Their point isn't that that's the best idea, but that we have lots of things that would actually work, and between them there was never any reason to worry too much about it.

Like you might not know what your going to eat next Friday, you don't know if the cafeteria might sell out of chicken, or if they'll be doing a special on your favourite fish. But that's different from "I will starve next Friday" or "I am allergic to nuts, and there will be nothing but nuts to eat" and it certainly doesn't mean you should put poison in your food today.

It's not physics that the limit, it's economics that suggests green hydrogen will probably be the winner, since as well as storage it has other uses. Similarly for batteries, the dual use tips the balance economically.

> Their point isn't that that's the best idea, but that we have lots of things that would actually work, and between them there was never any reason to worry too much about it.

And the above commenter's point is that it doesn't actually work.

The fact that so many support and energy policy that amounts to "whatever, we'll figure out storage eventually" is astounding. If that's the mentality you're going to take, just let fusion solve all our problems.

Energy storage is still hard, unfortunately. I don't think any gravity storage other than pumped hydro (where nature allows for it) is viable.

The question I've been asking myself in case we were to go for battery energy storage: would we be better off using decentralized system with solar + battery on every home / small community or just make massive installations and keep using existing power grid to move energy to homes?

Decentralized doesn't work so well for places that require a high ratio of electrical power to solar radiance - like refineries, factories, medium and high density housing, electric vehical fast chargers, low density housing in places that get cold in winter, and more. So a large fraction of society will need to import some energy from somewhere (either from the grid or a fuel like hydrogen).

Fully decentralised solar + battery might be the best option for rural / semi-rural settings, but even low-density suburbia somewhere sunny could likely benefit from having all those batteries and panels working together via the existing grid.

> Decentralized doesn't work so well for places that require a high ratio of electrical power to solar radiance

Yeah, another example that comes to mind are flats - the roof is a bit small to cover all residents' energy needs.

As always in life it seems that "it depends" but I think you are right about remote places. It is of course always better to have electrical grid since you shift the maintenance to someone else (as long as the power delivered is reliable and cost effective).

The one issue I can think of is current grid may not be able to handle many small energy producers - they can be cut off when peak power is a problem. In those cases individual prosumers would benefit from having a local battery storage system that fit their needs, even when connected to the grid.

Remember the goal to electrify everything. For the home owner this includes space heating. So if you live in the snowbelt you need to have the battery capacity to handle a two week Polar Vortex with temperatures below zero degrees Fahrenheit with very little sun with your fully decentralized solar system. This will require a very expensive battery system!

I think it will be a mix of both. Local storage at home is great for some grid independance during blackouts and usually you save some money when you have you own solar roof.

But local storage usually will be more expensive per storage capacity vs. larger storage facilities. This means, a large amount of storage will be there, because it is cheaper. Also the power company can control it better than home systems.

And of course there the electric cars which could partially contribute to the grid storage.

Even if in theory local storage us cheaper, most people won't want to invest in replacing their system every 10 years when it wears out.

I think we will see mostly utility scale storage. Most people will have an electric car that they can plug into, but that will only be done to keep the fridge cold when the utility goes out.

10 years seems like a short time, what if we make it 30 years - same as solar? You would need to update it roughly once during your lifetime.

The other idea is having small communities that manage their own energy needs. Meaning 1MWh energy bank for 100 homes instead of 1GWh for 100 000 homes.

Battery life doesn't always work the way you want it to.

I don't know what the limits of different battery chemistry is, but I suspect it won't work. Though 10 years was just a number I made up, I think it is reasonable for discussion.

Yeah, I think you might be right although AFAIK they still hold on to about 80% of their initial charge after that time (10y), which is quite a lot. 30 years was just a random thought that seemed like a sensible minimum to be somewhat low-maintenance solution.

I am just trying to think about different possibilities, they pros, cons and what might be net win in this case. Your remark on people not wanting to service yet another thing is spot on, grid always works for them.

On land you just can’t make it tall enough, you get roughly 2.5kWh of potential energy per km of delta-h per ton of mass. I think if you store energy in a gravity battery out in the ocean where the depths are 10km, you may end up with a system competitive with pumped hydro.

The incremental cost of a ton of mass and a ton of buoyancy are probably gonna be a factor of 2 to 10 less than lithium batteries. For any storage project: if it needs $1B of infrastructure costs for wires, dynamos, robots etc. just to start then you must be talking about building at least 10GWh before it is practical. so probably millions of tons for an oceanic gravity battery

Yeah it’s a terrible idea.

Pumped hydro or compressed air is way better on every front.

Isn't the round trip efficiency of compressed air terrible? You lose a lot of energy as heat when you compress air which you then have to resupply when expanding the compressed air to avoid things freezing over.

There is adiabatic compressed air, where the heat of compression is transfered to a thermal store, cooling the compressed air before it's injected into the storage cavern. Then, on discharge, the heat is recovered from the thermal store and used to reheat the air.

This illustrates, btw, that compressed air doesn't actually storage energy! The energy content of a gas is the kinetic energy of its molecules (and some small contribution from the potential energy of molecules at the moments they bounce off each other, but that's typically minor). The kinetic energy of the molecules is a function of temperature, but not of pressure.

What the air is doing is acting as a store of reduced entropy, which can later be exploited to convert that separate heat back to work at high efficiency. However, one could also do this by PTES, Pumped Thermal Energy Storage, where a reversible thermal cycle produces heat and cold, which are stored separately, then brought back together to recover the work. This is like adiabatic CAES, but instead of storing the cooled compressed air, it is expanded through a turbine and the cold of the resulting expanded gas is stored (say in a tank of mild cryogenic hexane).

I don't like that video, but yes, I don't think that design is the solution for the future. Using water als gravitational storage is quite well developed and has additional benefits (like storing precious water for droughts).

But that is the nice thing going forward: there are many different ways of storing electricity and many of them will be tried. I am sure there will be a lot of new feasible ways of doing so in the market soon.