Using Fuel Cells To Power Mobile Devices no Trivial Challenge, Apple Patents Show

increasingly complex, patents on Apple’s behalf for five years, with no sign of any commercial product. In June 2010, inventors Bradley Spare, Vijay Iyer, Jean Lee, Gregory Tice, Michael Hillman and David Simon filed for a “Fuel Cell System to Power a Portable Computing Device.” The patent document (2011/0311895) describes a stack of individual fuel cells, ganged together to increase the voltage, with bidirectional control communication between the stack and computer. As a “consequence” of the increased consumer awareness “to promote and use renewable energy sources” in portable devices, CE manufacturers “have become very interested in developing renewable energy sources for their products, and they have been exploring a number of promising renewable energy sources such as hydrogen fuel cells,” the patent document says. Hydrogen “can potentially achieve high volumetric and gravimetric energy densities, which can potentially enable continued operation of portable electronic devices for days or even weeks without refueling,” it says. “However, it is extremely challenging to design hydrogen fuel cell systems which are sufficiently portable and cost-effective to be used with portable electronic devices.” Since individual “proton exchange membrane” (PEM) fuel cells, using hydrogen as a fuel, generate voltages that are too low to run a mobile device, Apple has proposed electrically daisy-chaining many PEM cells together in a series, the filing says. A set of 25 PEM fuel cells is needed to deliver the 12.5-17.5 volts required to drive a laptop, mobile phone or “other type of compact electronic device,” it says. US 2011/0256463 from April 2010 acknowledged that connecting fuel cells in series to increase the voltage can be problematic. For example, if one cell fails, the whole stack may shut down, it says. So Apple has also been looking at cell connections in parallel, to give low voltage at high current, which is then up-converted to the working voltage needed to drive a mobile device. “The parallel configuration of fuel cells may represent a significant improvement in reliability over a series configuration,” Apple says. The patents leave no doubt that using fuel cells to power mobile devices isn't a trivial challenge.