Experimental performance of a dual-source heat pump coupled with shallow horizontal ground heat exchangers

Abstract

The present paper analyses the preliminary results about the performance of a dual-source

heat pump (DSHP), able to switch between air and ground according to operating rules for the air-conditioning system. The prototype is composed by a common air-to-air heat pump whose refrigerant

circuit has been modified for coupling through a plate heat exchanger with a geothermal closed loop, laid horizontally and edgeways into a shallow trench. As ground heat exchanger (GHE), the Flat-Panel solution has been chosen due to its higher performance in comparison with similar GHEs, that makes this solution suitable for the issue. To over/underload the GHE system according the air conditioning energy load, the closed loop can be reduced by means of valves. The switching between air and ground is then automatized with a control unit which controls valves according to rules based on air and ground temperature, air humidity, and frosting conditions at the evaporator. The prototype is fully monitored in terms of temperatures, pressures, flow rate and electricity supply, both at the refrigerant circuit and the closed loop. Moreover, a dedicated monitoring system collects data about weather conditions, ground temperature at several depths and distances from the Flat-Panels, and finally their heat flux. The heating performance of the DSHP is taken in comparison with the standard air-source solution, with evidence of the better behaviour, even for a closed loop drastically partialized.