Impact of standby losses and potential reduction by installation of isotherm blanket on the hot water cylinders

Air source heat pump (ASHP) water heater is an energy-efficient device for sanitary hot water production. The study focused on monitoring the electrical energy consumed to compensate for the standby losses of three hot water cylinders without and with isotherm blankets. Accordingly, the analysis of thermal energy losses was performed using 150 L high-pressure geyser and 150 L split and integrated types ASHP water heaters without hot water being drawn off throughout the entire monitoring period. Likewise, to experimentally determine the thermal losses, a data acquisition system (DAS) was constructed to measure the average ambient temperature and relative humidity as well as the cumulative electrical energy to compensate for the standby losses. The results on average electrical energy consumed to compensate for the standby losses of the geyser, split and integrated types ASHP water heaters without the isotherm blankets were 2.71 kWh, 1.33 kWh and 0.94 kWh, respectively. The introduction of a 40 mm thick isotherm blankets on the hot water cylinders resulted in the electrical energy reduction by 18.5%, 15.8% and 3.2 % for the geyser, split and integrated types ASHP water heaters, respectively. The multiple comparison tests revealed a significant difference on the geyser standby losses under the two configurations.