General: Gravity energy storage

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- CommentAuthorfostertom
- CommentTimeFeb 8th 2021
https://www.theguardian.com/environment/2021/feb/08/powering-up-uk-hills-could-be-used-as-energy-batteries
- CommentAuthorbhommels
- CommentTimeFeb 8th 2021
https://energyvault.com/
- CommentAuthorfostertom
- CommentTimeFeb 8th 2021
Looks like another example of similar, not about the one in guardian?
- CommentAuthortony
- CommentTimeFeb 8th 2021
It is slightly inefficient therefore increases overall energy demand!
- CommentAuthorEd Davies
- CommentTimeFeb 8th 2021
Posted By: tonyIt is slightly inefficient therefore increases overall energy demand!
All practical energy storage is at least slightly inefficient. Can you point to a viable energy supply for which we wouldn't need at least some storage?
- CommentAuthorWillInAberdeen
- CommentTimeFeb 8th 2021
I love that energy vault idea - an automatic tower crane builds a tower of bricks to consume energy, then dismantles it again to release the energy!

It would be like a gasometer, everyone in town could see at a glance how much energy is in store.

Both that and the pump-heavy-liquid-uphill story seem plausible but rather niche in scale. Who knows, little acorns .....

It's easy to focus on the next snazzy on-the-horizon invention, rather on boringly familiar stuff which can be deployed at the multi GWh scale at a speed consistent with a climate 'emergency'.
- CommentAuthortony
- CommentTimeFeb 8th 2021
We should manage supply and demand so as to not need to store energy - that would also in itself help us minimise demand
- CommentAuthorfostertom
- CommentTimeFeb 8th 2021
Total gd sense, as usual
- CommentAuthorbhommels
- CommentTimeFeb 8th 2021
Posted By: tonyWe should manage supply and demand so as to not need to store energy - that would also in itself help us minimise demand

Sure we should, but with 100% renewables this will be practically impossible. And what to do with an energy surplus, just put the wind turbines in vane mode or let the solar panels sit idle and not harvest it? Or store it for later, albeit with 85% (or less) efficiency?
- CommentAuthordjh
- CommentTimeFeb 8th 2021
Posted By: tonyWe should manage supply and demand so as to not need to store energy - that would also in itself help us minimise demand

Can you point to any study that suggests any viable method of doing that?
- CommentAuthortony
- CommentTimeFeb 8th 2021
No 🙂 but that does not rule it out as a goal

Re 100% renewables that is a very long way off generally 100% of all renewable generation can be used by balancing the grid and using fossil fuel based generation.
- CommentAuthordjh
- CommentTimeFeb 8th 2021 edited
Posted By: tonyNo 🙂 but that does not rule it out as a goal

Very true, but not one I'll be spending any time on until I see a feasibility study or even a madcap back-of-an-envelope proposal for how it could be done.

Re 100% renewables that is a very long way off generally 100% of all renewable generation can be used by balancing the grid and using fossil fuel based generation.

100% renewables is certainly some way off. It isn't even possible to use 100% of current renewables at the moment so I think 'generally 100% of all renewable generation can be used' is a bit far-fetched as well.
- CommentAuthorfostertom
- CommentTimeFeb 8th 2021
Thought experiment - if only renewable energy existed and was fairly easy and plentiful; if fossil fuels, even biofuel had never happened, would that be a terminal disaster for mankind? Would civilisation and technology never have happened? I think they would, but would have fitted themselves quite happily around the vagaries of fluctuating supply. So why does everyone, even on GBF, go along with the need to meet every whim of demand? hence on/off switchable burning of stuff, which is only still in play at all for that reason.
- CommentAuthorEd Davies
- CommentTimeFeb 8th 2021
Posted By: fostertomSo why does everyone, even on GBF, go along with the need to meet every whim of demand?
That's a bit of a parody [¹]. Thinking that there just might be a need for some storage to deal with still winter's nights is not quite the same as going along with the need to meet every whim on demand.

Current EU28 final energy use is around 2.8 kW per person. Demand management might well get it down to around 500 watts per person when needed. For 70 million people that'd still require 35 GW from somewhere. Nuclear and hydro aren't going to provide it so where do you suggest it comes from if not from storage?

[¹] And that's a bit of an understatement.
- CommentAuthorjms452
- CommentTimeFeb 8th 2021 edited
Energy vault - you need to make a lot of infrastructure (concrete) for that.

