Optimization of a residential heat pump system

With the constant increase in electrical energy costs in South Africa, households need to look at ways to either decrease their electrical energy usage or ways to supply their own electrical energy. This paper looks at the use of an automated heat pump system to decrease a household's electrical energy costs. A heat pump system was built in 2013, and optimized in 2018. The system contains a heat pump, hot water storage tank, measuring instruments and a Programmable Logic Controller (PLC), which is used to switch the heat pump on. The PLC in the system records the data generated by the measuring instruments and uses the data to calculate and predict a coefficient of performance (COP) value for the present and near future. Different methods of calculating the COP were evaluated for implementation in a real-time system. Various methods to predict ambient temperature, water temperature and the energy usage patterns were also investigated given the limitations of a small industrial PLC. An algorithm that uses these calculated COP values and the water usage pattern of the household decides which time of the day would be best to turn on the heat pump to achieve the highest efficiency. By using the new algorithm the electrical energy of the system could be reduced by 51.6% compared to the standard control algorithm of the heat pump itself.