Multi-objective optimization of integrated energy systems considering diversified hydrogen utilization and carbon capture system under ladder-type carbon trading interacting with green certificate trading

To address low-carbon transition and renewable integration, this study developed an integrated electricity-hydrogen-gas-heat energy system with diversified hydrogen utilization and carbon capture. The system integrated electrolysis, fuel cells, methanation with carbon capture, and hydrogen-blended combustion. A multi-objective optimization model considering total cost, carbon emissions, and exergy efficiency was formulated, which incorporated ladder-type carbon trading and green certificate trading with a price linkage mechanism. The ε-constraint and TOPSIS methods were used for solution and decision-making. Results showed that the hydrogen architecture reduced curtailment penalty by 78.89% and total cost by 14.9%, but increased emissions by 3.04% under pure economic optimization. Under the coupled trading framework, GCT revenue reached CNY 94,888.29, with additional 2.25% cost reduction and 31.5% emission reduction. The carbon-prioritized compromise achieved the best balance among objectives. This work provided a systematic optimization framework for park-level IES operation.