Hybrid AC-DC distribution system for building integrated photovoltaics and energy storage solutions for heating-cooling purposes. A case study of a historic building in Cyprus

One of the main concerns globally is the phenomenon of climate change thus we have to move to a cleaner and sustainable development in different energy sectors. An important step in this direction is the penetration of more renewables in the electricity grid. Therefore, with the increasing penetration of DC devices, the concept of hybrid AC-DC systems attract more and more attention. This study proposes an innovative hybrid storage system for buildings, in combination with a DC heat-pump to maintain thermal comfort, and a hybrid AC-DC distribution system for the interconnection of the photovoltaic system, battery and electrical loads of the building. Photovoltaics, battery and DC devices are connected to the DC part, avoiding losses from unnecessary conversions, while AC loads are connected to the AC part. This solution has been tested in a historical building in Cyprus and the results indicated significant benefits. For the case of the proposed system the imported energy (<5,4 kWh/day) is limited to the 1/3 compared to the case of typical prosumer. Finally, the overall share of renewables reaches values > 85%. This article describes the innovative system and assess its performance in real conditions regarding the energy consumption/production, indoor comfort conditions, and battery behavior.