Abstract

The performance of a novel heat exchanger unit (‘Solasyphon’) developed for a solar hot water system was investigated under indoor and outdoor operating conditions. The retrofit ‘Solasyphon’ system is cost effective since it avoids the costly replacement of an existing single-coil hot water cylinder (HWC) with a twin-coil for solar hot water applications. The performance of the ‘Solasyphon’ system was compared with a traditional twin coil (‘coil’) system. The experimental set up consisted of proprietary solar collector, solar loop and interchangeable ‘coil’/’Solasyphon’ loop. A series of tests were conducted on both systems under a solar simulator within a controlled environment. Outdoor testing was carried out on both systems separately over summer/Autumn conditions in Northern Ireland. The results showed that the ‘Solasyphon’ system delivered water at consistently higher temperatures than the ‘coil’ system under a standard EU domestic water usage pattern and was more effective under a transient solar input particularly on intermittent or poor solar days.