A GW is how fast you can go a GWh is how big the fuel tank is. 1.5GW of battery storage is meaningless with out the capacity. Battery storage is really good for grid load compensation on the second by second basis something that fossil power station do but a battery can do better. So batteries have been stealing one of the things fossil power stations were paid to provide and undermining the economic case for their continued operation. Which is a bad thing because we still need reliable generation so we have to pay them extra subsidies.
So keep the number easy. Winter peak is currently 60GW that's 60 million KW's. Imagine a renewables only future backed by batteries. So to last 3 days you need 3 days of 18 hours at 30 GW's and 6 hours at 60GW's [For illustrative easy numbers but not a million miles off].
So 18 times 3 = 54hours > 54 times 30 GW = 1,620GWh (1,620 million KWh's)
So 6 times 3 days = 18 hours > 18 times 60 GW = 10,80 GWh (1,080 million KWh's)
Total = 2,7 TWh or 2,700 GWh, or 2,700 million KWh's.
Assume we can build batteries for £100 KWh installed and connected price. A reasonable assumption in the long run.
£100 times 2,700,000,000 = £270Bn for 3 days storage.
Making the job easier: Plainly nukes will lower the demand up front and help with charging overnight if you build enough. £100 per KWh might be improved upon. Wind and solar is never truly zero but dropping to 10% of rated capcity for 3 days is statistically to be expected.
Making the job harder: gas for water and heating is being phased out in the long run. Fuel for cars is moving t eectricity. Potential demand could easily double.
Those numbers are illustrative but they show the size of the problem of a renewables only backed by battery future. Now you could build 9 Hinckley C's for that money even assuming no scaling cost benefit. That's 28.8GW of always on reliable electricity. Half the nations demand. A nuke will last 50 years with maintenenace batteries, well your guess is as good as mine.
Sadly she's just used as a meat shield to deflect any criticism, who is going to risk looking bad in the current world by arguing with a young autistic girl? Political suicide.
