[jcrawfordor]

You might be surprised how few sites are suitable for pumped hydro and how costly it is to build. I can easily see this being both cheaper and more efficient. Most pumped hydro installations outside of northern Europe end up requiring large dams to create a big enough impoundment uphill. A direct weight solution should have better conversion efficiency as well, Gravitricity quotes 80% which is on the high end of pumped hydro. The charge/discharge rate and response time also look better than a similar pumped hydro setup, unsurprisingly considering the lower inertia.

It so happens that pumped hydro was considered for the same site but abandoned last year due to the high cost estimate.

[pfdietz]

You might be surprised at the enormous numbers of sites that are potentially suitable for pumped hydro, if you go looking for them in areas with vertical relief.

https://re100.eng.anu.edu.au/global/

"ANU has identified 616,000 potential sites around the world." (note that not all countries are included in this because of lack of geographical elevation data)

A place like Nevada has an enormous surfeit of opportunities for pumped hydro, due to the Basin and Range geography. Here's a project going forward right now. Look how tiny the basins are for the energy stored:

https://www.whitepinepumpedstorage.com/

[ZeroGravitas]

I doubt any pumped storage project can beat solar and battery hybrid projects these days, especially in sunny places like Nevada.

People get very laser focused on the storage part, but energy you generate is entirely fungible with energy that you've stored so pumped hydro needs to compete with generation too.

edit: looking further into this to try to put some rough numbers on it, the 5 years it'll take to dig the holes means in this particular case I wouldn't be too surprised if batteries alone could beat it by the time it connects to the grid in 2031.

[XorNot]

I'm pretty pessimistic on storage these days, but I will admit that after running some back of the envelope numbers I'm actually a lot more optimistic about chemical batteries then any of the physical storage schemes.

Pumped hydro has a recharge problem - if your reservoir is much larger then your pump, you can't recharge the system in the time of cheapest energy (daytime when solar is active) before you'll be discharging again. The "roughly 4 hours" output of batteries lines up a lot better with this.

It's still too expensive, but when you plug that into the fact batteries can go in anywhere there's space, and they look a lot more attractive and definitely way faster to build. If Sodium-Ion batteries can be made to work and hit the right price point, things could change pretty dramatically though that's pinning hope on an unproven future technology.

[pfdietz]

Pumped hydro may work better with wind than with solar.

Consider the mismatch between supply and demand as a function of time; it has a Fourier transform with components at different frequencies (this is completely separate from the frequency of AC current in the system, please note). Some storage technologies are more suitable for different frequencies and different average charging times. Form's iron-air batteries, for example, would be suitable for frequencies an order of magnitude lower than Li-ion batteries. Operating a combined system with multiple storage technologies may at times involve discharging one to charge another.

[hollerith]

Your second link describes itself as "a 1,000 megawatt energy storage project".

I'm interested in how much energy the site can store, about which there is no indication on that page. Do you think maybe they mean 1,000 megawatt hour?

[pfdietz]

It's to be a 8000 MWh storage facility that can charge/discharge at 1000 MW. So, eight hours of storage.

[stubish]

More holes than we have fresh water to fill them with. Maybe someone will solve corrosion and we can use salt water.

[pfdietz]

Fresh water consumption is small compared to that evaporated cooling a nuclear plant of the same average power throughput.