[notmadnomad]

For fixed-site applications of sufficient land area and scale, it's difficult to beat pumped-storage hydroelectricity (PSH). The round-trip efficiency is around or above 70%, the same or better than CAES. CAES is probably best used in applications similar to flywheel (FES), away from occupied areas.

[justasitsounds]

The world's first commercial liquid air battery project has been commissioned to be built in Trafford, Greater Manchester, UK - it's a very residential area: https://www.gov.uk/government/news/greater-manchester-to-hou....

This guy (https://www.youtube.com/watch?v=tMLu9Dtw9yI) makes some good points about how cheap and scalable the technology is for medium-scale energy storage. It uses tried and tested, reliable and simple components for example

[doitLP]

Do you have any recommendations on how to learn more about this?

My brother has a steep hill on his property and Ive been wondering about the feasibility of PSH. How high the tank should be, the equipment, the power output.

[creato]

You could start by just calculating the potential energy of the volume of the tank you are considering, and the difference in elevation between the reservoirs (volume x 1 kg/L x gravity x elevation difference, plug in the units of your choice and let google figure it out).

I suspect the amount of energy is far less than you are imagining... It takes a lot of water to generate a useful amount of energy. This video (https://www.youtube.com/watch?v=66YRCjkxIcg) does an interesting demo and points out that a 5 gallon bucket on a ladder has the same potential energy as a watch battery.

[timeinput]

This isn't quite what you're after, but it's a pleasent read. https://ludens.cl/paradise/turbine/turbine.html there have been some discussions on here about it too.

It at least gets you all the right words to start googling for turbine options which helped me to do some back of the envelope math. It's a steeper hill than seemed feasible to me.

[ehnto]

Thid has reminded me of this gentleman who has been using gravity fed old washing machines as turbines for electricity generation on his property for 16 years https://youtu.be/Xb6TIWub6KU

He doesn't need the pumped storage part of the equation due to a natural water flow, but it is part of the solution at least.

[PaulDavisThe1st]

TFA already says that large scale CAES is probably a dead end and that small scale CAES is where we might/should focus our attention.