The much trickier problem is storage that's only needed once a week, once a month, or once a year. That's where we don't have batteries, yet.
Seems like there are only a few companies giving it a real go.
Wikipedia says energy density of 0.36-0.875 MJ/kg; assuming 0.5 MJ/kg and putting it into PE = mgh -> 0.5 MJ/kg * 1kg = 1kg * g * h -> h = (0.5 MJ/kg)/g = ~51 km
http://www.wolframalpha.com/input/?i=%280.5%20MJ%2Fkg%29%2Fg...
Where as lithium ion batteries generally get cheaper the more energy dense we make them (in the same chemistries, at least) because fewer resources go into making that same kWh of storage.
That said, naive me would would ask why we can't just fill ballasts with waste water or other dense waste materials on-site?
Energy density over a gravity battery's working lifetime is a different metric than "per-charge", and maybe more relevant for supplying energy back to a grid (compared to, e.g. a home).
My thought about them are mostly about learning curves, however. We have a long ways to go while we make lithium ion batteries cheaper, probably decades, and we improve a lot each year. Gravel, rock, stone, etc. and however we contain and move that around? That seems to be something that humans have been optimizing since our first days, and there doesn't seem to be much room for improvement at the moment.
My other assumption, which could be false, is that gravity batteries are not currently economical on our current grid with current electricity prices and price swings, an assumption I make because there are no installs I know of, and none planned. Instead of being uneconomic, they could just be untried, because the electricity industry is fairly innovative. If gravity batteries are economical today then I think there could be future for them.
https://www.thetimes.co.uk/article/blackout-alert-from-natio...
Last week, National Grid issued two electricity margin notices, the most serious security-of-supply alerts since 2016, both citing low wind farm output among the causes and urgently appealing for more power plants. To keep the lights on, Britain burnt coal in polluting old power stations that are due to close within a few years.
“Unusually low wind output coinciding with a number of generator outages means the cushion of spare capacity we operate the system with has been reduced,” it said last month, warning of “tight margins” on Britain’s power grid in the days to come.
Electrolysis isn't very efficient without nasty electrolytes. For massive scale, pumped water/air is still probably the most feasible in a reasonable timeframe and cost.
The sun is always shining somewhere but this does doesn't sound feasible simply due to geo-political and infrastructure reasons.
Have any serious plans been put forward for this idea?
Unless there are massive improvements in superconductive materials, of course.
If saharan electricity is the cheapest then nobody else can compete in hydrogen production.
Not to mention global annual battery production amounts to less than 1 hour of the USA's national electricity usage.
(I would be surprised if this was viable even with my suggested measure, no argument there!)
I absolutely accept that this is a poor solution, and that I am quibbling over a factor of perhaps 500 at most when it’s short by a factor of ~250,000.
It's energy intensive, and uneconomic - which is why people are stringing HVDC links across bodies of water - Denmark/Sweden, Australia/Tasmania, NZ North/South Islands instead.
https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_proces...
[1] https://en.wikipedia.org/wiki/Electric_power_transmission
[2] https://www.wolframalpha.com/input/?i=7079+MWh+%2F+265Wh%2Fk...
Converting it back-and-forth to electricity isn't easy nor very efficient, though. Hydrogen is a bit easier, although still lossy. I'd say it's doable, and not as bad as it sounds, if you really have excess production.
inb4 compressed air supertankers.
That said, it will in most cases be less expensive to use it as close to the originating point as possible if you can find a need for it.
But what about electrifying a small collection of households by batteries that are replaced from a truck every N weeks, instead of building many miles of power lines through (perhaps flammable) wilderness?
The point of a global energy grid would be that there's always sun and wind somewhere on the planet and you would smooth out time-of-day differences in usage. The point is NOT to outsource your country's entire electricity production.
Ah yes, because the other countries will magically have the spare capacity (both in terms of generation and transmission)?
We already see this play out in Europe: nobody there wants to do anything about russia because they control the natural gas supply.
>The point is NOT to outsource your country's entire electricity production.
Maybe, but the effects are the same. If you can't produce enough electricity to make it through the night, that puts you in very vulurable position. Even if it doesn't completely shut down the country, it might cause enough unrest to topple the current administration (eg. if they're only leading in the polls by a few percentage points and there's an election in a few months).
I believe simongr3dal’s argument is the invisible hand of the free market, not magic.
Optimistically, solar resources are more evenly distributed than oil and gas, so no country can act like Russia; pessimistically, Russia isn’t the first country to exert influence by threatening to cease supply of its resources, and it won’t be the last; the optimistic response to which is that there are many ways to solve seasonal issues, for example the UK (personal familiarity, no other reason for this example) could plan 18-hours local storage and enough local production for winter rather than summer.