Over the past several years micro fuel cells have come under criticism for failing to deliver on their promise as a viable source of energy for products such as mobiles phones, notebook computers and other devices. Aside from a few successful prototypes, the technology has taken much longer than expected to reach the mass markets, resulting in continued frustration for its proponents. However, a growing interest in energy harvesting may give micro fuel cells the kickstart they need to get going in a number of niche applications. In a recent paper at the 2008 Small Fuel Cells conference in Atlanta Georgia, the Sony Corporation presented a paper titled “Micro Fuel Cell System for Mobile Consumer Electronic Devices,” which introduced hybridization to compact fuel cells.

Sony’s prototyped fuel-cell system consists of a fuel cell unit, a micro-pump (referred to as a "regulator" in the paper) to supply fuel, a Li-polymer rechargeable battery and a control circuit. The fuel-cell unit is composed of six cells and uses methanol with a purity of 99%. In addition to the power management of the fuel cell and the Li-polymer rechargeable battery, the control circuit controls the micro-pump and protects the Li-polymer rechargeable battery. As a result of hybridization with the Li-polymer rechargeable battery, the latest fuel cell system reportedly enables the maximum output of 3 W or higher, although the fuel cell unit by itself can only output about 1 W. Sony presented a video clip demonstrating how a mobile phone powered by the latest fuel cell system displays TV broadcasts. In it, the user was able to watch TV for about 14 hours with 10 milliliters (mL) of methanol. The energy generated by the fuel cell unit with 1 mL of methanol is 1.1 Wh, which was more than three times higher than the company's 2005 prototype and about double that of the 2006 prototype.

A number of other companies are also taking a serious look at micro fuel cell technology. Motorola is currently looking at fabricating an ultra-small fuel cell system with a 3D structure for use in mobile phones. This system would be composed of fuel cells, a fuel cartridge and a compact Li-ion rechargeable battery with a volume of 8mL, which is the size of the Li-ion rechargeable batteries in existing mobile phones. The company intends to fabricate a 3D cell that can extend the reaction area of the cell, instead of the existing 2D (planar) cell. Specifically, the company formed a three-dimensional assembly of six cells in an area of 1cm2 on a silicon wafer. The research into this project is ongoing.

Sharp also announced a breakthrough in micro fuel cell technology by claiming to have achieved the world’s highest density for direct methanol fuel cells (DMFCs) at 0.3 watt/cc – which is a 7x improvement over their preceding fuel cell technology. What makes Sharp’s approach unique is a three-dimensional integrated stack structure through the use of thin cells produced through micro-fabrication. According to the company, the use of this technology will make it possible to develop fuel cells that have almost the same volume, but a longer continuous-use lifespan than lithium-ion batteries. Planned applications for this technology include devices such as PDAs, electronic dictionaries, and notebook computers. So despite the setbacks and delays, the micro fuel cell industry is still alive and active and research continues. Additionally, studies into non-consumer applications including auxiliary power, back-up power and remote power are also ongoing, and it will be interesting to see what breakthroughs 2009 brings.

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