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Ditch the Batteries: Off-Grid Compressed Air Energy Storage

lowtechmagazine.com

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Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#31

Post by mabbo »

> However, to store 360 Wh of potential electrical energy, the system requires a storage reservoir of 18 m3, the size of a small room measuring 3x3x2 metres. The authors note that “although the tank size appears very large, it still makes sense for applications in rural areas”.

This would light a home for an hour, with LED bulbs and careful usage. And all it requires is a room-sized storage tank.

So if I wanted something that ran my house all night, I'd need a storage tank larger than said house.

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#32

Post by josefresco »

Uhrheber wrote: post #19

When compressing air, a lot of heat is generated, and in most cases wasted. When the air is released, it cools down, and has to take heat from the surroundings. Which doesn't work very fast without additional heat exchangers, and especially not in cold environments. Compressed air storage is only efficient with additional heat storage, which is something that promoters of compressed air storage often "forget" to tell…

They didn't forget - it's addressed in detail. They are advocating "small scale"

The low efficiency is mainly since air heats up during compression. This waste heat, which holds a large share of the energy input, is dumped into the atmosphere. A related problem is that air cools down when it is decompressed, lowering electricity production and possibly freezing the water vapour in the air. To avoid this, large-scale CAES plants heat the air prior to expansion using natural gas fuel, which further deteriorates the system efficiency and makes renewable energy storage dependent on fossil fuels.

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#33

Post by JasonFruit »

virmundi wrote: post #12
newman8r wrote: post #3

An added benefit is you could power your air-tools with something like this without having to convert to electrical energy. As a former off-gridder, that's actually a really big plus. Another non conventional way to store energy is using gravity power modules (example: http://www.gravitypower.net/ ) Storing hydrogen from electrolysis via solar panels also sounds interesting. Basically once your batteries are charged…

The US government looks into this at a national level. Doesn’t look like it went too well though. https://arpa-e.energy.gov/?q=slick-sheet-project/fuel-free-c...

The article focuses on a small-scale approach that has its own challenges but is different from what your document discusses.

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#34

Post by sandworm101 »

tambourine_man wrote: post #30
newman8r wrote: post #3

An added benefit is you could power your air-tools with something like this without having to convert to electrical energy. As a former off-gridder, that's actually a really big plus. Another non conventional way to store energy is using gravity power modules (example: http://www.gravitypower.net/ ) Storing hydrogen from electrolysis via solar panels also sounds interesting. Basically once your batteries are charged…

My knowledge of physics is very basic and practical engineering is zero, but storing hydrogen in compressed tanks always seem very impractical to me. It's the most freaking volatile element in the universe. And atomic hydrogen reacts with pretty much anything. Leakage and corrosion. From my armchair perspective, storying it in chemical bonds (like nature does) makes a lot more sense.

The bigger deal is how easily hydrogen leaks. H2 is small enough to squeeze through tiny holes in rubber or plastic gaskets. It's fine in a car, but keeping it in big tanks for months is something else. At least when it leaks it floats away rather than collect on the floor looking for a reason to ignite.

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#35

Post by juliangoldsmith »

Uhrheber wrote: post #19

When compressing air, a lot of heat is generated, and in most cases wasted. When the air is released, it cools down, and has to take heat from the surroundings. Which doesn't work very fast without additional heat exchangers, and especially not in cold environments. Compressed air storage is only efficient with additional heat storage, which is something that promoters of compressed air storage often "forget" to tell…

I wonder how well it would work to have a compressed air storage system where the tank is in a loop with a solar water heating system. The heat from the loop could be used to provide heated water, or maybe drive something like a Stirling engine. You could use the output of the Stirling engine to compress a bit more air using the waste heat.

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#36

Post by brohee »

JustSomeNobody wrote: post #22
corey_moncure wrote: post #18

An early design for the automobile ran on compressed (liquid!) air. http://www.didik.com/ev_hist.htm It might work for some applications, but in 120 years we haven't been able to make it work for cars, at least.

> ... but in 120 years we haven't been able to make it work for cars... Ok, but has anyone worked on the problem in the past 120 years?

https://www.mdi.lu tried to make compressed air two person urban cars (Air Pod) but with the main inventor and visionary now dead I don't know if there is much momentum left...

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#37

Post by nightbrawler »

rossdavidh wrote: post #10

So, I seem to recall that the Amish sometimes use something like this to power their tools. Source: my own unreliable memory of an article I read somewhere. Anybody more knowledgeable out there able to confirm or disfirm?

While I was researching offgrid options a few years back I came across this site and their windmill for compressed air: https://www.cottagecraftworks.com/wind-compressor-wind-drive...

They also have quite a few interesting compressed air kitchen appliances...such as mixers, grain mills.

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#38

Post by harperlee »

tambourine_man wrote: post #30
newman8r wrote: post #3

An added benefit is you could power your air-tools with something like this without having to convert to electrical energy. As a former off-gridder, that's actually a really big plus. Another non conventional way to store energy is using gravity power modules (example: http://www.gravitypower.net/ ) Storing hydrogen from electrolysis via solar panels also sounds interesting. Basically once your batteries are charged…

My knowledge of physics is very basic and practical engineering is zero, but storing hydrogen in compressed tanks always seem very impractical to me. It's the most freaking volatile element in the universe. And atomic hydrogen reacts with pretty much anything. Leakage and corrosion. From my armchair perspective, storying it in chemical bonds (like nature does) makes a lot more sense.

It would be great if there was a (safe, efficient) way to store electricity in ethanol - but it seems that the process is not very efficient and requires carbon monoxide as input, which is not very safe at offgrid-home scale.

That is, unless electricity is used to light corn crops. Still not very efficient.

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#39

Post by hedora »

mabbo wrote: post #31

> However, to store 360 Wh of potential electrical energy, the system requires a storage reservoir of 18 m3, the size of a small room measuring 3x3x2 metres. The authors note that “although the tank size appears very large, it still makes sense for applications in rural areas”. This would light a home for an hour, with LED bulbs and careful usage. And all it requires is a room-sized storage tank. So if I wanted somet…

I thought this too, but read the rest of the article.

Spoiler alert: State of the art is 30x better

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#40

Post by skykooler »

brittohalloran wrote: post #11
newman8r wrote: post #3

An added benefit is you could power your air-tools with something like this without having to convert to electrical energy. As a former off-gridder, that's actually a really big plus. Another non conventional way to store energy is using gravity power modules (example: http://www.gravitypower.net/ ) Storing hydrogen from electrolysis via solar panels also sounds interesting. Basically once your batteries are charged…

Similar to those gravity power modules: a company called Ares ( https://www.aresnorthamerica.com/ ) is trying to use much smaller concrete 'cars' on rails to store energy. Not sure of the status of it but it looked promising to me. The direct use of compressed air is interesting. Taking it to the extreme, you could have compressed air as your primary utility piped through your home, and have appliances that run off c…

I assume you'd still need electricity for things like lighting, right? (I can't think of a way to directly generate light from air pressure without converting it to electricity first.)
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