DEVELOPMENT OF A RESIDENTIAL SOFC CHP SYSTEM

摘要

In this study, we developed a residential-use solid oxide fuel cell (SOFC) cogeneration system with the following characteristics. ? High energy efficiency The electric power efficiency of the system at the rated power is 46.5% LHV. To the best of our knowledge, this is the highest existing power efficiency for a commercialized residential combined heat and power (CHP) system. The overall energy efficiency amounts to 90% LHV. ? High CO_2 reduction and lower running costs Compared with the emissions of a house using conventional grid power, customers using the SOFC CHP can reduce their annual CO_2 emissions associated with household power usage by approximately 1.9 tons. In our trial calculation for a typical household, the SOFC saved 90,000 yen per year.? High salability due to compactness The installation space required is a mere 1.9 m~2, which is industry-leading in terms of space saving. It can be installed in narrow spaces, which is an important advantage in urban areas and apartment buildings with limited space. ? Development a system with a ten-year operation life During the development stages, one of our main goals was to improve the durability and reliability of our product. Our aim was to develop a system with a ten-year operation life and a start-to-stop heat cycle tolerability of 360 cycles. To assess our proposed solutions, we performed durability evaluations of the materials, stacks, and SOFC generator units under accelerated conditions. We attempted to clarify the effect of the specification changes of the developed stacks over short time periods. The advanced ceramic coating on the metal current collector was selected from hundreds of potential materials. Over 100 samples were tested simultaneously under varied temperature and current density conditions. In addition, field tests were conducted at more than 100 residential houses. The results demonstrated the required reliability and durability were achieved for commercial products. ? High reduction of electric power consumption due to high load flattery characteristics By consecutive running with high load flattery characteristics, the SOFC system can generate 80% of the electricity used by an average Japanese household, thus reducing demand from the power grid. Moreover, we also developed a new function that allows grid-independent operation in the event of a power outage. The following characteristics are under development now. ? Increase applicability to the residential market High power efficiency, compatibility with various fuels, and elimination of the need for expensive and precious metal catalysts are means of increasing applicability to the residential market. Due to the simplicity of the auxiliary machinery composition, there is great potential for cost cutting. ? Improve suitability for use in small businesses. High generation efficiency and adaptability to a wide range of power generation scales are both necessary to improve suitability of the SOFC CHP system for use in small businesses with minimal power consumption.