There are a lot of posts here pushing batteries.
Batteries are an expensive solution that doesn't scale well at the grid level. It is useful for grid stability (fast frequency response) but simply a non-starter when you're dealing with national grids.
Batteries are an added cost to the system, without producing more electricity, and as a result prices will go up.
A far cheaper source of flexibility is Demand Side Response. Particularly data centres that are willing to be market actors. Compute can happen anywhere, so it should happen where the wind blows and the sun shines. It is cheaper to transmit bits than Megawatts.
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