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Open AccessArticle

Comparative Analysis of Power Plant Options for Enhanced Geothermal Systems (EGS)

Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104-6315, USA
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Energies 2014, 7(12), 8427-8445; https://doi.org/10.3390/en7128427
Received: 31 October 2014 / Revised: 2 December 2014 / Accepted: 10 December 2014 / Published: 17 December 2014
Enhanced geothermal systems (EGS) extract heat from underground hot dry rock (HDR) by first fracturing the HDR and then circulating a geofluid (typically water) into it and bringing the heated geofluid to a power plant to generate electricity. This study focuses on analysis, examination, and comparison of leading geothermal power plant configurations with a geofluid temperature from 200 to 800 °C, and also analyzes the embodied energy of EGS surface power plants. The power generation analysis is focused on flash type cycles for using subcritical geofluid (<374 °C) and expansion type cycles for using supercritical geofluid (>374 °C). Key findings of this study include: (i) double-flash plants have 24.3%–29.0% higher geofluid effectiveness than single-flash ones, and 3%–10% lower specific embodied energy; (ii) the expansion type plants have geofluid effectiveness > 750 kJ/kg, significantly higher than flash type plants (geofluid effectiveness < 300 kJ/kg) and the specific embodied energy is lower; (iii) to increase the turbine outlet vapor fraction from 0.75 to 0.90, we include superheating by geofluid but that reduces the geofluid effectiveness by 28.3%; (iv) for geofluid temperatures above 650 °C, double-expansion plants have a 2% higher geofluid effectiveness and 5%–8% lower specific embodied energy than single-expansion ones. View Full-Text
Keywords: engineered geothermal system (EGS); flash type power plants; expansion type power plants; plant utilization efficiency; geofluid effectiveness; plant embodied energy engineered geothermal system (EGS); flash type power plants; expansion type power plants; plant utilization efficiency; geofluid effectiveness; plant embodied energy
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Li, M.; Lior, N. Comparative Analysis of Power Plant Options for Enhanced Geothermal Systems (EGS). Energies 2014, 7, 8427-8445.

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