| Abstract |
Used in conjunction with the Variable Phase Turbine and the Euler Turbine, the Variable Phase cycle and the Kalina cycle, respectively, can increase the net power production from enhanced geothermal and sensible resources by 30-50% relative to commercially available organic Rankine cycles. These technologies were discussed at the GRC 2010 in the paper “Performance of New Turbines for Geothermal Power Plants.” The technology and thermodynamic cycles will be reviewed briefly with primary focus on updates in the start-up of projects using these technologies. The Variable Phase Turbine consists of discrete nozzles impinging upon an axial impulse rotor and allows for direct drive of the generator with no gearbox. The turbine can operate under any range of two-phase flow conditions and isentropic efficiencies have been measured at over 80%. The Variable Phase cycle consists of a pump, liquid heat exchanger, Variable Phase Turbine, and condenser. Compared to a typical ORC system, the resultant system has fewer components and allows for a lower discharge temperature of the geothermal brine and, therefore, extraction of more energy from the heat source. The construction of a 1 MW geothermal Variable Phase cycle demonstration project with the DOE at Coso Geothermal is in progress and startup is scheduled in July, 2011. Another DOE project is currently underway for the development of a 500 kW hermetic Variable Phase Turbine and the design of a scale resistant heat exchanger that allows for lower return temperatures in geothermal bottoming cycles. Experimental testing of different scale inhibition techniques will be performed. The Euler Turbine is a radial outflow turbine developed for energy recovery in steam systems. This design, coupled with a high strength two-dimensional vane and blade profiles, enables the turbine to be rugged and erosion resistant and allows for expansions into the wet region. Commercial units have been developed and sold, and some are now operating with isentropic efficiencies near 80%. Euler Turbines have been selected as an ideal prime mover in the Kalina Cycle. A 550 kW gross Kalina cycle geothermal power plant using an Euler Turbine was commissioned in 2009 in Germany. A 50 kW rated system was demonstrated at the Shanghai World Expo in 2010 and was then relocated to Taiwan for a geothermal demonstration. Two more Kalina Cycles will use an Euler Turbine including a 100 kW geothermal plant in Japan using a high speed generator. This approach will both increase efficiency and allow for speed variation to maximize performance over a range of operating conditions. The other turbine will be incorporated into a Kalina cycle test laboratory in China for improvements in the design and production of Kalina cycle systems. |