These fuel-cells will not be powered by fossil fuel, but by renewable energy such as hydrogen fuel that is being used in hydrogen fuel cells. The result would be a device that could operate “for days or even weeks without refueling,” not to mention could be even smaller and lighter as it would essentially do away with the need for heavier and bulkier batteries.
However Apple admits that there are challenges in creating hydrogen fuel cell systems that are both portable and cost efficient. Given how Apple has prided their products on being green by featuring recyclable parts that are BFR- and PVC-free, moving towards renewable energy would definitely be in line with the company’s vision. Unfortunately as with most patents, it’s impossible to say if and when they will be made a reality.