Introduction
A reduction effective of greenhouse-gas emission is expected with the microgrid (Robert et al., 2004; Carlos & Hernandez, 2005; Takuma & Goda, 2005). In particular, the microgrid using a fuel cell is predicted to be a leading method of future energy supply. In order to effectively reduce greenhouse gases to a maximum, a microgrid should be maintained and operated at the highest possible generation efficiency. It is necessary to optimize the operation plan of a microgrid, as well as the capacity of the energy equipment based on the power demand pattern of the buildings connected to a grid. Therefore, to produce high generation efficiency of a microgrid, a power generator that can maintain high efficiency is required over a large range from high load to low load. However, it is difficult to maintain high efficiency over a wide operating range with the proton-exchange membrane fuel cell (PEFC) with a reformer. Then, the method of operating a water electrolyzer (Obara & Kudo, 2005a), and the method of divides a fuel cell and a reformer (Obara & Kudo, 2005b) were examined at the time of partial-load operation. The power load added to a microgrid is decided by composing the power demand characteristics of two or more buildings. However, the example of considered the relation between the loads pattern of a building and the power generation efficiency of a microgrid is not reported. If the power demand pattern of a certain building reduces the generation efficiency of the whole microgrid, this building sets the grid of another network with a group of other buildings, and overall generation efficiency may be improved. Therefore, the fuel cell microgrid (FC microgrid) is divided into multiple grids, and this Section considers the independent management of each grid. Two or more divided grids can operate in cooperation with other grids to improve generation efficiency. In this Section, partition cooperation management of the FC microgrid and its relationship to generation efficiency are investigated using the power demand pattern assuming typical buildings in Tokyo. In addition to this, the FC microgrid that is equipped with the cooperation operation of the partition grid is effective at 'Response to overload at the time of load fluctuation', 'Risk abatement at the time of accident due to distribution of power facilities' and 'Interruption of service not caused at the time of maintenance.