Scientists in Japan claim that they have developed a miniature fuel cell power source which is as small as a sugar cube. The one cubic centimetre solid-oxide fuel cell (SOFC) was created by researchers at Japan’s National Institute of Advanced Industrial Science and Technology (AIST).
Toho Gas Co., Ltd. (Toho Gas), which is examining small SOFC cubes for cogeneration purposes, evaluated the performance of the newly developed small SOFC bundle and confirmed that it can produce a high output power, even at operating temperatures of below 600°C.
The applications of SOFCs have previously been limited by their high operating temperatures, typically 800–1000°C, so realization of high output power SOFC modules that operate at lower temperatures have long been expected. The group states that this achievement should open the way to commercialize practical micro SOFC systems for auxiliary power supplies for vehicles, small cogeneration systems, and portable power units.
The SOFC bundle uses lanthanum cobalt as the air electrode material that forms part of the SOFC bundle. This made it possible to establish the technology for producing a small cubic SOFC bundle with a power output of 2W or more per cubic centimeter at below 600°C. This technology is suitable for mass production because it relies on basic ceramics-forming technology.
The actual micro SOFC cube bundle is an integrated structure that has a volume of one cubic centimeter and tubular cells with a diameter of 0.8–2.0mm. Toho Gas examined the performance of the SOFC bundles by flowing hydrogen into micro tubular SOFCs with 2mm in diameter, operating at 550°C. The tests confirmed that the SOFC cube bundle generated more than 2W of power. Test data show that a volume of one cubic centimeter can generate more than 2W of power for a current of 4.5A at the operating temperature of 550°C.
The tests confirmed that the SOFC bundle produces what is claimed to be the highest volumetric power density of any known fuel cell and does so at a current of 4.5A and an operating temperature of below 600°C. At the same time, the bundle is also said to be the world’s smallest fully-fledged micro tube SOFC cube with passages for fuel and air.
The newly-developed micro SOFC opens the prospect of stacking micro SOFCs to produce stacks and modules ranging in size from small mobile electric power units of several tens of watts with volumes of several tens of cubic centimeters to auxiliary power units for vehicles or household power units with outputs of several kilowatts and volumes of several thousand cubic centimeters. SOFCs are expected to be applied as distributed power units for household use, as power units for mobile electronics devices, and as auxiliary power sources for vehicles.
