A New High Efficiency Binary Expander Design: Low Temperature Geothermal Application Bottoming Beowawe Geothermal Flash Plant

Abstract

Through the development of a range of new high efficiency binary expanders applied to the Organic Rankine Cycle, lower than traditionally thought of as “commercially viable resource temperatures” can now be utilized for geothermal and waste heat applications. Generally not considered viable for utility scale deployment, the project demonstrates the technical and economic feasibility of electricity generation from nonconventional geothermal resources of 205°F, utilizing the first commercial use of a low temperature bottoming cycle at a geothermal flash power plant. In May of 2009, the U.S. Department of Energy’s (DOE) Geothermal Technologies Program (GTP) issued a Funding Opportunity Announcement (DE-FOA-0000109) to promote the development and commercial application of energy production from Low-Temperature Geothermal Fluids, between 150-300° Fahrenheit. Terra-Gen Power, LLC successfully received an award to demonstrate the technical and economic feasibility of geothermal energy production from these non-conventional geothermal resources. This paper intends to highlight; 1) the successful development of a new design axial turbine family for geothermal and waste heat applications, applied to 2) the successful utilization of a low temperature resource in a commercial utility power sale setting, and finally 3) the successful demonstration of flash bottoming binary cycle technology. Introduction to a New ORC Turbine Family In conjunction with Barber Nichols Inc (BNI), TAS has successfully developed an axial turbine – gearbox family for ORC applications. The turbine design is focused mainly on geothermal and waste heat applications using R134a and R245fa and as the primary working fluid, to cover gross power output from 500 kW – 5.0 MW output with temperatures from 200 – 500°F (97 - 260°C) designed to work with both water cooled and air cooled heat rejection.