Efficiencies and objectives in short term hydro scheduling

In short term hydro scheduling and optimization in a pure hydro system, a viable objective function is to minimize the water drawdown from a long term reservoir, thereby utilizing the characteristics and shape of efficiency curves for individual units, waterways and stations. This paper addresses the representation of key concepts related to these efficiencies, as represented by the generation and production functions in hydroelectric stations. To illustrate different aspects, data have been collected and analyzed for actual stations in the Icelandic hydro dominated power system and graphical results are presented for key concepts. These key results of the paper include marginal and average cost or objective function curves and definitions. The underlying objective could be to minimize water usage for all stations, as part of different possible objectives in short term hydro system optimization. The results should be helpful when designing optimization algorithms and interpreting their outputs, and in casting a light on what are important aspects in solving such practical optimization problems.