Energy Saving Potential and Economic Analysis of a Waste-to-Energy and Solar Thermal Coupling System Based on Cascade Utilization Principle

Conventional Waste-to-Energy (WtE) cogeneration plants suffer from low energy efficiency, typically around 21%. This study proposes and evaluates an integrated system to enhance performance by applying the principle of cascade energy utilization. Using the Shaoxing WtE plant as a case study, a thermodynamic analysis reveals significant exergy destruction from using high-grade extraction steam for low-temperature auxiliary heating. The proposed scheme substitutes this steam with on-site solar thermal energy and recovered flue gas waste heat. Results indicate this thermal substitution can increase net power generation by 1.76 MW, boosting overall energy efficiency from 21.0 to 22.1%. The economic assessment is highly compelling, yielding a static payback period of only 0.6 years, which is substantially superior to the 10 year payback for an alternative photovoltaic system. This research validates direct thermal integration as a highly profitable and effective strategy for upgrading WtE plants, offering a practical solution to improve sustainability in the waste management sector.