Apple has never shied away from filing patents that describe renewable energy-powered devices like solar-powered and movement-powered phones and tablets and the company is still doing just that. In a recent filing of a renewed patent for a "portable and cost-effective fuel cell system for a portable computing device," the company envisions a device that could use a number of different energy sources to power it through a fuel cell.
While so far the company has yet to produce one of these renewable energy-powered machines, Apple is likely going ahead and patenting anything that they could foresee one day integrating into their devices. In the patent Apple explains why using fuel cells is something they're interested in:
"Our country's continuing reliance on fossil fuels has forced our government to maintain complicated political and military relationships with unstable governments in the Middle East, and has also exposed our coastlines and our citizens to the associated hazards of offshore drilling. These problems have led to an increasing awareness and desire on the part of consumers to promote and use renewable energy sources."
The patent describes a design where the energy could come from "a fuel cartridge which is detachably affixed to the fuel cell system," meaning that when a fuel source runs out, you would need to replace a fuel-filled cartridge instead of recharging like with a battery. Apple names potential fuel sources as compressed hydrogen gas or liquid hydrogen, sodium borohydride, sodium silicate, lithium hydride, magnesium hydride, lithium borohydride and lithium aluminum hydride.
The idea for this device isn't far-fetched and, in fact, the timing of the patent renewal lines up with a fuel cell breakthrough related to Apple. Just recently British company Intelligent Energy developed an iPhone 6 that could go a week running off a built-in hydrogen fuel cell without needing to recharge the battery. The company, which is rumored to be working with Apple, incorporated a fuel cell system into the current iPhone 6 without having to change the size or shape of the device.
In the prototype, the hydrogen gas was refueled through an adapted headphone socket, but in the commercial version the company said that disposable cartridges filled with hydrogen powder would be slid into a slot in the bottom of smartphones and they'd be able to power the phones for a full week of normal use without having to plug in.
In the patent, Apple states that the fuel-filled cartridges could potentially power the device for days or even weeks without refueling. The device described in the patent is most likely a MacBook because there are several mentions of the MagSafe connector used on Apple laptops instead of the Lightning connector used on iPhones and iPads.
It's likely that a real-life version of this device would still include a rechargeable battery as a back-up energy source, much like the Intelligent Energy iPhone did.