Journal
ENERGY
Volume 98, Issue -, Pages 50-63Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.energy.2015.12.129
Keywords
Ground heat exchange; Ground surface temperature; Shallow geothermal energy; Finite line source; Ground source heat pump
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Funding
- Swiss National Science Foundation (SNSF) [200021L 144288]
- German Research Foundation (DFG) [BL 1015/4-1]
- Swiss National Science Foundation (SNF) [200021L_144288] Funding Source: Swiss National Science Foundation (SNF)
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BHEs (borehole heat exchangers) are the most common shallow geothermal applications. By approximating the BHE as a line source, semi-analytical models can describe the heat exchange within the ground. These models though always assume prescribed temperature at the ground surface. This work presents a formulation which expands existing finite line source models by implementing a more general Cauchy-type top boundary condition and in this way, a better estimation of the heat fluxes at the ground surface. The new formulation is numerically verified and examined in a dimensionless analysis. It is demonstrated that the discrepancy to prescribed temperature settings is significant near to the ground surface, and it propagates deeper when groundwater flow is absent and when strong decoupling between the thermal regimes interacting at the land surface is assumed. The new approach shows to be suited especially for short BHEs, both for more flexible and accurate prediction of the ground thermal regime as well as for long-term analysis of technological performance. (C) 2016 Elsevier Ltd. All rights reserved.
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