Thermal Impact Assessment of Groundwater Heat Pumps (GWHPs): Rigorous vs. Simplified Models

Bruno Piga, Alessandro Casasso, Francesca Pace, Alberto Godio and Rajandrea Sethi
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Bruno Piga: Department of Environment, Land and Infrastructure Engineering (DIATI), Politecnico di Torino, corso Duca degli Abruzzi 24, 10129 Torino, Italy
Alessandro Casasso: Department of Environment, Land and Infrastructure Engineering (DIATI), Politecnico di Torino, corso Duca degli Abruzzi 24, 10129 Torino, Italy
Francesca Pace: Department of Environment, Land and Infrastructure Engineering (DIATI), Politecnico di Torino, corso Duca degli Abruzzi 24, 10129 Torino, Italy
Alberto Godio: Department of Environment, Land and Infrastructure Engineering (DIATI), Politecnico di Torino, corso Duca degli Abruzzi 24, 10129 Torino, Italy
Rajandrea Sethi: Department of Environment, Land and Infrastructure Engineering (DIATI), Politecnico di Torino, corso Duca degli Abruzzi 24, 10129 Torino, Italy

Energies, 2017, vol. 10, issue 9, 1-19

Abstract: Groundwater Heat Pumps (GWHPs) are increasingly adopted for air conditioning in urban areas, thus reducing CO 2 emissions, and this growth needs to be managed to ensure the sustainability of the thermal alteration of aquifers. However, few studies have addressed the propagation of thermal plumes from open-loop geothermal systems from a long-term perspective. We provide a comprehensive sensitivity analysis, performed with numerical finite-element simulations, to assess how the size of the thermally affected zone is driven by hydrodynamic and thermal subsurface properties, the vadose zone and aquifer thickness, and plant setup. In particular, we focus the analysis on the length and width of thermal plumes, and on their time evolution. Numerical simulations are compared with two simplified methods, namely (i) replacing the time-varying thermal load with its yearly average and (ii) analytical formulae for advective heat transport in the aquifer. The former proves acceptable for the assessment of plume length, while the latter can be used to estimate the width of the thermally affected zone. The results highlight the strong influence of groundwater velocity on the plume size and, especially for its long-term evolution, of ground thermal properties and of subsurface geometrical parameters.

Keywords: shallow geothermal energy; groundwater heat pump; geothermal heat pump; thermal plume; FEFLOW; sensitivity analysis; advection; conduction; dispersion; aquifer (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2017
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (11)

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