Jack Ponton, Emeritus Professor of Engineering at the University of Edinburgh, Fellow of the Royal Academy of Engineering: Most renewable energy enthusiasts now seem to understand that powering a modern society will require something else in addition to intermittent electricity generation. The currently fashionable ’something else’ is storage. This paper will discuss storage technologies, Britain’s current facilities and what might be needed to provide reliable power from wind, solar and tidal generation. There seems to be no possibility that any existing storage technology can handle the intermittency of wind generation. Solar plus battery storage is probably already cost-competitive for locations in or near the tropics, where year-round load factors are acceptable and so only overnight storage is required. In the UK, low winter load factors mean that essentially no useful generation takes place in December and January.