> You could use the ocean for the bottom level and an artificial reservoir for the top level. You're not going to noticeably affect ocean levels.

Then you have to deal with the problem of sea water corroding everything it touches.

> You might pump 10 billion litres of water, which is .02% of the volume of Mjøsa.

It's not the amount of water that you pump, it's the amount * the elevation delta. Where are you planning on getting the elevation delta from?

Neither of these challenges is technically insurmountable, but this is a field where capex + opex/KWH is everything.

> Where are you planning on getting the elevation delta from?

Elevation delta is not hard to find in Norway! A typical pumped storage facility uses 100m of delta; I imagine Norwegian ones would use more.

> but this is a field where capex + opex/KWH is everything.

And pumped storage is significantly cheaper for seasonal storage than any proposed alternatives.

The original post is efficient for heat storage, but converting low grade heat to electricity is not efficient.

	▲	skybrian 8 hours ago \| parent \| next [-]
		For some applications, you don't actually convert the heat to electricity. This sounds pretty cheap if it works out: https://austinvernon.site/blog/standardthermal.html
	▲	kmacdough 8 hours ago \| parent \| prev [-]
		> A typical pumped storage facility uses 100m of delta Most projects seek 200-600m. This map doesn't even consider pumped hydro <200m: https://maps.nrel.gov/psh > And pumped storage is significantly cheaper for seasonal storage than any proposed alternatives. Based on what? Cost is particularly variable for pumped hydro. It can be one of the cheaper options when stars align. But you need 1) a suitable geography that minimizes the cost of damming or digging a resivoir with sufficient head 2) available for development without too much backlash 3) Near enough grid resources to minimize infrastructure and line losses. I'm surely leaving pieces out. It can be cheap, but it has far more hoops to jump than alternatives like batteries, hot sand and other "storage-in-a-building" designs which can be built where needed and using fairly standard industrial construction.