LONDON – LightSail Energy Inc., a 2009 startup developing energy storage based on compressed air, has raised $37.3 million in its latest funding round led by Bill Gates, Peter Thiel, Khosla Ventures, Innovacorp and others.
LightSail (Berkeley, Calif.) is based on the scientific advances by Danielle Fong, chief
scientist and co-founder. Fong is a graduate student at
Princeton University where she began work on her PhD at the age of 17.
Lightsail is attempting to apply thermodynamics to develop energy storage based on compressed air. Energy is recovered when air expands, and proponents argue that deployment of the technology on a megawatt scale is expected to provide economical energy storage for use alongside wind and solar farms.
The latest round of funding reportedly takes LightSail's total raised so far to over $52 million.
The investment round will allow LightSail to "bring its first grid-scale energy storage products to market," Steve Crane, co-founder and CEO of LightSail Energy, said in a statement.
The startup claims its thermodynamics technology "works at scale" and that the new funding puts in a position to deliver renewable energy locally and more cheaply than large, centralized fossil fuel-based power generation. "We want to democratize energy," Crane added.
"When deployed, LightSail's technology would reduce the need for transmission line investment, peaker power plants, and make renewable energy practical and mainstream for the first time," Vinod Khosla, founding partner of Khosla Ventures, said in the same statement.
Danielle Fong, chief scientific officer at LightSail Energy
LightSail's said its technology is able to use electrical energy to compress air and then reverse the process to deliver power when it's needed. During the compression phase, water is sprayed into the pressurized air, absorbing heat produced by the mechanical process. The hot water is stored. After expansion, water is again sprayed into the expanding atmosphere and the resulting energy is used to drive the expansion.
LightSail claims that the round trip from grid to storage and back to grid is 70 percent efficient.
The startup proposes that compressed air be stored in shipping container-lie tanks. The tanks could then be linked via pipes to form storage farms. The company's first product, the RAES-V1, is scheduled to begin shipping in the fourth quarter of 2013.
You're right that there are many ways to store electrical energy, then release the stored energy in time of need.
The difficulty is economic: the released energy must be cheaper than generating the same amount of energy anew.
Suppose, instead of water, you spray gasoline into the compressed air to absorb heat. Then when energy is needed, you spray hot gasoline into the compressed air to recover most of the original stored energy.
Then you ignite the gasoline/air mixture to get the multiplier effect. So you'll probably recover 100 joules from 1 joule of the original stored energy.
The problem with this imaginary scheme is economic. The energy recovered this way probably costs more than Lightsail's.
And probably both schemes might (?) cost more than just generating anew the same amount as that saved energy, from dirty but dirt cheap coal!
Well, it appears as though her primary contribution was to convert adiabatic compression into isothermal compression using water as the heat-sink (and thermal storage). She then recovers the energy by re-injecting the heated water leveraging the heat of vaporization. Not to undermine her insight, but it's a fairly straight-forward application of thermodynamics.
Bits and pieces of this have been done in different forms for quite some time. However, her insight into being able to actually capture the excess energy (between adiabatic and isothermal) in the form of thermal storage, then recover it through a spray is clever.
She certainly has a good publicity manager...
I also does not see anythig special in this startup. Maybe someone's idea was that "energy storage" and "ecology" are popular, so it would be easier to find investors. Any physical material could be used for storing energy, it could be air, water or even sand. See http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity . Of course they could invent some new kind of pump, air tank or turbine, but those has anything to do with "energy storing".
There is a Megawatt scale compressed air plant in the US in LA, or MS that has been in operation for over 20 years -- It is used to handle the peak daytime A/C load due to the suns heating everyones homes
Sylvie, this is an energy storage scheme. Like batteries. The energy expended in compressing the air is the energy that is being stored, theoretically to become available when it's needed.
I've seen this idea pushed previously, for cars, believe it or not. Compressed air engines. As I see it, in cars anyway, the problem is that the scheme requires a lot more energy storage volume than the alternatives need to carry.
The gas equation is PV=nRT. And both this compressed air scheme and, say, internal combustion engines, follow Boyle's Law (P1V1 = P2V2).
So, both the ICE and the compressed air cycle work on the principle that you can derive power from expanding a compressed gas. However the ICE multiplies this effect many times, by the fact that the gas is mixed with a fuel, under pressure, and its temperature (and therefore pressure) spikes way up when the fuel-gas mix is ignited. Only then is it allowed to expand.
The compressed air engine doesn't have this combustion "multiplier effect." So you have to make up in volume and/or pressure what you are giving up in the temperature change available to the combustion engine, between combustion and exhaust.
Says to me that if you have room for large volumes, and also can accommodate pressures up to the thousands of PSI, this should be viable.
How much energy is expended compressing the air in the first place though?
I suppose I should give Vinod the benefit of the doubt though, he's a smart cookie... I saw him speak at the SPARC 25 year celebration last week. He was one of the founding engineers at Sun Microsystems.
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