Gravitricity Czech Republic

[nowty]

Some info on undersea compressed air technologies here,
https://theliquidgrid.com/marine-clean- ... y-storage/

[dan_b]

I do feel that the window of opportunity for these relatively small storage projects like Gravitricity and others, is probably not going to be open for very long as grid scale battery storage seems to just be marching onwards at a relentless pace of increased energy capability at always reducing cost - with a combination of high round trip efficiency and seemingly very low maintenance costs, plus incredibly fast response.

[openspaceman]

That is a really good idea, as long as they are stable enough and not so rough (with steel support beams and suchlike) which would wreck the bladders.
I know a large part of coalmine work was keeping the roadways open and safe to use.

Of course it is not my idea to store air under water at constant pressure, as Nowty has pointed out it can be done under sea but our continental shelf means it is not deep enough. I like the idea as it lends itself to small scale isothermal compression rather than have to store heat to use again while the air is expanded, some heat again is needed else it will be very cold after the expansion, which may be a useful thing.

The compressing CO2 to 80 bar, to store as a liquid, is similar but needs a rather large balloon to store it after it is expanded. Again there is a requirement to store heat to turn it back into a gas and then apply more heat so that when it is expanded through an engine it exhausts at ambient temperature at least.

[pj]

https://www.vox.com/2016/4/28/11524958/ ... orage-rail

[Moxi]

Back to the first point: there are precious few places where pumped hydro can be put. Which is why we haven't seen any for half a century or more now.

Why not pump the bottom galleries dry, fit air tight bladders in them, allow them to flood a few hundred metres deep and use them to store compressed air at constant pressure?

Or airbags under the sea?

OMG ! I just had a eureka moment the house of commons is an energy storage system, after all its full of gas bags all spouting lots of hot air !

moxi

[AE-NMidlands]

I liked your train analogy, here in North Wales we have a lot of slate workings where the old haul roads are still evident with slopes typically 1 in 3 - they would be very easy to re rail and install winches' and weights with a generator and you would have a reproducible small scale system that could address the Grids rapid response requirements.

As far as I can see no one is doing anything with this ideal infrastructure - most likely because its not profitable but the the opportunity is there should it become financially viable at a later date
Moxi

going back to this thread and the deafening silence about storage and on-shore wind in our "government's" latest "green plan" (not) It seems to me that nothing will happen on storage in the UK for several reasons:
1) there is too much money (shares and investments/ vested interests) in the Grid as it is now (financially( structured so stopping pumped/ gravity storage having to pay grid charges both in and out just won't happen
2 The govt only care about how much money can be extracted out of the current situation by their backers, who make donations

I shall be writing to my MP again - and calling him out about their complacency and inaction. It's a scandal that wind power gets curtailed (at our expense) just because they are looking after vested financial interests to protect Grid revenues...

[smegal]

That is a really good idea, as long as they are stable enough and not so rough (with steel support beams and suchlike) which would wreck the bladders.
I know a large part of coalmine work was keeping the roadways open and safe to use.

Of course it is not my idea to store air under water at constant pressure, as Nowty has pointed out it can be done under sea but our continental shelf means it is not deep enough. I like the idea as it lends itself to small scale isothermal compression rather than have to store heat to use again while the air is expanded, some heat again is needed else it will be very cold after the expansion, which may be a useful thing.

The compressing CO2 to 80 bar, to store as a liquid, is similar but needs a rather large balloon to store it after it is expanded. Again there is a requirement to store heat to turn it back into a gas and then apply more heat so that when it is expanded through an engine it exhausts at ambient temperature at least.

The energy dome concept really intrigues me.

Looks like they do use a thermal store.

[media]https://energydome.it/wp-content/upload ... ry_Def.mp4[/media]

[openspaceman]

The energy dome concept really intrigues me.

Looks like they do use a thermal store.

[media]https://energydome.it/wp-content/upload ... ry_Def.mp4[/media]

Yes, I wonder if we will see them.

The video demonstrates a few points as it shows how the compression is adiabatic so there is limited heat loss in the compressor and the CO2 is subsequently cooled with water to ambient where it also gives up its latent heat, as it changes state to a liquid, at ambient temperature. The liquid can be stored indefinitely but the hot water only a limited time, so again we are only looking at a few day's storage rather than weeks.

Similarly when it is expanded through the turbine, thus doing work it requires heat put back into it so it is exhausted at ambient temperature again.

If you do the compression in little steps with cooling between each stage less power is needed but the heat is all lost between each stage. On changing the liquid CO2 to gas and expanding it you would then need an external heat source.

In the case of liquid or compressed air the heat source could be natural gas and in effect you would just have half of a gas turbine, the combustion chamber and power turbine.

I wonder if anyone remembers the "cooling the tube" competition for London Underground . My "entry" suggested compressing air with a gas turbine configured to give little shaft output but bleeding off air from the compressor and cooling it to ambient above ground then passing the cool compressed air to the train tunnels and expanding it through a series of turbines with ambient air heat exchanges between each stage with the shaft driving a generator feeding the rail.

I never got a reply .

[AE-NMidlands]

The energy dome concept really intrigues me. Looks like they do use a thermal store.

[media]https://energydome.it/wp-content/upload ... ry_Def.mp4[/media]

I think all the ones which rely on compressed gas have to, otherwise half the energy is wasted. I think the compressed air one SW of Manchester has a sodium acetate phase-change thermal store - can that be right? I have just looked it up and there is no reference to that bit that I can find, but it must need some way of supplying heat to the expanding air if the whole thing is not to freeze up.

Perhaps this is the attraction of the much simpler underwater reinforced-concrete sphere, where the air initially in it is just the compressible cushion and the work is done by incompressible water.