Design and technical assessment of photovoltaic and vanadium redox flow battery systems for residential buildings based on time-of-use electricity pricing strategy

Abstract

This study investigated the technical feasibility of a photovoltaic and vanadium redox flow battery (PV-VRFB) system for residential power supply in urban environments. A three-dimensional transient model of the VRFB unit was established using COMSOL to analyze battery performance under different current densities. The VRFB unit simulation demonstrated good agreement with experimental results, showing a relative voltage error of 1.34 %. The research focused on a typical residential community in Shenzhen, utilizing time-of-use electricity pricing as an energy management strategy. The simulation results indicated that the current density of VRFB had a significant impact on charge–discharge time, efficiency, as well as the stored and output energy. At a current density of 40 A/m², the coulombic efficiency, voltage efficiency, and energy efficiency of the VRFB were 93.18 %, 84.77 %, and 78.99 %, respectively. Higher current densities adversely affected overall system energy performance. An increase in VRFB current density from 40 A/m² to 60 A/m² resulted in decreases of 2.19 % in PV self-consumption rate (PRSR) and 2.30 % in load coverage rate (LCR). The PV-VRFB system achieved annual average PV self-consumption rate and load coverage rate values of 59.40 % and 62.08 %, respectively. The PSCR and LCR values were improved by 18.07 % and 14.18 % compared to the PV-Only system. The research results show that, in the current system, the levelized cost of energy (LCOE) is 0.7416 CNY/kWh and the dynamic payback period (DPP) is 22.65 years. Introducing a PV-VRFB system in residential areas significantly enhances renewable energy utilization, while highlighting the critical importance of controlling the VRFB current density.