Techno-economic comparative analysis on the renewable energy use potential in multi-family houses in Belgium

The buildings sector is growing rapidly, and this trend is expected to be maintained. Globally, buildings and construction combined represent roughly 39% of energy-related CO2 emissions. It is therefore crucial that the widespread implementation of low-carbon solutions for buildings and the use of renewable energy is accelerated rapidly. This study investigated the extent to which the energy system of a residential multi-family house in Belgium can be designed to maximise the share of renewable energy in its heating and household electricity demand, and in this way reduce its operational CO2 emissions. The technologies that were focused on in the different energy systems that were modelled are ground and air source heat pumps, rooftop photovoltaics, solar thermal collectors, battery electric storage and hot water thermal storage. In a first phase, the technical and environmental performance is assessed, while the second phase consisted of a thorough economic analysis. The results show that a primary renewable energy share of roughly 30% to 34%, and a reduction in the operational CO2 emissions compared to the business-as-usual scenario of approximately 69% to 76% could be achieved. Furthermore, regarding the operational cost of the different systems, a reduction of 42% to 47% compared to business-as-usual practices could be reached. To see the long-term impact of this sharp decrease in operational cost, combined with the results of the capital cost, the net present value was calculated for the different scenarios, and a sensitivity analysis was carried out. Initial results showed a net present value for the two most promising options of roughly 6% to 12% lower than that for the business-as-usual scenario. However, these results appeared to be quite sensitive to changes in certain parameters. Changes to the cost of energy, price-ratio of electricity to gas or a decrease in cost for PV and batteries had a significant impact on the net present value results. In many cases these changes resulted in the business-as-usual scenario becoming the least attractive option from a long-term cost perspective