COMPARATIVE PERFORMANCE ANALYSIS OF SOLAR HEAT EXCHANGERS FOR SOLAR HOTWATER SYSTEMS

The aim of this study was to experimentally evaluate and compare the performance of a novel retrofit heat exchanger (‘SolaPlug’) developed for solar hot water cylinder with a traditional twin coil (‘Coil’) solar cylinder under controlled operating conditions. ‘SolaPlug’ as a retrofit solution for solar hot water heating systems avoids the cost of replacing a single coil cylinder with a solar acceptable twin coil cylinder. The experimental set up consisted of proprietary tube evacuated collector, hot water cylinder integrated with ‘Coil’ and ‘SolaPlug’ heat exchangers and interchangeable ‘Coil’/ ‘SolaPlug’ loop. The tests were conducted under different solar simulated conditions with a 30 and 20-tube collector under no draw off and draw-off conditions. Under low solar input condition, the performance of the ‘SolaPlug’ system was marginally better than the ‘Coil’ system whereas the overall ‘SolaPlug’ system efficiency was slightly lower than the ‘Coil’ system when operating under high solar input conditions. The ‘Solaplug’ system heated the upper volume of the store at a higher rate than the ‘Coil’ system. The average temperature in the upper half of a cylinder for the ‘SolaPlug’ system was approximately 9 to 12% higher depending on the test conditions.