Research on the annual performance and regulation of solar greenhouses for integrated cold-heat-electricity utilization under dynamic operating conditions

Efficient energy utilization is critical for sustainable greenhouse agriculture. However, the variability of solar energy poses significant challenges, leading to inconsistent crop yields and quality. To address this issue, this study proposes an active solar photovoltaic direct-driven combined cooling and heating supply (PV-CCHS) system, utilizing excess solar energy passively absorbed within the greenhouse as an auxiliary heat source. The system employs an adaptive control strategy that dynamically adjusts heat sources based on crop-specific requirements, stabilizing photovoltaic power generation and internal greenhouse conditions. The PV-CCHS system was experimentally implemented in a 24.5 m2 strawberry greenhouse located in a subtropical highland region, and its cold-heat-electricity coupling performance was studied under variable environmental conditions. Findings show that the PV-CCHS system enables stable, efficient year-round operation, achieving a photovoltaic self-sufficiency rate (SSR) of up to 0.97 and an annual SSR of approximately 0.75. The energy utilization rate increased by 48.7 % compared to conventional heat pump systems. Additionally, the investment payback period was reduced to 3.2 years. This study provides a practical reference for optimizing energy coupling in greenhouse systems that promotes sustainable agricultural development.