Jamie D. Holladay

Miniature Fuel Processors for Portable Fuel Cell Power Supplies

Miniature and micro-scale fuel processors are discussed. The enabling technologies for these devices are the novel catalysts and the micro-technology-based designs. The novel catalyst allows for methanol reforming at high gas hourly space velocities of 50,000 hr-1 or higher, while maintaining a carbon monoxide levels at 1% or less. The micro-technology-based designs enable the devices to be extremely compact and lightweight. The miniature fuel processors can nominally provide between 25-50 watts equivalent of hydrogen which is ample for soldier or personal portable power supplies. The integrated processors have a volume less than 50 cm3, a mass less than 150 grams, and thermal efficiencies of up to 83%. With reasonable assumptions on fuel cell efficiencies, anode gas and water management, parasitic power loss, etc., the energy density was estimated at 1700 Whr/kg. The miniature processors have been demonstrated with a carbon monoxide clean-up method and a fuel cell stack. The micro-scale fuel processors have been designed to provide up to 0.3 watt equivalent of power with efficiencies over 20%. They have a volume of less than 0.25 cm3 and a mass of less than 1 gram.

Fuel processor development for a soldierportable fuel cell system

The remarkable recent advances in wireless and portable communications devices (e.g., laptop computers, cellular phones, portable digital assistants) have fueled a need for high-energy-density portable power sources for consumer use. Similarly, interest in portable power sources has increased in the military and intelligence communities. Currently, portable military electronics are dependent on batteries to supply electrical power for long-duration missions. This poses two major problems which result from the low energy density of current battery systems: excessive weight/bulk, and reduced mission duration.

Radiolytic microscale power generation based on single chamber fuel cell operation

Proof-of-principle test results are presented for a nuclear-to-electric power generation technique utilizing closed-cycle fuel cell operation. The approach being developed is to first use the decay energy of a radioisotope to generate H2 and O2 from water, and then to utilize these species in a fuel cell to generate electricity. The principle of operation allows the device to regenerate its own reactants and operate continuously as a closed system for as long as the primary source of power, namely the radioisotope, is active. With micro engineering and fabrication techniques available today, a miniaturized integrated package of 1 cm3 in size and producing power in the 10 mW range appears feasible in a mature design. Smaller devices producing less power would also be possible. For this project, a unique fuel cell capable of utilizing mixed reactants at room temperature has been developed. The efficiency of this early fuel cell design falls in the range between 10 and 20%. Measured power output from a radioisotope fueled test cell approached 0.45 mW for several hours with a radiation leakage rate estimated at 490 mrem yr−1.

Sub-watt Power Using an Integrated Fuel Processor and Fuel Cell

A sub-watt power system is being developed as an alternative to conventional battery technology to better meet energy and power densities needed for operating wireless electronic devices, such as microsensors and microelectromechanical systems. This system integrates a microscale fuel processor, which produces a hydrogen-rich stream from liquid fuels, such as methanol and butane, and a microscale fuel cell, which uses the hydrogen as fuel to produce electric power. Battelle, Pacific Northwest Division and Case Western Reserve University are developing and demonstrating this technology for the Defense Advanced Research Projects Agency. This paper describes work being performed by Battelle on the fuel processor, in particular, catalyst and reactor design and testing.