MTI MicroFuel Cells has inked a deal with NeoSolar to develop fuel cells for extra-small tablet PCs and other portable devices, the companies announced Thursday.

The agreement calls for the companies to work together to integrate fuel-cell prototypes into chargers and embedded power sources for various digital products.

The news is MTI’s third development partnership for consumer mobile devices. 

The company, a subsidiary of Mechanical Technology (NSDQ: MKTY), in 2006 partnered with Samsung Electronics to develop fuel cells for cell-phone applications, and renewed its agreement for two years in 2007 (see Samsung, MTI Micro Sign Deal).

In May, MTI also said it signed a deal with an unnamed Japanese camera manufacturer to adapt its fuel-cell technology to digital cameras and other imaging applications (see Fueling More Flash).

Fuel cells, which produce power by mixing fuel with air and water between a thin, reactive film membrane, are meant to fill the so-called "power gap” caused by increasingly power-hungry devices and traditional batteries’ failure to keep pace. Advocates say they are greener than batteries, some of which contain toxic heavy metals.

But while fuel-cell believers have touted the potential of these technologies for years, releasing announcement after announcement, numerous challenges and delays have turned many former advocates into skeptics (see Fuel Cells Follies). There certainly have been far more announcements than actual products on shelves.

Based in Seoul, South Korea, NeoSolar makes what it calls “ultra-mobile portable computers,” which are smaller than traditional laptops and even tablet PCs, under the “Wibrain” brand. The annual market for ultra-mobile laptops grew from $93 million in 2003 to $343 million in 2007, according to Frost & Sullivan, which projects it will cross the $500 million mark in 2010. 

The company also makes energy products, including solar cells.