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

Groundwater Heat Pumps (GWHPs) are increasingly adopted for air conditioning in urban areas, thus reducing CO2 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...

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Published inEnergies (Basel) Vol. 10; no. 9; p. 1385
Main Authors Piga, Bruno, Casasso, Alessandro, Pace, Francesca, Godio, Alberto, Sethi, Rajandrea
Format Journal Article
LanguageEnglish
Published Basel MDPI AG 01.09.2017
Subjects
advection
Air conditioners
Air conditioning
aquifer
Aquifers
Carbon dioxide
Computer simulation
conduction
dispersion
FEFLOW
geothermal heat pump
Groundwater
groundwater heat pump
Heat
Heat exchangers
Heat pumps
Heat transport
Heated water
Mathematical models
Plumes
Propagation
Sensitivity analysis
shallow geothermal energy
Sustainability
Thermal analysis
thermal plume
Thermal plumes
Thermal properties
Urban areas
Vadose water
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Summary:Groundwater Heat Pumps (GWHPs) are increasingly adopted for air conditioning in urban areas, thus reducing CO2 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.
ISSN:1996-1073
1996-1073
DOI:10.3390/en10091385