Scientists at Motorola have demonstrated a prototype of an integrated, ceramic-based miniature direct methanol fuel cell (DMFC) system and have also built several of the key components required for a miniature, ceramic-based reformed methanol to hydrogen fuel cell (RHFC).
According to Motorola, the key to successfully miniaturising a DMFC system for small consumer electronics is scaling down the system components surrounding the actual fuel cell device.
Previous DMFC systems have used discrete components to process and deliver methanol to the fuel cell, determine the methanol concentration within the fuel cell, and separate the carbon dioxide generated within the fuel cell from the liquid fuel.
Last year, Motorola announced a multi-layer ceramic technology for processing and delivering the fuel and air to the fuel cell membrane electrode assembly (MEA).
The researchers have now integrated many of these other components, including a methanol concentration sensor and liquid-gas separation for CO2 release, directly in the ceramic device. Miniature pumps and control and conversion electronics were also built into the device.
The ceramic DMFC experimental assembly, measuring about 5cm by 10cm and less than 1cm thick (without electronics or fuel) reportedly produces over 100mW net power continuously. In the lab, the fuel cell system has been operated continuously for a week at a time, with little degradation in performance.
Motorola Labs is also doing research on a related fuel cell technology in which methanol is converted to hydrogen as needed and supplied to a more conventional hydrogen fuel cell MEA.
Similar to the DMFC, the key to successfully miniaturising an RHFC system is scaling down the system components surrounding the actual fuel cell device and integrating them both structurally and thermally.
Previous RHFC systems have used discrete metal components to vaporise the methanol fuel, reform the methanol to hydrogen, clean up the output of the reformer, and house the fuel cell stack.
Using its multi-layer ceramic technology, Motorola researchers are said to have demonstrated an integrated vaporiser, a miniature methanol steam reformer, and separately, a miniature chemical heater, which make up three of the key components in the RHFC system.
The reformer assembly, measuring 38mm x 13mm x 1mm thick, integrates both the fuel vaporiser and methanol steam reformer. The chemical heater, with the same dimensions as the reformer, is said to provide a simple structure for converting a percentage of the methanol fuel into heat to drive the reformer reaction.
Eventually Motorola plans to integrate all of these components, along with a fuel cell, into a single device producing 1W or greater power.