A large, slow-moving body of water gives a high torque (turning force), and a waterwheel can make use of this to operate machinery directly. However, the low rotational speed makes it difficult to use a waterwheel for electricity generation; it’s easier to make electricity with a fast flow of water that can be channelled to hit a turbine at high pressure. Waterwheels are also more expensive to construct than small turbines and need more maintenance. Having said that, with some 8,000 mills or mill sites recorded in Britain, a small number may be suitable for generating electricity - so it could be worth looking into. A hydro turbine installed a few years ago at Gants Mill in Somerset generates up to 12kW of electricity and feeds into the local grid.
