Economic Feasibility of Flat Plate vs Evacuated Tube Solar Collectors in a Combisystem

The aim of this research is to determine the economic feasibility of a solar thermal system used for Domestic Hot Water and Radiant Floor Heating. A two floor house is modeled to create a thermal load. The system design and thermal analysis is studied using TRNSYS. The technical-economic analysis is performed using Microsoft Excel. The optimal type/number of solar thermal collectors and thermal storage size were determined based on the economic figures. The optimum system configuration for the case of evacuated tube system resulted in 8 collectors using a storage relation of 40 L/m2 whereas flat plate system resulted in 12 collectors using a storage relation of 50 L/m2. The return on investment for the flat plate system was calculated in 9 years and the evacuated tube system resulted in approximately 11 years.