Comparative capacities of residential solar thermal systems versus F-chart model predictions and economic potential in an equatorial-latitude country

Abstract

One popular simulation tool for predicting solar thermal (ST) performance is the F-chart model, whichhas not been validated for the conditions in equatorial-climate countries. In this work, the performanceof two ST systems (evacuated tube collectors (ETCs) and flat plate collectors (FPCs), widely used forsupplying domestic hot water (DHW) was assessed and compared with F-chart simulation results. Theenergy demands were simulated by scheduling hot water discharges and measuring the backup energyrequirements to fulfil DHW needs. Then, the difference between the calculated solar fraction using theF-chart model and the measured solar fraction was obtained. Both the measurements and simulationsshowed that the ETC systems performed better than the FPC systems in a city located on the Ecuadorianhighlands with distinct climate conditions. The results showed that ETC systems are, on average, up to18.5% more efficient than FPC systems. A comparative economic analysis was carried out consideringthat domestic water heating systems are backed up with liquified petroleum gas (LPG) or electricity,both with and without state subsidies. However, due to the higher cost of ETC technology comparedto FPC technology, and despite ETC’s higher efficiency than FPC’s, only US$0.34 per month can besaved on average because of the impact of energy subsidies. Thus, the FPC technology seems moreprofitable, under the mentioned conditions, because of its lower capital costs. With backup systemspowered by unsubsidized energy, the two technologies are nearly comparable. The ETC technologyappears suitable only under the unsubsidized electricity scenario. The novelty of this research is thatreal ST systems installed under similar conditions are integrated, the operation of ST technologies forDWH is simulated, and the different inclinations and orientations of solar collectors are considered.The results are compared with simulations from the F-chart model, and each system is economically assessed