Binary power generation from waste heat : a feasible improvement to operating geothermal power plants

Abstract

Geothermal steam power plants often utilize separated steam to run steam turbines and generate electric power. Except for the case of high enthalpy geothermal reservoirs, the steam flow from the separators is often only 20-25% of the total flow. Therefore, the waste water disposed from the separators represents a significant fraction of the total thermal energy of the resource. Likewise, in the case of non-condensing geothermal steam turbines, the exhaust steam is generally released to the atmosphere at temperatures of above 100 C. The poor efficiency of both cases results in rapid reservoir depletion and loss of useful heat. A binary power plant is considered suitable for the utilization of these resources in the expansion of an operating power plant's installed capacity to generate additional electric power. The report deals with two cases; the existing binary power plant installation at the Svartsengi geothermal power plant in Iceland, where the turbine exhaust steam is used for production of power, and a proposed binary power plant in Bacman I geothermal power plant in the Philippines, where the heat source for the binary cycle is the waste water from the separators ...