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Low cost planar DMFC cathode with integrated air pump

IP.com Disclosure Number: IPCOM000005816D
Original Publication Date: 2001-Nov-08
Included in the Prior Art Database: 2001-Nov-08
Document File: 4 page(s) / 684K

Publishing Venue

Motorola

Related People

Chenggang Xie: AUTHOR [+3]

Abstract

Low cost planar DMFC cathode with integrated air pump

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Low cost planar DMFC cathode with integrated air pump

Chenggang Xie, Jeanne Pavio and Joseph Bostaph

Wireless power sources for portable electronics should be lightweight, and have small form factor, high efficiency and high energy density.  Currently this requirement is met almost exclusively by battery power.  Direct Methanol Fuel Cells (DMFC) have the potential to replace the widely used rechargeable batteries because of their potentially higher energy density.  However, in order to achieve high energy density, it is absolutely critical to minimize the physical dimensions of the overall DMFC system.  This includes any auxiliaries necessary for producing conditioned power for the user and any amount of non-methanol liquid, such as water, carried in the system.  In one of the approaches developed at Motorola Labs, an air pump is used to provide oxygen to the cathode surface and remove water accumulated on the surface.  Water is then re-circulated into the mixing chamber.  This technique significantly reduces the amount of water stored in the system.  Therefore, it increases the system’s energy density.  Up to now, off-the shelf pumps are used; in spite of their large size and high power consumption.  Obviously, they are not suitable for portable energy power levels the program is set to achieve.  Therefore, there is a desire to develop a low cost, planar DMFC cathode with an integrated air pump.  It is believed that successfully developing such a cathode gives us an edge over our competitors in the field.

Motorola Labs has demonstrated the use of an air pump to supply oxygen to the electrode surface and re-circulate water.  Based on our current understanding, the desired pumping rate for air is about 400 ml/min for a 1 W DMFC system.  Power consumption for an air pump to achieve the flow should be less than 100 mW. The preferred geometry of the pump is a planar structure, which is consistent with the planar structure of our fuel cell.  Recently, Honeywell Labs at Plymouth, MN has developed an electrostatically actuated, dual-diaphragm pump (DDP) under a DARPA program led by Dr. Cleo Cabu...