ToU-driven energy storage scheduling for enhancing energy flexibility in a nearly zero-energy building

With the deepening electrification of buildings, the supporting role of energy flexibility in the efficient utilization of clean energy has become increasingly prominent. Integrating energy storage systems (ESS) into energy systems can effectively enhance the energy flexibility of nearly zero-energy buildings (NZEBs). Current ESS operations predominantly rely on SOC-Controlled rules, failing to incorporate dynamic economic signals from Time-of-Use (ToU) tariffs, which limits their effectiveness in alleviating grid stress during peak periods. This study proposes a ToU-driven energy storage operation strategy (ToU-ES) for NZEB multi-energy systems and first establishes four quantifiable evaluation metrics for energy flexibility. The adaptability of this strategy is analyzed under three electric vehicle charging modes: conventional alternating current charging (AC-L1), direct current fast charging (DCFC), and battery swapping system (BSS). Coupling effects impacting flexibility are systematically investigated. All models are validated through a TRNSYS-MATLAB co-simulation platform. Results demonstrate that the ToU-ES strategy achieves synergistic regulation through valley-charging and dynamic peak-discharging, significantly reducing grid reliance while improving renewable energy utilization efficiency. The system exhibits enhanced flexibility and economic performance across multiple temporal scales. Coupling effect analysis reveals dead zones in economic benefits where excessive increase in charging power or SOC trigger limits yields diminishing returns under fixed equipment configurations, necessitating capacity expansion to break through benefit boundaries. This research provides a scalable technical framework for “NZEB-transport-grid synergy” decarbonization, while the proposed evaluation metrics offer theoretical support for related studies.