Large-scale electrical energy storage

The review has been prepared by staff of the CEGB who are actively studying different aspects of large-scale electrical energy storage. Some areas, such as pumped storage, have been studied in considerable depth, since this technique has been exploited commercially for many years in many parts of the world. Other topics, such as superconducting magnetic storage, are at a much less advanced stage of development and are still at the laboratory and paper study stage. The review starts by examining the role of storage on an electricity-supply system. At present, the major use is put to reducing the flexibility requirements on other plant, but in the future, load smoothing for use with those systems with a large nuclear component could be important. The benefits and limitations of storage in conjunction with renewable energy sources are also discussed. Turning to the technical possibilities, a description is given of the widely used pumped hydrostorage technique. Potential development such as the use of an underground lower reservoir are discussed. It is possible to store the compression energy of a gas turbine as compressed air in an underground cavern. A plant operating on this principle has been built at Huntorf in Germany, but it requires a premium fuel such as natural gas or distillate oil. The possibility of developments leading to a reduction or elimination of this fuel requirement are discussed. It is also possible to store hot water at a power station and re-use it in the steam cycle. This technique has had some practical use for many years and its advantages and disadvantages are discussed. Batteries have been used for storage for many years, but current types are generally too expensive for use for large scale electrical utility applications. The state of development is discussed of new types, which although primarily envisaged for use with electric vehicles, could be used in central stores. Flywheels are also being developed for use with electric vehicles an- their potential application to large-scale electrical energy storage is reviewed. Perhaps the most technically advanced storage technique would be to use a large superconducting magnet. The status of studies of this possibility is described. Finally, the relative advantages and disadvantages of the various technical possibilities are discussed.