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A discounted cash flow analysis (DCFA) and a cost benefit analysis (CBA) have been implemented in order to investigate the economic aspects of ground-coupled heat pump (GCHP) for space heating and cooling, in comparison to traditional condensing boiler (CB). The DCFA allows the analysis of investment costs, operating costs and savings of the two different systems in order to understand if the GCHP’s pay back periods (PBPs) is more interesting than that of CB in coming years. The first financial model (DCFA) takes account for economic factors as prices, costs and growth, while the economic approach (CBA) include the carbon price into the calculation, considering the social costs of carbon dioxide emissions. The whole analysis is implemented adopting a parametric approach, in which all the economic terms are linked to energy labels, degree-days and energy mix ratios (EMRs), the latter obtained as ratio between the cost of electricity and natural gas paid by the householder. Relating to different EMRs, the PBPs are presented in matrixes in which energy labels and degree-days are the row/column indexes, to confront the benefits of choosing between GCHP versus CB. The PBPs are also calculated with the introduction of the carbon price, so that some considerations about the environmental aspects are presented. The results show that all higher energy labels have a good profitability ratio between costs and payback periods and demonstrate that GCHP system does pay off

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Air-source and ground coupled heat pumps are depicted as energy efficient systems. Nevertheless, the ground coupling incurs in expensive extra-costs owing to the ground heat exchangers (GHEs), whereas the air exploitation suffers lower temperatures and frosting conditions. Coupling both solutions in a dual-source heat pump system (DSHP) can mitigate the former drawbacks. The present paper analyses the performance of a DSHP experimental prototype, installed as the airconditioning system of a testing room at the University of Ferrara, Italy. The prototype is composed by a common air-to-air heat pump and a geothermal closed loop. The refrigerant circuit of the heat pump has been modified to couple on demand the closed loop by means of a plate heat exchanger. As GHE type, the Flat-Panel solution has been chosen due to its higher performance respect to all other horizontal and shallow exchangers. The switching between air and ground is automatized by mean of a control unit, according to the best thermal conditions, and the closed loop is also partializable to evaluate the length impact on the switching rules. The DSHP flexibility has allowed better performance than the original air-to-air heat pump, especially under hard weather conditions, and therefore an overall energy saving.

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The use of a horizontal ground heat exchanger may represent a reliable and cost effective option for ground-source thermal applications. This study presents the thermal performance analysis of a drainage trench used as ground heat exchanger (GHE) coupled with underground thermal energy storage (UTES). The trench is dug in shallow soil and filled with encapsulated phase change materials (PCMs) as granular filler. Two types of PCMs with different melting points are supposed to operate in summer and winter. Fluid flow and heat transfer in porous media are solved via a 2D finite element model to perform a yearly simulation under hourly-scale boundary conditions. The equivalent heat capacity approach is applied to consider the latent heat of the PCMs. The results show a significant capacity of the trench to smooth thermal waves produced by the heat pump. The effect of the PCMs is analysed by comparing with the corresponding case using coarse gravel as filling material instead of PCMs. The case without PCMs still shows good performance, but PCMs offers the advantages of a seasonal UTES and smoothing thermal wave as well. The proposed solution can be therefore considered as an advanced alternative to other widespread common GHEs

Ground-coupled and air-source heat pumps (GCHPs and ASHPs, respectively) are regarded as energy efficient systems for air conditioning. Their coupling in a dual air and ground source heat pump (DSHP) can offer a further performance improvement by reducing the drawbacks of each standalone technology. In the present study, a DSHP coupled with a Flat-Panel as a horizontal ground heat exchanger (HGHE) is numerically analysed in comparison with its counterparts GCHP and ASHP, by implementing COMSOL Multiphysics to simulate heat transfer in the ground operated by the Flat-Panel. The DSHP operativity is provided by a function set to control the switching between air and ground sources, according to their temperatures and trigger thresholds. A parametric analysis has been then carried out in order to propose a preliminary guideline to size the Flat-Panel for a balance between energy saving and installation cost. The DSHP shows a higher efficiency in comparison with either ASHP or GCHP due to the switching between two sources to more favourable working temperatures, and can offer a profitable hybrid solution providing protection against frosting and size reduction of the HGHE, therefore helping to promote the penetration of heat pumps in the residential market.