We do have a very simple large-scale storage system that's already in use across the world: pumping water uphill. It's just not as economical as rain when you factor in the efficiency losses from generating and transferring power twice.

And pumping water uphill is a regional solution that requires specific regional geography, to me that does not class as "scalable".

I should be more specific in that to me "scalable" is a solution that can be deployed anywhere without require specific regional properties. Maybe you think this is unneeded and that a lot of region specific solutions can cover the storage requirements.

However another posted did point out that 1 mile by 1 mile of batteries is apparently enough to store US energy requirements.

Unless there is big improvements in battery tech I don't see it as a solution. Lithium batteries have their own environmental problems and die after 10 years.

Pumped hydro requires the geography, building new capacity tends to flood large areas and release huge amounts of greenhouse gases initially.

Simply lifting weights on cranes or rail tracks is looking more efficient and can be adapted anywhere. It will probably win out in many cases.

> Simply lifting weights on cranes or rail tracks is looking more efficient and can be adapted anywhere.

The energy density of that kind of scheme is a joke. Thought experiment: a fully charged Tesla, how often could it climb a hill the size of that crane if it skips recuperation on the downhill leg? That's how much lower the energy density of a crane storage would be. Pumped storage works (where the geography allows it) because water is by far the cheapest and the most easily transported ballast and geographic height differences dwarf almost every human made structure.

If you want something that scales everywhere, look no further than compressed air. It's usually ignored because of the big thermal losses, but if you have a direct application for coolant they are not that bad and even without, it serves as an almost trivial lower bound to the storage problem. We can calculate how much intermittent energy production we would need with compressed air to serve a power demand profile and everything else is just a possible improvement.

Since when was energy density ever been a problem for grid storage? Even in the most crowded cities on earth it's not a constraint.

Unless you are talking about portable applications it's all about round trip efficiency and cost, I'm not sure if you are getting confused about terms here or talking about an entirely different subject.

Compressed air efficiency isn't great. Using it for cooling lowers the efficiency even more.

Crane and rail gravity storage are pushing 80-90% round trip efficiency.

Previous HN discussion: https://news.ycombinator.com/item?id=17789456

Nuclear power plants are also regional solutions that requires specific geography....

Nuke plant siting is vastly less constrained than pumped hydro facilities.

It doesn't require specific geography. You can create entirely artificial pump systems isolated from any natural water. These are called closed loop systems. You could create an closed loop pumped hydroeletric system in the middle of the Sahara if so desired. Incidentally you could power the entire world with a solar area taking up a single digit percent of the Sahara.

These haven't been actively developed in the past because we don't have much need for massive storage and they also take something on the order of a couple of years to plan, develop, and execute. You need the demand to be there before the storage is built, but the demand won't exist until the storage is built. Fun problems. Because of this batteries are a more practical immediate solution. They can be deployed anywhere, at practically any scale, with negligible time requirements. And similarly for manufacturing. Since they aren't 'geo locked' their market flexibility is much greater.

The Sahara-global-solar-facility scale starts bumping up a lot when you factor in realities.

PV efficiency, spacing factors, panel replacement cycles, storage requirements, the fact that we're looking at total energy use and not just electricity, first-world rather than third-world per-capita use rates (presuming we're not going to freeze the entire world at its present state of energy consumption), and projected population growth.

You can still provide most or all the hypothetical demand from the Sahara, but you're well above 1% land use. I've sketched this out elsewhere previously, don't have numbers handy.

Beware optimistic estimates.

I worked out the numbers several years back and it was around 5%. Efficiency improvements since then should have improved this a fair amount. Even if you bump it up by an order of magnitude it's still rather remarkable how easily we could power the entire world on solar alone.

However, I completely agree on the real issue being one of longterm consumption. I would say this is something that's regularly ignored. The developing world starting to consume developed world electricity/capita alongside increasing world population is easily going to increase energy consumption by some orders of magnitude in the foreseeable future.

