Matching Horizons: Heuristics for PV-BESS EV Stations; Hitting the PV/Load Knee, Autonomy That Delivers, and the Oversizing-to-Export Tipping Point

Electric-vehicle (EV) charging station must maintain reliability in spite of high peak power, varying load profiles and PV intermittency. This study develops practical sizing rules for grid PV-battery energy storage (BESS) stations by sweeping PV capacity and battery autonomy in PVsyst for a representative hot-arid site (Kerman). Three stochastic demand profiles are evaluated: Neutral, Bursty, and Quiet. Stage ۱ sweeps PV/load power ratios while autonomy is constant. Stage ۲ is built up on stage ۱ as it fixes PV/Load ratio for an autonomy range. Key metrics are grid reliability, unmet load and curtailment. In this regard ۳۰ cases were simulated. Results show reliability index rises monotonically with PV size but with diminishing returns around PV/Load ۴-۵. Curtailment index is modest until PV/Load ۳ and then increases sharply, indicating that oversizing beyond the knee point mainly inflates curtailment. Autonomy exhibits a strong "first-step" effect. Raising autonomy from ۰ to ۰.۵ day yields the largest reduction in unmet energy and the biggest solar-fraction jump. Therefore, PV/Load ۴-۵, with ~۰.۵ day autonomy can be regarded as a high-leverage baseline. Moreover, in highly bursty load profiles, considering ~۱ day autonomy can be feasible. This analysis is constrained by PVsyst default dispatch behavior and by assuming fixed converter characteristics.

Keywords:

PV sizing , EV charging Station , Battery Sizing , On-Grid Systems , V۲G