SOFC-PEFC Combined Microgrid

SOFC-PEFC Combined Microgrid

DOI: 10.4018/978-1-4666-5796-0.ch011

Abstract

This chapter consists of two sections, ‘Power Generation Efficiency of Photovoltaics and a SOFC-PEFC Combined Microgrid with Time Shift Utilization of the SOFC Exhaust Heat’ and ‘Power Generation Efficiency of an SOFC-PEFC Combined System with Time Shift Utilization of SOFC Exhaust Heat’. The 1st section proposes the combined system of a solid-oxide fuel cell (SOFC) and a proton-exchange membrane fuel cell (PEFC). The proposed system consists of a SOFC-PEFC combined system and a photovoltaic system (PV) as the energy supplied to a microgrid. The 2nd section studies a microgrid by introducing a combined SOFC and PEFC. This study investigates the operation of a SOFC-PEFC combined system, with time shift operation of reformed gas, into a microgrid with 30 houses in Sapporo, Japan.
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General Introduction

The summary of the 1st section is as follows. In this section, the combined system of a solid-oxide fuel cell (SOFC) and a proton-exchange membrane fuel cell (PEFC) is developed. The proposed system consists of a SOFC-PEFC combined system and a photovoltaic system (PV) as the energy supply to a microgrid. The exhaust heat of the SOFC is used for the steam reforming of the bio-ethanol gas with time shift utilization of the exhaust heat of the SOFC in optional time. The SOFC-PEFC combined system with the PV was introduced in a microgrid of 30 residences in Sapporo, Japan. The operation plan of the system has three cases: without solar power, with 50% and with 100% of solar output power. Moreover, three types of system operation of using the SOFC independent operation, PEFC independent operation and SOFC-PEFC combined system are used to supply the demand side. A comparative study between the types of system operation is presented. The power generation efficiency is investigated for different load patterns: average load pattern, compressed load pattern and extended load pattern. This study reported that the power generation efficiencies of the proposedsystem in consideration of these load patterns are 27% to 48%.

The summary of the 2nd section is as follows. A microgrid, with little environmental impact, is developed by introducing a combined SOFC (solid oxide fuel cell) and PEFC (proton exchange membrane fuel cell) system. Although the SOFC requires a higher operation temperature compared to the PEFC, the power generation efficiency of the SOFC is higher. However, if high temperature exhaust heat may be used effectively, a system with higher total power generation efficiency can be built. Therefore, this study investigates the operation of a SOFC-PEFC combined system, with time shift operation of reformed gas, into a microgrid with 30 houses in Sapporo, Japan. The SOFC is designed to correspond to base load operation, and the exhaust heat of the SOFC is used for production of reformed gas. This reformed gas is used for the production of electricity for the PEFC, corresponding to fluctuation load of the next day. Accordingly, the reformed gas is used with a time shift operation. In this study, the relation between operation method, power generation efficiency, and amount of heat storage of the SOFC-PEFC combined system to the difference in power load pattern was investigated. The average power generation efficiency of the system can be maintained at nearly 48% on a representative day in February (winter season) and August (summer season).

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