Congratulations Danielle, that's absolutely awesome. I'm still very sorry that you didn't get funding for some of your more off the beaten path ideas but this is as good as it gets.
If there is one person that I wish would find a connection like this it is you, I'm sure you'll amaze us all with what you're going to achieve now that your toolbox is filled.
Congrats to DaniFong and the rest of the LightSail team.
Large scale energy storage is an unappreciated problem. Our current grid has to quickly scale up and down with demand, because there is no way store excess capacity when demand is down (and therefore, no way to reuse previous excess capacity when demand is up).
When this problem is actually solved (crossing fingers until LightSail actually ships ...), the grid is going to undergo a serious transformation for the first time - from a just-in-time economy to an inventory management economy.
I think there are many more players than you hear about, in this space. The company I work for builds distributed, large-scale energy storage (I work on the management and monitoring system that controls the "distributed" part), though we're relatively unknown right now. There are several other companies that we're aware of, all shipping products today and beginning to carve out parts of the market with relatively little fanfare. I chalk it up to their / our technology not being as "sexy" as something like LightSail, but nevertheless many are beginning to deliver results right now.
Hopefully I don't sound like I'm disparaging LightSail or any of the other possible avenues - I think we need continued investment in new methods as we should always be pursuing improvement, and the LightSail approach sounds very promising. I hope Thiel and Gates' involvement in this industry will bring even more visibility to it. However, I do want to make the point that there are people doing this today, in consumer and commercial applications, and having real effects.
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 electrical energy through some inverse process (powering rotary screws?). Unfortunately compressed air is very hot and difficult to store. Instead water droplets can be injected into the compressed air container. These droplets will absorb most of the energy of the compressed air. The vapour is separated from the compressed air and stored in other containers (still as vapour?). How is the vapour then converted back to electrical energy? Isn't the vapour just as hot as the compressed air? Is it easier to deal with because it can be stored in a larger volume?
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.
> Unfortunately compressed air is very hot and difficult to store.
Not OP but a few comments on what you just said. If you ever tried to manually compress air in a metal pump (say when inflating a bicycle tire), you probably noticed that the outside of the pump gets very hot when you press down. That is because gases have a property of increasing their temperature when pressure increases. So now in order to maximize your ability to store energy efficiently, you are facing two problems: (1) how to prevent gas from escaping, (2) how to prevent heat from dissipating through pipes/pistons. It looks like OP had managed to solve (2) by efficiently capturing the heat using water vapor, though I'm not sure about specifics.
It is not super clear what the innovation is here as I am sure someone must have thought of storing compressors heat with water before.
I think maybe the novel thing is to pass the water as a mist through the compressor cylinders where it can transfer energy from air much faster than if, for example there was just a heat transfer closed circuit around the cylinders.
Their website states:
"We have achieved these high thermodynamic efficiencies at higher RPMs than many thought possible. This is crucial to achieving low cost: the higher the RPM, the higher the power of the same machine and the lower the cost per kW."
So basically you need fewer compressors and heat transfer systems for the same amount of power. I guess as long as the added complexity and maintenance doesn't add too much cost it could be more economical than using the higher number of compressors.
They do mention in the WSJ article that one challenge is preventing 'hydrolock' which, if I understand correctly, would happen if you accidentally injected too much water in a cylinder. Since water is not compressible, you could bend or break your piston rod, crank shaft or 'cause the cylinder to explode'.
What I find really intriguing about this is Thiel's participation - it's one thing to get funding from Khosla, who is a cleantech cheerleader, it's really amazing to get funding from Thiel, who is a cleanteach skeptic.
The Thiel quote made it sound like he invested in it because DoE rejected it. I'm not sure if having such an ideologue as an investor is a good idea, especially in the heavily regulated energy sector.
An old bad idea -> Many years ago i thought up an idea of creating a FEC - A self contained unit that would convert heat from a forest fires, etc... into energy. The units would be taken by helicopter and dropped into forest fires. Once the fire was over move the units into a grid that could supply energy to millions of homes.
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 get a conversation when talking with grant agencies. So most things are misunderstood and they default to funding based on seniority.
At the time, our competitors were not taking the water based approach...
The advantage of world class investors is that, even if they disagree with you, they think for themselves, so you can actually talk to them.
