The world’s largest advanced compressed air energy storage is ready for commercial operation 3

[cmoreride]

The largest and most efficient advanced compressed air energy storage (CAES) national demonstration project has been successfully connected to the power generation grid and is ready for commercial operation in Zhangjiakou, a city in north China’s Hebei Province, announced in a press release the Chinese Academy of Sciences lat week. The project is the world’s first 100-MW CAES power plant.

https://interestingengineering.com/...BeDiC0L9yyJ1FbzIZY4-qwX2_qjrewWq8ME-drEJVwbl4

 

[TugboatEng]

Carnot enters the chat.

 

[GregLocock]

CAES is a great white hope, you either store the red hot air in insulated pressure vessels, and then expand it efficiently, or you let it cool in vast cheap caverns, losing energy and hence efficiency, and when it expands your expansion device freezes up. They discovered all that 140 years ago.

Looks like they are using heat exchangers and some sort of supercritical (molten salt?) storage. They claim 70.4% efficiency, 400 MWh of storage, 100 MW. Not a bad start. They claim 132 GWh per year, so basically emptying it and filling it 330 times a year.

A cynic might point out that 70% is near as damn it the usual 85% turbine compressor efficiency in series with an 85% efficient expander. Hopefully their analysis has a bit more rigor to it than that!



Cheers

Greg Locock


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[BrianPetersen]

Multiple stages of compression with intercooling between them, can reduce the work of compression. If you can find some way to heat up the compressed air (geothermal?) then you can have a simple (?) heat engine.

Wonder how large the storage cavern is, and how they avoid leakage?

 

[TugboatEng]

I could see this working if the storage caverns were 12+ kilometers deep to provide storage temperatures of 300+°C in order to get any meaningful efficiency out of the thing. However, at that point you may as well be dumping water into the same cavern instead of compressing air.

What do they do with the exhausted air? Lots of nasty stuff deep in the ground including arsenic, hydrogen sulfide, radioactive materials, etc...

 

[SnTMan]

This modified and optimized CAES uses artificial air storage vessels to improve energy storage density and reduce dependence on large gas storage caverns.

Whatever that means...

During hours of peak electricity demand, high-pressure air is set free from the storage caverns and combined with fuel to drive turbines resulting in power generation.

So, Gas turbines. Not exactly what CAES sounds like. I suppose they reduce the fuel usage thru previous compression and heat recovery.

OK, BTW if you haven't watched video in the article, it is NOT about the plant featured in the article.



The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[TugboatEng]

Well that explains the combustor cans.

 

[GregLocock]

I think we're confusing different plants?

Cheers

Greg Locock


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[LittleInch]

It wasn't easy to work out the different designs from that one report, but looks like they are using some sort of heat recovery system and if Greg's numbers are correct they are filing and discharging every day so don't need to store for that long.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TugboatEng]

I guess the process could be fairly adiabatic, rock does make a decent insulator.

 

[SnTMan]

I think we're confusing different plants?

Tugs' image is from the vid in the linked article. It is from a plant in Alabama. The vid is dated 2015. Both plants seem to use gas turbines and burn fuel, so similar operations, I guess.

The Chinese plant described in the article "uses artificial air storage vessels" whatever that may be.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[SnTMan]

OTOH, the Hydrostor plant linked late in the article seems to use no fuel, expanding the compressed air only thru the turbine. Link is from 2021, wonder how it's coming along...

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[GregLocock]

There's the 3 paths torpedoes went down, the original system that kept freezing up, because they couldn't insulate the tanks, an external burner to heat the expander, or inject fuel into the high pressure air and expand hot, high pressure, air (this is the way). So it is all Victorian/Edwardian technology!

The OP system relies on adiabatic storage, a much more efficient way forward, but of course it means higher plant cost for a given power output.

Cheers

Greg Locock


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[LittleInch]

It's difficult to find details but looks like it's a big salt cavern 1000m down and there's mention of low temperature 325C molten salt heat storage. I guess there's a lot lost in translation....

Most of the articles you can find are nearly a year old and just repeat the press release.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[GregLocock]

I was gently thinking about their efficiency claim 70.4%. Presumably with an adiabatic system the inefficiency of the compression side doesn't matter as much, as the extra work goes into heat in the working fluid?

Cheers

Greg Locock


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[TugboatEng]

It's still a Brayton cycle. Compression, storage, heating, expansion. It's just the storage step that is extra. However, 70% efficiency on a Brayton cycle certainly isn't possible. I think they're ignoring the portion of.tbr cycle as that was to be wasted power anyways. The 70% efficiency is only for the expansion portion of the cycle.