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How do they work around the ”heat problem” with compressed air storage. When you compress the air, it heats up, and actually there's a big part of the energy th
by littlestymaar 3y ago
How do they work around the ”heat problem” with compressed air storage. When you compress the air, it heats up, and actually there's a big part of the energy that get stored in the form of heat, not pressure. When you want the energy out the pressured air cools down during depressurization.
If you were able to keep the air hot the whole time the process is almost symmetrical so that's not an issue, the “heat problem” as I call it is how do you store this heat for an extended period of time? At scale, it's much harder to keep than just the pressurized air.
The prototypes I've seen in the past were not storing the heat, but relied on industrial fatal heat (that was lost anyway) but this also has scale problem as you don't have that much available power except near very specific industries (NPP are an option, as are other heavy industries, but the supply is necessarily limited)
- bluGill 3y agoIf the energy input is free/renewable they can ignore this to some extent. Yes they lose a lot of energy, but who cares if the wind is blowing/sun is shining making more energy than you need right now - the other option is turning those systems off - either way they cost the same $$$.
- littlestymaar 3y agoThe problem is that you need this energy when you want to provide electricity from the storage, which isn't the moment where energy in general is cheap. The positive aspect of such a system is that the thermal energy you need is not subject to Carnot's law, so the temperature of the heat source doesn't matter unlike most use of thermal energy (and that's why you can use waste thermal energy in the first place) but you still need a way to get that energy.
- bluGill 3y agoThe air still is there whes you need it. The thermal energy is lost but the pressure isn't.
- littlestymaar 3y agoYes, but without the thermal energy you cannot depressurize it in a turbine, because it gets so cold the air will start condensing, and then you'll have droplets of nitrogen destroying your turbines!
- lolc 3y agoThey store the heat in a tank and feed it back on decompression.
- littlestymaar 3y agoDo you have any additional info about how they do that? (especially cost-efficiently)
- lolc 3y agoIf the the air is compressed to higher than storage pressure and routed through a heat exchange, they could extract all the compression heat before letting the air into underground storage. The compression heat could simply be kept in liquid storage on the surface. But that's just me guessing.