I am going to use an over-simplification (you know, "assume a cow is a uniform sphere of milk" type stuff) to try to get a number. Sphere within a sphere to get the volume of the troposphere.
That means that California would use 0.00000019% of the troposphere per day if every single home was powered using compressed air energy storage.
Put a different way: It would take nearly 1.5 million years to process all of the air in the troposphere.
I'm not sure if the above is complete nonsense or not. The problem is far more complex than these quickie calculations might suggest. On first inspection it sounds like we have plenty of air to go around.
Would there be any environmental and/or air quality issues stemming from this approach? Do we end-up with cleaner air locally because of the process?
Interesting stuff.
.
EDIT: A few more data points.
How big of a container is required to store all of this air?
The original assumption was that 1 m3 of air would compress into a 5L bottle, or 0.005 m3.
Storage cube side length: 348m
Storage sphere diameter: 431m
How much would this much air weigh?
1 m3 of air at 20C = 1.204 kg
8,400,000,000 m3 = 10,113,600,000 kg
The question, for me, begins to be about how realistic it might be to construct enough smaller storage vessels to capture this volume safely.
The article mentions something about 40ft standard shipping containers. Assuming that the storage vessel has the internal dimensions of a standard 40ft container:
This is akin to a battery, so there is a 'charge' and a 'discharge' cycle, you'd be using the charge cycle when there is an excess and the discharge when you need more than is available or when the price of your stored energy is lower than what you'd be buying from the grid. So likely while you're charging (I'm assuming that's the better part of a day) you're not consuming from the device.
So your 50KWh initial value is more likely only half of that or even less, the portion that you'd be consuming that was previously stored. I've lived off a 48KWh lead/acid battery and it would - in a very energy efficient home - power the house for up to 5 days before needing a top-up absent sufficient sun and wind. This still holds when the storage capacity is centralized, only the flow would be slightly different and the houses would be in 'sink' mode all the time.
Another point regarding consumption:
Conservation is the best possible starting point for any renewable installation, large scale or small scale does not matter. It is easier to save a KWh than it is to generate or store one, up to a point, so that low hanging fruit is where you start.
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 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.
The real problem with your analysis is you want far less energy storage than that. A reasonable goal for vary high levels of 'green' tech is ~1% or ~15 minutes of grid energy storage. Beyond that it's much more valuable to simply build some peaking power plants and have excess capacity.
Great news, congratulations on the deal! I dare say you're a big inspiration to a lot of young inventors out there, and we here are all awaiting big things from you and LightSail in the near future (no pressure!).
Why not use excess energy to lift millions of tons of worthless rock off the ground and then when power source fails, use the winding down via gravity to turn generators?
Gravity is never going away and never going to run out.
Awesome news congratulations Dani! I've just finished 6 exams in 3rd year mechanical engineering and it's visionary companies like Lightsail and SpaceX that inspire all of us to keep going.
Congrats! The ideas behind this are amazing, and I'm happy to see some folks really trying to make a difference in this market even in the wake of some nasty history (albeit not your own).
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.
schraeds - You may be interested in knowing that nobody will see your useful answer to the question posed, because you were capriciously hellbanned 218 days ago due to your unpopular opinion of the baby boomer generation.
This looks very promising. Can anyone compare and contrast with supercapacitors, flywheels, and/or simply pumping water uphill and running it through a generator when needed?
[+] [-] jacquesm|13 years ago|reply
If there is one person that I wish would find a connection like this it is you, I'm sure you'll amaze us all with what you're going to achieve now that your toolbox is filled.
This is really great news!
[+] [-] DaniFong|13 years ago|reply
Funding isn't the constraint now, it's time. But believe me there are more off the beaten path ideas where that came from ;-)
[+] [-] cpeterso|13 years ago|reply
Any references? I'd love to read more.
[+] [-] beagle3|13 years ago|reply
Large scale energy storage is an unappreciated problem. Our current grid has to quickly scale up and down with demand, because there is no way store excess capacity when demand is down (and therefore, no way to reuse previous excess capacity when demand is up).
When this problem is actually solved (crossing fingers until LightSail actually ships ...), the grid is going to undergo a serious transformation for the first time - from a just-in-time economy to an inventory management economy.
