Low-head hydroelectric power using pneumatic conversion

New hydroelectric power installations at low-head river sites are often an uneconomic proposition using conventional water turbines. The author deals with alternative power-conversion systems based on air as an intermediate fluid which are aimed at achieving a more economic solution to the problem. A novel water-to-air power-conversion system has been built at Borrowash on the River Derwent which utilises a flexible membrane as a self-oscillating interface between water and air to drive an air turbine and generator. Problems of this new technology are discussed and a number of improvements are proposed which should lead to a viable and economic alternative to conventional low-head hydro stations