Cryogenic heat engines

Calliban · 2023-02-16 11:53:16

This is an interesting idea that was recieving some development interest 10 years ago. But it appears to have gone nowhere in terms of commercial projects.
https://www.imeche.org/news/news-articl … ry-systems

The idea is to store energy in liquid air. This is stored in an insulated tank. Ambient heat is used to vaporise the liquid air, converting it to high pressure gas which powers an engine. The maximum possible expansion energy is about 0.7MJ/litre of liquid air. This is less than 1/20 of the available work energy of diesel. But it is comparable to the energy density of lithium ion batteries.

The concept is being developed for static grid energy storage. But it could be viable as a transportation energy source as well, within its limitations. I could see this working well as a fuel source for large container ships. It could either use the ocean water as a heat source, or make use of diesel engine waste heat. In this way, diesel consumption per tonne-mile of a large container ship could be halved.

Another benefit of liquid air as an energy storage medium, is that the systems that create it and use it are entirely mechanical in nature. We could use a solar thermal powerplant to make liquid air by coupling a compressor directly to the steam turbine. Few electronics would be needed. In the UK, we could build mechanical wind turbines, with dozens of large turbines driving a liquefaction plant using hydraulics or even a directly coupled shaft. Again, no electronics are strictly needed. This could be entirely mechanical.

A well insulated pipeline could be used to distribute liquid air to consumers that are hundreds or even thousands of km away. In this way, liquid air could support a modern transportation network. Solar powered liquefaction facilities could be built in Texas and New Mexico. A liquid pipeline would carry the air to refilling stations up the east coast. Liquid air could be stored in large tanks or underground cavities for interim storage and demand buffering. It would essentially be stored at atmospheric pressure. Boil off rate would be limited through use of insulation. In many cases, this would be in the form of the soil and rock around a pipe or tank.

Last edited by Calliban (2023-02-16 11:58:45)

Void · 2023-02-16 12:01:38

The query phrase that might work is "Liquid Air battery". Articles can be fetched with that.

As I see it would be a great partner of molten salt storage.

I may be wrong, but I am thinking that the molten salt could be in a tank, rather than flowed, so you could extract the heat even when the salts become solids. Electric heaters could heat the salts.

I am thinking that this might have a place with wind energy for Europe.

It would be nice to find a way to also use solar concentration so melt the salts as well.

I hope it is OK that I posted this.

Done.

Last edited by Void (2023-02-16 12:02:06)

tahanson43206 · 2023-02-16 12:15:51

This is for Calliban, with a nod of appreciation to Void....

It would seem (to me at least) that heat must be removed from air to liquefy it.

Void's suggestion of parking the heat in molten salt seems (at first glance) to be a way of sourcing thermal energy to boil liquid air.

In other words, aside from inefficiency in the mechanical systems that may occur, this would amount to an energy storage system.

What would you estimate the total efficiency of such a system might be?

The competition may be flow batteries, which use chemical reactions to store and to release energy.

A key difference between the two energy storage systems would ** seem ** to be that the heat battery is able to deliver power directly to a load, such as the propeller of a container ship, as you suggested.

As a side note.... the operators of the Panama Canal require that vessels traversing the canal switch to less polluting fuel when they are in the canal. Many vessels use a low grade of fuel for deep ocean navigation.

The Canal authorities would (presumably) be ** very ** happy with a vessel that powers itself with liquid air, at the expense of cooling the canal water.

(th)

Calliban · 2023-02-16 12:17:51

Void wrote:

The query phrase that might work is "Liquid Air battery". Articles can be fetched with that.
As I see it would be a great partner of molten salt storage.
I may be wrong, but I am thinking that the molten salt could be in a tank, rather than flowed, so you could extract the heat even when the salts become solids. Electric heaters could heat the salts.
I am thinking that this might have a place with wind energy for Europe.
It would be nice to find a way to also use solar concentration so melt the salts as well.
I hope it is OK that I posted this.
Done.

Molten salts would be a good heat source because the high temperature difference between that salt and cryogenic liquid, would permit compact heat exchangers. Thermal shocking could be an issue. At the extreme upper end of temperature, maybe molten silicon could be used as a hot source? This will store 1MWh of heat per cubic metre. That is about 0.5kWh per kg. Better even that Li-ion batteries.
https://www.theengineer.co.uk/content/n … gy-storage

Void · 2023-02-16 12:21:11

Good News! Liquid Glass?

Done

Last edited by Void (2023-02-16 12:21:31)

Calliban · 2023-02-16 12:27:44

tahanson43206 wrote:

This is for Calliban, with a nod of appreciation to Void....
It would seem (to me at least) that heat must be removed from air to liquefy it.
Void's suggestion of parking the heat in molten salt seems (at first glance) to be a way of sourcing thermal energy to boil liquid air.
In other words, aside from inefficiency in the mechanical systems that may occur, this would amount to an energy storage system.
What would you estimate the total efficiency of such a system might be?
The competition may be flow batteries, which use chemical reactions to store and to release energy.
A key difference between the two energy storage systems would ** seem ** to be that the heat battery is able to deliver power directly to a load, such as the propeller of a container ship, as you suggested.
As a side note.... the operators of the Panama Canal require that vessels traversing the canal switch to less polluting fuel when they are in the canal. Many vessels use a low grade of fuel for deep ocean navigation.
The Canal authorities would (presumably) be ** very ** happy with a vessel that powers itself with liquid air, at the expense of cooling the canal water.
(th)

Round trip efficiency can be as low as 25% without cold recovery, or up to 70% if coupled with a low grade heat source.
https://en.m.wikipedia.org/wiki/Cryogen … gy_storage

This suggests that cryogenic energy storage works best as a hybrid concept. If a cryo energy store is constructed close to an existing powerplant producing lots of hot water, then we get the best results. We also eliminate the need for cooling towers. That is a big saving on capital cost.

