Proposal of a Holistic Design Procedure for Ground Source Heat Pump Systems

An innovative approach to the design of ground source heat pump (GSHP) systems has been developed, based on the evaluation of energy exchange during the operational time and on cost-benefit considerations. Alternative algorithms are suggested, in order to switch from the "reference design months" approach to a method based on monthly energy performance evaluation. This latter procedure is also suited for examining the energy performance of design solutions in which GSHPs are coupled with other heat generation technologies. All the three macro-systems governing the monthly energy balance of GSHPs are taken into account: building envelope energy loads, heat generator efficiencies, and thermal behaviour of the ground source. The outputs of the procedure are: thermal capacity of heat pump and back-up generators, length of the borehole heat exchangers, flow rate in the ground-coupled loop, monthly energy contribution to be requested to the GSHP, energy use during multi-year practise, together with an assessment of installation and operational costs. A test case is presented, in which the proposed algorithm is applied and its effectiveness as a tool for system designers is demonstrated