Abstract
Waste heat from factories and power generation stations can be regarded as one of the most important local energy sources that should be utilized nearby the site of waste heat sources. It is clear that there is a tradeoff between the amount of waste heat to be utilized and the cost for constructing a system to make this utilization possible. A detailed knowledge on this tradeoff is valuable when the proper location and the scale of this utilization system are to be determined over a region.
In this paper, we present a multiple objective optimization model in which the amount of utilized heat is to be maximized and the total capital cost for constructing the system is to be minimized. In this model, optimization is carried out in two-level hierarchy. That is, the entire distribution network is divided into primary and secondary networks and optimization is first carried out with respect to the secondary network. Then the resulting tradeoff curve for each secondary network is used in the optimization with respect to the primary network. The model is nonlinear reflecting the existence of economies of scale in capital cost and linear approximation is used to carry out the actual calculation. It is shown that the linearized problem has a special structure which makes it possible to determine an optimal solution directly. Thus, large scale, real problems can be solved without incurring too much computation.
A numerical example is presented, in which the usefulness of the calculated tradeoff curve is shown in detail.
