Grid-scale batteries: They’re not just lithium

When size and weight don't matter, lots of other battery chemistries can work.

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[raxx7]

There are also synchronous condensers for grid stabilisation. They are like an electric motor with no shaft. A few have been installed in South Australia recently. SA being a good test bed for renewable energy grids, with variable renewable energy “generation provided at least 70% of its total generation during half of the year in 2023”**, and renewables reaching 100% at times.

**
https://reneweconomy.com.au/south-a...e-boundaries-of-renewable-energy-integration/
https://en.wikipedia.org/wiki/Synchronous_condenser
https://www.energymagazine.com.au/sa-synchronous-condensers-installed/

Trivia about synchronous condensers:
In theory we could repurpose the generators of decommissioned power plants as synchronous condensers.

 

[raxx7]

I was thinking about this. The lead-acid accumulator is a well-established, mature technology. While the materials are heavy, they are not too expensive and it can go through many cycles of charge and discharge. It can also deliver a lot of power fast, on demand. I'm thinking that the last bit is less necessary for power grids that have a lot of cells rather than the single battery that starts a car. At the time, maybe the telcos chose the tech that was most accessible, and they might choose otherwise now.

Lead-acid batteries don't actually last very much if you cycle them often.
So they work OK~ish for backups applications where they're rarely called up but not for applications like grid storage where they're being cycled often.
For these applications Li+ ends up being cheaper once you account for the replacement/maintenance costs.

 

[raxx7]

Interesting. Does the entire tank need to be at 300 °C or just the fluid at the anode, cathode, membrane junction?

I am not a chemist but I think it's the beta-alumina electrode you need to keep at 300 C to have enough ion conduction.
But I think you also need to keep the sodium and sulphur above their melting points (98 and 115 ºC) too.

In practice these high temperature sodium-sulphur batteries are built of cells like these (c) and the entire pack is kept at high temperature.

 

[raxx7]

And in 2023 Wabtec delivered one battery electric heavy locomotive. Lithium chemistry, apparently from GM. Even when your mass budget is 200 tonnes, a maximum power demand of 3 MW is significant. The whole concept relies on regenerative braking, as 7 MWh storage is not that much range. Probably in a hybrid consist that still has diesel locomotives.

However long distance battery electric rail of any chemistry is pointless. This problem was solved 100 years ago, with overhead wire electrification. Unlimited range. Regenerative braking back to the grid. No time spent recharging. Less mass for storage, leaving more for power or other conveniences or run lighter. Less hazard from energy storage in the event of a collision. Fewer conflict minerals.

Copper is a conflict mineral too.
In fact cobalt is usually mined as a secondary product of copper mines.

We really need to fix the "conflict" part here.

 

[raxx7]

to kill you if you get too close.

So you need proper tools and training to work on a live 25 kV line.

Or you're get
Well, that answers that! Presumably the train makes connection with a bare wire; maybe not?

Yes the train makes connection to a bare wire.

But it's not easy to make a usable tap without getting killed.

You'd want to securely bond your tap wire to the messenger wire and then securely (and discretely) tie it to the bracket and down the mast.
Keep in mind all that stuff moves and shakes with wind and passing trains.

But pretty much everything but the mast is liable to make you crispy in a flash.
So you need proper tools and training to work on a 25 kV line.

 

[raxx7]

I'm surprised copper is used in that application. I'd have expected aluminum.

Most wiring is still copper because it's a better conductor and it's more cost effective.
Pretty much the only reason not to use it is when people steal it frequently.

In particular being a better conductor means you need fewer traction substations (supply points) to power the overhear wire system.

 

[raxx7]

You don’t have to place power stations closer. You can just use large gauge wire. 50% more aluminum results in the same resistive losses as copper. The aluminum will weigh half as much, be twice as strong, and will cost 1/6th that of the copper it replaces, while allowing the support towers to be placed further apart.

That makes sense.

No idea why copper is still used for overhead wire.