A novel fully electrified solar heating system with a high renewable fraction - Optimal designs for a high latitude community

Abstract

Abstract Solar energy use in Nordic countries suffers from a high seasonal mismatch of generation and demand. However, given a large enough community, seasonal thermal storage could be utilized to store summertime heat gains for use in winter. This simulation study examined a Finnish case of fully electric solar heating, where heat pumps (HP) powered by photovoltaic (PV) panels were used for generating heat for both immediate use and for seasonal storage through a borehole thermal energy storage (BTES) system. Multi-objective optimization of LCC and energy use was performed by a genetic algorithm and TRNSYS simulations. Comparison was done between communities of a 100 and 500 buildings. The need for purchased electricity was between 40 and 26 kWh/m2 per year for the optimal configurations. For the same cases the life cycle cost was between 220 and 340 €/m2. Up to 98% renewable energy fraction was obtained for heating, showing that even in Finland it is possible to provide practically all heating by solar energy. The PV-type heating system was also compared to a solar thermal heating system from a previous study and it was found that the new design had as much as 36% lower life cycle cost.