Bi-level optimization of a near-zero-emission integrated energy system considering electricity-hydrogen-gas nexus: A two-stage framework aiming at economic and environmental benefits

Abstract

Decarbonization is increasingly highlighted to realize emission peak and neutrality targets, while relevant low-carbon measures remain price high, especially for industrial end-users. This paper thus focuses on a specific design for park-level integrated energy systems with near-zero emissions. Solar photovoltaic and distributed wind power are applied as the main power supply together with the help of the local grid. The decarbonization sector is composed of power-to-gas (P2G) and carbon capture units where electrolyzers are separated from P2G and constitute the hydrogen subsystem together with hydrogen tanks and fuel cells. The system is also considered under the dynamic market environment where electricity, hydrogen, and emission exchanges are included. Then, the system behaviors are determined by an optimal operation model considering an uncertain power supply. Based on the stochastic operation, system configuration optimization considering economic and environmental objectives is constructed as a multi-objective integral model that is solved by an enhanced firefly algorithm in the first stage. Next, the optimal result is concluded according to subjective judgment and objective distribution in the second one. A case study in Gansu province, China is carried out to validate the system, and results indicate that 1) optimal result investing 5.285 million $ could avoid 7.4542 kilotons of emissions annually with a 20.1 % loss of self-power supply rate on average, 2) up to 51.72 kg of hydrogen fuels or 47.90 kg of gas could be generated besides daily load satisfaction, 3) carbon exchange incentive above 4.2 $/t could promote additional emission reduction.