An all-in-one machine coupled with a horizontal ground heat exchanger for the air-conditioning of a residential building

Heating, ventilation and air conditioning (HVAC) systems are considered of great importance in the building sector, as they represent a significant part of the energy demand in buildings. Moreover, they are deeply related to indoor environmental quality, which strongly affects occupants' quality of life. This paper presents the analysis of a compact all-in-one and plug-and-play machine providing heating, cooling and controlled mechanical ventilation to a low energy residential building. In particular, the system is composed of an air-to-air heat pump coupled to a heat recovery unit which can pre-heat the fresh air and contribute to domestic hot water production. In the present work, an additional heat exchanger embedded in the building's foundations has been included in the system to pre-heat or pre-cool the outdoor air before it enters the heat recovery unit. The compact energy system has been mathematically modelled, and its operations have been monitored in a real residential building recently constructed in Udine (North-East of Italy). The annual energy performance of the all-in-one machine has been obtained, and the system layouts with and without ground heat exchangers have been compared. The use of the ground heat exchanger helps to decrease the primary energy consumption and the operating costs (in heating, 14% and 11% respectively), improving, at the same time, the thermal comfort conditions inside the building.