| Title | Performance of New Turbines for Geothermal Power Plants |
|---|---|
| Authors | Welch, Phil; Boyle, Patrick; Sells, Marc; Murillo, Isaac |
| Year | 2010 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Kalina cycle; Variable Phase cycle; Orgainc Rankine cycle; ORC; Binary cycle; Geothermal utilization; Low temperature geothermal efficiency; Exergy; Thermodynamic cycle; Radial outflow turbine; Axial impulse turbine |
| Abstract | Two high efficiency turbines have enabled the economic use of novel geothermal power cycles, the Variable Phase cycle and the Kalina cycle. Utilizing the Variable Phase Turbine and the Euler Turbine, respectively, the net power production can be increased by 30-50% from enhanced geothermal and sensible resources relative to commercially available organic Rankine cycles. These technologies were introduced at the GRC 2009 in the paper “New Turbines to Enable Efficient Geothermal Power Plants.”1 An outline of the technology and thermodynamic cycles as well as updates on the design and start-up process of a number of projects will be presented. The Variable Phase Turbine consists of discrete two-phase nozzles impinging upon an axial impulse rotor. The turbine achieves high isentropic efficiency while also allowing for direct drive of the generator with no gearbox, thus avoiding the efficiency loss while eliminating the need for a lube oil system and reducing capital cost. The Variable Phase cycle consists of a pump, liquid heat exchanger, Variable Phase Turbine, and condenser. Besides reducing complexity and cost, this cycle can produce between 30 and 50% more power from a given resource than a standard ORC, leveraging the total cost of the geothermal project. The design of a 1 MW geothermal Variable Phase cycle pilot project is currently underway. Details of the design are presented. The Euler Turbine is a radial outflow turbine with numerous benefits compared to radial inflow turbines. For this reason, Euler Turbines have been selected as an ideal prime mover in the Kalina cycle. A geothermal power plant using the Kalina cycle with a 555 kW (net) Euler Turbine was started-up in November 2009 in Germany. Two more Kalina cycle start-ups utilizing an Euler Turbine are planned. Descriptions of the designs and measured test performances are provided. |