The effect of electric vehicle charging demand variability on optimal hybrid power systems with second-life lithium-ion or fresh Na-S batteries considering power quality

Second-life batteries (SLB) in energy storage systems (ESS) can provide an economical solution to hybrid power systems (HPS) by reducing environmental concerns in battery production. Could Na-S batteries be a suitable alternative for ESS applications if the toxicity problem can be solved? This article performs the optimal sizing and feasibility analysis of an electric vehicle charging station with a minimum cost objective under daily, hourly, and hybrid demand variability with multi-year sensitivity analyses for both ESS technologies. Moreover, the scope is deepened with sensitivity analyses based on solar horizontal irradiation, wind speed, and electricity selling prices. Due to the HPS connection to the distribution busbar, power quality issues are included in the cost-based optimization framework, and the effects of power quality issues on the sizing and feasibility outputs are compared at higher demand variability. The results show that using SLB at wind speeds lower than 4.7 m/s and irradiances lower than 3 kWh/m2/day or above 0.035 $/kWh electric sale price is not economical. Gridconnected HPSs can increase current and voltage harmonics at the distribution busbar by up to 55.3 % and 4.3 %, reduce the power factor by up to 46.8 %, and extend the payback period by up to 1 year.