[Tangwe, 3(10): October, 2014] ISSN: 2277-9655 Scientific Journal Impact Factor: 3.449 (ISRA), Impact Factor: 2.114 http: // www.ijesrt.com (C)International Journal of Engineering Sciences & Research Technology [504] IJESRT INTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCH TECHNOLOGY A Techno-Economic Viability of a Residential Air Source Heat Pump Water Heater: Fort Bueafort, South Africa Stephen L. Tangwe*, Michael Simon and Edson L. Meyer Fort Hare Institute of Technology, University of Fort Hare, Alice, Eastern Cape, South Africa Abstracts sThe utilization of an air source heat pump (ASHP) to retrofit geyser can significantly reduce electricity consumption for sanitary hot water production. Furthermore, optimal operation of the system based on ambient conditions and capacity of hot water usage would enhance both achievable performance and payback time. The study focus on using a data acquisition system to evaluate the performance of an efficiently installed ASHP water heater and hence determine the payback period of the system. Preliminary results depict that during the four months of performance monitoring of the system, the average month-day input energy, coefficient of performance and volume of hot water usage was 3.0 kWh, 260 L and 2.2 respectively. An average monthly energy saved of 125 KWh was achieved while the average ambient temperature and relative humidity of 24.6 oC and 64.2% were recorded for the entire time of operation of the system. Finally, using a multiple comparison test, it was demonstrated that no mean significant difference occurred in both the average week electrical energy and COP for each of the different months throughout the observations. The payback period of the ASHP unit was determined to be less than 6 years from a conservative approach method. Keywords: Air source heat pump (ASHP); Sanitary hot water; Coefficient of performance (COP); Payback, multiple comparison test, Data acquisition system (DAS). Introduction The commonly applicable type of heat pump heaters employ for sanitary hot water heating are the air source and the geothermal or ground source systems. These systems operate on the principle of vapor compression refrigerant cycle. The geothermal air source heat pump water heater possesses a better techno- economic potential to an ASHP water heater by virtue of its relatively constant and higher COP [1, 2]. Both systems can be classified as a renewable energy device, as they all use a given form of renewable energy from their immediate surroundings where the evaporator is located during the vapor compression cycle. The ground source heat pump water heater extract waste heat from underground in the form of geothermal energy while ASHP water heater utilized the heat from the air as aero- thermal energy. The capital cost of ground source heat pump water heater is much higher as compared to an ASHP water heater. ASHP water heat is fast gaining maturity in the market as sanitary hot water production constitutes a significant percentage of monthly energy consumption in the residential sector worldwide. In South Africa, residential hot water heating can contribute to more than 50% of the monthly energy utilization [3]. A far-reaching research conducted to justify in terms of energy usage revealed that the hot water contribution in the domestic sector of South Africa is between 40% to 60% on an average monthly basis [4, 5]. It is worth mentioning that despite the daunting electrical energy consumed for hot water production, not all the thermal energy gained by the hot water is effectively utilized. There are always standby losses which are responsible for 20% to 30% of the total thermal energy gained by hot water contained in a storage tank [6]. Although, ASHP water heater coefficient of performance (COP) value can range from 2 to 4 [7, 8]; it is crucial to note that the system COP depends on the COP of the ASHP unit and the ambient climatic condition [9]. Clearly, the COP could be defined as the ratio of the useful thermal energy gained when water is heated to set point temperature and the electrical energy used by the system during the vapor compression refrigerant cycle. A salient and better understanding of refrigeration cycle of heat pump water heater was given by Ashdown et al. (2004) and Sinha and Dysarkar, (2008) [10, 11]. Moreover, the performance can be severely affected by standby losses. Heat pump water heaters also render an extra benefit of dehumidification and space cooling because they pull warm vapor from the air [12]. An efficiently installed residential ASHP water heater can guarantee an improvement on the system performance [13]. The study deal with an in depth performance monitoring of a residential split type ASHP water heater installed in a middle class home (compose of 2 adults and a child) in