> 5.6 GW of hydro storage capacity

The unit police issues you a warning! Storage is measured in watt-hours (or Joules), so 5.6 GWh in this case?

But watts are defined as Joules/second so it should be (Giga)Joules/second/hour

A (Giga) Watt-hour is Watts multiplied by hours, not divided! Joules are the SI unit of energy, so you must multiply the wattage by an amount of time to get back an energy.

The unit police is technically correct (best kind of correct), but has no jurisdiction here. The synonym police is on duty here: the word "capacity" was a poor choice leading to ambiguity. A better choice would have been "ability to absorb up to 5.6 GW with the hydro storage infrastructure."

The vast majority of wind that is unharvested is curtailed due to constraints on the transmission network between Scotland (lots of wind) and England (lots of demand). There is a significant amount of pumped hydro (and battery storage) in Scotland to help in these instances but there are still enormous costs associated with curtailment (approx. £1 billion per year).

Pumped Hydro and battery storage are a drop in the ocean of the amount of storage needed to secure the grid, especially as people shift to electric cars.

I take the opposite view - as more people have electric cars there are more batteries available. With some sort of dynamic pricing, and bearing in mind most commuter mileage needs only 1 full charge a week, you could encourage consumers to charge up when it's windy and/or hold off charging when it's not, so better matching demand to supply and reducing curtailment.

This is already a thing in some places. In Norway we have spot pricing of electricity, market price hour by hour. This means that it's possible to have a contract that lets you pay the market price at the time you use the electricity (timespotavtale). Even with the usual contract (spotprisavtale) where you pay the average price each day you can see that price (set by Nordpool) by looking on line or by subscribing to a service that notifies you when the price drops and decide whether or not to charge the car.

The Nordpool price today in the region where I live is 0.80 NOK/kWh, that's 0.074 GBP/kWh or 0.056 USD/kWh.

https://strøm.no/dagens-str%C3%B8mpris

How many people actually do this and are happy with it though?

Here in the Netherlands there are also contracts like that, but people that are interested in them tend to put a lot of time and effort in then tracking those prices. I don't see regular consumers as a whole ever being interested in that. For now, the benefits are also small, and I happily pay a few percent extra (net) to not have to bother.

I also feel like it's not a good direction to move it: consumer energy markets are actually quite predictable so taking out long term contracts should stay the norm (consumer contracts and supplier contracts). Using car batteries as storage for solar can be addressed better by making it more attractive to charge at work, where I assume most park their EVs in the day, but right now pay full price despite providing a place to store surplus.

Why “especially”? Demand for electricity will go up a lot, but people buy electric cars with much larger batteries than they need most of the time.

So, by many people would be able to postpone charging their cars. Steep variable pricing easily would make them do that.

Especially, because most energy used is currently not electricity:it fossil fuels. We need 4x for a zero-carbon grid and to be secure we need over a week's stored electricity: 10s of TWh. The plan for the UK grid has 50 Two in it. Will people really postpone charging their car for a week if they hit a cold still week in January?

You do realise that UK electricity demand has dropped ~20% over the past 10 years.

Meanwhile the EV fleet has risen to 3.5% of the total car fleet.

To thoroughly abuse statistics, theres an inverse correlation between EV ownership and electricity use.

Here in Norway we have 20% of private cars electrified. No impact on the grid and not a lot on total electricity use. If all energy used in the transport sector were to switch to electricity today it would add about 50% to the demand for electricity. But EVs are about 90% efficient versus about 25% or less for ICE vehicles so in fact it would add less than 15% to the electricity demand.

https://publikasjoner.nve.no/rapport/2023/rapport2023_35.pdf

The issue isn't current electricity use—it's current power use and most power used isn't electricity (by a factor of 4-5x).

If everyone shifts to EVs and Vehicle to Grid becomes a normal thing then securing the grid would be a solved problem. Most cars spend more than 90% of the time standing still. If every parking space was fitted with a mid-range, say 7 KW charging point that would go a long way to providing sufficient grid storage.

My Tesla S 70D could supply my house for at least 24 hours if it had V2G.

To secure the grid in a zero-carbon world, we need to supply 4-5x as much electricity and be able to run without renewable generation for over a week.

Often the high costs of "curtailment" are inflated by counting the cost of gas plants in England that run to fill in for transmission blockages.

Of course, if the previous government hadn't effectively banned onshore wind in England, the cheapest source of energy available, you'd be able to deliver that energy for a quarter of the cost.

And, for extra added irony, this is an occasion that the classic "the wind doesn't always blow" line backfires, as either a) if it's windy in Scotland then it will be windy in England avoiding the gas cost or, b) the wind across that distance is decorrelated and you can displace even more expensive gas from the grid.