Solar Assisted Small-Scale Biomass District Heating System in the Northern Part of Sweden

Abstract

This article presents a case study of a projected solar assisted biomass district heating system in the north of Sweden. It is generally known that a biomass district heating system combined with solar heat brings many important benefits. The most common system solution is to install a heat store and a large solar collector field near the heating central. No plant of this type is however in operation in the northern part of Sweden. The main reason for this is that the solar irradiation at these latitudes is very low when the demand for heat is high. Solar heat could however be useful during summer in order to generate hot tap water. One problem is that the heat losses, calculated as percentage of the delivered heat, become very large during these months. This article presents the idea of allowing the connected households to generate their own hot tap water using solar collectors and heat stores installed in each house. The district heating network can therefore be closed in summer, which eliminates the heat losses outside the heating period. A case study of a projected plant has been carried out and it is shown that it is possible to reduce the heat losses by 20% compared to a conventional system. This idea also provides many other important technical and economic benefits.