A long-term performance analysis of three different configurations for community-sized solar heating systems in high latitudes

This paper proposes various community-sized solar heating systems configurations for cold climate. Three configurations were proposed, (I)a heat pump connected to two tanks in parallel, using charged borehole storage, (II)a heat pump connected between two tanks, using charged borehole storage to directly charge the lower temperature tank, and (III)two heat pumps used in series, one between the tanks and the other between the lower temperature tank and ground. In configurations (I) and (II) the vertical borehole field is used as a seasonal storage, in (III) it is used to extract heat only. The studied energy flows are heat and electricity. The border consists of energy production systems, heating grid and buildings. The impact of the considered system solutions on the heating renewable energy fraction, on site electrical energy fraction, purchased energy and full cost as a function of the demand, solar thermal and photovoltaic areas, tanks and borehole volumes has been evaluated. The dynamic simulations results shows that an average renewable energy fraction of 53-81% can be achieved, depending upon the energy systems' configuration. Furthermore, Energy System II utilizes less energy compared to other systems. In all three systems medium-sized solar thermal area is more beneficial instead of large area. (C) 2017 Elsevier Ltd. All rights reserved.