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Comment by jjk166 | Hacker News Reader

I have to imagine building 2.5 swimming pools worth of water storage is cheaper than filling a single swimming pool with a heavy liquid. They typically go for $100-$1000/kg, with the non-toxic ones of course being the more expensive.

No idea what the article is talking about wrt being able to utilize lower heights, as the amount of power you can get from a certain drop is independent of density. Higher density decreases the size of the pipes and turbines, so there is a potential economic benefit, but it doesn't change what locations are viable.

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>They typically go for $100-$1000/kg...

I was doing some searching, but was unable to pin down precise numbers for industrial water rates, but I am seeing something in the single dollars ($3-8) per thousand gallons.

Assuming I did not bork my conversions, at $5/1000 gallons, that would be roughly $0.001/kg for water. So, a novel heavy liquid priced at the whole dollars per kg sounds like an enormous capex for a large installation when it could use water instead.

The article mentions their plan is to bury the tanks. That is stupid expensive, and one of the reasons existing water storage tanks are never buried in the US.

Buried water storage tanks are not rare. The San Francisco Water Department has some in their system.[1][2] They're basically roofed concrete reservoirs. Those store clean, processed water.

Those could have been fully buried or hidden, but, being visible only from the air, it wasn't worth it.

[1] https://earth.google.com/web/@37.48236017,-122.3128578,104.7...

[2] https://earth.google.com/web/@37.53843703,-121.85711496,126....

That's easy and cheap per volume: Drill a small hole into a mountain. Add a nuke.

It's not for water suitable for consumption, but it doesn't have to be.

Just nuke a mountain, that'll solve climate change. Peak HN.

I'm imagining two connected olympic swimming pools, at the base and on top of a mountain, filled with liquid mercury...

https://www.bing.com/images/create/two-connected-olympic-swi...

Voila! Three connected pools, none of them Olympic or at the top :-)

That’s not to far off something you’d see in Zelda, Zora’s domain.

> heavy liquid. They typically go for $100-$1000/kg

This company has their own proprietary heavy fluid called R-19. Their formula isn't public, but presumably they understand the success of their company depends on it being affordable.

> No idea what the article is talking about wrt being able to utilize lower heights

It means that, if pumped storage starts to look worth it to you (given budget, etc.) with tanks of size V and a height difference of H, then with their system it might be worth it if the tallest hill available to you is H/2.5.

Or you can keep the height the same and reduce the volume. Or keep both the same and increase the storage. The point is that they claim to offer a better trade-off.

They claim they have a fluid. The patent says "minerals", water, and "surfactant." Translation: mud/sand.

I can't help but notice that the name they're using is the same as an insulation material; seems almost purposeful to make looking up anything about it very difficult.

I don't think they have anything and this is just a patent troll or someone trying to pull a fast one on investors. I'd be willing to bet they have a long list of reasons why they can't come up with demonstration unit that is room or building-sized...

It could be something like bentonite/baryte or similar drlling muds:

https://en.wikipedia.org/wiki/Drilling_mud

Drilling mud, however, needs to be at least somewhat viscous, so it will carry rock fragments from the drilling back to the surface.

Sure, but it depends also on the kind of drilling and of the terrain that is drilled, drilling mud is used also when drilling with buckets large holes, in those cases the use is only that of avoiding the collapse of the walls of the bore.

The generic idea behind these supposedly high efficiency reservoirs is to have something that is at the same time liquid enough and much heavier than water, most probably the actual formulation will be a compromise.

> This company has their own proprietary heavy fluid called R-19. Their formula isn't public, but presumably they understand the success of their company depends on it being affordable.

That assumes they plan to ever deliver anything real. There are very few substances cheaper per unit mass than water, and I would not take on faith that something that isn't even being mass produced yet could ever possibly compete.

> It means that, if pumped storage starts to look worth it to you (given budget, etc.) with tanks of size V and a height difference of H, then with their system it might be worth it if the tallest hill available to you is H/2.5.

That's not how turbines work. Pressure head is independent of volume.

> Or you can keep the height the same and reduce the volume. Or keep both the same and increase the storage. The point is that they claim to offer a better trade-off.

And I am saying that I do not believe their claim that they offer a better trade off.

> That's not how turbines work. Pressure head is independent of volume.

I'm not talking about pressure head. I'm talking about energy storage. If everything is held constant (reservoir volume, height difference) but the density of the fluid changes, then the energy stored changes. Because gravitational potential energy is E = mgh. And m = volume * density.

But since you mentioned pressure head, if volume changes, it doesn't affect pressure. But if the fluid density changes (and all else is equal), then that DOES affect pressure. That's why if you measure pressure in mmHg you will get a different number than if you measure it in mmH2O. So if you took a pumped hydro storage system and drained the water out and replaced it with denser fluid, the fluid would press harder on the turbine.

The equation for potential energy is U = m ⋅ g ⋅ h, so higher density factors into higher mass (per unit volume) so directly into higher energy storage capacity.

But as they stated it translates into higher energy storage capacity (per unit volume). This translates into smaller footprints as volumes go down, but that’s it. Now, mercury is almost 14 times more dense than water so that’s nothing to sneeze at.

Which generates more energy, dropping 1000 tons of water 100 meters, or dropping 1000 tons of steel 100 meters?

Volume matters for the sizing of components, it doesn't matter for the amount of energy you can extract from a height differential.

Storage tanks are limited by volume, not mass.

Which falls under the category of component sizing. But assuming you have however much mass at a given height, a denser fluid won't let you extract the same amount of energy from a lower height, which is what the company is claiming.

There is also craned power generation BTW.. Concrete blocks are stacked with a crane.. They are then dropped to the ground and the potential energy harvested by the cranes motor

You need to generate enough pressure to run the turbines efficiently. High density means high pressure with a small drop.

A small drop means you don’t need a mountain to build the facility.

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