An Optimal Renewal Planning of Energy Supply System From Economic Viewpoint

An optimal planning method of renewal planning for energy supply systems is proposed to determine the proper renewal year and selection as to what kind of equipment is suitable for several types of buildings from economic viewpoint. In this method, they are determined together with maximum contract demands of utilities such as electricity and natural gas so as to minimize the annual total cost in consideration of system’s annual operational strategies corresponding to seasonal and hourly energy demand requirements during every evaluation year considered. A numerical study is carried out for an office building with a total floor area of 15 000m², where the system is consisted of an electric refrigerator and a steam boiler. Through the numerical calculation, the influence of the following items are clarified on the optimal renewing year and selection of renewing equipment of the system by the parametric study; (a) upgrading technology of the equipment in the future; (b) initial capital cost of equipment; (c) renewing construction cost and trade-in value rate; and (d) interest rate.