Effects of a MIP start for solving weekly operational planning problem of a residential energy system

An optimal operational planning problem of residential energy system has been formulated by Mixed Integer Linear Programming (MILP). The decision variables of optimal operational planning problem are energy and mass flows, equipment's operating statuses, and energy level of storage. Many kinds of energy supply equipment are available for householders in Japan. Of course, in operational planning problem, the increase of integer variables which means equipment's on/off status, is linked to the increase of calculation time. It is important to assess the impact of introducing an energy system for a house based on the suitable planning horizon of this problem. Energy storage brings the energy in the form of hot water and electricity to the next d a y. The operational strategy of energy system including storage should be evaluated through few days toward various energy demand. The optimal planning problems become large scale because many pieces of equipment to introduce and long evaluation period are required. This paper analyzes characteristics of energy systems caused by planning horizon. Additionally, we propose a hierarchical method as heuristic method for solving large MILP problem easily, and the proposed method is tested the effectiveness. Our finding shows that the proposed search method for better feasible solution has good performance in comparison with default settings of conventional MILP solver in terms of calculation time.