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This paper compared the coefficient of performance (COP) of two residential types of air sourceheat pump (ASHP) water heaters using statistical tests. The study determined the COPs and theelectrical energies consumed, by a 1.2 kW split type and 0.9 kW integrated type ASHP with tank sizeof 150 L. The COPs were determined after series of the controlled volume of hot water (150, 50 and100 L) drawn from each tank at different time of use for both the summer and winter seasons. Powermeters, flow meters, and temperature sensors were installed on both types of ASHP water heatersto measure the data needed to determine the COPs. The results depict that the mean COP of the splitand integrated type ASHP water heaters were 2.965 and 2.652 for the summer and 2.657 and 2.202for the winter seasons, respectively. In addition, the p-values of the average month-day COPs forthe split and integrated type ASHP systems during the winter and summer season was 7.09×10-24and 1.01 × 10−11, based on the one-way ANOVA and Kruskal-Wallis tests. Furthermore, themultiple comparison test was employed together with one-way ANOVA and Kruskal-Wallis statisticsto show that there exists significant difference between piece-wise COPs groups’ pairs at 1% significance level among the four COPs groups.

Renewable energy technologies that can provide optimum and cost-effective energy savings to mitigate global warming, energy crisis and to achieve energy efficiency continue to be of paramount importance. The present study focused on identifying critical parameters such as the volume of hot water drawn off; ambient temperature; relative humidity; refrigerant temperatures at the inlet and outlet of the compressor and condenser; and deterministic quantities such as time used, power consumption and coefficient of performance (COP) as indicators to benchmark the performance of both the split and integrated types of air-source heat pump (ASHP) water heaters. The basis for analysis was on two predominant scenarios: first-hour heating rating and the heating cycle due to controlled volume of hot water drawn-off wherein both the integrated and split types ASHP water heaters experienced vapour compression refrigeration cycles. A data acquisition system was constructed and implemented to monitor the performance of both systems. The results obtained during summer season showed that, under the scenario of 150 L hot water withdrawal, the average COP of the systems was 3.18 and 2.85 for the split and integrated types respectively. The average power consumed was 1.29 (split type) and 0.85 kW (integrated type). The times of operation were 84 minutes (split type) and 138 minutes (integrated type).

The purpose of the research was to evaluate the coefficient of performance (COP) of both 150 L split and integrated type air source heat pump (ASHP) water heaters via experimental analysis, statistical tests and mathematical modelling. The ASHP water heaters are used as a potential replacement of inefficient geyser for the production of sanitary hot water due to the excellent efficiency of COP ranging between 2 and 4 and also the capability of reducing the electrical energy consumption by 50-70%. Both types of ASHP water heaters together with a 150 L geyser that served as the control experiment were set up such that distinctive real-time simulated volumes of hot water (100, 50 and 150 L) were drawn off from each of the storage tanks per day over a full year. A data acquisition system (DAS) was designed and built comprising of power meters, flow meter, temperature sensors, ambient temperature and relative humidity sensors in order to monitor the electrical, thermo-physical and environmental contributions of the various hot water heating devices. The hot water set point temperature on each of the technologies was 55oC and the volume drawn off corresponded to the demand during the morning, afternoon and evening, respectively. This mimic the profile of a typical middle or highincome family (3-4 adults) in South Africa. The results depicted that the average annual COP, load factor, and energy saving of the split and integrated type systems was 2.95 and 2.45; 10.2 and 16.7% and 2.770 and 2.499 MWh while the simple payback period was 3.9 and 5.2 years, respectively. The reliefF test revealed that the predictors (ambient temperature and relative humidity) were secondary factors while the electrical energy consumed, the difference in the temperature of the refrigerant at the inlet and outlet of the compressor and condenser were the primary factors to the COP. The derived multiple linear regression models exhibited an excellent determination coefficient of over 90% between the calculated and modelled COP of both types of ASHP water heaters. Finally, the 2D multi-contour plots simulation was accurately used to show the variation of each predictors to the COP. Also, a simulation application to simultaneously compare the COP of both types of ASHP water heaters was developed in the Simulink environment utilising the derived mathematical models. Heat pump manufacturers and energy service companies can employ both the 2D multi-contour plots simulation and the simulation application to show the variation of the specific predictors with the COP and to predict the COP of both types of ASHP water heaters. Conclusively, the research provides substantial evidence for both policy makers and home owners to justify the techno-economic and social benefits of retrofitting a geyser with an ASHP water heater.