would increase the volume of insulation.
You’ll also need to store 360 liters of compressed air at 100 atmospheres. This seems like the main cost of your proposal. Just the raw steel for an ASME tank that can do that is going to be $300/kWh. (20 ksi working strain, 40 cents/pound for steel). And since 20% of the stored heat is in the air, it looks like you might want to insulate this tank too.
Right now, the difference between the cost of electricity at night and during the day in California is something like 2 cents/kWh.
To pay off the cost of the air tank, you’ll need to cycle the full storage capacity 15,000 times. The water tank will require another 500 times. If you are just storing the difference between day and night usage, that’s going to take decades.
It looks like you are planning to build and ship compressed air tanks. Those must be for some application that cycles full storage a couple of times per hour at least. You will only approach utility-scale storage when you use underground solution-mined caverns in salt.
Final thought: do you have a plan for filling a compressed air tank at constant pressure? The usual idea is to keep the pressure swing small by using an chamber deep underground pressurized with a water column and a lake or equivalent at the top. So long as the chamber height is small compared to the depth of the top, pressure swing is small. The bug is that for 100 atmosphere storage, you’ll need a 1 km height pressure stack. That’s a fine depth to hunt for salt domes, but a water tower that high is asking quite a bit.
Dear Danielle,
in your levelized cost comparison you use gas price of $7/mmbtu. Gas CCGTs are currently one of the most used and the most economical option for meeting peak demand or for balancing the increased share of intermittent power. In a way they’re your benchmark. Did you ever consider rolling out your technology in places where gas is more expensive (EU ~$12-$20/mmbtu) and the share of renewable & intermittent energy is higher than in US (Denmark, soon Germany)?
In my line of work I do quite a bit of modeling of energy systems in terms of backup&grid expansion vs energy storage investments (eg. mass adoption of electric cars). It would be interesting to consider compressed air. Do you have a projected spec of the technology ( how would it perform in say 10 years and how much would it cost)?
Keep up the great work!
Alfredas
It’s a good idea, and we will definitely deploy in Europe soon.
In a later post (and entry at SciAm) you wondered where the “90%” figure originated. It originated here.
I see.
Well, that’s not what we intended. In engineering, you break out efficiencies — electrical efficiency, mechanical efficiency, etc, and then multiply them all together to get a roundtrip efficiency, electrical to electrical.
Since it is so confusing for people, we should just remove it, or somehow explain it better. Unfortunately at the time we were not ready to showcase mechanical or electrical efficiency because we had not optimized it. We will be ready soon though, and then hopefully the confusion will end.