Geothermal Power Plants with Improved Environmental Performance: Assessment of the Potential for an Italian Site

Abstract

The goal of a 2050 Carbon neutral scenario is providing a big push for the development of renewable energy technology. Amongst renewables, geothermal energy could become a considerable contributor to the reduction of greenhouse emissions, thanks to the new technologies that have been developed in the last years. One of the most interesting new technologies is the total reinjection one, which guarantees the total reinjection of the geothermal fluid (including Non-Condensable Gases – NCGs, which are currently vented to the atmosphere with the “traditional” technologies). Within this manuscrpt, a solution for complete NCGs reinjection is presented, and the Torre Alfina geothermal case study is analysed. The Torre Alfina geothermal site is a water-dominated reservoir at relatively high pressure (44 bar) and a temperature of 140°C, with moderate content of Non-Condensable Gases (2%). The developed power plant models include energy and exergy balances, as well as energy-economic and energy-environmental analysis. The overall environmental performance is evaluated by Environmental Footprint 2.0 methodology. Different solutions are compared, considering the possibility of sub- or super-critical power cycles as well as different renewables. For the subcritical case, the obtained LCOE is 13.33 c€/kWh, while for the supercritical cycle the obtained LCOE is 13.11 c€/kWh. The developed LCA confirms that geothermal power plants with complete NCG reinjection are among the cleanest renewable energy technologies.