The structure of objective functions in the reservoir optimization problem indicates the type of attitude to operation. This article presents an analytical framework to improve the structure of objective function by comparing 6 various forms of single-objective and bi-objective problems. Problems 1 and 2 were defined to compare two perspectives of operation, water supply versus energy generation. Problem 3 was also designed to examine the effect of the intra-annual electricity demand which was ignored in problem 2. Comparison of problems 4 and 5 shows the simultaneous effect of realistic water and electricity demand scenarios on finding an optimal Pareto front. Problem 6 considers a supply policy in which maximum hydropower generation in peak months is main strategy to reduce socio-economic tensions. These problems were analyzed for a period of 72 months in the operation of the Dez reservoir in the southwest of Iran. The results of comparisons showed that the average annual water supply in problem1 is 334 Mm3 higher than problem2, while the mean annual hydropower generation in problem2 compared to problem1 increases by 58.9 GWh. Hydropower generation in problem2 compared to problem3 experiences a 31.8% decrease in the peak period and a 111% increase in the non-peak months, it can impose significant problems on the National Electricity Network. The Pareto front for the problem 5 is better than the problem 4 at all points, meaning that the demand coefficient improves the Pareto front. The solutions of problem 6 can result in efficient meet of water and electricity demand in critical periods and incredibly improve practical planning.
We analyzed different single/bi-objective optimization problems to improve the structure of objective function through a comparative study.
Considering demand scenarios improves performance parameters of reservoir.
Implementation of strategy of maximum hydropower generation in peak months leads to find a set of optimal Pareto solutions that can provide practical planning.