Historical building renovation and PV optimisation towards NetZEB in Sweden

Retrofitting historical buildings towards net zero energy building (NetZEB) in Northern countries is facing some issues confirmed in the literature review of this study. Following a holistic approach proposed by the authors, a 150-year old castle situated in Helsingborg, Sweden, was used to evaluate the potential of historical buildings in the Nordics to be turned into a NetZEB building. Following a retrofit tailored to achieve energy-savings in the historical building which was done in a previous study, the installation of a photovoltaic (PV) system, to cover the primary energy use of the building on a net annual basis was proposed. Building integration of the PV system was proven not to be realistic due to historical sensitivity as well as low irradiation due to overshadowing on the roofs of the historical buildings. Alternatively, the concept of landscape integrated PV was followed and the system covering the energy use of the castle was optimised in azimuth and tilt to provide the highest possible monetary results for electricity expenses for the castle weighed with the rate for feeding electricity to the grid. A second PV-system was optimised in azimuth and tilt, however, according to the maximum electricity generation. Life-cycle costing (LCC) calculations using the Net Present Value (NPV) method were used to determine the viability of both PV systems according to nine financial scenarios. A comparison of generated primary energy and primary energy use of the historical building was presented for two scenarios and it showed that reaching NetZEB was possible for the presented case study object.