Underground Energy Storage for Electrical Power Generation
Authors: Lang William J. 
Published: December 2007

This paper was prepared for the Second Midwest Oil and Gas Industry Symposium of the Society of Petroleum Engineers of AIME, to be held in Indianapolis, Ind., March 28–29, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.
Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
The electrical power industry has turned strongly over the last decade to gas turbine and pumped hydro peaking systems to supplement power from the large base load power plants. Petroleum fuel shortages and limitations of acceptable pumped hydro sites are seriously restricting these sources of peaking power. Underground compressed-air storage for electrical power generation combines many of the best qualities of the two peaking systems while eliminating or peaking systems while eliminating or minimizing undesirable aspects of both. Aquifer reservoirs ideally lend themselves to this type of large scale energy storage and simplify many of the problems associated with energy conversion.

Introduction
The availability of low cost electrical energy in this country and all industrialized nations has resulted principally through the practice of building larger and larger power practice of building larger and larger power generating complexes. These installations must be operated continuously at or near maximum output to yield electricity efficiently and at low costs. For this reason they are only suitable for the production of the base load electricity, that production of the base load electricity, that is, the minimum nighttime load requirements.
Base load coal or nuclear plants supply the bulk of the total electric energy (kilowatt hours) of a power system. Peak demand periods, however, occur for a few hours a day and consume a relatively small portion of total energy but necessitate having portion of total energy but necessitate having generating capacity two or three times greater than the base load. The generating plants which supplement the base load power plants which supplement the base load power production are smaller and fast responding production are smaller and fast responding plants which normally operate on oil, refined plants which normally operate on oil, refined oil products or natural gas. These plants must also be relatively inexpensive in terms of capital cost per kw of generating capacity because they remain idle much of the time.
Over the past decade the trend toward larger base load plants has been accompanied by a trend toward gas turbines for providing peak power. peak power.