To be fair much of Scotland used to be covered in forestry and has been denuded. There are some interesting projects showing what happens if the land is simply

To be fair much of Scotland used to be covered in forestry and has been denuded. There are some interesting projects showing what happens if the land is simply protected from over grazing (particularly by deer). As for grid scale storage, the Tesla battery in Australia is 185Mwh, or roughly a 10th of the amount of power the UK receives from France in an hour as a result of their overproduction of nuclear power. It's a drop in the ocean compared to what would be needed to get us though a stormy night when the offshore wind shuts down in high winds. Pumped hydro is great but is hugely dependant on topology. There are some interesting developments like liquid metal batteries that might one day answer the storage problem but none which have demonstrated the scale required to go completely free of carbon emissions. I think load shaping will probably play a larger part than most people give it credit for. There are some interesting developments, including solid state circuit breakers, which could be switched on and off over a network to reduce the load or to take advantage of over capacity of renewables.