GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 3.1 GNGTS 2024 SpiderTherm: Optmizing Geothermal Extracton for Sustainable Energy Transiton A. Molossi 1 , G. Gola 2 , A. Manzella 2 , M. Pipan 1 1 Università di Trieste, Dipartmento di Matematca e Geoscienze, Via E. Weiss 1, Trieste, Italy. 2 Insttute of Geosciences and Earth Resources, Natonal Research Council, via Giuseppe Moruzzi, 1, 56124, Pisa, Italy The geothermal resource presents at least three advantageous aspects: i) it is a ubiquitous and contnuous source of energy; ii) it can contribute to the thermal and electrical energy needs in residental and industrial sectors; iii) it can aid the energy transiton process towards renewable energy sources. Geothermal fuids are valuable energy sources with various applicatons depending on their temperature range: between 40°-60°C, they are mainly used for greenhouse heatng and aquaculture; between 60°-70°C, common applicatons include building conditoning and domestc water heatng; above 70°-80°C, water can be integrated into industrial processes or used for absorpton chillers in refrigeraton cycles; and startng from 100°C, the primary fuid can be used in binary geothermal systems for electricity producton. Conventonal geothermal applicatons utlizing natural hydrothermal systems face challenges in exploraton due to uncertainty in subsurface lithology and fuid distributon, corrosion and mineral precipitaton during producton, and environmental impacts such as subsidence and induced seismicity. Economic feasibility is another limitaton, primarily due to high drilling costs, but retroftng abandoned wells, originally drilled for the oil industry, ofers a cost- efectve alternatve. An unconventonal approach to harness geothermal energy is the deep borehole heat exchanger (DBHE), involving coaxial pipes in single wells. However, its low efciency restricts its applicability in geothermal power producton compared to conventonal systems. Recently, deep closed-loop geothermal systems (DCHE) have been proposed to enhance efciency by connectng multple wells horizontally, demonstratng potental for geothermal power producton under favourable conditons. The energy performance of DCHE depends on various parameters, such as environmental, design, and operatonal variables. With respect to the diferent parameters, Gola et al. (2022) demonstrated by a sensitvity study that the following factors play a primary role: the undisturbed geothermal gradient, the dimensions (vertcal depth and horizontal length) of the closed-loop, , the fow rate, , and injecton temperature. This study aims to analyze the long-term performance of an innovatve DCHE confguraton, varying the number of reused exploraton wells (N), vertcal (H) and horizontal (L) lengths, fow rate per well (q), injecton temperature (Tin), heat exchange (DT), and geothermal gradient (Ggeo). The goal is to identfy conditons that achieve the recommended minimum long-term producton temperature of 100°C for binary geothermal power plants.