A review on the performance assessment and optimization techniques of air source heat pump water heaters used in South Africa

Heat pump water heaters (HPWH) are classified as renewable energy efficient technologies and have had a high market penetration in South Africa since 2008. The market of this technology is fast gaining maturity and sales are expected to increase significantly in the upcoming years. This could be explained by their low energy consumption (about 67% lower than conventional geysers), relatively low operation cost, their environmental friendly nature and possibly the ease to retrofit with the old inefficient technologies. Therefore, we need to examine critically the performance of HPWH to ascertain its optimal operation in South Africa. This study deals with reviewing works carried out to assess and optimize the performance of Air Source HPWHs for efficient use in South Africa's weather conditions. It brings together the different models and simulations employed and developed for HPWH as well as the different findings and suggestions towards a better performance. The results show that, the COP of Air Source HPWH in South Africa is influenced by the combined effects of the ambient temperature and relative humidity, hot water usage profile, the size and shape of the evaporator as well as the condenser, type and configuration of compressor, the filling capacity of the refrigerant, standby losses and even the efficient installation of the system.