[cupofpython]

emphasis on massive scale.

Moving 500,000 kg (over 1 million pounds) 7.5 meters (~25 feet aka the height of a house) will give you about 10 kWh of energy. This is equivalent to running a 425W device all day, like a small air conditioner. The relationship is linear. Double the weight or the distance to double the energy. All of the metal at a scrap yard I know of amounts to less than half that weight, for reference.

I'm also a fan because pumped storage is a really interesting storage method, but it is beyond niche. It is very tough to move that kind of weight around efficiently for what you get back. Pumping water to great heights is not easy either. (see also: moving rail-carts up a mountain)

[SECProto]

> All of the metal at a scrap yard I know of amounts to less than half that weight, for reference.

That's not a great reference point when you're trying to visualize to pumped storage, as water is 1t/m3 while steel is up around 7 or 8. Also, 500t of steel at a scrapyard seems very small - 70m3?

A better reference might be a back yard pool, which might be in the 30-40t range - so like lifting 15 back yard pools the height of your house to power a tiny AC.

[cupofpython]

good point, and yes its a small scrap yard. I was trying to emphasis that it's possible for a full-time commercial operation moving heavy metal to involve less weight than what was referenced. The backyard pool paints a better picture though

[xyzzyz]

> Moving 500,000 kg (over 1 million pounds) 7.5 meters (~25 feet aka the height of a house) will give you about 10 kWh of energy.

In dollar terms, 10kWh is worth around $1. 1 million pounds is the weight of 2-5 residential homes, depending on size. Think about it: the cost to lift a couple of entire houses three stories up into the air is literally just one dollar. That’s why gravity energy storage only makes sense at a massive scale.

[cupofpython]

it's also why "storage" is a very loose term for gravity based energy storage. at a massive scale it is still only best at storing/discharging the difference between demand and supply - while still trying to keep actual energy production as close to demand as possible at all times. It really should never be used to power a city the way we would use a battery to power our phone. As in, spend significantly less time charging it than discharging it

[PaulHoule]

They are building a lot of them in China

https://en.wikipedia.org/wiki/List_of_pumped-storage_hydroel...

[cupofpython]

Makes sense, it is definitely a useful tool. I just think it is insufficient to act as storage. It can be good at producing variable amounts of Watts on demand but not so good at storing enough Watt-hours to keep things running for very long. I can see a great appeal for it to help with load-balancing for a significant amount of choppiness between supply and demand on the hour timescale.

For something like solar, where we will want to store over half our daily energy production at peak storage (ideally 2-3 days worth I think) - I don't think it holds up. Additionally, it doesnt seem like a good bet as a primary mechanism for either storage or on-demand generation if energy consumption continues to increase due to the rather large coefficients involved for scaling it up.

"The United States generated 4,116 terawatt hours of electricity in 2021"[1]

4,116 TWh/year = 11.2 TWh/day

The storage capacities for the largest items listed on the wiki is on the magnitude of GWh. The scale goes kilo-, Mega-, Giga-, then Terra. So we are talking about a need on the order of a thousand pumped storage facilities per country. The US would need over 50 of them per state (on average) in order to keep everything running without production for 24 hours. Doesnt matter how many solar panels we have, if we get 1 dark day then we would run out of power. If we tried to rely on solar entirely, we'd also still need very roughly half that amount of storage just to get through the night.

lithium batteries are obviously much better suited for overnight storage, but I have no idea what the numbers are on how much lithium is physically available to use as such storage.

If we want to get on the order of monthly to yearly storage to allow, for example, solar panels in alaska to provide enough energy for a resident to get through months of darkness - I have no idea what the leading storage options are, probably lithium still

[1]https://www.statista.com/statistics/188521/total-us-electric...

[kenhwang]

It's not "beyond niche", it accounts for 95%+ of worldwide stored energy and is the de-facto energy storage mechanism that all new battery storage technologies are compared against. It also has round trip efficiency comparable to the li-ion batteries (80-90%), which is incredibly hard to beat.

[cupofpython]

95% stored energy by what measurement? See my other comment. It is not accessible to everyone, nor can it be made accessible to everyone, and the current storage capacity is a marginal fraction of what we actually use. It's a short term load balancing tool that operates within a small energy window.

[jcrben]

It also doesn't consistently depreciate the way that batteries do.

[fy20]

That's around the weight of a fully loaded A380.

[im3w1l]

What if you go down instead of up? Drill like a kilometer or two and then build a huge cavern at that depth.

[cupofpython]

that is something people are doing. Also when you go down into rock, you are able to leverage pressure as energy storage as well - which is similar to what this article is about.

There was 1 design I saw where they have a large cylinder cut out of the ground but left in place (so it is loose). Pump water underneath it to raise the cylinder up, then flip the valve and the cylinder squeezes the water back out for power through gravity. I am not sure how the sealing works on that, probably similar to hydraulics

[merely-unlikely]

Old mine shafts have been used.