The objective of this study is to assess the suitability of the analytical infinite moving line source (MLS) model in determining the temperature of vertical grouted borehole heat exchangers (BHEs) for steady-state conditions when horizontal groundwater advection is present. Therefore, a numerical model of a grouted borehole is used as a virtual reality for further analysis. As a result of the first analysis, it has been discovered that established analytical methods to determine the borehole thermal resistance as a mean value over the borehole radius can also be applied to BHEs with groundwater advection. Furthermore, the deviation between a finite MLS and the infinite MLS is found to be only less than 5% for BHEs of a depth of 30 m or more, and Péclet numbers greater than 0.05. Finally, the accuracy of the temperature change calculated with the infinite MLS model at the radius of the borehole wall compared to the temperature change at a numerically simulated grouted borehole is addressed. A discrepancy of the g-functions resulting in a poor dimensioning of BHEs by the infinite MLS model is revealed, which is ascribed to the impermeable grouting material of the numerical model. A correction function has been developed and applied to the infinite MLS model for steady-state conditions to overcome this discrepancy and to avoid poor dimensioning of BHEs.
<p>The heating and cooling sector needs a large-scale transformation to achieve the climate neutrality goals by 2050 as outlined in the European Green Deal. Heat pumps coupled with a borehole heat exchanger (BHE) are a frequently discussed option for reducing greenhouse gas emissions from the heating and cooling of residential buildings. The thermal interference between BHEs makes the calculation of the technical potential on a regional scale computing intensive. Here, we use a steady-state solution of the finite line source to rapidly calculate the technical geothermal energy potential for a study area of ~35.000 km&#178; and for up to 8.6 million BHEs. The results show that the proposed methodology can be used to calculate the potential of ground source heat pumps for heating on a regional scale with a high accuracy. Limitations of the study include the random placement of BHEs within parcels (with regulatory restrictions applying), and the non-consideration of ground water flow.</p>
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