Utilizing Geothermal Resources Below 150 C (300 F)

Except for the steam-dominated geothermal field at Geysers, Calif., the use of geothermal energy in the US has been minimal. We have been so preoccupied with searching for the high temperature resources (above 350 F), for generating electricity, that we have largely ignored the greatest potential for geothermal energy, that at temperatures below 150 C (300 F). These waters are much more abundant than the higher temperature ones, and, therefore, represent 10 or more times as much useable energy than the total of the energy in all the high temperature waters. The problems have, in part, been technological—how to economically convert these lower temperature geothermal waters to useful energy—and in part institutional. This paper describes the last five year’s program, largely centered at the Idaho National Engineering Laboratory, to make it more practical and economical to harness the lower temperature geothermal resources.