A comparative study of residential building energy performance in Belgium utilizing three different solar panel configurations

In order to decarbonize building energy systems, renewable energy generation is necessary. For residential buildings, the most used renewable energy source is solar radiation. In Belgium, the typical renewable energy system consists of PV panels on the roof of the building providing electricity, combined with a heat pump which uses the produced electricity to provide space heating and domestic hot water.

However, in urban environments the amount of space available for placing PV panels can be limited, and the generated energy might not be sufficient to provide for the demand of the building. In an effort to optimize the energy yield, PV panels can also be combined with solar collectors into PVT panels, which provide both electricity and hot water. The downsides of the PVT panels are the lower electrical efficiency due to the higher panel temperature and the increased cost compared to PV panels. A third option is to use the thermal energy generated by a PVT panel as an energy source for the cold side of the heat pump.

This reduces the temperature of the cells and thus increases the efficiency, while it also increases the COP of the heat pump due to the higher supply temperature. It does require a different type of PVT panel, in which the thermal collectors are not insulated from the ambient air such that heat can also be extracted from the ambient if there is no solar radiation.

To analyse and compare the three different options, dynamic building energy system simulations are performed in Modelica. A lumped parameter thermal model of the PV and PVT panels is made and validated with experimental data. The electricity production of the PV(T) panels and the electricity use of the heat pump is evaluated over a reference year with the weather data of Belgium. A terraced dwelling with a space heating demand of 47 kWh/(m² year) is used as reference building.

When comparing the PV panel to the PVT panel situation, the electricity use of the heat pump is slightly lower in the latter case, while the electricity production of the latter is also slightly lower. The situation with the PVT panel connected to the heat pump results in higher electricity production and lower heat pump electricity use. However, in the winter months the panels operate at sub-zero temperatures, so defrosting of the panels will require attention to ensure proper operation.