Qualitative Methodology for comparison of Performance of Air Source Heat Pump Water Heaters

Abstract

This paper presents a statistical comparison of the electrical energy consumed due to the operation of two residential types of air source heat pump (ASHP) water heaters. The study focused on the determination of the electrical energies consumed and coefficient of performance (COP), by a 1.2 kW split type ASHP without an electric backup and a 0.9 kW integrated type with an auxiliary resistance element of 0.5 kW and both tank size was 150 L. The COPs and the electrical energies consumed were determined from the controlled volume of hot water (150, 50 and 100 L) drawn from each tank at different time of use (morning, afternoon and evening) periods for both the summer and winter seasons. Power meters, flow meters, and temperature sensors were installed on both types of ASHP water heaters to measure the data needed to determine the electrical energies consumed, the COPs and the thermal energies gained. The results depicted that the mean month-day electrical energy consumed by the split and integrated type ASHP water heaters in summer and winter periods was 1.24 and 1.35 kWh, and 1.56 and 1.89 kWh, respectively. Lastly, the p-value from the one-way ANOVA and the Kruskal-Wallis tests for the electrical energies consumed among the four groups was 1.63 x 10-5 and 1.60 x 10-3, respectively. It can be concluded that, despite the favourable seasonal performance of both the split and integrated type ASHP water heaters, there exists a significant difference in the electrical energies consumed at 1% significance level among the four groups.