Abstract
This study quantifies the potential of a 4.0 kW air source heat pump (ASHP) unit retrofitted to a 12.0 kW, 1000 L electric boiler coupled to a 1000 L storage tank. A data acquisition system was built to monitor the performance of the electric boiler and the ASHP water heater. The annual electrical energy saving and the load factor reduction from the electric boiler because of the ASHP unit retrofit was 34,805.94 kWh and 0.124. The net present value payback period of the ASHP system was 1.60 years. A Wilcoxon rank sum test was employed to compare both the volumes of hot water and electrical energy consumed by the two systems. Linear regression models of the daily volumes of hot water and electrical energy consumed by both systems were established. The results should be of great value to the management of universities that are considering energy-efficient interventions with a significant return on investment.
Highlights
Air source heat pump (ASHP) systems are widely used in the domain of sanitary water heating for their ability to act as both renewable and energy-efficient technologies
To establish linear correlations of the daily volumes of hot water consumed to the electrical energy consumed by the electric boiler and the air source heat pump (ASHP) water heater in summer and winter
To compare the daily volumes of hot water and electrical energy consumed by the electric boiler and the ASHP water heater, for both summer and winter using the Wilcoxon rank sum test
Summary
Air source heat pump (ASHP) systems are widely used in the domain of sanitary water heating for their ability to act as both renewable and energy-efficient technologies. The energy and cost savings from installing ASHP water heaters as replacements for electric boilers can be determined through analytical methods using experimental data. Lloyd and Kerr (2008) performed an energy payback analysis for an electric-boost solar flat plate heat pump system as a function of both COP and hot water usage for a given value of embodied energy. Wang et al [25] conducted an energy, exergy, economic and environmental analysis of an air source transcritical CO2 heat pump water heater and determined that the payback period was less than 1 year and the CO2 reduction was 378.01 tons. Experimental research conducted in South Africa demonstrated that both the split and integrated types of residential ASHP water heaters are viable technologies for sanitary hot water heating [26]. Eskom’s residential ASHP water heaters rebate scheme served as part of the solution to reduce the demand on the national grid [27]; he rebate program was discontinued at the end of 2015 due to a lack of funding to sustain the scheme [28]
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