This poses unique challenges few are considering. For instance nuclear also runs into problems here with resource availability. The technology is already rather cost prohibitive and for future energy needs if it became a primary source you'd absolutely need to move to breeder reactors alongside saltwater uranium extraction which would both push the prices up significantly higher than even present. High energy demands alongside high energy prices might make the production owners/shareholders happy, but not much of anybody else.

In any case sooner or later we'll end up relying on solar simply because nothing else can compete on gross energy availability. The sun's a fusion reactor that could fit about 1.3 million Earths inside of it. That enables practically unlimited power out there just waiting to be harnessed one way or the other.

There are several solutions to supply-demand matching and buffering which either do or should work.

A key is to think of this in terms of matching supply and demand rather than simply as storage. We've adapted over the course of a century or so to a regime of dispatchable supply energy, with little use of dispatchable demand. There's also been little consideration of major behavioural, social, economic, and land-use changes which will be prompted by changes to the energy regime. Much the same way as major impacts of internal combustion engines on land-use, construction, transport, and trade were almost wholly unanticipated, most discussion today is framed in terms of "how do we sustain present behaviours and activities under a novel energy regime" (if not quite so explicitly). The short answer is: you don't.

Automobiles, rail, air transport, and powered shipping gave rise to suburban sprawl, transcontinental trade networks, same-day globe-spanning travel and light cargo, and transoceanic shipping centres, along with tremendous centralisation of activities in zones of maximum productivity (often, yes, through massive externalised costs). Little of those impacts was foreseen in the popular or academic literature of a century (or even half-century) ago.

There's much of economics that's badly broken, but a part that's useful is the notion that behaviours do change tremendously in the face of changes to real and expressed costs. The Jevons Paradox cuts both ways: increased efficiency increases total use, whilst increased costs will decrease total use of some resource or factor. (Increasing efficiency is equivalent to saying "decreasing cost".)

Addressing energy specifically:

Expect to see far more dispatchable load, effectively, "making hay whilst the sun shines". High-load, but bufferable uses such as thermal heating (water, space, thermal storage), electrically-driven refinement (aluminium smelting, electric arc furnaces), reverse osmosis desalination, and the like, can if not "store electricity", then cache useful activity whilst supplies are abundant. Smaller industrial, commercial, residential, and possibly transport loads may also see time-shifting on a similar basis.

For direct storage, pumped hydro, compressed air energy storage (CAES), grid-scale batteries (an area with frustratingly slow development, though some promise, especially with cheap-and-abundant if not highly-efficient electrolytes), are presently proven. There are a number of schemes which don't work particularly well -- flywheel storage doesn't seem useful for much besides replicating today's "spinning reserve", nor do supercapacitors look as if they'll offer much beyond grid-scale power conditioning.

Two areas which offer tremendous promise and fairly high probability of success are grid-scale thermal energy storage with regeneration and electrically-based fuel synthesis appear at least on a back-of-the-envelope basis to provide national-scale grid-level storage capacity good for weeks (thermal) to millennia (fuel synthesis). The round-trip efficiencies are not great, but the simplicity, safety, and in the case of fuel synthesis, exceedingly long-duration storage, transportability, and utility of the derived medium are huge advantages.

Thermal energy electrical storage is mostly used now in solar thermal generation plants, but could be utilised in other forms. Large insulated tanks of molten salt driving traditional steam turbine generation could offer weeks worth of grid storage for the US in a total storage capacity roughly of the magnitude of extant oil transport storage facilities in Oklahoma.

Synthetic fuel generation, first suggested for nuclear power at Brookhaven National Laboratory in the 1960s and researched for over 50 years at Brookhaven, M.I.T., and the US Naval Research Laboratory, has yet to be proven at national scale, but the basic chemistry works, it's similar to coal-to-oil processes used by South Africa and Germany since World War II, produces direct analogues to current fossil fuels (methane through bunker oil) but is carbon-neutral as the carbon itself is sourced from current biosphere reserves, principally seawater.

Otherwise: expect to see tremendous differences in how energy is used, in construction based around heating and cooling loads, lighting, transport, and other processes.