On the possibility of achieving high solar fractions for space heating in temperate climates

Abstract

The paper considers solar space heating in a temperate climate. An algorithm was developed to determine the daily average temperatures and heat fluxes. The calculation algorithm was based on the concept of solar utilizability. The influence of various process parameters on heating performance was studied: the area of the solar collectors, the volume of the storage tank, the angle of inclination of the collectors and the maximum temperature of the tank water. Special attention was paid to the discharge of excess heat from the tank outside the considered system during the summer. It was found that this process does not deteriorate the efficiency of building heating, characterized by the solar fraction parameter, because lowering the tank water temperature intensifies heat transfer in the collectors and reduces heat loss from the tank to the ground. Changing the collector inclination angle from 40° to 90° with a surface area exceeding 20 m² can reduce the size of the tank almost by half if the maximum water temperature in the tank is below 90 °C. It was also found that when heating rooms in temperate climates, it is possible to achieve full coverage of heat demand by solar energy. The results of own calculations and those obtained from the TRNSYS application were compared.