With regard to the construction of a compressed air energy storage (CAES) plant in Switzerland, two fundamental questions need to be clarified.
First: the legal situation regarding underground construction seems to be unclear. There is currently no corresponding law at federal level, which is why the cantons decide on the use of the land beneath public and non-arable areas.G. Ruiz, “Niemandsland unter der Schweiz”, Horizonte No. 118, Swiss National Science Foundation, September 2018 The legal situations vary at cantonal level. However, due to the increasing use of underground areas, for example through geothermal energy or the storage of natural gas and CO2, efforts are being made to clarify the legal situation.A. Abegg and L. Dörig, “Rechtsgutachten: Untergrund im Recht”, Zurich University of Applied Sciences, School of Management and Law, Winterthur, October 2018 “Geologische Daten zum Untergrund”, report of the Federal Council in fulfilment of the Vogler postulate 16.4108 of 16 December 2016, December 2018 Despite the uncertainties, it can be expected that the construction of CAES plants will benefit in part from the experience gained during the construction of underground structures such as machine centres for pumped-storage systems.
Secondly: it is not clear which laws and regulations could apply to the underground storage of air at high pressures. Since air is not flammable in itself, Federal Law 746.1, which regulates the storage of liquid and gaseous combustibles and fuels, does not appear to be relevant.
As there are no clearly defined legal requirements, it is to be expected that a comprehensive risk analysis will have to be conducted prior to the construction of the first large CAES plant in Switzerland. Until now, it appears that risk analyses for only diabatic compressed air reservoirs with storage cavities in salt deposits or empty gas reservoirs have been carried out. P. L. Hendrickson, “Legal and Regulatory Issues Affecting Compressed Air Energy Storage”, Report PNL 3862, Pacific Northwest Laboratory, Richland, Washington, USA, July 1981 M. C. Grubelich, S. J. Bauer and P. W. Cooper, “Potential Hazards in Compressed Air Energy Storage in Depleted Natural Gas Reservoirs”, Report SAND2011-5930, Sandia National Laboratories, Albuquerque, New Mexico, USA, September 2011
An obvious risk is posed by the rapid, explosive escape of the compressed air. At the existing facilities in Huntorf and McIntosh, there is no indication that any such event was imminent in the salt caverns. In the case of CAES plants with storage cavities in the rock, such events could be prevented by monitoring the deformation of the storage cavity and immediately reducing the pressure in the event of any unusual behaviour. Such measurements have already been carried out at the pilot plant in Ticino.G. Zanganeh, “Demonstration of the ability of caverns for compressed air storage with thermal energy recuperation”, Final Report, Federal Office of Energy, November 2016.
