Pompe di calore operanti con fluidi naturali per il riscaldamento e la produzione di acqua calda sanitaria: analisi dei costi e delle prestazioni stagionali in accordo con i regolamenti europei

Most recent statistics from Eurostat indicate that the European building ensemble is responsible for 40% of the final energy consumption of the EU. Depending on the building destination, 30-50% of this energy is spent in space heating and 10-25% is spent on sanitary hot water (SHW) production. For this reason, the 2010/31 Directive prescribes that new building have to be nZEB (nearly Zero Energy Buildings) by 2020 and that energy efficiency has to be increased while retrofitting new systems on existing buildings. There is consensus on the fact that heat pumps are more efficient than gas and electric boilers. This larger efficiency must be quantified, nowadays, according to the new 811-812-813-814/2013 Regulations, which give a single metrics to use (named water heating/space heating efficiency) for all technologies providing heating and SHW below 70 kW, allowing for a direct comparison among them. Moreover, F-Gas Regulation 517/2014 is phasing out HFC refrigerants commonly used in heat pumps for environmental reasons (high GWP). The industry is investing on substitutes, such as HFOs and natural refrigerants, each with their own strengths and weaknesses. Given this context of a push for higher energy efficiency from one side and the substitution of HFC refrigerants from the other, in this work propane and CO2 heat pumps for space heating and SHW production (30-50 kW) are evaluated by means of modelling, validation with experimental data from the NxtHPG project, and simulation. The performance is calculated according to the laws and in some realistic global system scenarios. The global system is composed of a final user (located in a certain climate and with its own load profile, either SHW or space heating, residential or not), a stratified hot water storage (in the case of a SHW user), a control logic and the heat pump itself. Critical aspects such as the choice of the refrigerant based on the climate and the user, the sizing of the heat pump and storage as a couple, the control logic (on/off systems, inverter driven systems, “night&day” logic), and the type of energy source to exploit (geothermal/air) are examined and an estimation of plant and running costs is given.