Organic Rankine Cycle
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Publication Name: New turbines to Enable Efficient Geothermal Power Plants
Original File Name Searched: 77_Geothermal_Resources_Council_2009_Paper.pdf
Page Number: 001
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New turbines to Enable Ef cient Geothermal Power Plants
Phil Welch and Patrick boyle Energent corporation
Geothermal utilization, low temperature geothermal, ef cien- cy, exergy, thermodynamic cycle, binary cycle, Kalina cycle, Variable Phase cycle, organic Rankine cycle, radial out ow turbine, axial impulse turbine
mental results of operating the rst two-phase closed cycle power system with a Variable Phase Turbine will be presented.
Low temperature geothermal resources, enhanced geothermal resources and separated brine from ash plants, are huge sources of energy. However, because of their characteristically low tem- perature, these projects and power systems have a high cost per installed kilowatt of power. To produce power from these resources the energy conversion system must maximize the conversion of available energy to power.
Ef cient resource utilization is critical in the viability of geo- thermal projects. Novel thermodynamic energy conversion cycles exist that are superior to the traditional organic Rankine cycle. Two new turbines have been developed that enable the economic and ef cient implementation of these cycles that maximize the geothermal resource utilization. The turbines, the Euler Turbine and the Variable Phase Turbine, can increase power production by as much as 30-50% from low temperature resources and enhanced geothermal resources when compared to commercially available organic Rankine cycles.
Typical ORC Thermodynamic Cycle
GRC Transactions, Vol. 33, 2009
Heat Source ORC
1 3b 4
The Euler Turbine is a radial out ow turbine originally devel- oped for energy recovery in steam systems. Commercial units of 275 kWe capacity are operating on steam, some with isentropic ef ciencies above 80%. The Euler Turbine is also currently being implemented in a 600 kW Kalina cycle in Bruchsal, Germany.
The Variable Phase Turbine uses axial impulse turbine technol- ogy that is well adapted to the expansion of transcritical or ashing liquid ow. The high isentropic ef ciency, typically greater than 80%, enables a liquid heat exchanger cycle1 to be used, avoiding the pinch point limitations of the evaporator in an organic Rank- ine cycle. Because this cycle can use a signi cantly lower exit temperature, signi cantly more energy can be extracted from a given resource. The resulting power advantage of 30-50%, lever- ages the total development cost of the geothermal project. A 40% increase in power production from a given geothermal resource lowers the total capital cost—including exploration, drilling, and surface plan— by 29%.
20% 30% 40%
Results of analytical models for cycles utilizing the Euler Turbine and Variable Phase Turbine will be presented along with geothermal power plant designs for both. Additionally, experi-
Figure 1. ORC temperature pro le.
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