Empirical Equation for Spacing of Ground Water Heat Pump Systems

Literature provides a good knowledge base to understand geothermal heat pumps. Therein two principle types are defined: Ground-coupled heat pumps and groundwater heat pumps (GWHP). In this paper small-scale GWHP typically used for heating of single family homes are investigated. One important parameter to ensure optimal performance of GWHPs is the spacing of production well (PW) and injection well (IW) because wrong design leads to hydraulic and thermal breakthrough. Due to a general insufficient knowledge about the required spacing of PW and IW regarding thermal breakthrough the aim of this study is to develop an empirical equation for spacing design. Additionally three dimensional tracer and temperature maps as well as a sensitivity analysis of varying parameters (flow rate, injection temperature, horizontal/vertical conductivity, longitudinal dispersion and base flow gradient) are provided in this article. A comparison of the equation with official guidelines shows that for single family homes the horizontal spacing can be reduced up to 90%.