Heat pump and photovoltaic systems in residential applications - Performance, potential, and control of the system

Air-source heat pumps coupled with photovoltaic systems are going to be a more and more promising technology, as its widespread application in residential houses will help achieving the decarbonisation of the building sector, which is strongly promoted by the European Union. The aspects that inspire confidence for this solution are that: i) the average quality of heat pumps has recently improved; ii) new and renovated buildings, with well insulated envelopes, are more suitable for low-temperature heating systems; iii) photovoltaic modules price is significantly decreased and still shows a diminishing trend; iv) the share of the electricity production from renewable sources is progressively increasing, making the use of electricity more ecologically favourable and v) heat pump and photovoltaic systems can make the residential sector flexible and ready to face the changes in the electricity system. The aim of this thesis is to analyse the manifold relationships between the building, the HVAC system and the boundary conditions, as well as the interaction of this system with the electricity grid. The work is almost entirely based on the dynamic simulation, which is performed by using more or less detailed models, depending on the objective of the single study. The heat pump is a crucial element, since its behaviour is influenced by many factors. Therefore, particular attention is pointed toward the modelling of this component and its control. The general approach mainly adopted is the comparison between a reference system, defined case by case, and other similar scenarios in which one or more variations are introduced. Since different aspects are investigated, the variations can concern either the system component (building and HVAC system), the boundary conditions or the control strategy. In particular, one of the studies provide an extensive analysis on how the climate impacts the behaviour of the system, involving nine European cities in a wide range of latitude. The role of the thermal storage (water tank and building thermal mass) is also studied, showing that its potential is exploited only when it is properly controlled. The last part of the thesis focuses on the system control, which influences the system performance more than expected. Despite this, the benefits of applying the proposed smart control strategies are not as great as those deriving from the addition of the electrical storage, in a system in which only the thermal storage is present. Even better results can be obtained by applying control strategies that also manage the battery charging/discharging. A general conclusion is that rule-based control strategies would be cheap and e↵ective; however, they require a tailored implementation and their development for the mass-market is not easy