ENEL's experience with large pumped-storage plants

Power supply is necessary for providing normal daily activities. ENEL has about 7000 MW of pump-storage capacity, having undertaken major program of pumped-storage development since the 1960s. Some of typical large stations are described, and operational experience in comparison with pure hydro stations is discussed. Ternary units (motor-generator, turbine, and pump) are used. Each includes two separate hydraulic machines, turbine and pump. Both can be optimized for their specific functions. Reversible pump-turbine units with guidevanes represent the modern, optimal solution from point of view of installation costs. High efficiency can be achieved both in generation and pumping modes. Single-stage and multi-stage machines are used. Single-stage units perform better as far as the operating availability is concerned.