The most widely used definition of renewable energy is ‘energy flows which are replenished at the same rate as they are used.’ Renewable energy may be direct (such as solar water heating) or indirect such as biomass (generated by photosynthesis), wind (derived from thermal air currents) and hydro (derived from the hydrological cycle). Most renewable sources stem directly from the sun, whereas to some extent conventional energy sources involve ‘mining historical sunlight.’ Many critics of renewable energy point out the scale of, for instance wind-farm development, which would be necessary to replace conventional power generation plants. However, it seems likely that the UK, like other Northern European countries before us, will move towards more locally distributed generation, with many smaller plants from a variety of sources located much nearer to where the energy is to be used. In this scenario, each new plant would be expected to make only a marginal contribution to overall supply, while a much smaller proportion of the heat as well as electricity generated would be lost, for instance through cooling towers and in transmission to final users.