Setting the Record Straight
By Bill Moore
How durable are today's automotive fuel cell stacks? That's the question I put to DaimlerChrysler's Wolfgang Weiss in Sacramento during a SAE fuel cell workshop. The initial answer he gave me was 200 hours, a number that surprised me and also resulted in the headline to my first report from the event in late February, 2004.
That headline also set in motion a flurry of emails and telephone calls that eventually resulted in the president and CEO of Ballard Power Systems, which supplies the fuel cell systems to DaimlerChrysler, Ford and Honda, asking to be interviewed so he could personally set the record straight. During the course of our 40-minute long discussion, EV World learned more about the engineering issues of fuel cell stack development than we've gleaned from numerous symposiums. We also learned a lot more about Ballard's business plans and engineering goals.
The first question I put to Campbell was how durable are Ballard fuel cell stacks? He responded forthrightly by explaining that each of the three major types of systems Ballard develops, has its own durability profile. Whereas the company's Nexa standby power unit is designed and warranted for 1,500 hours of operation, which Campbell said is comparable to internal combustion engine standby generators, Ballard's long-life co-generation system built for the Japanese home market is designed to operate continuously for 20,000 to 40,000 hours or more, running 24 hours a day for at least 10 years.
Automotive fuel cell applications, however, are a breed apart. "The automotive product has a targeted life of about 5,000 hours, which is equivalent to 150,000 miles... basically the accepted life of a vehicle."
But the technology isn't at that level yet, Campbell explained.
One Apple at a Time
"As you know, we've got vehicles that we've put into the market with our OEM partners, Honda, DaimlerChrysler and Ford Motor Company, that are out there for two to three year field trial programs. So, in two or three years, you can expect the car is going to run 1,500 hours, maybe 2,000 hours, depending on the duty cycle. We've designed these products to support that level of durability.
"In terms of achieving the 5,000 hours target for the ultimate car, we're... taking this thing one step at a time. You can design a fuel cell for long-life or you can design it for transient response and power density, power efficiency, fuel economy, freeze start, low temperature capability; all these different, competing parameters for design and as you would expect, in the development stage, you pick one apple at a time. Ultimately, when we go commercial, we've got to meet all those parameters."
Campbell said that for the moment, Ballard and its partners are focused on fuel efficiency, transient response and vehicle performance.
The Layers of the Cake
I asked Campbell to take a moment and explain exactly how a fuel cell module is constructed. He likened it to a five or seven layer cake with the center layer representing the proton exchange membrane -- from which the acronym PEM is derived. It is this thin, Saran-wrap like material that allows the passage of the hydrogen proton through the membrane while blocking the electron, thus creating the necessary electric circuit. He added that the thickness of the membrane is an important variable in the design, determined by the nature of the application and desired durability.
Presumably, though we didn't go into this, the thicker the membrane, the more durable it is, but the less responsive it is to the demands of an automotive application. Conversely, the thinner the membrane, the more responsive it is, but less durable. So, the science of modern fuel cell technology is, in a way, the art of getting just the right thickness, consistently to meet the needs of the vehicle manufacturer and their customers.
Back to the cake. On both sides of this layer are the platinum catalyst electrodes, the anode on the hydrogen gas side and cathode on the oxygen side. It is the platinum that is the most costly single material in the fuel cell, representing some 40 percent of the device's cost.
On outside of the electrode layer are the carbon diffusion modules which separate out the hydrogen and oxygen atoms so they can reach the platinum catalyst. The last two layers are the flow field plates that channel and evenly disperse the gases across each cell. These can be made of thermo-set carbon or metal, an alternative being explored by Honda. [Click to view expanded fuel cell componentry illustration].
To create a fuel cell stack, you literally "stack" the individual cells together, much like the plates in a lead-acid battery, to build up the collective voltage potential of the stack. The more cells, the higher the voltage.
Will Asia Leap-Frog Detroit?
Campbell believes that emerging markets like India and China could well end up leading the world in the deployment of large numbers of fuel cell-powered vehicles, not because of their technological prowess necessarily, but because they haven't invested as heavily in 20th century engine technology as has the West. The numbers of automobiles in both countries are still relatively small compared to the West and their automotive industries remain comparatively immature, though both are rapidly expanding with the recent emergence of an increasingly prosperous middle class.
The relative simplicity of a fuel cell and the recyclable nature of the materials in it, which consist largely of carbons and plastics, makes it ideally suited for low cost, high volume mass production, something the Chinese, in particular, have become very adapt at. In his words, a fuel cell is "environmentally friendly in its operation and in its disposal, unlike batteries."
This view naturally assumes that the costs of fuel cells can be dramatically dropped from today's ionospheric levels, and also assumes that the first applications in these countries will not be in private passenger cars, but in mass transit buses upon which the masses of both countries heavily depend.