[+] [-] firemanx|13 years ago|reply
Hopefully I don't sound like I'm disparaging LightSail or any of the other possible avenues - I think we need continued investment in new methods as we should always be pursuing improvement, and the LightSail approach sounds very promising. I hope Thiel and Gates' involvement in this industry will bring even more visibility to it. However, I do want to make the point that there are people doing this today, in consumer and commercial applications, and having real effects.
[+] [-] tptacek|13 years ago|reply
You're one of those people where 10 years from now it is going to blow my mind that I got to share an Internet message board with you.
[+] [-] DaniFong|13 years ago|reply
[+] [-] foobarqux|13 years ago|reply
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 electrical energy through some inverse process (powering rotary screws?). Unfortunately compressed air is very hot and difficult to store. Instead water droplets can be injected into the compressed air container. These droplets will absorb most of the energy of the compressed air. The vapour is separated from the compressed air and stored in other containers (still as vapour?). How is the vapour then converted back to electrical energy? Isn't the vapour just as hot as the compressed air? Is it easier to deal with because it can be stored in a larger volume?
[+] [-] johnrgrace|13 years ago|reply
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.
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.
[+] [-] DaniFong|13 years ago|reply
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...
[+] [-] bluekeybox|13 years ago|reply
Not OP but a few comments on what you just said. If you ever tried to manually compress air in a metal pump (say when inflating a bicycle tire), you probably noticed that the outside of the pump gets very hot when you press down. That is because gases have a property of increasing their temperature when pressure increases. So now in order to maximize your ability to store energy efficiently, you are facing two problems: (1) how to prevent gas from escaping, (2) how to prevent heat from dissipating through pipes/pistons. It looks like OP had managed to solve (2) by efficiently capturing the heat using water vapor, though I'm not sure about specifics.
Water vapor sounds like a good (if obvious) solution since water has the third highest specific heat capacity of all liquids, after ammonia and liquid lithium (http://en.wikipedia.org/wiki/Heat_capacity#Table_of_specific...).
[+] [-] BenoitEssiambre|13 years ago|reply
I think maybe the novel thing is to pass the water as a mist through the compressor cylinders where it can transfer energy from air much faster than if, for example there was just a heat transfer closed circuit around the cylinders.
Their website states: "We have achieved these high thermodynamic efficiencies at higher RPMs than many thought possible. This is crucial to achieving low cost: the higher the RPM, the higher the power of the same machine and the lower the cost per kW."
So basically you need fewer compressors and heat transfer systems for the same amount of power. I guess as long as the added complexity and maintenance doesn't add too much cost it could be more economical than using the higher number of compressors.
They do mention in the WSJ article that one challenge is preventing 'hydrolock' which, if I understand correctly, would happen if you accidentally injected too much water in a cylinder. Since water is not compressible, you could bend or break your piston rod, crank shaft or 'cause the cylinder to explode'.
[+] [-] tryitnow|13 years ago|reply
[+] [-] guelo|13 years ago|reply
[+] [-] kirpekar|13 years ago|reply
[+] [-] DaniFong|13 years ago|reply
[+] [-] bbuffone|13 years ago|reply
This technology is one missing piece.
[+] [-] rdl|13 years ago|reply
[+] [-] DaniFong|13 years ago|reply
- 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 get a conversation when talking with grant agencies. So most things are misunderstood and they default to funding based on seniority.
At the time, our competitors were not taking the water based approach...
The advantage of world class investors is that, even if they disagree with you, they think for themselves, so you can actually talk to them.
[+] [-] robomartin|13 years ago|reply
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 US use per day?
http://wiki.answers.com/Q/How_much_electricity_does_an_avera...
I'll use 50KWh per day
1kWh = 1,000W x 3,600s = 3,600,000J
This typical house, then, consumes 180,000,000J per day
How much air do we need to compress to provide all of the energy needs of this one house (per day)?
180,000,000J / 300,000J = 600 m3
How many homes in California?
http://quickfacts.census.gov/qfd/states/06/06037.html
Let's say it's about 14,000,000 homes
How much air do we have to compress every day to service these homes:
600 m3 x 14,000,000 homes = 8,400,000,000 m3
OK, there's a number, whatever it means.
Hmmm. How much of the available air are we using?
What's the volume of air of the atmosphere?
