Every air separation plant (you know, the kind used to make oxygen for steelmaking) employs expanders for recovering energy from cryogenic nitrogen. This is an off the shelf technology.
We have plenty of experience with flywheels. I bet there's millions of cars built every year that have a flywheel in them. Does that mean energy storage using giant flywheels is guaranteed to be insanely cheap and way cheaper than the existing storage systems?
Just because we have plenty of experience using a given technology in one application doesn't mean it's guaranteed to be a smash hit in a different application.
Now, whether LN2 (or LAir) energy storage is practical is another matter. The efficiency seems poor unless you have a source of waste heat to juice the process.
> It's off the shelf technology for chemical processes. It's not off the shelf technology for energy storage.
The while point I'm making in these last few comments is that just because a certain technology is effective for one application doesn't guarantee it's effectiveness for a different application.
1. https://en.wikipedia.org/wiki/Air_separation#Applications
But you can't do this for cryogenic air storage. The whole point is to produce liquid nitrogen (or liquid air) that can be stored and then reheated later to drive an engine to generate electricity. If you ran the liquid nitrogen output through the input stream like in typical air separation, you'd warm the output stream and turn it back into a gas. So even though the two systems both involve cooling systems they're actually substantially different processes. One of them is separating air's constituent gases, and mixes the input and output streams to achieve efficiency. The other is essentially a big liquid nitrogen plant.
Unfortunately the only existing cryogenic air storage plant delivered 15 MWh of storage at a cost of 8 million pounds [1]. That's about $650 per KWh, as compared to ~$130 per KWh for battery storage. Like I said, just because a technology is effective in one application, doesn't mean it's guaranteed to be effective in another one.
1. https://en.wikipedia.org/wiki/Cryogenic_energy_storage#cite_...
We build plenty of flywheels. Does that mean energy storage based on giant flywheels is guaranteed to be efficient at scale because we have experience using flywheels in other applications like automobiles?
Similar deal with ammonia energy storage. We've got plenty of experience with synthesizing ammonia for fertilizer production. We've got very little, if any, experience using synthesized ammonia as a form of energy storage.
It was you, not I, that started this tangent about air separation in this comment [1]. I was, from the beginning, talking about energy storage systems.
Do you imagine the ammonia knows why it is being synthesized, and would balk at being synthesized and tanked for energy storage or fuel? Do you imagine it will object to being burnt in a combined-cycle turbine?
Your credibility is at zero.
Ammonia storage would first require a source of hydrogen. Currently almost all hydrogen is produced through steam reformation which releases carbon dioxide. So this has to be replaced with electrolysis, which is more energy intensive and has issues with corrosion of electrodes. Then there's the issue of heating up this hydrogen and nitrogen to ~400C and compressing it to fix the nitrogen into ammonia. Currently this is done through combustion of fossil fuels. That too needs to be replaced with an electric source. All these changes drastically increases the cost of producing ammonia over existing processes.
Cryogenic storage is essentially producing liquid nitrogen by refrigerating air, and then hearing the nitrogen to create a pressure gradient to drive a heat engine. Cooling the air is a huge energy sink, and releasing the energy often has to be coupled with a heat source in order transition the liquid nitrogen to a gas. It's actually using the heat gradient of the ambient air and the liquid nitrogen to drive the heat engine, and that ambient air often doesn't have the required energy density to produce more than a few dozen megawatts. Existing prototypes often scavenge waste heat from a fossil fuel power plant. But again, not an option if you plan to eliminate fossil fuels.