Concepts and design optimisation of a liquid-based photovoltaic-thermal solar panel to be the source of a heat pump as a field

With climate change underway, the energy transition is a matter of absolute urgency. In our Western societies, it can be broken down into several areas: reducing the need for energy, by changing our way of life on the one hand and increasing energy efficiency on the other, and producing what is needed through a decarbonised mix of resources. In Europe, space heating and domestic hot water production in buildings is a prime target for this transition, because it has a major impact on the climate, and there are already many solutions for reducing it. One of these is technological: heat pumps which produce heat from renewable thermal energy and electrical energy. The two main sources of thermal energy are the ambient air and the ground. The first is simple and quick to install, at a relatively low cost and with good performance. The second requires more extensive work and costs, but generally leads to significantly higher performance. A solution with interesting potential would be to boost the performance of the ambient air source with solar thermal energy. It falls into the category of solar-assisted heat pump systems with solar panels in series with the heat source. This thesis deals with heat pump systems in which the sole heat source is a field of liquid-based photovoltaic-thermal (PVT) solar panels to supply energy to a water heating system and a domestic hot water tank. It focuses on the design and optimisation of such panels with a view to ensuring that the system performs better than or equal to that expected from the reference air/water heat exchanger. A multi-disciplinary optimisation (MDO) problem has been formulated to provide the framework for the approach. An existing numerical study has already established the link between the thermal performance of a PVT panel and the performance of the system. Initially, the links between the hybrid panel concept or its geometric characteristics and its thermal performance were highlighted. In addition, for a selected concept, a design optimisation was carried out using CFD modelling. Secondly, for a class of designs known as ‘flow distribution', a study was carried out to establish the link between their hydraulic characteristics and their hydraulic performance: head losses and flow distribution. Tests were carried out to compare the predictions of the models developed with experimental measurements. Finally, various experimental sequences on different test benches were carried out to evaluate the performance of certain designs when connected in a row of panels and the system-wide performance when a field of such designs constitutes the sole heat source. This thesis presents the design and optimisation approach for liquid-based hybrid solar panels intended to be the heat source of a brine/water heat pump, the numerical models developed in this context that can be used for similar problems, and the advantages, limitations and perspectives for this type of system.