Abstract

Space heating represents the largest share in the energy demand of the built environment, in temperate and cold climates. Therefore, the use of solar thermal systems to convert solar into thermal energy for space heating, along with domestic hot water production, represents a challenge in these climates where the number of sunshine hours is rather low during the cold seasons, when heating is needed. Novel solar thermal collectors with nonrectangular shape (trapeze) and different colours (red, blue, green) were developed in the Renewable Energy Systems and Recycling Research Centre in the Research and Development Institute of the Transilvania University of Brasov, Romania, to increase the coverage factor, social and architectural acceptance when integrated in buildings facades. The results for an entire year (2017) are presented as monthly thermal energy produced by novel trapeze versus commercial rectangular flat plate solar thermal collectors installed on the vertical southern facade of an outdoor testing rig. The specific thermal energy produced by trapeze collectors is 28.7% lower than commercial collector over the entire year, but this drawback is compensated by higher coverage factor which can be obtained by using trapeze instead of rectangular solar thermal collectors.