In this respect, Campbell may not only be right on target but way ahead of the competition, for when it comes to fuel cell-powered buses, Ballard is just about the only game in town.
The company began experimenting with fuel cell buses back in 1993. Today, the company has thirty Mercedes Citaro buses powered by Ballard fuel cells in daily revenue service in ten European cities, an achievement in which Campbell is rightly proud.
"This is probably the biggest field trial in history and we are gaining enormous experience with these vehicles. The people love them. The drivers love them. The passengers love them."
He recounted a recent trip to London in December, 2003 for the official inauguration of its three fuel cell buses. They drove the bus across Tower Bridge in East London and parked it next to the classic red, double-decker London bus. Campbell said you could feel the vibrations from the diesel bus inside the Citaro bus, even though it was running.
"The contrast was striking," he said. He added that these buses trials are going to help people better understand what fuel cell technology is all about and get comfortable with it.
No Breakthroughs, Just Hard Work
I asked Campbell about where and why fuel cells fail. He replied that there are two basic categories: in the ancillary support components that process the hydrogen and oxygen, plus humidify and cool the stack; and in the membrane, itself, which he admitted is a "fragile component."
"Being able to come up with a design and a system that allows that membrane to live for a very long time, under very demanding circumstances is one of the challenges for the industry."
In order to tackle this challenge, Ballard is working with virtually every company who is actively experimenting with new membrane materials. While Campbell is excited about some promising developments, he said he couldn't characterize any of them as "breakthroughs."
"In this business, it's a series of hard-fought inches of progress that we make on a steady basis every day in our laboratories." He noted that he considers Ballard's laboratories as the best in the world for testing and developing fuel cell technology, but like Edison's famous line, "it's 99 percent perspiration and one percent inspiration."
He is, however, excited about several recent directions research has taken them, including eventually replacing the noble metals like platinum with lower cost materials in the catalyst.
The Technical Hat Trick
Ballard's goal this year is to accomplish what Campbell referred to as the "technical hat trick." This means the company wants to demonstrate in 2004 a fuel cell that is "best in class" for durability, lower costs by reducing the amount of platinum group metals, and shows the ability to freeze start at below 0 C (32F), a "trick" recently demonstrated by Honda.
While Campbell acknowledged Honda's recent success, he added the caveat that it's not enough to show this capability at the expense of durability, coming back again to the challenge of incorporating all these desirable but often conflicting characteristics into a single fuel cell. "While one guy can do a low-cost stack, and another guy can do very durable stacks, and a third guy might do a stack that starts up in cold weather, we think the leadership is going to be characterized by the ability to do all three of those things at the same time, without giving up power density, performance, efficiency or any of the other important parameters."
Evolving Fuel Cell Supplier Chain
Like any manufacturer, Ballard is dependent on the quality of the materials supplied to it by its vendors. Here Campbell reported, with an obvious upbeat tone in his voice, that the fuel cell vendor marketplace is rapidly evolving, as more and more highly qualified companies jump into the ring.
"A couple, five years ago, when we needed something, we basically had to do it ourselves, whether it was a hydrogen valve or a component, anything that we need for our system, there weren't suppliers out there willing to make the investments or willing to participate in this industry. That's all changed. We see more and more world-class suppliers coming to the table saying, 'I am willing to invest in fuel cells, what do you need? How can I help you?' "
While the quality of the supplier chain is improving, so is the industry's recognition of the need for uniform technical standards, as illustrated by the problem of hydrogen. One of the fastest ways to wreck a fuel cell is to allow impurities into the system. One of the worst culprits is carbon monoxide, which can quickly deteriorate the platinum catalyst.
In order to insure a PEM stack's longevity, you need to feed it extraordinarily pure hydrogen; I've heard something on the order of five nines or 99.999 percent pure. That appears to be one reason why the industry is evolving away from on board reformers of carbon-based fuels. Achieving that level of purity complicates the system and adds significant cost and efficiency penalties. It also argues for the need to create hydrogen from energy sources other than carbon-heavy fuels such as natural gas or even methanol; and here water electrolysis would appear to have the upper hand.
For his part, Campbell is confident that a hydrogen infrastructure will evolve, and in Part Two of our discussion, he elaborates in some detail on the factors he sees driving it at an increasing pace. For him the larger challenge is that of hydrogen storage, getting enough hydrogen on board the vehicle to provide it with acceptable range. At present, he said, most prototype cars carry about 2.5 kilograms of hydrogen, enough for, at most, 150 miles range. He said we need to get this amount up to 5 to 7 kilograms. [See EV World's report last week on the hydrogen storage challenge]
In terms of the cost of hydrogen, he pointed to the recently released National Research Council report that suggests we may be able to someday create hydrogen that is, on a cost-per-mile basis, less expensive than gasoline.
"We see a lot of challenges, but also a path to solving those challenges."
Part Two Concluded Next Week