Optimal design of interdependent hydroelectric schemes based on optimal timing

In countries, where electricity generation is based on an active or dynamic expansion of hydroelectric systems, it is important to determine the optimal design of projects and whole project configurations or sequences. This paper looks at this design process assuming interdependent projects as components of schemes or fixed sequences in a defined expansion path. The paper then analyzes economical criteria for the system optimal stage-wise expansion and their impact on individual project design. For instance, dam volume will depend on dam dimensions while the chosen tunnel width could generally be independent of the dam design. Both may impact cost and timing of individual project and thereby the cost of the whole sequence. Optimal timing of projects may also be linked to optimal definition of project output or capacity, based on matching increasing operating cost with time and load to an expansion step. The principal findings are that the optimal size can be adjusted by a marginal adjustment factor (MAF) to take into account the impact of sequential dependencies between adjacent projects. The calculations should be carried out iteratively within larger sequences, in order to reach optimum size based in optimum timing for projects.