Experimental study of heat retention performance of thermal diode Integrated Collector Storage Solar Water Heater (ICSSWH) configurations

Integrated Collector Storage Solar Water Heaters (ICSSWHs) can support growing hot water demands of off-grid populations and reduce harm to human health and the environment. Despite their simple design and fewer associated components, stored thermal energy dissipates easily in foul weather. While thermal diodes are beneficial heat retention enhancement features in ICSSWHs, other simple additional strategies can enhance heat retention without significantly complicating the fabrication process. This article examines techniques of differing levels of complexity for the improvement of heat retention of a basic thermal diode ICSSWH. A basic thermal diode ICSSWH is adapted into a scalable Asymmetric Formed Reflector with Integrated Collector and Storage (AFRICaS) system and tested for heat retention performance along with other thermal insulation measures. The AFRICaS system improves heat retention efficiency and reduces heat loss coefficient to at least 35% and 1.46 W/K respectively. These results contrast with a heat retention efficiency and heat loss coefficient of 20% and 2.25 W/K respectively for a basic thermal diode ICSSWH. The AFRICaS prototype is potential launchpad for sustainable solar energy cogeneration.