Energy management opportunities exploration in a residential air source heat pump water heater

Abstract

Air source heat pump (ASHP) water heaters are classified as renewable and energy efficient device for sanitary hot water production. The study focused on the investigation and quantification of the wasted thermal energy dissipated at the ASHP's condenser of a 1.2 kW, 150 L split type residential ASHP water heater undergoing vapour compression refrigeration cycles due to controlled volume of hot water drawn off. Power meter, flow meters, temperature sensors, ambient temperature and relative humidity sensor were installed at designated positions on the ASHP water heater. Specific control volume of 150, 50 and 100 L were drawn off from the ASHP water heater during the morning, afternoon and evening periods each day throughout the monitoring period (October 2015 to September 2016). The results depicted that during the summer and winter periods the average input electrical energy consumed was 1.40 and 1.70 kWh, while the dissipated and the useful thermal energy were 13.65 and 4.10 kWh for summer and 14.70 and 4.07 kWh for winter, respectively. It can also be concluded that during the summer and winter periods only 30.01% and 27.63% of the dissipated thermal energy from the condenser was harnessed as useful thermal energy by the sanitary hot water stored in the 150 L geyser with the heating element disabled. Hence, by the application of energy management, almost 70% of wasted thermal energy can be utilized for space heating or as backup storage, provided the ASHP water heater is designed to function as both hot water and space heating device with an additional backup thermal storage.