Geothermal Heat Pumps (GHPs) are systems combining a heat pump with a ground heat exchanger. Borehole heat exchangers (BHEs) are the most frequently adopted solution for ground assisted heat pump applications due to the low impact of works at ground surface and good thermal behaviour. In either winter or summer operation, the favourable ground temperature allows high coefficients of performance to be achieved, provided that the BHE is properly designed. Furthermore, as the BHE strongly affects the overall plant cost, the correct sizing of the ground heat exchanger is a compulsory task in order to achieve the financial sustainability of the plant. In this paper a review of existing methods to model and design the BHE system is discussed with reference to transient modellisation at different time scales. In particular, a tool developed by the authors, the code TecGeo, is presented with reference to physical modelling, code feature, application ranges, and results. A comparison with results obtained with other commercial codes for BHE modelling is finally performed in terms of monthly average carrier liquid temperature and monthly temperature peak values for some typical thermal load configurations pertaining to the Italian climate.
A Tool for Borehole Heat Exchanger Design for Ground-Source Heat Pump Applications
FOSSA, MARCO
2007-01-01
Abstract
Geothermal Heat Pumps (GHPs) are systems combining a heat pump with a ground heat exchanger. Borehole heat exchangers (BHEs) are the most frequently adopted solution for ground assisted heat pump applications due to the low impact of works at ground surface and good thermal behaviour. In either winter or summer operation, the favourable ground temperature allows high coefficients of performance to be achieved, provided that the BHE is properly designed. Furthermore, as the BHE strongly affects the overall plant cost, the correct sizing of the ground heat exchanger is a compulsory task in order to achieve the financial sustainability of the plant. In this paper a review of existing methods to model and design the BHE system is discussed with reference to transient modellisation at different time scales. In particular, a tool developed by the authors, the code TecGeo, is presented with reference to physical modelling, code feature, application ranges, and results. A comparison with results obtained with other commercial codes for BHE modelling is finally performed in terms of monthly average carrier liquid temperature and monthly temperature peak values for some typical thermal load configurations pertaining to the Italian climate.
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