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Peter Thiel, Bill Gates, Khosla fund LightSail Energy in $37M Deal

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Re: Peter Thiel, Bill Gates, Khosla fund LightSail Energy in $37M Deal

#81

Post by ph0rque »

DaniFong wrote: post #68
robomartin wrote: post #37

How much air would you need to supply all the power required by all the homes in California? Here's my attempt to answer that question: The first stop is to get a sense of what the realistic energy density of these approaches might be. A quick search lands you here: http://en.wikipedia.org/wiki/Compressed_air_energy_storage#E... My take-away: 1 m3 of air = about 300,000 J How much energy does a typical house in the U…

Your calculations appear be within an order of magnitude of correct :-) One other way to think of the number of shipping containers needed: actually the average american home uses 30 kwh/day. At our target energy density and efficiency we've been attempting to reach 30 kwh per m^3. 1 m^3 is approximately the internal volume of a refrigerator. So each home gets 1 fridge worth of storage. Not so bad ;-)

I know it's probably not in your immediate future, but man does a refrigerator-sized LightSail Energy unit for my house sound awesome.

Re: Peter Thiel, Bill Gates, Khosla fund LightSail Energy in $37M Deal

#82

Post by johnrgrace »

foobarqux wrote: post #31

Can you explain in detail what problem this solves and how it works to someone with a basic background in physics? Below is what my understanding: Current energy storage mechanisms (batteries) are inefficient. In theory one way to store energy that would be more efficient (why?) is to use the energy to compress air (with a conventional air compressor?). The air is stored in a container until it is converted to electr…

Energy Storage is important because the supply of electric power has to match the demand in real time. Renewable power has problems doing this which creates demand for energy storage.

Many powerplants such as Nuclear or Coal can take hours to startup and shutdown. The power markets and grid management orgs spend a lot of time scheduling power production and balancing supply and demand. Plants tell grid operators, we're running from 2-6pm on Tuesday - and face fines if the power isn't delivered. Some plants get paid to be on "standby" to deal with surges in demand.

The price of power can at times become negative, because for some plants it is cheaper for the operator to get zero or even negative revenue for a short period vs. shutting down. Wind power Tax credits and carbon offsets at times mean windfarms can make money with a negative powerprice.

Wind power can have problems meshing with the grid and scheduling/dispach of power. If you're producing power when you're not scheduled and demand is low the price a plant gets can be very low, even negative, because it isn't needed. Part of this is because of market rules, and part of it is actual operations.

  So if the wind is blowing during a period of time that people are not using much power the windfarm operator makes very little or nothing.  If you can store energy for even a few hours it can be moved from periods of low demand to high demand which makes a lot of money and ensures you are not fined for failure to deliver power.
The big economic impact here is that there are a lot of powerplants called peakers that only run durring periods of peak demand. Peakers tend to be the least efficent plants out there because they are run so little, like burning 1.5-2 times more natural gas per unit of output. If you can store energy then you can build efficent power plants that produce all the time and use a lot less fuel.

Yes, I was an Energy Economist and part of the Enron Power Trading desk years ago.

Re: Peter Thiel, Bill Gates, Khosla fund LightSail Energy in $37M Deal

#83

Post by robomartin »

DaniFong wrote: post #70
lutorm wrote: post #60

Earlier quoted context omitted.

I didn't read the article super-carefully, but my impression was that they were using the heat of vaporization of water for energy storage, not PdV work of the air. I haven't done a calculation, but my guess is that this is much more efficient.

You have to store both. Also, you can't vaporize much air at low temperatures, which we aim for. You have to hold onto water for its sensible (no evaporation) heat capacity.

Do you have a number for the amount of air and water you need to store per kW-h of energy delivered to the load?

What's the real energy efficiency of the system?

What's the estimated energy loss per unit time of the storage system?

Re: Peter Thiel, Bill Gates, Khosla fund LightSail Energy in $37M Deal

#84

Post by DaniFong »

jpdoctor wrote: post #74
DaniFong wrote: post #66

Earlier quoted context omitted.

