Comment by Brakenshire | Hacker News Reader

Comment by Brakenshire | Hacker News Reader

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At the moment you just maintain a gas backup infrastructure. Depending on how large your grid is and the intermittency and variation of its sources of electricity, you can assume a certain level of output, then the gap between that and maximum demand needs to be maintained as backup. That’s not necessarily a bad thing, gas plants have a low up front capital cost, with a high marginal fuel cost, so having plants available but used less frequently is not a serious economic barrier.

In the long run energy storage techniques will come in which will displace some use cases for gas, how quickly that happens depends of technological development. As you say long term storage isn’t likely to be achieved by Lithium ion batteries, it’s more likely to be Flow batteries or Hydrogen production. Although Lithium batteries can shift storage throughout a day, and also balance the grid on near instantaneous timescales, which is useful.

Another possibility is overbuilding renewable generation, if solar is very cheap you could produce twice as much as you need in Summer in order to produce enough to meet demand in Winter. That can drastically reduce the need for long term storage, but depends on the properties and cost of the renewable technology in a particular location.

What do you mean by producing twice as much in Summer to meet demand in Winter? Because much of our energy consumption is immediate, and can't be easily stored (e.g. heating, cooking, browsing the internet etc).

I think the GP meant having a peak capacity twice the size of peak demand.

>> it’s more likely to be Flow batteries or Hydrogen production.

From an engineering point of view, this statement probably should be correct. Hydrogen in particular has such wonderful potential.

But, we have to consider future economies of scale in production. We don't know how long it's cost-performance may continue to improve, but of the three technologies mentioned, unfortunately only LiIon is currently on an improvement curve that makes it feasible for large scale storage in the short-to-medium term.

At the moment Lithium batteries are cost effective for about 2-4 hours of storage, if you halve costs that would go down to 4-8 hours, but the point is that it’s very unlikely that you will ever get reductions large enough to store energy over weeks or months. Even 2 days would require costs to fall to 10% of where they are now.

There seems to be an error in those assumptions.

Halving costs need not be equivalent to doubling of economic capacity. It might just as well cause an order of magnitude or higher of increased capacity.

I would not be able to estimate those factors, but it's almost certainly incorrect to assume a linear relationship between cost and productive capacity.

Each halving in cost doubles the amount of storage you can apply to any one project for the same cost. 2 hour storage on a solar or wind farm costs around about £5 per MWh, levelized over the batteries lifetime. There is no way to get around that, as far as I can see.

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