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Solar Photovoltaics with Battery Storage Cheaper than Conventional Power Plants (cleantechnica.com)

submitted 4 months ago by [email protected] to c/[email protected]

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I'll note that aggregate system cost still benefits significantly from including wind and other non-solar sources of energy; having a mix of different intermittent sources (and some firm generation such as geothermal) means less storage is needed.

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[–] [email protected] 4 points 4 months ago (2 children)

How does solar + pumped hydro compare? I thought I read somewhere the cost of pumped hydro per unit of storage was crazy cheap (assuming suitable enough sites are available). I think that kind of system probably makes a whole lot of sense too for places where the geography allows.

[–] [email protected] 6 points 4 months ago (1 children)

Pumped hydro is great but limited by site availability

[–] [email protected] 2 points 4 months ago

Yep, it's great that batteries have gotten cheaper as they can be used basically anywhere.

I'm selfishly thinking of Australia in particular where we have almost 70 TWh of potential storage.

[–] [email protected] 3 points 4 months ago* (last edited 4 months ago) (1 children)

Pumped hydro is great for taking advantage of the geography but it's thousands of times less energy dense. There was this guy that made a pumped hydro water tank on his roof and by his calculations a cubic meter of water was equivalent to a AA battery. A professional damm might be a bit more efficient though.

I'm looking forward to see more heat based storage, like molten salt, heated sand, or pumped geothermal.

[–] [email protected] 4 points 4 months ago (1 children)

There was this guy that made a pumped hydro water tank on his roof and by his calculations a cubic meter of water was equivalent to a AA battery.

That sounds crazy. Let's do some math. From what I can find, a double A battery contains about 10-14 kilojoules of energy. Let's use 14 to be charitable.

A cubic meter of water weighs about 1000kg. We know the formula for potential gravitational energy U = mgh. So if we used all the energy from the battery, we could lift the water:

14000 = 1000 * 9.81 * h
h = 14000 / (1000 * 9.81) ≈ 1.43 meters (4 feet 8 inches)

That assumes 100% efficiency of course. Still, lifting a ton of water even two feet ain't nothing to sneeze at. Batteries have a lot of energy.

[–] [email protected] 2 points 4 months ago

Thank you for doing the math! I think this was the video of the fella doing his water tank battery: https://youtu.be/CMR9z9Xr8GM?si=go28fQ6DYXyW1GTi