The 290-MW Huntorf peak shave power plant of NWK is the first installation in the world where energy is stored in off-peak periods by means of compressed air in two 150 000 m3 salt caverns at pressures up to 75 bar. Construction was begun in 1975, normal operation commenced at the beginning of 1979. In the meantime there are extensive logs regarding thermodynamics, rock mechanics and salt content of the air available. At normal operation the maximum temperature difference in the cavern is only 16 K, and there was no evidence of large scale collapses or convergence. The salt content of the cavern air is less than 1 ppm.
Research work has been conducted for many years on how peak current can be generated by a gas-turbine power plant which is combined with sub-surface compressed-air storage facilities. In 1973, Nordwestdeutsche Kraftwerke AG (NWK) pioneered in realizing this new technology by awarding the contract for the construction of a prototype works. Brown, Bovery & Cie (BBC) was charged to construct the gas-turbine power plant, and Kavernen Bau- und Betriebs-GmbH (KBB) to establish the compressed-air caverns in a saltdome. The whole plant was constructed from 1974 through 1977, and it was taken over by NWK in late 1978 for peak current generation after an extensive series of trial rund had been conducted. There is a selection of detailed publications relating to the design, construction and commissioning of the compressed-air caverns (Mattick, Haddenhorst, 1975; Herbst, 1978; Schaumberg, 1976; Quast, Lorenzen, 1978). In this paper an attempt is made to summarize the most essential details of the cavern plant in the design, construction and operation phases and also to describe the performance range of the compressed-air storage caverns.
The high air flowrates of the power plant, combined with the demand for the lowest possible frictional pressure losses, require large flow cross-sections in the boreholes. In accordance with technical and financial optimization a final casing string diameter of 24 1/2 " and a production cross-section fixed by an exchangeable production string of a diameter of 20 "/21 " were selected. Due to the high cost of such large-diameter wells and in view of the risk of striking unsuitable geological formations at the selected locations, the geological conditions of the sites were explored using small-diameter test wells prior to sinking the cavern wells. Large-diameter wells are only drilled if adequate salt formations exist at the depths where the caverns are to be developed. These wells (casing pattern, Fig. 1) were drilled using the air lift/Rotary process. The distance from the test well refilled with cement was 20 m respectively. Five test wells and two cavern wells were drilled from November 1974 through November 1975.
The NWK project was intended to be implemented on the Huntorf saltdome. The technical equipment required for cavern development by the dissolution of salt with freshwater (raw water) could be provided by the EWE high-pressure natural gas storage plant located close to the NWK estates.
