Simulation study of a combined solar and heat pump system for heating and domestic hot water in a medium rise residential building at Concepción in Chile

Combined solar and heat pump (SHP) systems have not yet been introduced massively in Chile. On the other hand, large-scale residential buildings offer an interesting emplacement for applying these kinds of systems, but the methodologies for predicting accurately its performance are not so obvious. Thus, this paper presents the modelling of a SHP system designed for a five floor residential building, developed in TRNSYS 17. First, a detailed model of a residential building is done to understand their thermal behaviour. In this analysis, it is determined that the heat load of each building apartment depends strongly on its location. Notably, the first floor is the most demanding one, reaching the highest load for an apartment: 7.52 (kW). The total heat load of the buildings is 348.35 (kW) and the total space heating energy demand in winter season is 932,295 (kWh). On the other hand, two parallel SHP systems with air-to-water heat pumps are simulated: one for the domestic hot water demand; the other one for the heating demand. For evaluating the latter, a reduced simulation model is considered by coupling the system to 18 different air nodes, selected in function of their location in the building. The results show that the SPF for a same system in different apartments depends primarily on its heating demand. Thus, the individual components performance remains practically invariant. This allows to estimate the overall performance of a centralized heating system for the whole building, whose predicted SPFheat is 4.64 using Flat Plate Collectors (FPC) and 4.88 using Evacuated Tube Collectors (ETC). On the other hand, the performance figure of the DHW system is lower, reaching SPFDHW of 3.93 and 4.27 using FPC and ETC respectively ETC in a system that provides around 378,353 (kWh) useful energy a year.