Design of borehole heat exchangers for ground-source heat pumps: A literature review, methodology comparison and analysis on the penalty temperature

• Published in: Energy and buildings Vol. 55; pp. 369 - 379
• Main Authors: Capozza, Antonio, De Carli, Michele, Zarrella, Angelo
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 01.12.2012; Elsevier
• Subjects: Applied sciences; Borefield design; Borehole heat exchanger; Building technical equipments; Buildings; Buildings. Public works; Computation methods. Tables. Charts; Energy; Energy management and energy conservation in building; Environmental engineering; Exact sciences and technology; Finite line source; Geothermal energy; Ground-source heat pumps; Infinite line source; Natural energy; Structural analysis. Stresses; Infinite line source; Borefield design; Ground-source heat pumps; Borehole heat exchanger; Finite line source; Temperature; Methodology; Heat pump; Geothermal energy; System design; Modeling; Case study; Penalty function; Energetic efficiency; Heat exchanger; Formulation; Comparative study
• ISSN: 0378-7788
• DOI: 10.1016/j.enbuild.2012.08.041

[Display omitted] ► The efficient design of borehole heat exchangers (BHE) is still a crucial point. ► Complex design methods are available; simpler procedures for designers are required. ► Sizing of the BHE length is affected by the penalty temperature parameter. ► An easy-to-use approach for the evaluation if this index is presented. ► An analysis of the proposed method is performed on a real case-study building. Better energy efficiency of ground coupled heat pump systems in comparison with traditional applications leads to continued growth in the number of installations for space conditioning. The solution with vertical heat exchangers is the most widespread. The design of the borehole heat exchangers (BHEs) is a nodal point, both from an energy efficiency and an economic point of view. In literature, several methods to design these systems are available. However, to promote their application, easy-to-use procedures are required; furthermore designers very often are discouraged from the use of not-open or complicated computational tools. Among the literature models, the ASHRAE method is surely the simplest procedure and, as a consequence, it is suitable for this goal. In this approach, sizing of the BHE length is strongly affected by the parameter named penalty temperature, which is an index to evaluate the long-term behaviour of the borehole field. In this paper, a review of this index is reported and in addition a new approach for its evaluation is presented. Furthermore, a detailed analysis of the proposed method is performed on a real case-study building with only heating conditioning.