An Improved Mathematical Model for Green Lock Scheduling Problem of the Three Gorges Dam

In recent years, the environmental pollutions at the Three Gorges Dam have become an increasingly concerning issue of the Chinese government. One of the most significant environmental problems is the carbon emissions from the lockage operations at the two ship locks of the Three Gorges Dam. Currently, due to the large amount of vessels passing through the dam, there is always a long queue of vessels on both sides and the average waiting time is long. This has further lead to an increased amount of fuel consumption and carbon emissions. Therefore, it is of great importance to develop a decision-support model for a better navigation scheduling and planning of the lockage operations at the Three Gorges Dam. This paper proposed an improved mixed integer non-linear programming model for the green lock scheduling problem at the Three Gorges Dam. The model aims at minimizing the carbon emissions and the waiting time in the lockage process through scheduling the vessels in a fairer and more efficient manner. Moreover, a greedy particle swarm optimization (G-PSO) algorithm is developed to solve the complex optimization problem. The proposed mathematical model and algorithm are validated through a numerical experiment. The result shows that it may lead to a significant reduction on carbon emissions by giving a specified speed to each vessel with a pre-optimized sequence. Meanwhile, the fairness and efficiency of the lockage process may also be improved.