Tokyo Gas, Kyocera, Rinnai, and Gastar Achieved the World's Highest Output Efficiency with Pressureless SOFC Power Generation Unit Using Horizontal-Strip Cell Stacks Operated at Low Temperature
Joint Development for Practical Application of Highly Efficient Solid Oxide Fuel Cell (SOFC) Power Generation Systems
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May 15, 2006
Tokyo Gas Co., Ltd.
KYOCERA Corporation
Rinnai Corporation
Gastar Co., Ltd
May 15, 2006 - Tokyo Gas Co., Ltd. (President: Mitsunori Torihara), Kyocera Corporation (President: Makoto Kawamura), Rinnai Corporation (President: Hiroyasu Naito) and Gastar Co., Ltd. (President: Hideo Nishiwaki) today announced the development of the pressureless SOFC power generation unit*1 in the direct current 2.5-kW class, and achievement of the world's highest DC generator output efficiency, 56.1%LHV (50.5%HHV). In February 2004, the four companies launched a joint development project for the highly efficient power generation systems using Solid Oxide Fuel Cells (hereafter "SOFC") which are expected to achieve the highest power generation efficiency among fuel cells.
Background: Horizontal-Stripe Cell Stacks Operated at Low Temperature*2
This DC power generation unit incorporates horizontal-stripe cell stacks operated at low temperature as a power generator. These cell stacks have been mainly developed by Tokyo Gas and Kyocera. The cell stacks are based on the horizontal-stripe electrode configuration designed by Tokyo Gas, and they are developed using Kyocera's material and production technologies for flat tube cells.
The horizontal-stripe cell stacks are designed to sinter many cells on a single ceramic substrate, and connect the cells on the substrate in series. Therefore, they can obtain high voltage while operating at low current by using a relatively small quantity, and it is possible to attain highly efficient power generation by reducing the loss of energy. Also, they provide advantages such as elimination of the need for the cell lamination process during production and the use of inexpensive materials. It is expected to reduce costs through mass production in the future.
Generally, the operating temperature of SOFC is as high as 1000 . However, the cell stacks use different materials in order to achieve long life and improve reliability, and provide consistent operations at low temperatures of around 750.
Background: Direct Current Power Generation Unit
In addition, the direct current power generation unit is developed mainly by Tokyo Gas, Rinnai, and Gastar with a focus on optimizing the ability of the horizontal-stripe cell stacks operated at low temperature. Some challenges needed to be resolved. For example, the unit had to be made smaller in order to restrain heat radiation loss from the surface of the power generation unit, which is critical for the independent heat operations of the cell stacks. Also, the distribution of the internal temperature and the flow should be optimized to achieve the same level of performance in several cell stacks. The companies addressed these challenges by using the heat-exchange technologies and fluid-control technologies that have been accumulated through the development of gas equipment.
As a result, a pressureless SOFC power generation unit was successfully developed in the 2.5-kW direct current class, and achieved 56.1% LHV (50.5% HHV). The unit achieves the world's highest DC generator output efficiency when methane, the main ingredients of town gas are used as fuel under the conditions of independent heat operation.
The four companies focused on the development of the cogeneration systems targeting a variety of applications for the future business market, such as use in the common areas of housing complexes. The companies will strive to develop and put to practical use the pressureless SOFC cogeneration systems in the several-kW class, and achieve 50% LHV (45% HHV) or higher in AC generator output efficiency by around FY2008 through the integration of a DC/AC inverter and various supplementary pieces of equipment into the DC power generation unit as packages.
The four companies will continue to develop the environmentally friendly, energy saving SOFC power generation systems in the future, and provide new energy supply systems to contribute to reducing the impact on the environmental.
Details of the achievement will be announced in the 13th Fuel Cell Symposium hosted by the Fuel Cell Development Information Center in Tower Hall Funabori (Edogawa-ku Sohgoh Kumin Hall, Tokyo) on May 16.
*1Outline of the power generation unit
The DC power generation unit*1 consists of cell stacks that form the power generator, the device to transform fuel such as town gas, the heat exchanger, and so on. It is a device that outputs a direct current using fuel such as town gas. Technology plays a central role in the SOFC systems. Cogeneration systems incorporate the unit, the DC/AC inverter, the exhaust heat recovery device and supplemental equipment as a single package.
(*) Normally town gas is used. Methane is used on this occasion.
(**) To remove the agent causing the odor in town gas. As methane gas is used, it is not needed.
The DC Power Generation System
*2 Features of the horizontal-stripe cell stacks operated at low temperature
Conventional SOFC (Solid Oxide Fuel Cell) systems are operated at high temperature of 1000. They have difficulty in independent heat operations, and there are limitations to the materials that can be used at high temperature. In practical applications, therefore, there is demand for operating the systems at lower temperature. By taking advantage of the horizontal-stripe SOFC simulation technologies and material design technologies concerning low-temperature operation developed by Tokyo Gas, and material, molding and sintering technologies of flat tube SOFC cells designed by Kyocera, the four companies substantially reduced the operating temperature of the horizontal-stripe SOFC from 1000 to 750 and verified that the output for each cell stack was approximately 10W. Also, the horizontal-stripe cell stacks are designed to sinter more than one cell on a single ceramic substrate. Therefore, there is no need for the production process to be concerned with the connection of cells. The product reduces costs by generating a high voltage with a single ceramic substrate.
The Horizontal-Stripe Cell Stacks Operated at Low Temperature
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