Battery capacity design and optimal operation control of photovoltaic-battery system considering electrochemical aging

In recent years, the distributed photovoltaic battery (PVB) system is developing rapidly. To fully utilize photovoltaic production and increase the penetration of renewable energy, battery storage in distributed photovoltaic systems becomes essential. Despite plenty of studies dedicated to the capacity design and system control strategies under different work conditions, few research pay attention to the sophisticated battery storage aging problem and its effect on the system performance. This paper develops a five-parameter photovoltaic model and the electrochemical lithium battery model for the PVB system considering the residential load uncertainty in the distributed photovoltaic system. The battery and system performance under different capacity design and operation strategies are discussed. The results show that the oversize of the battery capacity design contributes to the capacity loss, leading to the increasement of levelized cost of storage, and the capacity design of 6, 8, 10 kWh under 100 %, 80 %, 70 % state of charge (SOC) charging limit is recommended in this case. Under the 100 % SOC limit, the battery capacity declines by 22 %-28 % annually, which is much higher than the limit of 80 % and 70 %. Meanwhile, the battery lifetime based on recommended capacity design can be improved further by 8.6 %, 4.0 % and 2.0 % with controlling the battery charge rate. Besides, a comparison between the electrochemical and traditional battery models is conducted, demonstrating that both models present a high consistency in system energy flow, while the traditional battery model lacks the internal electrochemical aging mechanism. The electrochemical battery model gives out a more precise battery aging result and reveals the different performances under varied control strategies.