Hacker News Reader

Comment by ChuckMcM | Hacker News Reader

It is a fun idea, I tried to convince a large internet company to do something similar outside their data centers at one time, they chose not to bite.

A much better solution is this one: https://www.heindl-energy.com/wp-content/uploads/2017/10/Bro... it stores energy by pumping water into a tank to lift up a giant concrete piston. When you want the energy back you just let it down by running the turbo pumps.

The nice thing about gravity storage like this are that it doesn't need anything but a hole in the ground and existing hydroelectric technology. The down side is that it can freeze at low temperatures, you get some back because at the depth these cylinders would be dug there is significant below ground heating but there would be days when it would be too cold to run these things without warming them (and thus impacting your efficiency)

View on HN

The actual facility is one cost. Others include extending the grid to your new generators, and the benefit of the system in the article compared to those built out of mountains, etc, is that it can be easily built on the sites of abandoned power stations, which have all the infrastructure in place (or at least resurrectible).

I love these ideas though, including yours. As the article points out, it's definitely an investment area worth getting into.

Existing, but abandoned, mines also work as prospective sites. They usually have a large vertical drop, and they often have existing energy infrastructure "wiring" them into the grid.

I'd love to see some of the deepest mines in the world turned into gravity storage systems. Some of them are in areas that are amazing for solar, so you could hook the solar up to a motor to lift the weights, and then use the weight to power generators on the way back down.

Are there any motor designs that work close to equivalently as generators? If so then the system can be simple and self switching. If the energy from the solar is strong enough it lifts the weight, if it's not, it generates electricity.

Except recouping the CO2-expenditure of the concrete piston will take a long time. A simpler solution is to use the gravitational potential energy of the water directly. Pumped hydro, as this is known, is super simple if you have a mountain and maybe even an existing hydro-power plant to take the energy back out.

I have never checked this, but a Swiss friend of mine once explained the Swiss energy system as being centered around pumped hydro using free surplus power from the French nuclear power plants.

The entire point of hydraulic hydro is that energy capacity scales by r^4 (dimensions of the piston + height within the hole). It is possible to just carve out the piston head from existing rock with wire saws. Systems with 1.6TWh storage capacity are not impossible.

There's a local company which has developed exactly this concept: https://heindl-energy.com/technical-concept

Efficiency of around 80% (comparable to pumped hydro), capacity of 8GWh for a 250m diameter piston.

How do you keep water from leaking past the piston?

> Except recouping the CO2-expenditure of the concrete piston will take a long time.

When the idea was described to me it was proposed to carve the piston out of sheer rock (obviously requiring fitting geology).

my the mountains are high today.

Water batteries: Pumped hydro storage 'the unsung hero' of the US grid.

https://www.spglobal.com/marketintelligence/en/news-insights...

that does look like a lot of concrete. I suppose ideally it would be a shell filled with the dirt removed to create the hole, even then it would be substantial at 150m in diameter (the smaller one)

You create the rings of concrete around the cylinder while you are carving it, so actually not so much concrete. I am puzzled about the engineering required for the base, but on the paper it looks quite neat.

It's a nice idea but are there implemenatations yet except prototypes? I'm only aware of activities in Weilheim/Bavaria in Germany: https://www.haustec.de/energie/wie-pumpspeicherkraftwerke-im... and http://gravityenergyag.com/demoanlage-weilheim/ but this still looks like it will take a while to complete

@gorgoiler: that's a "classical" pumped storage facility, not the concrete (or stone) piston version proposed here.

According to this press release https://www.stawm.de/energie/strom/speicherung.html, in April last year they were hoping to be able to start building the Weilheim prototype by December. The seal technology was undergoing trials near the Baltic Sea (translating from the press release).

While this sounds interesting, building the "cylinder" and the "piston" to fit exactly at the huge dimensions they are envisioning, and getting the seal to work at these dimensions and in the long term sounds like a pretty big challenge...

The sealing technology is a rolling diaphragm. Rolling diaphragms do not have any sliding action, and as long as the diaphragm is fastened on both sides and not punctured, the seal remains intact, without close clearances. They are used already on valves and pneumatics/hydraulics applications of various sizes.

Dinorwig in (under!) Snowdonia is another implementation of the idea, at a large scale:

https://en.m.wikipedia.org/wiki/Dinorwig_Power_Station

That's impressive. The scheme opened in 1984, payed for itself in 2 years, can supply 1.7MW, and stores 9.1GWh.

Why is this not being done more?

We're sponsoring a company working on a similar solution. We also believe that underground pumped hydro storage holds great promise. https://www.terramenthq.com/

It seems like such a simple solution and could work extremely well, I just wonder what the downsides are? Could these systems be a maintenance nightmare in 10-15 years? It seems simple enough that we could roll this out today with enough money?

Is that Eduard Heindl? He first proposed sawing cylinders out of natural granite mountains some years ago, seems he dropped that.

Reply on news.ycombinator.com