Energy storage systems (ESSs) operate as independent market participants and collaborate with photovoltaic (PV) generation units to enhance the flexible power supply capabilities of PV units. However

the dynamic variations in the profitability of ESSs in the electricity market are yet to be fully understood. This study introduces a dual-timescale dynamics model that integrates a spot market clearing (SMC) model into a system dynamics (SD) model to investigate the profit-aware capacity growth of ESSs and compares the profitability of independent energy storage systems (IESSs) with that of an ESS integrated within a PV (PV-ESS). Furthermore

this study aims to ascertain the optimal allocation of the PV-ESS. First

SD and SMC models were set up. Second

the SMC model simulated on an hourly timescale was incorporated into the SD model as a subsystem

a dual-timescale model was constructed. Finally

a development simulation and profitability analysis was conducted from 2022 to 2040 to reveal the dynamic optimal range of PV-ESS allocation. Additionally

negative electricity prices were considered during clearing processes. The simulation results revealed differences in profitability and capacity growth between IESS and PV-ESS

helping grid investors and policymakers to determine the boundaries of ESSs and dynamic optimal allocation of PV-ESSs.