A multiobjective short‐term optimal operation model for a cascade system of reservoirs considering the impact on long‐term energy production

Abstract

AbstractThis paper examines the impact of short‐term operation on long‐term energy production. We propose a multiobjective optimization model for the short‐term, daily operation of a system of cascade reservoirs. The two objectives considered in the daily model are: (1) minimizing the total amount of water released and (2) maximizing the stored energy in the system. Optimizing short‐term operation without considering its impact on long‐term energy production does not guarantee maximum energy production in the system. Therefore, a major goal of this paper is to identify desirable short‐term operation strategies that, at the same time, optimize long‐term energy production. First, we solve the daily model for 1 month (30 days) using a nondominated genetic algorithm (NSGAII). We then use the nondominated solutions obtained by NSGAII to assess the impact on long‐term energy production using a monthly model. We use historical monthly inflows to characterize the inflow variability. We apply the proposed methodology to the Qingjiang cascade system of reservoirs in China. The results show: (1) in average hydrology scenarios, the solution maximizing stored energy produces the most overall long‐term energy production; (2) in moderately wet hydrology scenarios, the solution minimizing water released outperforms the maximizing stored energy solution; and (3) when extremely wet hydrology scenarios are expected, a compromise solution is the best strategy.