Fuel Cell Research Uses Alternative Approach

Sep 20, 2006 11:04 AM
By Mark Valentine, Technical Editor, Power Electronics Technology

In addition to electrical testing, another high-throughput mechanical screening process has been developed to test the tensile strength of the membrane compositions. In this test, the force required to perforate the membrane is carefully measured in a rapid, point-to-point fashion. When performed after exposing the membrane to operating conditions, mechanical strength serves as an indicator of membrane durability, which is one of the major limitations of today’s membrane technology. A more durable, longer-lasting membrane would equate to lower cost per unit energy.  Membranes rupture due to chemical degradation and mechanical stresses, causing fuel crossover, drastic drops in performance, and require replacement of the fuel cell.

A final screening test measures both the permeability and absorption of water in parallel at multiple points on the library. Water is essential to proton transport within the membrane. Today’s membranes dehydrate at temperatures above 80°C, posing a limit to the operating temperature. Operation at higher temperatures, however, would allow the use of less expensive (less pure) hydrogen fuel, such as reformed methanol. As a result, achieving membrane hydration at higher temperatures is another method of making fuel cells more cost effective.

The most difficult aspect of this process of screening is that the membranes must have a combination of several complex properties: ionic conductivity, chemical stability, and water transport and sorption. The strategy behind the use of this screening process is to evaluate the properties of blended materials in order to avoid the more costly synthesis of a single material that has the multiple desired characteristics. The research primarily seeks to minimize the total amount and the unit cost of the material that provides this combination of properties.

This project is sponsored by a grant from the Department of Energy (DOE). Dr. Meredith is presently working with Arkema, the primary grantee and a global chemical company, in the use of this process to evaluate new PEM materials. Recently Dr. Meredith was also awarded a competitive Honda Initiation Grant to continue this research area. The project has already produced positive results, so it’s not too soon for power designers to begin thinking about the best circuit topologies for interfacing familiar loads to PEM fuel cells.

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