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Emerging Technology Report #26: October 3, 2002

Micro Fuel Cell Development in Japan

Global Emerging Technology Institute

Growing market demand for portable devices such as laptop computers, PDAs and cellular phones increase is a function of the expansion of computing capacity and processor speed. This, in turn, has expanded the functionality of these devices and, as a result, has led to a greater demand in more reliable and long-lasting power sources for such devices.

New generations of mobile devices offer advanced features such as wireless communication on the PDA, picture transmission via a cell phone, or video recording on a digital still camera. These features require device makers to search for more reliable and longer lasting power sources beyond what is currently available. Lithium-ion batteries have met the growing power demand for the past several years but next generation devices will need much more. Consumers will find it increasingly inconvenient to replace or recharge conventional batteries more frequently as more sophisticated mobile devices and services become affordable in the near future. The perceived demand for more efficient power sources is driving incumbent electronics manufacturers and new entrants to develop micro fuel cell systems for portable electronics applications. In Japan, Sony announced the development of a new membrane with improved performance by a micro fuel cell last summer. This improved performance was due to the use of new materials that help enhance power generation performance. This announcement was followed by a number of press releases dispatched by competitors regarding the development of key technologies and even prototypes of micro fuel cell systems.

Roughly speaking, micro fuel cell systems can be divided into two groups. One is the system that directly converts fuel such as methanol into electricity. The other is the system consisting of a fuel reformer and a power generation cell. Both approaches have their own pros and cons. For example, a direct methanol fuel cell (DMFC) system is simple in structure and consists of a small number of components. However, methanol needs to be diluted in order to prevent the fuel from going through the electrolyte membrane to the cathode side (this phenomenon is called "methanol crossover"), which lowers power generation efficiency. On the other hand, the reformer-based system can achieve much higher power generation efficiency because it extracts hydrogen out of the fuel and directly supplies hydrogen to the power generation cell. However, thereformer is complex in structure and needs a number of components. In addition, the reformer becomes as hot as 280 degrees C and therefore needs a highly efficient heat insulator.

In Japan, Casio Computer is aggressively developing a reformer-based micro fuel cell system using MEMS technology. The company announced the development of a prototype in March 2002 and plans to bring the first-generation product to market in 2004. Among the many companies developing portable and micro DMFC systems, NEC uses carbon nanohorn and nanometer-size platinum particles to improve the performance of electrodes and is working to develop carbon nanohorn mass-production technology. The company has announced a series of micro fuel cell prototypes for cellular phone applications, and the latest prototype consists of 4 power generation cells and achieves an output of 2W. Toshiba’s DMFC system uses a mixing tank and liquid pump for diluting high-concentration (95%) methanol using water generated as by-product from the power generation cell. For Toshiba, the challenge is how to improve the electrolyte film to achieve high conductivity and low methanol permeability and how to reduce the size of auxiliaries such as the mixing tank and liquid pump. In addition, the safety of the fuel cartridge tank must be ensured because it contains high-concentration flammable fuel. The company has demonstrated that the DMFC system is capable of running a PDA for 40 hours, 5 times the operational time of a built-in lithium-ion secondary battery, using 10 cc of fuel.

In order for micro fuel cell systems to be widely accepted in the marketplace, it is important to be able to efficiently mass produce them at a reasonable price. People must also be able to safely recycle or dispose of the used cartridges in an environmentally friendly manner. Safety concerns regarding the aforementioned will be a key issue in the standardization of fuel cartridges. These concerns include the handling and transportation of hazardous and flammable fuels. For instance, Japanese regulations prohibit methanol from being transported by an aircraft. Some deregulation will be necessary in order to promote the widespread use of micro fuel cell systems. Given the differences in power generation principles, it would be almost impossible to develop standards and would require a consensus among suppliers. Manufacturers of micro fuel cell systems should develop strategic partnerships with electronics system developers, fuel producers, distributors, and even with recycling business companies as they continue to develop key technologies for micro fuel cells.

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