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PostPosted: Jan 11, 2013 8:40 am 
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Compressing air is a cheap and simple way to store energy. Although it is terribly inefficient as much of the energy gets lost through conversion to heat. At least that was the conventional wisdom until a young lass came up with a way around this limitation and started a company called Lightsail to commercially exploit the technique. The company just received a pile of funding from the likes of Peter Thiel and Bill Gates suggesting this lass can at least convince some big name venture capitalists that theidea has serious merit. More on the technology here:-

http://lightsailenergy.com/tech.html

I'm hoping others might be able to share some insight on how or if this changes the energy equation.


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PostPosted: Jan 11, 2013 9:06 am 
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There is nothing new to this except the particulars of how they store the heat. Personally, I think a phase change medium would be better.

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PostPosted: Jan 11, 2013 10:16 am 
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KitemanSA wrote:
There is nothing new to this except the particulars of how they store the heat. Personally, I think a phase change medium would be better.


That requires a lot of equipment in heat exchange. Basically the entire heat store becomes a heat exchanger, which isn't economical.

I think a simple molten salt thermocline system would be an economical option, using NaNO3-KNO3 eutectic and silica sand. Store the high grade heat in a thermocline using more compact heat exchangers and pumps.

In fact, what's wrong with just storing hot air in a cavern? Initially the cavern will be heated and extra natural gas will be needed to heat the turbine later. But after some time the cavern becomes saturated and insulated via thermal diffusion barriers, and most of the heat is retained.


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PostPosted: Jan 11, 2013 1:54 pm 
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If you have a cavern handy that is an excellent idea. But for manufactured volumes...

You can buy PCMs in what amounts to metal straws. Pile them in temperature graded bundles inside the air inlet/outlet pipe and there you go.

By the way, I agree with the idea of using NG to superheated the air when there is not an over abundance of excess power.

Then again, it might just be cheaper to build plenty of LFTR capacity. :mrgreen:

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PostPosted: Jan 12, 2013 3:23 am 
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I myself would like a local niche use of wind energy stored as compressed air, when the wind blows. The compressed air could be used through pneumatic motors for mechanical work as and when required. For local use, conversion to electricity will be counterproductive due to higher costs of electrical equipment and limited efficiency of conversion and battery costs. I wonder if the injection of water spray will help conserve the heat of compression. I would rather have a buried storage of air and heat exchanged with ground.
For lighting via CFL and other electronic uses, I would prefer thermo-electric/photoelectric conversion of sunlight and storage in cost-effective lead-acid batteries and use as 12V DC low cost system used in the vehicles.
Sunlight could also be used directly for limited heating use like hot water or solar cooking.
Wind farms and compulsory feeding to grid are not worthwhile. The grids should be increasingly fed through nuclear energy including the LFTR.


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PostPosted: Jan 12, 2013 4:53 am 
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KitemanSA wrote:
If you have a cavern handy that is an excellent idea. But for manufactured volumes...


Manufactured volumes? What do you mean? If you mean aboveground storage in compressed tanks, that is not economically feasible by at least 1 order of magnitude. If you mean natural caverns, that isn't necessary. Leaching salt caverns is cheap, and salt domes are widespread across the world, one of the main selling points of CAES. Sometimes existing mined cavities or already leached salt caverns can be used, but it matters little in the total project cost.

So it seems to me that storing hot air with a high temp compressor must be attractive, even though it would need 3x more cavern space per kg of air stored (due to the Ideal Gas Law).


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PostPosted: Jan 12, 2013 7:47 am 
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Do they have such natural cavern capacity in the windy northern plains? Or on the tundras or in the frozen forests of Alaska where small villages spend ~$8/gallon for diesel for their generators and are looking to wind to save some $. Somehow I doubt we'll see a LFTR suitable for a village of 50 people any time soon.

And since they generally need to build a tower to lift the mill up high, maybe that tower (which needs to be strong for wind load sake) could be made bigger around and serve as the flask. Just a thought.

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PostPosted: Jan 12, 2013 8:39 am 
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Most of the US has suitable formations.

http://ars.els-cdn.com/content/image/1- ... 20-gr1.jpg


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PostPosted: Jan 12, 2013 10:50 am 
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I guess we have different definitions of "suitable".

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PostPosted: Jan 12, 2013 10:57 am 
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In my opinion, air compression is not cheap. The heat exchanger and equipment as was mentioned is an added capital cost. Anyone trying to convert their car to run on compressed natural gas has run into the economic problem of high cost of compression/storage both at the filling station and the on-board tanks. The higher the pressure the more useful the compressed air and the more expensive the storage tank and the compressor.

However, if you are paying 8.00/gal for diesel fuel in a village of 50 in Alaska then lots of things can look cheaper. underground storage of heat in Alaska would bring up another problem . Melting permafrost, which is bad if you house in on it. http://englishrussia.com/2006/09/21/russian-roads-4/


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PostPosted: Jan 12, 2013 11:14 am 
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Ida-Russkie wrote:
In my opinion, air compression is not cheap. The heat exchanger and equipment as was mentioned is an added capital cost. Anyone trying to convert their car to run on compressed natural gas has run into the economic problem of high cost of compression/storage both at the filling station and the on-board tanks. The higher the pressure the more useful the compressed air and the more expensive the storage tank and the compressor.


Hency my interest in eliminating the heat exchanger by storing hot air :lol: , and swapping the expensive pressure vessel for a cheap leached salt dome or aquifer.

The compressor will be more expensive due to higher operating temperature (need fancy alloys for the later stages), as will some of the piping.

