Cascaded sCO2 Brayton–Transcritical ORC–adsorption cooling cycle for gas-turbine waste-heat trigeneration: Thermodynamic and exergy optimization

This study proposes and optimizes a three-stage waste-heat trigeneration system that cascades a supercritical CO2 Brayton cycle (SCBC), a transcritical organic Rankine cycle (TRC), and an adsorption chiller (ADC) to efficiently recover multi-grade heat from a Titan-250 gas-turbine exhaust. While most waste heat recovery (WHR) studies focus on dual-cycle or power-centric configurations—often neglecting staged recovery across the entire exhaust temperature spectrum, particularly at low temperatures—the proposed SCBC–TRC–ADC cascade enables simultaneous electricity generation, cooling production, and hot-water storage. This configuration achieves complete valorization of high-, medium-, and low-temperature heat levels. Real exhaust data were employed to ensure practical applicability, and component-level thermodynamic and exergy models were validated against published benchmarks. Sequential quadratic programming (SQP) optimization was performed under realistic process constraints, including pinch-point, pressure-drop, and subcooling limits. Among five candidate TRC fluids, R1234ze(E) demonstrated the highest exergy efficiency and environmental compatibility. Under optimized conditions, the integrated system produced 7.14 MW of net electricity—931 kW more than the standalone SCBC—while delivering 216 kW of cooling at 9.08 °C and storing 15,115 L of 73.8 °C hot water every 900 s. The overall plant and exergy efficiencies reached 35.11 % and 63.26 %, representing more than a 70 % improvement in total useful energy utilization relative to a single-cycle baseline. Sensitivity analysis identified recuperator effectiveness and TRC turbine-inlet pressure as dominant performance parameters. The results establish a validated, thermodynamically optimized cascade framework that demonstrates the feasibility and energy-service flexibility of multigeneration from gas-turbine waste heat, providing a benchmark for next-generation industrial decarbonization systems.