Energy, exergy, environmental and economic analysis of a solar-assisted heat pump-driven enclosed drying system with liquid desiccant dehumidification

Drying process, as one of the most energy-intensive processes, plays a significant role in a variety of agricultural, residential and industrial applications. Existing solar or heat pump drying systems have not been well promoted and applied due to their instability or inefficiency. In order to achieve a stable and efficient drying process, a novel solar-assisted heat pump-driven enclosed drying system with liquid desiccant dehumidification is proposed in this study, in which total waste heat recovery structure and operation modes transition control strategy are carefully designed for better system performance. A comprehensive analysis incorporating energy, exergy, economic, and environmental assessments are performed based on established mathematical models. Results demonstrate that the proposed system achieves a maximum coefficient of performance of 7.84, an energy utilization ratio of 11.09, and a specific moisture extraction rate of 14.87 kg/kW·h when solar radiation exceeds 640 W/m². Exergy analysis further reveals that over 80 % of exergy loss occurs in the solar collector, with the system attaining an exergy efficiency of 50.1 %. When annual solar radiation values reach 1580 kW·h/m² and 1300 kW·h/m², the system reduces electricity consumption by 36.64 % and 29.82 %, respectively, compared to traditional cascade enclosed heat pump drying systems, achieving a payback period of approximately 5 to 18 months. Additionally, the novel system cuts annual CO₂ emissions by 27.65 % compared to conventional drying methods, highlighting its significant environmental benefits.