Avista Labs redesigns PEM fuel cell

Pam Boschee

Associate Editor

In October, Avista Laboratories Inc., Washington Water Power`s (WWP) affiliate, received a $2 million technology development award from the Department of Commerce`s National Institute of Standards and Technology (NIST) Advanced Technology Program. WWP is adding another $1.22 million over a two-year period for Avista Labs` continued development of its proton exchange membrane (PEM) fuel cell. Avista Labs plans to work on technology that will increase the energy density of its fuel cell design, providing more power in the same footprint. It will also develop multiple fuel processing approaches using propane, methane and methanol as base fuels to integrate into its fuel cell subsystem.

Traditional PEM fuel cells, which are based on stacked graphite-plate architecture, are expensive to build, can`t be maintained by the user, and require that the entire unit be taken off-line for maintenance and repairs.

Avista Labs PEM generator`s modular design replaces graphite with thermoplastics, and uses less expensive and more readily available materials for other components. Kim Zentz, Avista Labs` president, said graphite accounts for 80 percent of the Ballard fuel cell cost. In contrast, thermoplastics account for only 5 percent of Avista Labs final fuel cell cost.

Power cartridges, the size of VCR cassettes, each supply 60 W (Avista Labs plans to increase the power density to 200 W per cartridge). The cartridges are racked, and may include 12 cartridges in a subrack (providing 720 W total). The subrack manufacturing prototype is roughly the size of a small air conditioner, and weighs about 94 lbs. (see photo). Subracks can be connected in series or parallel. Five or six subracks in a cabinet result in a refrigerator-sized unit, illustrating its space-saving feature.

An embedded control system continually monitors the modules` moisture, temperature and performance. If a problem is identified, the control system shuts off the gas to the identified cartridge and allows the remaining ones to operate. The problem cartridge may then be removed and bypassed as power generation continues uninterrupted.

Currently, the Avista Labs fuel cell uses an off-the-shelf membrane, but plans to develop a proprietary membrane.

The fuel cell operates in temperatures ranging from minus 20 C to 35 C using hydrogen gas (see figure), which can be reformed from a variety of sources, including methane, propane, methanol, ammonia, ethanol, natural gas, liquefied petroleum gas, diesel, gasoline and jet fuel. Hydrogen is also available as a byproduct of many industrial processes. However, a high degree of purity is required to ensure long component life within the power modules.

PEMs need a consistent supply of moisture to operate. Because of its self-humidified operation, traditional support systems such as air compressors and liquid cooling systems are not required-only a fan and air filtration subsystem make up its balance of plant.

In October, Zentz said alpha testing continued, logging 1,000 continuous hours of operation of a subrack up to that time.

Beta testing is slated for May 1999. Zentz said the cost to the customer would depend on the final manufacturing specifications as the product development continues. The goal is to bring the fuel cell to customers at a price equivalent to average energy costs per kWh. Targeted applications are 2 kW to 10 kW stationary installations for small business or commercial customers, and backup generation.

Click here to enlarge image

The modular design makes the unit scalable to match a customer`s specific load characteristics. Photo courtesy of Avista Labs.

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