Introduction
An energy supply system using a microgrid constitutes the optimal system for energy demand. Therefore, its use as a clean energy supply technique is expected to spread (Obara, 2008a; Aki et al., 2006; Jiayi, Chuanwen, & Rong, 2008). A microgrid using a PEFC (proton exchange membrane fuel cell) may become the mainstream of future distributed energy. In addition, the application of green energy to a microgrid is desired. Accordingly, this Section examines the PEFC and a photovoltaics compound system. Power can be supplied to a grid from each PEFC and photovoltaic component in this system. The hydrogen supply method to the PEFC assumes that the steam reforms the LPG (liquefied petroleum gas). However, the power generation output characteristics and PEFC exhaust heat with a steam reformer are nonlinear with a load factor (Obara, 2006a). Furthermore, although the power and exhaust heat of the proposed system are utilized effectively, battery installation and a heat storage tank are planned. Consequently, the operation plan of the proposed microgrid must be optimized as a nonlinear system considering electricity and heat storage. Concerning operation optimization of a nonlinear system with heat storage, we have summarized the use of a GA (genetic algorithm) (Obara, 2006b, 2007a, 2007b). In addition, it is necessary to predict unstable photovoltaic electricity production for every sample time while optimizing operation of a compound microgrid with a PEFC and photovoltaics. Accordingly, numerical weather information (NWI) is used to predict photovoltaic electricity production (Online data service, 2009; Data of Japan Meteorological Agency, 2009). Anyone can obtain NWI in Japan through the Internet. However, there is an error in the photovoltaic electricity production calculated using NWI compared to using the actual meteorological data. Consequently, the operation plan of the system using the NWI differs from operation under actual weather. The cause of this difference in operation is not addressed in this Section. Instead, the relation between the NWI error and the operation results of the system is clarified. It is shown that installing the operation optimization algorithm using NWI is important for operation of a PEFC microgrid with photovoltaics. The objective of this study is to develop an analysis algorithm to optimize operation of a PEFC microgrid with green energy.