Unlocking annual efficiency potential of waste-to-energy plants through in-plant optimization and seasonal thermal storage: A case study in northern China

The widespread adoption of waste-to-energy (WtE) incineration is crucial for sustainable municipal solid waste management; however, its total system efficiency remains suboptimal owing to its high internal consumption and the discharge of unutilized low-grade waste heat. Concurrently, the decarbonization of fossil-fuel-dominated district heating systems is required. This study addresses these issues by proposing a synergistic strategy for transforming a WtE plant into an efficient multi-energy hub. Through an in-depth case study of a typical plant in northern China, thermodynamic inefficiencies were diagnosed and in-plant optimizations (e.g., cascaded air preheating, biogas repurposing) were implemented, increasing net power generation by 1.35%. Subsequently, a conventional heating-season cogeneration scheme and an innovative seasonal thermal energy storage (STES)-Integrated large-temperature-difference annual heating scheme were designed and compared. The conventional scheme, although cost-effective (heating cost: 28.72 CNY/GJ), achieved a high seasonal but low total system efficiency (33.73%), leaving most waste heat unutilized. Conversely, the STES-integrated scheme overcame seasonal limitations, enabling year-round heat supply, boosting the annual total system efficiency to 89.84%, delivering 402.32 × 104 GJ of annual heat and reducing CO2 emissions by 46.76 × 104 tons per year, with a heating cost of 55.72 CNY/GJ, which is also cheaper than natural gas boilers. Therefore, the combination of in-plant thermodynamic optimization and regional thermal-electrical decoupling via STES can unlock the full annual efficiency potential of WtE plants, providing a technical pathway for their transition into key pillars of low-carbon urban energy systems.