Apple is looking to create lighter, more efficient hydrogen fuel cells for portable devices, according to a report.

Apple Insider spotted two new patent applications published by the US Patent and Trademark Office that outline how Apple could build smaller and lighter hydrogen fuel cells for portable devices.

Fuel cells work by converting a fuel into an electrical current. Though an individual cell creates only a low voltage, a stack of them can be used to power higer-voltage devices.

However, fuel cells are typically quite heavy and a the size of a stack needed to power a portable device such as a mobile phone would make the device impractically heavy.

Apple's patents suggest that this problem could be overcome by arranging the cells in such a way that they can share electrodes between adjacent fuel cells in a stack, making the stack lighter.

Though we've not heard of Apple considering hydrogen fuel cells before it has looked at other greener energy sources such as solar power before, even applying for patents involving solar-power sources for portable devices.

The hydrogen fuel cell patent applications were first filed in April 2010.