Raising 1000kg a meter is 0.003kWh of energy stored
A quick google says concrete circa 100kWh/1000kgto make

i.e. that is likely 1000s of cycles to even store the energy it took to make the concrete in the first place

I've seem balloons pulled under water as a concept - while still tricky would be lower carbon to make and less dramatic of they failed.
- CommentAuthordjh
- CommentTimeFeb 8th 2021
Posted By: fostertomif fossil fuels, even biofuel had never happened, would that be a terminal disaster for mankind? Would civilisation and technology never have happened? I think they would

I don't think they would. If we didn't discover and control fire; we wouldn't have got to most places. We wouldn't have been able to cook, for starters. Without coal it would be much harder to make steel or even iron and without them, the chances of building a semiconductor manufacturing plant or a dam or a turbine or a solar panel seem pretty slim. So apart from primitive men pottering around various bits of the warmer landscape, eating fruit, nuts and maybe raw meat (worms?) I don't think there'd be much here, apart from a lot of happy, red in tooth and claw wildlife.
- CommentAuthorWillInAberdeen
- CommentTimeFeb 8th 2021 edited
I'm spending far too much time running a home school at the mo (hence all my GBF posts). Today we learned that the Roman/Celtic/Viking/Saxon economic systems could support a British population around 1.5million, albeit with a low life expectancy, and this was the cap on population for a thousand years.

Steadily increasing resource consumption, especially through the industrial revolution, has enabled an extra 60m lives to be lived in the UK at the moment, each lasting for more years and with a higher quality of life (I wouldn't swap). I quite like people, so I count that as a huge success, despite the resources consumed, and I am optimistic that there is a clear path to carbon neutrality by 2050 so many more lives can be lived in future 🙂

There were several occasions recently when renewable generation exceeded demand by so much that they couldn't give it away and had to pay people to consume it, but also occasions when they had to unretire coal power because of calm weather, so some more storage seems inevitable. I'm also sure that demand will move to plentiful-supply times if they're cheaper, and that so many renewable generators will be built to supply unplentiful times, that there will often be surplus power on windy days. That surplus, waste power will be effectively free for somebody, if not the consumer.
- CommentAuthorbhommels
- CommentTimeFeb 8th 2021 edited
Posted By: jms452Energy vault - you need to make a lot of infrastructure (concrete) for that.

Raising 1000kg a meter is 0.003kWh of energy stored
A quick google says concrete circa 100kWh/1000kg to make

i.e. that is likely 1000s of cycles to even store the energy it took to make the concrete in the first place

On their website they say the blocks can be made of "industrial waste materials, including materials diverted from landfills, repurposed into an energy storage solution". Nuclear waste would make a very high capacity one
- CommentAuthordjh
- CommentTimeFeb 9th 2021
Posted By: WillInAberdeenso many renewable generators will be built to supply unplentiful times, that there will often be surplus power on windy days. That surplus, waste power will be effectively free for somebody, if not the consumer.

I tend to agree. I have a strong suspicion that the 'somebody' will be people building storage systems to arbitrage the difference. ( I was considering answering Tom's post with the thought that the only proven renewable system we have with predictable output is tidal (apart from the limited hydro on this island) which requires at least double nominal capacity to be built to satisfy all demand (because high tide changes from day to day), so there's bound to be extra capacity. I think that having storage is a Good Thing, for the avoidance of doubt (FAoD?)
- CommentAuthorbhommels
- CommentTimeFeb 9th 2021
Posted By: djhI was considering answering Tom's post with the thought that the only proven renewable system we have with predictable output is tidal (apart from the limited hydro on this island) which requires at least double nominal capacity to be built to satisfy all demand (because high tide changes from day to day), so there's bound to be extra capacity. I think that having storage is a Good Thing, for the avoidance of doubt (FAoD?)

This is why a tidal dam with preferably a river providing some "back fill" would make an awesome scheme. Instantaneous generation when the tide is going in and out, and built-in storage by adjusting the dam sluices, both adjustable on the fly. It is a shame the ecological effects of a Severn Estuary dam are probably severe and hard to predict, from an energy engineering angle it should have been built yesterday.
- CommentAuthorjms452
- CommentTimeFeb 9th 2021
Posted By: bhommelsOn their website they say the blocks can be made of "industrial waste materials, including materials diverted from landfills, repurposed into an energy storage solution".

The figure I gave for concrete already includes some recycled aggregates. for the blocks shown you probably also need rebar for integrity and attach points. Then there's the cranes...

