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Thermo-electrical production from geothermal energy is based on the deployment of a conventional steam turbine and electricity generator equipment. By drilling wells into the reservoir, hot liquid and steam from the production well enters the power plant and the steam is expanded powering the turbine to convert its energy into electricity through the generator. There are three types of exploitation technologies, depending on the reservoir’s temperature, pressure and steam-to-liquid ratio: direct steam, flash steam and binary cycle power plants. These are typically deep geothermal systems (500m-5000m) and can either include a petro-thermal system or a hydro-thermal system. A petro-thermal system involves the performance of hydraulic stimulation, where water is injected into the subsurface under pressure to reactivate the naturally occurring fractures in rocks, like granite, with the view to increase the permeability of the reservoir and create an artificial subsurface heat exchanger (often referred to as Enhanced Geothermal System (EGS), although the term EGS can include non-petro-thermal systems) (Mannvit hf 2013[1]; US Department of Energy 2004[2]; Breede et al. 2013[3]; Breede et al. 2015[4]). Hydrothermal systems, on the other hand, rely on existing aquifers to pump hot geothermal fluid for electricity generation in the case of low-enthalpy resources, vs. self-flowing wells in high enthalpy hydrothermal resources.

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References

[1] Mannvit hf. 2013. Environmental Study on Geothermal Power GEOELEC Project – WP4 D4.2.

[2] US Department of Energy. 2004. Geothermal Technologies Program. The Environmental, Economic, and Employment Benefits of Geothermal Energy. Washington.

[3] Breede, Katrin, Khatia Dzebisashvili, Xiaolei Liu, and Gioia Falcone. 2013. “A Systematic Review of Enhanced (or Engineered) Geothermal Systems: Past, Present and Future.” Geothermal Energy 1(1):4.

[4] Breede, K., K. Dzebisashvili, and G. Falcone. 2015. “Overcoming Challenges in the Classification of Deep Geothermal Potential.” Geothermal Energy Science 3 (1): 19–39. https://doi.org/10.5194/gtes-3-19-2015.