Void · 2023-02-16 17:22:01

May I test your patience a bit?

I have wondered about ships that harvest energy from the wind, by traveling under sails, where the resulting flow of water turns a turbine in the water.

I have concerns for sea life for that.

But, if this could sustain a thermal charge of the type recently discussed, could the power of it then be used to manufacture fuels and Oxygen? Maybe some fertilizers?

I had the roaring 40's, 50's, and 60's in mind, but think they are far away. I wonder for the North Atlantic.

A sail might be lighter than air. But Hydrogen bags and lightning...............

Any thinking?

Done.

Terraformer · 2023-02-16 17:34:55

This suggests that cryogenic energy storage works best as a hybrid concept. If a cryo energy store is constructed close to an existing powerplant producing lots of hot water, then we get the best results.

A way to make nuclear power dispatchable?

Calliban · 2023-02-16 18:53:59

Void wrote:

May I test your patience a bit?
I have wondered about ships that harvest energy from the wind, by traveling under sails, where the resulting flow of water turns a turbine in the water.
I have concerns for sea life for that.
But, if this could sustain a thermal charge of the type recently discussed, could the power of it then be used to manufacture fuels and Oxygen? Maybe some fertilizers?
I had the roaring 40's, 50's, and 60's in mind, but think they are far away. I wonder for the North Atlantic.
A sail might be lighter than air. But Hydrogen bags and lightning...............
Any thinking?
Done.

That is an interesting idea. One of the things that limits the amount of sail a ship can carry is the turning moment of the wind force. It tends to push the bow of the ship into the water. If you have a hydrogen filled sail or a kite sail, it can be attached to the bow of the ship. You can carry much more propulsive force without pushing the bow underwater, because the force is applied much closer to the waterline and turning moment is reduced. Such a ship could tow a hydraulic turbine capable of generating power. Power could be used for synfuel production. Ammonia would be a good storable carbon free fuel.

Lighting won't be a problem for a hydrogen filled balloon if the surface skin is electrically conductive. There is no risk of explosion because the hydrogen is not mixed with air. Loss of bouyancy is a problem with hydrogen. The molecules gradually diffuse out of the balloon, even if gas proof materials are used. The ship would need a way of refilling the hydrogen throughout the voyage.

Last edited by Calliban (2023-02-16 19:03:38)

Calliban · 2023-02-16 19:12:29

Terraformer wrote:

This suggests that cryogenic energy storage works best as a hybrid concept. If a cryo energy store is constructed close to an existing powerplant producing lots of hot water, then we get the best results.
A way to make nuclear power dispatchable?

Could be. I don't think dispatchability is as big an issue when a power source can generate 24/7 at 100% power. It is when output fluctuates uncontrollably that we have a problem. If energy from wind turbines can be converted into a relatively energy dense and storable liquid with high efficiency and low overall cost, then intermittency becomes a smaller problem. But to get good recovery efficiency from liquid air, we need a supplemental heat source. Geothermal or stored solar heat would do. But nuclear waste heat is free and available in huge quantities at nuclear sites.

Last edited by Calliban (2023-02-16 19:13:07)

Terraformer · 2023-02-17 02:12:05

I was thinking more of how demand fluctuates throughout the day. Of course, certain things can be set to use electricity at night, when it's cheap, but not everything. And there are peaks throughout the day as well. In a fully nuclear grid we would still want some storage.

In the grid we have at the moment in Britain, dispatchable power is even more valuable. Our nuclear reactors produce ~5GW, so how much waste heat is that? The existing fleet could support a fair bit of storage.

tahanson43206 · 2023-02-17 07:11:25

For Calliban and Terraformer ....

Nuclear reactors all over the world are dumping waste heat into the local environment.

My assumption is that the engineers in each country have tried to extract every bit of usable energy from the reactor, so whatever goes into the nearby cooling system would appear (on the face of it) to be unrecoverable.

Your conversation (Calliban and Terraformer primarily) seems to offer hope that more of that thermal energy might be recovered.

There's a ** lot ** of low grade thermal energy on (and in) this planet. Ways to enlist some of that energy for useful purposes would be welcome.

(th)

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#1 2023-02-16 11:53:16

Cryogenic heat engines

#2 2023-02-16 12:01:38

Re: Cryogenic heat engines

#3 2023-02-16 12:15:51

Re: Cryogenic heat engines

#4 2023-02-16 12:17:51

Re: Cryogenic heat engines

#5 2023-02-16 12:21:11

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#6 2023-02-16 12:27:44

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#7 2023-02-16 17:22:01

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#8 2023-02-16 17:34:55

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#9 2023-02-16 18:53:59

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#10 2023-02-16 19:12:29

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#11 2023-02-17 02:12:05

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#12 2023-02-17 07:11:25

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