Toshiba today unveiled its latest fuel cell prototypes, this time targeting Flash- and hard disk-based MP3 players. The test units are integrated into the players rather than attached to them externally.

Don't expect to see the players or the fuel cells on sale any time soon - even Toshiba now reckons they won't see commercial availability until 2007 at the earliest. The two units are based on the pump-less fuel cell system Toshiba unveiled in June 2004. Then, it was forecasting it would be able to commercialise the technology in 2005, after releasing a PC-oriented version late 2004.

Clearly, it has revised its timeline somewhat...

In its latest announcement, Toshiba discussed two direct methanol fuel cells, one generating 100mW of power, the other 300mW. Both fuel cells are built into audio players, one using Flash storage, the other of the HDD type, and can be refilled.

Both cells store methanol fuel in a 99.5 per cent concentration before diluting it to ten per cent for the power-producing reaction to take place. The reaction chamber comprises two membrane-separated zones, one containing the methanol, the other containing air. Both zones have an electrode. The methanol reacts with water in the presence of a catalyst to produce hydrogen ions and electrons. The ions and electrons pass through the membrane to react with the oxygen to form water - which can be used to dilute the methanol. Besides power, the only byproduct of the reaction is carbon-dioxide.

The two cells essentially differ in capacity: 3.5ml for the 100mW unit and 10ml for the 300mW cell. The 100mW cell can generate sufficient current for 35 hours of playback time, while the larger unit can operate the HDD-based device for 60 hours. ®