Stack Durability Research Articles

Development of Fuel Cell Stack Durability based on Actual Vehicle Test Data: Current Status and Future Work

Development of Fuel Cell Stack Durability based on Actual Vehicle Test Data: Current Status and Future Work

Development of a small vehicular PEM fuel cell system

This paper reports the development of components in a stack assembly and measurements of electrochemical characteristics of a proton exchange membrane (PEM) fuel cell stack. A novel test fixture together with a superposition approach is utilized to assess the Ohmic resistance across the stack. Then, a Tafel-kinetic equation for describing the voltage and current curve for all processes including electrode activation, Ohmic resistance and mass transfer was reported. It was found that the Ohmic resistance inside the fuel cell stack was markedly impacted by clamping torque of the stack. An optimum clamping torque of 90 kgf cm was determined based on measured Ohmic resistance. Uniformity and stability in the stack was verified by measuring cell voltage and temperature distribution. Finally, stack durability was tested by impelling a buggy over a relatively long duration.

Performance investigation of 2.4 kW PEM fuel cell stack in vehicles

The aim of this paper was to investigate the behaviour of a 2.4 kW PEM stack in dynamic conditions typical of vehicle applications, including urban driving cycles taken from European legislation. A management strategy of the main fuel cell system auxiliary components was chosen with the scope of minimizing the energy consumptions associated to humidification, cooling and reactant feeding operations. The results obtained provided the definition of a correlation diagram power–temperature, in particular the application of a statistical indicator of the cell voltage uniformity (coefficient of variation C v ) allowed the specification of a reliable working field in terms of stack durability in real applications. The tests effected on European driving cycles R40 and R47 evidenced that stack power increase rates up to 500 W/s were acceptable for the fuel cell system used in this paper, while for higher dynamics the stack working regularity was limited by low stoichiometric ratio values ( R < 1 ) . However, during fast transient phases (10 s as order of magnitude) excursions outside the optimal conditions of power, temperature and R resulted acceptable in terms of C v (mostly lower than 4%).

Compatibility and Durability of Fuel Cell Materials

In fuel-cell systems, components such as plates, gaskets, and hoses can impact stack durability by releasing species in a manner that adversely affects the mechanical- and chemical properties of the membrane electrode assembly (MEA) or those of the components themselves. Contamination may originate from the main constituents of the components, from incomplete processing of the materials, or from small quantities of additives used to facilitate processing. Cell tests and autopsies reveal some of the complex interactions that can lead to failure and show that periods of dormancy can exacerbate the impact of the contaminants. Compatibility tests have been performed to help identify materials that meet practical durability, cost, and performance targets.

SOFC Stack Development at United Technologies Corporation

United Technologies Corporation is developing a low-cost solid oxide fuel cell stack technology that offers long-life durability and thermal cycling robustness for building cooling heating and power applications. Our design philosophy decouples the coefficient of thermal expansion and oxidation requirements for metallic interconnects, enabling us to use oxidation resistant nickel-based superalloy interconnects. Innovative interconnect designs along with non-contaminating seals offer tremendous advantages in producing long-life, thermal cycle tolerant stacks. 1-cell and 3-cell stack tests for up to 4500 hours and 20 thermal cycles show excellent stack durability.