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Energy Exploitation of High-Temperature Geothermal Sources in Volcanic Areas—a Possible ORC Application in Phlegraean Fields (Southern Italy)

Department of Mechanical, Energy and Management Engineering, University of Calabria, Via P. Bucci-Cubo 46C, 87036 Arcavacata di Rende, Cosenza, Italy
Energies 2018, 11(3), 618; https://doi.org/10.3390/en11030618
Received: 9 February 2018 / Revised: 1 March 2018 / Accepted: 6 March 2018 / Published: 10 March 2018
(This article belongs to the Section Sustainable Energy)
This work aims to investigate the energy performances of small-scale Organic Rankine Cycles (ORCs) for the exploitation of high temperature geothermal sources in volcanic areas. For this purpose, a thermodynamic model has been developed, and a parametric analysis has been performed that considers subcritical and transcritical configurations, and different organic fluids (isobutane, isopentane, and R245ca). The investigation illustrates the significant effect of the temperature at the entrance of the expander on the ORC behaviour and the rise in system effectiveness when the internal heat exchange (IHE) is adopted. As a possible application, the analysis has focused on the active volcanic area of Phlegraean Fields (Southern Italy) where high temperature geothermal reservoirs are available at shallow depths. The work demonstrates that ORC systems represent a very interesting option for exploiting geothermal sources and increasing the share of energy production from renewables. In particular, the investigation has been performed considering a 1 kg/s geothermal mass flow rate at 230 °C. The comparative analysis highlights that transcritical configurations with IHE guarantee the highest performance. Isopentane is suggested to maximise the ORC electric efficiency (17.7%), while R245ca offers the highest electric power (91.3 kWel). The selected systems are able to fulfil a significant quota of the annual electric load of domestic users in the area. View Full-Text
Keywords: organic Rankine cycle; geothermal source; transcritical cycle; internal heat exchange; domestic application; electricity production; volcanic area organic Rankine cycle; geothermal source; transcritical cycle; internal heat exchange; domestic application; electricity production; volcanic area
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Algieri, A. Energy Exploitation of High-Temperature Geothermal Sources in Volcanic Areas—a Possible ORC Application in Phlegraean Fields (Southern Italy). Energies 2018, 11, 618.

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