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Tham khảo tài liệu 'electricity infrastructures in the global marketplace part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Geothermal Power Generation Global Perspectives 5.8.3.5 Use of a Back Pressure Steam Turbine Another approach for the higher enthalpy two-phase heat source is use of a back pressure steam turbine which generates extra power from excess steam not required for the vaporizer of the ORC. Part of the preheating of the organic fluid is now done with low-pressure steam exiting the backpressure steam turbine Figure. 5.12 . 220 Electricity Infrastructures in the Global Marketplace The gap between the steam and the preheating line of the organic fluid could be filled even more efficiently by a multi-stage two or more backpressure steam turbine with extraction of steam between the stages. But the decision on the number of stages is based on consideration of trade-off in process optimization between higher efficiency and complication and cost of the system. 5.8.3.6 Geothermal Combined Cycle 38 For high enthalpy fluids with very high steam content a solution is the geothermal combined cycle configuration where the steam flows through the back pressure turbine to the vaporizer while the separated brine is used for preheating or in a separated ORC Figure 5.13 38 . Source Ormat Technologies Inc. USA Fig. 5.13. Geothermal combined cycle 5.8.4 Deployment As of 2007 the capacity of geothermal plants using advanced power cycles worldwide is close to 1 000 MW approximately 10 of the total geothermal capacity installed in the last 50 years. A breakdown of the 1 000 MW of plants in commercial operation is as follows 60 MW of ORC plants designed or built by Ben Holt Turboden and Barber-Nichols one 2 MW of Kalina cycle plant and more than 900 MW of ORC and combined cycle plants. 5.8.5 Enhancing Sustainability and Cost Effectiveness Geothermal resources are complex geological structures that provide conduits for natural heat of the earth to heat underground waters that may then be utilised to convey heat to the surface. Technology to assess the heat content of geothermal resources is .