You might be able to reduce that figure a little - but the line about repurposed waste is so vague it doesn't address the energy and CO2 needed to make the infrastructure which is really considerable.
- CommentAuthordereke
- CommentTimeFeb 9th 2021
Posted By: jms452I've seem balloons pulled under water as a concept - while still tricky would be lower carbon to make and less dramatic of they failed.

Here is an article which looks into these concepts in a bit more detail:

http://euanmearns.com/a-review-of-underwater-compressed-air-storage/
- CommentAuthorbhommels
- CommentTimeFeb 9th 2021 edited
Posted By: jms452
You might be able to reduce that figure a little - but the line about repurposed waste is so vague it doesn't address the energy and CO2 needed to make the infrastructure which is really considerable.

I don't disagree. But then the footprint of the other schemes is not considered either, and details are equally vague (mineral rich dense fluids...?) . What I like about the energy vault is that it is not tied to an abandoned mine shaft or hills and can be plonked down pretty much anywhere. Although I have to see (from a safe distance) how it would fare on a gusty day in North Scotland!
- CommentAuthorWillInAberdeen
- CommentTimeFeb 9th 2021 edited
The blocks on the top level of the tower crane pile, obviously store energy more effectively than those on the bottom. Maybe the bottom of the tower could be housing, and they could hoist blocks on and off the rooftop to store energy for the residents? Maybe it could be retrofitted to existing blocks of flats?

Yes the whole thing is bonkers but it made me smile 😂

If 10t of blocks were hoisted onto a 50m block of flats, the energy stored would be 10000*9.81*50 = 5MJ = 1kWh.....

Edit to add: if it takes ideas 20years to get from brainwave to deployable at multi GWh scale, and we want schemes built and operational in plenty of time for net zero in 2050, then I think the only realistic candidates are: batteries, pumped storage, hydrogen, demand shifting, thermal stores.
- CommentAuthordjh
- CommentTimeFeb 9th 2021
Posted By: bhommelsthe footprint of the other schemes is not considered either, and details are equally vague (mineral rich dense fluids...?) .

Yeah, the 'proprietary fluid' bit put me off. There's so many possible nasties hidden in those two words. Fluids that separate into their individual components over time, fluids that wear the turbines, or react with the pipes or air or soemthing. Plus if the higher density is used to compensate for the reduced height of hills needed, then you're still going to need pretty large tanks to match the capability of a reservoir of water.

I liked the schemes that were proposing running trains up and down hills in the desert. They seemed like fun. Pumping water up a hill, compressing air, synthesising some fuel like methane, heating to get molten salts all seem far more likely and I suspect most of the more unusual schemes won't get tested until we've exhausted the simpler schemes first.

Q for Tony. If we're going to do without storage then we should close all the existing hydro storage schemes first. What will you replace them with?
- CommentAuthortony
- CommentTimeFeb 9th 2021
The hydro storage is mostly for high demand management, the amount stored is infinitesimal compared to usage.

They can almost instantly boost the grid at problem moments but can’t do it for long allowing time for other generation to be ramped up.
- CommentAuthorbhommels
- CommentTimeFeb 9th 2021
Posted By: tonyThe hydro storage is mostly for high demand management, the amount stored is infinitesimal compared to usage.

They can almost instantly boost the grid at problem moments but can’t do it for long allowing time for other generation to be ramped up.

Sorry, I wasn't clear enough - I referred to it in the context of an estuary dam: huge area but little height difference. The stored energy can be very large but it will not react as quickly as a couple of lakes with a few 100m vertical denivelation.
- CommentAuthorrenewablejohn
- CommentTimeFeb 15th 2021
Posted By: tonyThe hydro storage is mostly for high demand management, the amount stored is infinitesimal compared to usage.

They can almost instantly boost the grid at problem moments but can’t do it for long allowing time for other generation to be ramped up.

Would be easy enough to set up a high pressure hydraulic grid system. Oh wait a minute we already had them in London, Manchester and Liverpool. Just a shame they were scrapped as they could be really useful now and they dont suffer from transmission losses like electricity does. Bit of a myth saying its only a short term boost that only applies to one site but then it is the only site most people are aware of.
- CommentAuthortony
- CommentTimeFeb 16th 2021
A much better form of battery would be “switching things off instead” as the need for stored power arises. Truly smart, 100% efficient, simple, doable, .....
- CommentAuthorfostertom
- CommentTimeFeb 17th 2021
I agree - "if only renewable energy existed and was fairly easy and plentiful; if fossil fuels, even biofuel had never happened ... would have fitted themselves quite happily around the vagaries of fluctuating supply."

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General: Gravity energy storage