Portable power supply structure

Japanese and Korean companies are the most involved in portable power units for electronic devices, and have recently launched a series of products that are mainly based on direct methanol-fuelled PEFC; large-scale commercialization of these devices is planned in the coming years.

For moderate energy demands in portable electronics, supercapacitors are suitable as rechargeable stand-alone power sources. In conjunction with rechargeable batteries in uninterruptible power supplies, supercapacitors can handle short interruptions and can extend battery life.

Two broad definitions of portable FCs exist in the literature. The first definition includes FCs that are built into – or charge – products that are designed to be moved, excluding vehicles.

To power this range of products, portable FCs are being developed in a wide range of outputs, ranging from less than 5 W up to 500 kW. This range has necessitated further sub-classification; 'FC Today', for example, classify units with power up to 5 W as 'micro FC', and units up to few hundred watts as 'mini FC'.

For military applications, another advantage of PEFC-based power systems is that they could be easily masked against thermal sensors, while other generation systems operate at higher temperatures and emit much waste heat. Here, cost is not a problem; fuel storage and supply logistics are the main limiting factors.

This distinction is useful because smaller personal devices – such as cameras and mobile phones – tend to draw about 3 W, while laptops and other large electronics devices can use up to 50 W. Other criteria are also available in the literature.