Hacker News Reader

Comment by Podgajski | Hacker News Reader

Why are they not using the excess solar power to lift large weights above the ground that can be released and lowered to power generators during the night?

View on HN

Because the physical infrastructure to do that is very large and expensive.

To put it in perspective: a cubic yard of concrete costs roughly US$125, and the amount of energy you can store by lifting one of those cubic yards 10 meters into the air is worth something on the order of $0.01, assuming perfect efficiency.

I pay about 20 cents per cubic yard of water at home.

Which is pretty fantastic, all things considered. You pay 20 cents for 1,700 kilograms of safe, drinkable water, which is enough to comfortably last 500 days for one person.

This is done in some places in the world, water gets pumped into reservoirs that provide energy again when they discharge.

They have cheaper options to use first like:

* exporting to neighbouring grids

* charging batteries

* reducing hydro output

Which you can see in action here today:

https://www.caiso.com/TodaysOutlook/Pages/supply.html#sectio...

(You can change the date to March-May to see it actually go negative on imports, i.e. export excess.)

Setting up large enough weights to lift is incredibly expensive - it’s a terrible way to use power, let alone store it.

Just make them out of water.

Still very expensive you don't have geography that gives you elevated storage containers for free.

Dig a hole!

California has pumped hydro, so they are.

This is being experimented with. So far it seems to work best in abandoned wells which provide a controlled space for horizontal movements.

Reply on news.ycombinator.com