PEM Fuel Cell Bus Stack Durability:Improvements and Current Research

Over the past 30 years Ballard’s PEM fuel technology evolved from proof-of-concept single cells via sub-scale and full-scale prototype systems to products in the areas of motive power (buses and materials handling), back-up power, co-generation, and distributed power generation which have been deployed extensively in demonstration programs  and field trails.  Today, Ballard is a leader in fuel cell stack design and manufacturing with products being commercially deployed in the materials handing and back-up power markets which both benefit from attractive financial value propositions. Furthermore, extensive research and development is also focused on bus stack and large scale distributed generation technology.

In early technology demonstrations and field trials specifically in the transportation sector fuel cell performance was the key attribute under consideration; however, today the emphasis is on durability and cost which are the two major challenges that still hinder large-scale commercialization of fuel cell technology across all markets.

Since 1991 Ballard’s fuel cell bus technology has been deployed in a variety of demonstration projects and today 49 fuel cell buses are in operation worldwide. The largest bus fleet deployed in 2009 in Whistler, B.C. has accumulated more than 150,000 hours of operational hours and a total driving distance of >3 million kilometers. The figure on the right shows the average cell performance of the buses which exceeds the warranted operational life of 8000 hours of the HD6 stack.

As opportunities in the fuel cell bus market have accelerated over the last decade and with the development of over six generations of fuel cell modules, Ballard has overcome technical barriers related to power density and reliability. To date, the bus transportation platform developed by Ballard has been proven to meet the demands of range and duty cycle expectations, but the key barriers pertaining to cost and durability under the wide range of operating conditions necessary for transportation fuel cell stacks still remain.

Ballard’s overall activities on reducing product cost have been driven by several approaches; (1) product design improvements that include reduced platinum loadings, lower part counts, and enhanced durability, (2) reduced sourcing costs through lower materials costs and increased volumes, (3) increased manufacturing efficiencies including use of continuous, automated assembly, (4) production scale up through increased market penetration. Since 2003 Ballard has achieved substantial cost reductions while increasing stack operational life 4-fold.

Ballard’s large numbers of demonstration programs and field trials have been instrumental in providing insight into stack and MEA failure modes and this understandingtogether with modeling and fundamental research has been a driver in durability improvement through MEA design opportunities and operational mitigation strategies.

The work that will be presented will provide an overview of Ballard’s Fuel Cell bus program, discuss the different aspects of stack durability that has been achieved over the last 10 years, and provide an insight into current research and development that is needed to narrow the durability and cost gap for large-scale commercialization.