A two-level hierarchical optimization framework for grid-connected photovoltaic-wind-battery systems in greenhouse energy management

Abstract

Greenhouse operations are energy-intensive and face increasing pressure from high operational costs, carbon emissions, and grid reliability constraints. This study develops a grid-connected photovoltaic-wind-battery hybrid energy system and proposes a two-level hierarchical optimization framework for greenhouse energy management. At the upper level, greenhouse operations are optimized using two alternative strategies: energy demand minimization, which aims to reduce heating, cooling, and ventilation loads, and energy expense minimization, which focuses on minimizing energy costs under time-of-use electricity tariffs. At the lower level, energy system scheduling is addressed through renewable energy utilization maximization and comprehensive cost minimization strategies, the latter accounting for electricity purchases, battery degradation, and carbon emissions. Simulation results demonstrate that the comprehensive cost minimization strategy achieves the best overall balance between economic performance and environmental benefits, reducing total operational costs by 45.30% and carbon emissions by 69.25% compared with the baseline. Sensitivity analysis further reveals that the battery unit cost is the most influential factor affecting the economic performance of the system. The proposed framework provides practical guidance for designing cost-effective and low-carbon greenhouse energy systems, supporting reliable and sustainable energy networks.