The representation of variable hydro potential in long-range electricity planning models

The long-range planning of electricity supply in countries for which hydro power constitutes a sizeable proportion of total capacity should take into account the effects of variable hydro inflow. Fluctuations occur in the water intake to storage lakes from year to year; reserve generating capacity is required to ensure that demand can still be met in years of low water intake. The least cost choice for reserve capacity must take into account not only the capital costs of generating capacity but also the extra fuel and operating costs, the latter costs being incurred only when water intake is low.This paper describes an LP model of the long-range planning problem in which the effects of both low water inflows and high water inflows are included. The formulation used to represent these variable elements in the model was designed to minimise the number of additional constraints required.