You might be overfitting the data. The initial series A, and B were essentially a seed round. I can tell you, this was certainly an upround!

Congratulations. Was it led by outsiders?

Lead by Peter Thiel, an outside investor.

Re: Peter Thiel, Bill Gates, Khosla fund LightSail Energy in $37M Deal

#85

Post by DaniFong »

rdl wrote: post #25
DaniFong wrote: post #14

Earlier quoted context omitted.

A knee-jerk reaction by poorly informed and motivated reviewers, which included a fear of: - Hydrolock (solved by default) - Corrosion (solved) - Inability to separate water and air (easy to solve and quickly solved) - a lack of understanding that water could provide heat to air on expansion (proven...) We actually disproved all of their claims within 2 weeks of their decision. The problem, however, is that you don't…

I am curious how you solve corrosion in a high pressure thermal cycling environment for what are presumably very tiny water fog nozzles. But maybe that is trade secret or whatever. Naively I'd just switch out the air for N2, since it's mechanically the same and cheap. But then, once you're using special gas, I'd look at using low and high molecular weight (say, He and maybe some long chain which isn't going to detona…

We want to use air because of the cheap, gravitational pressure vessel we have on this planet. :-)

Re: Peter Thiel, Bill Gates, Khosla fund LightSail Energy in $37M Deal

#86

Post by Gravityloss »

DaniFong wrote: post #73
foobarqux wrote: post #31

Can you explain in detail what problem this solves and how it works to someone with a basic background in physics? Below is what my understanding: Current energy storage mechanisms (batteries) are inefficient. In theory one way to store energy that would be more efficient (why?) is to use the energy to compress air (with a conventional air compressor?). The air is stored in a container until it is converted to electr…

Hopefully our website might be more enlightening... lightsail.com I give a 3 minute TR35 award talk on the concept at the emTech conference this year. Starts at 5:27 http://www.livestream.com/emtech2012/video?clipId=pla_cdd4c6...

Very concisely laid out. I want to believe.

Stupid question: why can't you store all the energy in warm water, eliminating the problematic (big, dangerous) pressure vessel altogether?

I envision a compressor, a heat exchanger (mist or otherwise) and an expander. The expander and compressor are connected mechanically (they can be the same device like in a piston engine or can be rotating machinery connected via shaft like in a turbine).

During storing, or water warming, the expander produces less power than the compressor so you need electrical energy to spin the system.

During energy release, or water cooling, the expander produces more power than the compressor needs and you can use a generator to extract that.

This is pretty much a standard heat pump or refrigerator arrangement.

I assume this is not efficient because of some not at first sight obvious quality of thermodynamics. It'd be cool to get a little bit insight into that.

By the way, your diagram's first picture with the piston is off: either the shaft should be thicker or it should depict sealing between piston edge and cylinder, now the volume of the pressure vessel changes very little when the piston moves.

Re: Peter Thiel, Bill Gates, Khosla fund LightSail Energy in $37M Deal

#89

Post by rdl »

DaniFong wrote: post #85
rdl wrote: post #25

Earlier quoted context omitted.

I am curious how you solve corrosion in a high pressure thermal cycling environment for what are presumably very tiny water fog nozzles. But maybe that is trade secret or whatever. Naively I'd just switch out the air for N2, since it's mechanically the same and cheap. But then, once you're using special gas, I'd look at using low and high molecular weight (say, He and maybe some long chain which isn't going to detona…

We want to use air because of the cheap, gravitational pressure vessel we have on this planet. :-)

Get rid of all the plants, wait a few (hundred? thousand?) years.

Re: Peter Thiel, Bill Gates, Khosla fund LightSail Energy in $37M Deal

#90

Post by Gravityloss »

tocomment wrote: post #21

I'm confused why this technique is better than just compressing air?

Air heats as it compresses. If you cool it, you lose pressure and thus energy. So you would have to keep it hot. It's problematic because it's less dense then and because you'd have to insulate it.

Water stores much much more heat per volume and you don't have to handle the pressure if you keep the heat modest.

This way your air pressure vessel can be smaller and probably uninsulated.

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