Optimal Renewal Planning of Energy Supply Systems for Buildings : Problem Formulation and Economic Analysis

An optimization method has been proposed for the renewal planning of energy supply systems installed into buildings. Assuming the raise of future equipment's energy efficiency, the renewal year is determined optimally together with the structure of renewal system. In the mathematical optimization formulation, the average value of the annual total cost of the system during the evaluation period is minimized in consideration of system's operational strategy corresponding to seasonal and hourly energy demands requirement. Through the numerical study for an office building, it is shown that 2-3% reduction of the average value of the annual total cost could be achieved if the renewal planning could be optimized based on the proposed method. The influence of the following items on the renewal solution is also clarified; i.e., available types of equipment to be installed newly, upgrading rates of performance, and so on. For example, it is recognized that the optimal renewal year becomes later if the future upgrading rate of equipment's performance is assumed to be high enough.