By Danielle Fong (Co-Founder & Chief Scientist, Lightsail Energy) LightSail Energy is a green energy startup company that’s trying to make it possible, and economical, to power the world with nothing but clean, green energy. We’re tackling what some call the holy grail of green energy -– how to economically and efficiency store energy such that intermittent renewables such as solar and wind can reliably and economically power our electrical grid.
To do this, we’re taking compressed air, an elegant technology from a more civilized age, and using it to store energy. Compressed air is already considered to be the most inexpensive method for storing energy. Our objective is to make it more efficient.
When you compress air, what you’re really doing is converting mechanical energy into heat energy, inside the air. Conversely, when you expand air, you’re converting the heat energy in the air to mechanical energy. The amount of energy converted, for a given mass of air, is proportional to the temperature of the air. The trouble starts when the air is compressed. To achieve a high energy density, compressed air energy storage systems compress to more than 100 times atmospheric pressure, or higher. In doing so, the air reaches extremely high temperatures, nearly 1000 C. This is too hot to manage practically, and so the air is compressed in stages, rejecting heat to the atmosphere after every stage.
By rejecting heat to the atmosphere, you lose the energy you’ve stored. Conventional systems add heat back by burning natural gas, but that still presents both a carbon footprint and inefficiency.
We have a different approach. By spraying water into the air during compression, the most of the heat goes into the water, rather than the air. And water has a much higher capacity than air -– 3300x at standard conditions. You don’t need to spray in much before what would have been a temperature rise of, say, 800 degrees C, becomes a temperature rise of around 20 C -– much more manageable. We can then just hold on to the water, and the heat in a tank. We then spray the water back in during expansion, recovering the heat energy and converting it back into mechanical energy. We then convert the mechanical energy to electrical energy, using a motor generator.
On Being A Cleantech Entrepreneur -- A Day In The Life
There isn’t a very typical day at LightSail, but I often begin my day with coffee and breakfast with my cofounder, Steve Crane –- a lapsed Caltech geophysicist who found himself first in the 3D graphics industry, and then the entertainment business, responsible for some of the biggest hits in history. He tried to hire me for a videogame startup; I ended up convincing him to join me as cofounder, and funding our first efforts through the sale of a house. We talk about everything. We talk about our technical challenges; the engineering and testing effort, the physics, we (try to) invent solutions to the challenge of the day, we try to figure out how to make our team as happy and effective as can be, we discuss the broader implications and applications of our technology, we talk about our philosophy, and duty as a company, and we talk about the world at large; everything from oceanography to filmmaking to dancing to the philosophy of science to the finer points of Italian cuisine. We’ve become best friends.
Then it’s off to the lab -– a converted historical Firehouse in Oakland’s Lake Merritt/Chinatown district. Our laboratories occupy the bottom two floors. In the bottommost floor we have a test cell with a control center behind bulletproof glass (just in case), a machine shop with a CNC-mill, and an assembly and quality control room. In the stable (the fire engine used to be drawn by horses) we have a laser lab for imaging sprays, and a conference room. The tower where they used to dry the canvas hoses has been converted into an exhaust manifold, outfitted with a muffler and a heat exchanger. We converted the hayloft to our electronics lab, and upstairs are our main offices.
We’re a little jam-packed in there. There are nearly 30 of us in total, so we’re moving to our new facilities (a 25,000 ft2 former chocolate factory) in October. Until then, we’ve got our design room in the fire captain’s quarters, our experimentalists, electricians and technicians in the living room/kitchen/dining area, and our CTO and third cofounder, Ed Berlin, in a bedroom he’d converted to an electrical lab. The remainder are scattered throughout the machine shop, hayloft, and much of the analysis and business team (which includes Steve and I) reside in a penthouse in a second building across the street.
(I should mention that both Steve and Ed were prodigies in physics and engineering to the same extent that I was. Steve won his first research grant at 13, and entered MIT at 16; Ed, another MIT grad, built his first circuit at 3 and won the engineer of the year award from Grumman Aerospace –- a 30,000 person company, mind you, at 21. People make a big fuss about me entering college at 12, but it was mostly that I had to find somewhere other than my dysfunctional middle school after dropping out. Plenty of other people could – and have –- done it.)
The heart of the company is really the test cell, and we have a ‘driver’ from the racing industry (actually he focused on dynamometer tests, never racing in a car!) running most of the full-scale system tests. There’s a desk full of screens and controls, and one graph in particular, the pressure volume curve, draws particular interest from our theorists, and passersby.
If the test cell is the heart of the company, the whiteboard in the dining room area is the head! We often start discussions there, and people will drop in as they overhear and contribute. Our technical discussions can get quite intense, and we calculate much of what we need to make decisions by hand, in real-time, to verify the contentions and work that happens at our desks. All of our management comes from a deeply technical background, we all get our hands dirty, and we all dig into things and calculate them ourselves; especially with the most important technical decisions. There’s some replicated work, true, but we’re fast, and this gets us all on the same page. It helps to have generalists!
I’ll walk around the company, checking up on progress and issues, checking in to see if I can help people do their jobs, or if people are stuck, or need someone else to do something first to make progress. We spend a lot of time making sure people understand everything, and making sure that internal communication is handled correctly -– it’s hard to get 30 people on the same page all the time! To that end, we get everyone lunch on Thursdays, which we have called “stupid question day.” Everyone is encouraged to ask their stupid questions – and people are obliged to answer them graciously!
Some days, we interview candidates. Our interviews are pretty comprehensive. We give a tour and the hiring manager introduces the position and the company. For most positions, we ask that people give a presentation on their previous work/explorations/education, and we ask lots of questions. Many people interview the candidate, and in the process we give both an in-person and a take home exam. The in-person exam involves much at the whiteboard, and sometimes we get people into the lab and have them solve an experimental puzzle and describe their solution. We have a world class team; the best that any of us have worked with.
I’ll return to my own desk at some point, and answer a slew of emails. Internal communication is critical! Then, every day, I’ve made a pact to myself to do at least one hardcore engineering thing –- either in analysis, or making a spec, or designing a new experimental approach, or inventing something practical.
Maybe I’ll bike back, or grab dinner with Steve or friends. The evening and night are for big picture thoughts, and maybe a little music (I love my keyboard and guitar).
Then it’s to bed, and then, another day!
This interview was originally posted at Danielle Fong's blog.
Editor's note: Got a question for our guest blogger? Leave a message in the comments below. About the guest blogger: Danielle Fong is Co-Founder and Chief Scientist at Lightsail Energy, a green energy startup that's harnessing compressed air to allow intermittent renewable energy sources, like wind and solar, to reliably and economically power the world. She is an honors physics and computer science graduate of Dalhousie University, earning a university medal at 17, and performed graduate studies at Princeton's Plasma Physics Lab. She publishes essays online at DanielleFong.com. Follow her on Twitter at @daniellefong.