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Comment by didericis | Hacker News Reader

By “at scale” I mean building enough pumped storage facilities to meet current energy demands when the wind isn’t blowing and the sun isn’t shining. It seems much more likely that we could build sufficient pumped storage facilities than the kind of battery farms the poster I was replying to rightly points out are not likely to meet required needs for the foreseeable future, if ever.

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That depends on the geography.

Bangladesh, The Netherlands, Kansas, maybe Texas, etc? No, not useful.

Norway, Wyoming, Idaho, California, Switzerland, Nevada, Arizona, etc.? Oh yeah. Very doable.

My personal pet idea: a big ‘tower’ on the seafloor. Yes, costs are immense, but scaling would really work well. (Making the ‘well’ or tower twice as big would not make the cost double).

In ascii art:

   ———|  |——

      |  |                       

      |++|

With ‘| |’ the walls of the well or tower, —- the sealevel, and ++ the water inside the well. Energy would be gained through letting seawater go ‘into’ the well/water tower. (Edit: attempt to make ascii art work)

You don't need a tower. A boat with a winch and a weight does the job cheaply. For extra credit, more weights.

Limited by the displaced water weight. Prone to storm damage. But the general idea could work and you could even do it entirely under water, saving you from having to dig out a mineshaft, just sink a bunch of caissons to create an underwater tower. As long as they stack and can be re-inforced so they don't end up shearing under the pressure of flowing water. Maybe even open up the sides to a lattice to reduce that resistance.

Existing supertankers can displace in the hundreds of thousands of tons. New, they cost under $100M. Scrap, much less.

They are not bothered much by weather, in normal operation. With that much weight hanging well below the surface, they would be very stable. (Racked together side by side, moreso.) Think of it as a very long oil platform. Those endure any weather with no difficulty.

No need for anything attached to the bottom except anchor chains.

When planning ocean operation, make sure almost everything is at or well above the surface, and everything complicated (motor/generator, winch, power conversion) is well protected from exposure. Ocean deployments that expose expensive stuff to wave action or put it underwater fail, reliably. (Expect tidal generation that puts generators underwater to fail spectacularly.)

Offshore wind has the nacelle well encapsulated and everything that moves far above the waves. Nothing is underwater except the pilings, the end of the support post, and a wire.

Yep, I tried to acknowledge that in the original comment when I said it’s geographically dependent.

It still seems like the only solution that currently exists and actually works on the scale required. I’m not sure what realistic solutions are for regions where hydro pumped storage is not a viable option.

A handful of hours storage, 60% curtailment (with most of the surplus used to create hydrogen and such for chemical feedstock) and a small amount of HVDC leaves a remainder small enough that meeting it with biogas and existing hydro is possible, meeting it with hudrogen is not costly, or meeting it with LNG is not a huge problem.

https://www.nature.com/articles/s41467-021-26355-z

The world produces about 3TW of electricity, 2022's battery production was 760GWh and it's growing 30-50% yoy.

Ideally degrowth happens, but while we negotiate that, the |bhattery industry is at the scale required and is rapidly shedding critical mineral requirements (sodium ion is at GWh scale now, and much larger supply chains with all abundant materials come online in june).

> I’m not sure what realistic solutions are for regions where hydro pumped storage is not a viable option.

Pumped thermal.

https://aip.scitation.org/doi/10.1063/1.4994054

It is not either/or.

It is all/and. There will be many kinds of storage.

True, yes. It just seems to me like conventional battery farms are not going to make much sense in a lot of places, and hydro pumped storage will. Another user pointed out that the size inefficiency is severe enough with hydro pumped storage that it is less grid scale suitable than I thought, so that difference between hydro pumped storage and conventional battery farms is less than I thought. Regardless, energy storage is a huge problem that’s going to require lots of deference to practicality and as many simple solutions as possible. Frankly I’m not sure it is possible, which is why I’m a big advocate for nuclear.

Building out enough storage will be a huge task.

We can't use much of it yet because we haven't the renewable generating capacity to charge it from. (Charging it from fossil fuels would be beyond stupid.) Several varieties are getting cheaper very fast, and new, cheaper ones are being invented, so when the time comes it will cost a lot less. Likewise, carbon capture: building that out now would be stupid if it diverted money that could be spent building renewables that displace carbon emission.

It is also why building nukes is stupid: they displace way less carbon emissions, per dollar, than renewables, and first spend a decade displacing none at all. For the price of the coal burned waiting for the nuke to come on line, you could build that much solar, never mind what you are wasting on building the nuke, and it would start displacing carbon emissions almost immediately.

Batteries and pumped hydro are very far from the only practical storage media. But the assertion you read that pumped hydro does not scale is deliberately deceptive.

I would read Tom Murphy's posts from a different light. His message has consistently been 'unbounded exponentials aren't real, why are you pretending they are?'.

In that light 'pumped hydro can't scale' means 'stop trying to use this for Petawatt hours of energy storage you idiot, you'll destroy everything'.

Some of his more recent posts have been worryingly easy to coopt by the 'maek moar fossil fuels and nuclear' crowd, which his previous posts indicate he should be even more strongly opposed to.

The general message of degrowth and steady state economy is positive even if 'pumped hydro can't scale indefinitely' sounds a bit like 'pumped hydro can't decarbonize the current scale of the economy', and he gets the scale required to maintain status quo consumption a bit wrong.

I do wish he'd make this distinction clearer though.

I would be satisfied to see him stick to facts.

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