Modelling the performance of a calorifier installed at a university residence intended to be retrofited by an air source heat pump

Sanitary hot water production contributes significantly to the electrical energy consumption in the university campus. An in-depth understanding of the current hot water technology, number of students, capacity of water used per student, time of use of hot water, total volume of hot water consumed and the total energy used on an average weekday in a university residence are very crucial in opting for energy efficient technology like an air source heat pump (ASHP) water heater. The study focused on quantitative and qualitative analysis of data collected for the hot water profiles in one of the university residences (Elitheini 1) from the conduction of experiment and questionnaires. The results revealed that 94% of the 75 students used hot water during the Eskom morning peak and 61% during the Eskom evening peak. In addition, the average daily energy consumption of the 12 kW Calorifier was 139.49 kWh, while the measured volume of hot water usage was 1950 L which is in strong agreement with the total volume (1945 L) of hot water consumption from the questionnaires. The p-value of the average volume of hot water usage measured by experiment and questionnaires was 0.7 and is of no mean significant difference. The monthly energy consumption for the week days was projected to be 2929.31 kWh. By retrofitting of calorifier with an ASHP unit, the energy consumption could reduce to 976.43 kWh based on its consecutive coefficient of performance of 3. Finally, from the energy consumption reduction analysis and the current Eskom tariffs, it can be alluded that the payback period of the proposedASHP unit as a retrofit to the calorifier is going to be less than 2 years and is worthy to invest into such technology under this study due to its favourable payback period and the reliability and lifespan of the ASHP unit