I'd like to see an efficiency and cost calculation of this scheme.


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PostPosted: Jan 12, 2013 11:15 am 
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KitemanSA wrote:
I guess we have different definitions of "suitable".


What's your definition?


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PostPosted: Jan 12, 2013 3:03 pm 
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Cyril R wrote:
KitemanSA wrote:
I guess we have different definitions of "suitable".
What's your definition?
Generally somewhere that you can't screw up an aquifer.

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PostPosted: Jan 12, 2013 5:05 pm 
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KitemanSA wrote:
Cyril R wrote:
KitemanSA wrote:
I guess we have different definitions of "suitable".
What's your definition?
Generally somewhere that you can't screw up an aquifer.


I'm not sure if these are fresh water aquifers. I've heard a lot of talk of using the deeper, saline aquifers, for CAES.

I'm not sure if aquifers would be suitable for this storage of hot air, anyway. The water would absorb too much heat and produce troublesome steam. For the same reason, a water compensation column can be probably not be used. That's a shame since such a column allows near isobaric operation of the cavern.

Hard rock can also be excavated. It is more expensive than either leached salt domes or aquifers, but in many cases not prohibitive.


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PostPosted: Sep 11, 2018 11:43 am 
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LightSail Energy Enters ‘Hibernation’ as Quest for Game-Changing Energy Storage Runs Out of Cash

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The air has gone out of LightSail Energy. The Berkeley-based startup hoped to revitalize compressed-air energy storage with a more nimble and efficient technology. Its quest "to produce the world’s cleanest and most economical energy storage systems" drew funding from VC royalty including Khosla Ventures, Peter Thiel and Bill Gates. But after eight years and approximately $80 million raised, it has run out of cash before reaching commercialization. The company went through another round of layoffs and has essentially ceased operations, co-founder and CEO Stephen Crane confirmed to Greentech Media. "It may come back in some form or another, but at the moment it’s kind of in hibernation while we try to figure out what our future is," Crane said of the company. That future should be clear by February, he added. The company was developing a compressor technology that Crane said operated for hundreds of hours, as well as gas storage tanks that endured "months of field trials." Both technologies, he said, were ready to commercialize, but suffered from insufficient funding. The company raised more money than most cleantech startups ever see, having come up in the heady days before the venture funding bubble burst. LightSail sported many of the trappings of a Silicon Valley darling, with grand promises and a larger-than-life founder to match. Reports eventually emerged of extravagant spending and aloof leadership. The company purported to fill a glaring gap in the electrical grid -- cheap, long-duration storage -- with a superior understanding of the laws of thermodynamics. The pitch worked for investors, but failed to translate into physical reality.

Storage iconoclasts
Most recent growth in the energy storage industry has been in lithium-ion, with a few companies chasing alternatives like flow batteries or thermal storage. LightSail instead chose to resurrect the concept of compressed-air energy storage, which had languished due its requirement for geologically specific underground caverns to pump full of air. The company's central proposition was that it could perform CAES aboveground in specialized carbon fiber tanks, thus achieving cheap and scalable storage for surplus renewable energy. There was also an idea early on about using this technology to power cars. No other company had pulled off the aboveground compression trick, in part because compressing air wastes considerable energy as heat, and putting it in smaller vessels sacrifices the massive scale that helps CAES be competitive underground. Startup SustainX gave it a shot, but gave up in 2015 and switched over to traditional underground storage. LightSail founder and Chief Scientist Danielle Fong emerged in 2009 with new IP. By spraying the tank with water droplets, she claimed the process would save heat energy and boost efficiency. Fong, who did not respond to a request for interview, also happened to be a wunderkind who'd dropped out of school to start a Ph.D. at Princeton's plasma physics lab by the age of 17. It was a heady time, in the late 2000s, before cleantech VCs had gotten hung up on all the money they were about to lose. So Fong and co-founder Crane gathered an eventual total of $80 million from some of the biggest names out there and got started.

Delayed satisfaction
Fong repeatedly insisted, across multiple public platforms, that the technology really worked. But it never got far enough to deploy outside of the studio. "We would have liked to have gotten a bit further," Crane said. Eric Wesoff chronicled the company's descent in a May 2016 article, at which point LightSail had gone through two rounds of layoffs that cut a staff of 60 down to 15 or so. At GTM's 2015 Energy Storage Summit, Fong explained the company was pivoting to pressurized tank manufacturing to yield short-term profits, which could then tide the company over until the storage product arrived. After claiming, in 2014 and 2015, to have sold tanks for compressed gas storage, Fong tweeted in 2016 that the company was shipping its first product. A source familiar with the situation explained to Wesoff why this business was unlikely to succeed: "The CNG industry is very conservative; any mission-critical CNG or mobile pipeline applications would favor the incumbent with a strong operating history rather than a glamorous upstart from Silicon Valley with no experience, no fleet, no service network, even if they can claim cost advantages." More recently, the tanks had attracted interest from members of California's burgeoning hydrogen fuel-cell industry, Crane said. LightSail won three California Energy Commission grants to demonstrate its technology, but withdrew from them without fulfilling the projects. Along the way, the company spent money on assets like gourmet coffee and kombucha on tap. Sources reported that Fong was "getting paid $225,000 a year when coming to work one day per week on average." She also got a company loan to buy a Tesla Model S. It's not yet clear whether a new investor will emerge, or if the company will be forced to sell its scraps via bankruptcy. After years of attempts to reimagine compressed-air storage, all the profits still lie buried deep beneath the earth.


LightSail Energy Storage and the Failure of the Founder Narrative


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