The aim of this paper is to develop an optimal scheduling strategy model for a grid-tied photovoltaic(PV) system to power a heat pump water heater (HPWH). The system is composed of PVmodules that are grid-tied and a backup battery. The PV is capable of supplying power simultaneouslyto the HPWH and domestic load, whilst the grid and the battery are complementary sources.The objective function of this model is energy cost. The time-of-use (TOU) electricity tari istaken into account in the optimal scheduling model. The control variables are the power flowswithin the branches of the system. The optimal control strategy of this grid-tied PV system canbe implemented to reduce the energy cost while meeting the technical and operational constraints.This model has shown to have more economic benefits than solar thermal heaters, because of thepossibility to turn the dwelling into net-zero energy or energy-positive buildings with the attractivenessof the feed-in tari . A case study is done based on 3x16 kW HPWH installed at a Pretoriahotel in South Africa. Simulations are run for a year on selected seasonal date using the actualHPWH demand. The optimal control results show how the battery status of charge and TOU a ectthe power scheduling strategy of the HPWH. The energy and cost savings are presented in thispaper as well.
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