How to store power in soil and salt

Giant towers of building blocks rising into the sky and huge vats packed with volcanic rock or molten salt are being used as massive batteries. They are the latest ideas for storing energy generated by the sun and the wind – so you can keep the lights on when it’s dark or the wind isn’t blowing. We meet the entrepreneurs and scientists who are trying to harness the fundamental forces of physics to power the world. Presenter: Tom Colls Image: The Energy Vault tower (c/o Energy Vault)