Heat storage wells: key to large-scale cogeneration

Studies carried out by General Electric Co.--TEMPO show that large-scale co-generation combined with a heat storage well system can conserve 35 percent of the energy consumed and reduce air and water pollution enough to make co-generation of heat and power attractive to both industry and utilities. TEMPO's storage design is based on two conventional water wells drilled in a pressurized confined aquifer. Ground water is circulated through a heat exchanger, injected into a warm well, and later withdrawn from a hot well and passed through the heat exchanger and back into the warm well. Successive recycling increases heat recovery efficiency. Capital cost estimates range from $17 to $37 per kilowatt and pumping costs at about 10 cents per million Btu. While insulated tanks would be prohibitively expensive to build and pressurized in addition to requiring expensive land purchases, wells require only a small area. The U.S. now has only 500-600 co-generation systems and 50 to 100 large district heating systems, although total energy systems are more prevalent in Europe where hot water is easily transported to and from central plants. Plants facing fuel curtailments where coal is not a viable option may find co-generation agreements with municipal utilities compatible withmore » local community needs. Large seasonal storage systems are needed if the hot water from electric generation is not of immediate use. Demonstration programs for industry will be followed by demonstrations of residential and commercial application. (DCK)« less