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.
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.
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?
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.
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.