3 September

This is my favourite method of storing electricity. A gravity battery. Surplus renewable energy in the daytime is used to lift very heavy blocks to the top of the tower. Then as the sun goes down they’re lowered slowly, and drive a generator, generating electricity. (There are lots of different ways to do this.) Hugely efficient, simple in an engineering sense and therefore incredibly reliable. You can also use huge flywheeels to do the same.