Apple Considers a Shift to Highly Advanced Fuel Cell Plates for Portable Devices
On October 20, 2011, the US Patent & Trademark Office published a pair of patent applications from Apple that reveal their consideration if not right-out intention of shifting to fuel cell plate power for portables. While supplying more power in a smaller space, one of the side benefits may be a portable device's resistance to water damage. Report Updated Dec. 2011
Apple's Patent Background
Fuel cells provide electrical power by converting a source fuel, such as hydrogen or a hydrogen-containing compound, into an electric current and a waste product by electrochemical means. In particular, a fuel cell contains an anode, a cathode, and an electrolyte between the anode and cathode. Electricity may be generated by two chemical reactions within the fuel cell. First, a catalyst at the anode oxidizes the fuel to produce positively charged ions and electrons. The electrolyte may allow ions from the oxidation process to pass through to the cathode while blocking passage of the electrons. The electrons may thus be used to drive a load connected to the fuel cell before recombining with the ions and a negatively charged atom (e.g., oxygen) at the cathode to form a waste product such as carbon dioxide and/or water.
Because fuel cells are typically associated with low voltages (e.g., 0.5-0.7 volts) multiple fuel cells may be combined to form a fuel cell stack. For example, a fuel cell stack may contain a number of stacked bipolar plates. Each bipolar plate may provide an anode on one side and a cathode on the other side. To form fuel cells within the stack, the catalyst and the electrolyte may be placed in between the bipolar plates. The fuel cells may then be connected in series to increase the voltage of the fuel cell stack.
However, existing fuel cell stack architectures may have a number of disadvantages. First, each fuel cell may represent a single point of failure in a series-connected fuel cell stack. In addition, a fuel cell may be subject to a number of failure modes, including accumulation of nitrogen in the anode, poisoning of the catalyst, degradation of the electrolyte, and/or water flooding in the anode or cathode. Consequently, the reliability of a fuel cell stack may decrease as the number of fuel cells in the fuel cell stack increases.
Second, bipolar plates for fuel cell stacks are typically manufactured using materials that are both conductive and corrosion-resistant, such as stainless steel. However, the high density of such materials may result in heavy bipolar plates that restrict the use of fuel cell stacks in portable applications. For example, adoption of a fuel cell stack design as a power source for portable electronic devices may be hampered by the weight of the resulting fuel cell stack, the majority of which is in stainless steel bipolar plates.
Hence, the use of fuel cells as power sources may be facilitated by improvements in the reliability, weight, and/or size of fuel cell stacks.
Apple's Parallel Fuel Cell Stack & Reduced-Weight Fuel Cell Plate
Apple's patent FIG. 1 shown below illustrates a schematic of a system in accordance with the disclosed embodiments. The system may provide a power source to a portable electronic device, such as a mobile phone, laptop computer, portable media player, and/or peripheral device. As shown in FIG. 1, the system includes a number of fuel cells 110-124 arranged in a fuel cell stack 102, a power bus 104, and a voltage-multiplying circuit 106.
As shown in FIG. 5 above, the corrosion-resistant sealant may also be applied in the form of one or more co-molded gaskets 502-504. Gaskets 502-504 may cover one or more edges of the fuel cell plate with an elastomer such as silicone. In addition, gaskets 502-504 may be co-molded onto the fuel cell plate to seal off exposed edges of the substrate both along the perimeter of the fuel cell plate and around holes that span the layers of the fuel cell plate. Gaskets 502-504 may also include channels and/or passages to allow water vapor to escape from the surface of the fuel cell plate if the elastomer covers the cathode side of the fuel cell plate.
Apple's patent FIG. 3 shown below illustrates a set of fuel cells 302-308 in accordance with the disclosed embodiments. Fuel cells 302-308 are sandwiched between two cathode endplates 348-350 and are formed from four cathodes 310-316 and three anodes 318-322. As shown in FIG. 3, fuel cell 302 includes cathode 310 and anode 318, fuel cell 304 includes cathode 312 and anode 320, fuel cell 308 includes anode 320 and cathode 314, and fuel cell 308 includes anode 322 and cathode 316.
Apple states that the fuel cell stack may be used in lieu of a battery pack in driving a load.
Both of Apple's patents respectively titled "Parallel Fuel Cell Stack Architecture" and "Reduced-Weight Fuel Cell Plate" were published today and originally filed in April 2010. While the patents were highly technical and boring to read, the message was what was important: more power, smaller package: Gooood! Update December 22, 2011: Also see our latest report on this subject matter titled "The Race is on for Next Generation Fuel Cell Powered Devices."
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