Tough question to answer. I think the number we'd want would be that of the Troposphere.
http://en.wikipedia.org/wiki/Atmosphere_of_Earth
I am going to use an over-simplification (you know, "assume a cow is a uniform sphere of milk" type stuff) to try to get a number. Sphere within a sphere to get the volume of the troposphere.
Average Earth diameter: 12,742km
http://www.universetoday.com/15055/diameter-of-earth/
Troposphere thickness: 17km
http://en.wikipedia.org/wiki/Troposphere
Troposphere volume: 4,341,334,943,758,290,000 m3
That means that California would use 0.00000019% of the troposphere per day if every single home was powered using compressed air energy storage.
Put a different way: It would take nearly 1.5 million years to process all of the air in the troposphere.
I'm not sure if the above is complete nonsense or not. The problem is far more complex than these quickie calculations might suggest. On first inspection it sounds like we have plenty of air to go around.
Would there be any environmental and/or air quality issues stemming from this approach? Do we end-up with cleaner air locally because of the process?
Interesting stuff.
.
EDIT: A few more data points.
How big of a container is required to store all of this air?
The original assumption was that 1 m3 of air would compress into a 5L bottle, or 0.005 m3.
Storage cube side length: 348m
Storage sphere diameter: 431m
How much would this much air weigh?
1 m3 of air at 20C = 1.204 kg
8,400,000,000 m3 = 10,113,600,000 kg
The question, for me, begins to be about how realistic it might be to construct enough smaller storage vessels to capture this volume safely.
The article mentions something about 40ft standard shipping containers. Assuming that the storage vessel has the internal dimensions of a standard 40ft container:
http://en.wikipedia.org/wiki/Intermodal_container
Container volume: ~ 67 m3
Containers required to store enough compressed air to supply homes in California: ~627,000 units.
That's a lot of containers, even if the calculations are off by 100%.
[+] [-] jacquesm|13 years ago|reply
This is akin to a battery, so there is a 'charge' and a 'discharge' cycle, you'd be using the charge cycle when there is an excess and the discharge when you need more than is available or when the price of your stored energy is lower than what you'd be buying from the grid. So likely while you're charging (I'm assuming that's the better part of a day) you're not consuming from the device.
So your 50KWh initial value is more likely only half of that or even less, the portion that you'd be consuming that was previously stored. I've lived off a 48KWh lead/acid battery and it would - in a very energy efficient home - power the house for up to 5 days before needing a top-up absent sufficient sun and wind. This still holds when the storage capacity is centralized, only the flow would be slightly different and the houses would be in 'sink' mode all the time.
Another point regarding consumption:
Conservation is the best possible starting point for any renewable installation, large scale or small scale does not matter. It is easier to save a KWh than it is to generate or store one, up to a point, so that low hanging fruit is where you start.
[+] [-] DaniFong|13 years ago|reply
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 ;-)
[+] [-] lutorm|13 years ago|reply
[+] [-] Retric|13 years ago|reply
[+] [-] creamyhorror|13 years ago|reply
[+] [-] ck2|13 years ago|reply
Gravity is never going away and never going to run out.
[+] [-] technotony|13 years ago|reply
More details: http://physics.ucsd.edu/do-the-math/2011/11/pump-up-the-stor...
[+] [-] jswanson|13 years ago|reply
I'm sure there are a bunch of interesting tradeoffs between using water or a bunch of rocks though.
[+] [-] DaniFong|13 years ago|reply
[+] [-] tjmc|13 years ago|reply
[+] [-] DaniFong|13 years ago|reply
[+] [-] tylerlh|13 years ago|reply
[+] [-] DaniFong|13 years ago|reply
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[+] [-] tocomment|13 years ago|reply
[+] [-] Gravityloss|13 years ago|reply
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.
[+] [-] throwit1979|13 years ago|reply
[+] [-] newman314|13 years ago|reply
[+] [-] schraeds|13 years ago|reply
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[+] [-] DaniFong|13 years ago|reply
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[+] [-] socratees|13 years ago|reply
[+] [-] DaniFong|13 years ago|reply
[+] [-] rms|13 years ago|reply
[+] [-] DaniFong|13 years ago|reply
[+] [-] mhartl|13 years ago|reply
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[+] [-] jpdoctor|13 years ago|reply