Fuel cell futures no longer a dream

  • 02-Nov-2015 09:08 EST
Honda Clarity Fuel Cell Stack.jpg

Honda PEM-type fuel cell as used in the Clarity FCV. For this compact new power unit, Honda’s original wave flow-channel separators were further advanced and the number of cells was reduced by 30%. Its cells measure only 1-mm each, reducing their total thickness by 20%.

The knock on fusion power is that “It is the energy source of the future, and it always will be.” It has seemed like the same criticism could be levied against fuel cell vehicles, as their seemingly magical ability to turn stored hydrogen and atmospheric oxygen into motive power for personal transportation — with only water as a by-product emission —has remained tantalizingly out of reach for decades.

Indeed, some environmentalists charged that the George W. Bush administration’s support for automotive fuel cells was a cynical play to perpetuate fossil fuel consumption, because, they insisted, fuel cells weren’t a realistic automotive power source.

But the truth is, as manufacturers begin to dribble out hand-built, lease-only, limited-market fuel cell cars to meet California’s zero-emission requirements, the technical obstacles to fuel cells have been overcome. What remains is some challenging crossing of ‘t’s and dotting of ‘i’s, because exorbitant costs and challenges like freezing temperatures have been left in fuel cells’ rear-view mirror.

“We are looking at fuel cell vehicle production to exceed tens of thousands by 2020,” predicts Morry Markowitz, president of the Fuel Cell and Hydrogen Energy Association. “Some of the leading manufacturers have spent billions of dollars and products are now reaching showrooms,” he said. “That speaks volumes to the commitment these companies have and the future of this technology."

“The major challenge we’re facing is the scale-up, both for the infrastructure and for the mass production of vehicles,” stated Bryan Pivovar, Fuel Cell Group Manager for the National Renewable Energy Lab. While breakthroughs in basic science used to stand in the way of practical fuel cell vehicles, those obstacles have been overcome, he said. “Now, we’re to the point where we’re pretty close and incremental advances might be sufficient.”

The march toward production is proceeding with a certainty unseen previously. At the 2015 Tokyo Motor Show, Honda introduced its next-generation Clarity Fuel Cell car that it will begin leasing to Japanese customers in March, 2016.  In his introductory remarks at the show, Honda President and CEO Takahiro Hachigo acknowledged that the road to production has been a long one.

“Approximately 13 years ago, in December 2002, Honda opened the door to the future by becoming the world’s first automaker to put the ultimate clean car, a fuel cell vehicle, into practical use,” Hachigo said. “Since then, Honda has been advancing and improving the performance of its fuel cell vehicles, including success in making it possible to drive a fuel cell vehicle in areas with cold climates, which was thought to be difficult.”

Toyota showed the far-out FCV Plus concept and the Lexus LF-FC. The FCV-Plus is an ambitious, eye-catching concept with in-wheel electric motors, while the LF-FC is a design study hinting at the next iteration of the Lexus LS flagship sedan, but shown with a potentially optional fuel cell drivetrain.

Hyundai offers a fuel cell-powered version of its Tucson crossover SUV, with a mileage counter on the company’s web site showing more than 750,000 miles of fuel cell travel so far in its vehicles.

BMW said at Tokyo that its first fuel-cell vehicle would likely be a larger-sized sedan which would go on the market after 2020, when its hydrogen development partnership with Toyota (launched in 2013) concludes. In the partnership BMW is developing a process to compress hydrogen at ultra-low temperatures to increase its storage volume, using a fuel cell stack developed by Toyota. BMW officials claim that their FCV will have greater range than the 435 mi (700 km) claimed by Toyota for its Mirai.

The Mirai, now reaching a few California customers, is a dedicated model with its own unique styling to underscore its alternative powertrain. The nascent fuel cell market will have to determine whether customers prefer specific fuel cell models or if they are happier with fuel cell versions of existing popular vehicles. NREL's Pivovar thinks Toyota is on the right track with a dedicated FCV.

“I think it is the correct approach and it has worked for them before,” he said, noting the popularity of Prius’s success as a pioneer in the hybrid-electric market.

Japan is investing heavily in fuel-cell technology and hydrogen infrastructure as part of a national policy to foster a 'hydrogen society' where the zero-emission fuel would power homes and vehicles.

Partnering for success

Honda’s development partnership with General Motors lets the two companies create a fuel cell product arc, starting with the Chevrolet Equinox FCVs of 2008, continuing through the Generation-1 2011 Honda FCX Clarity, the new Generation-2 2016 Clarity FCV and onward to vehicles using a jointly developed fuel cell system by 2020. The companies label this their “Generation-3” fuel cell.

The fuel cell in the Clarity FCV is 33% smaller and makes 60% more power than that in the FCX Clarity. A key milestone is that the entire system now fits under the car’s hood like a conventional powerplant, leaving space in the rear seat for three passengers, so the new car carries five people instead of the old car’s four.

Though Honda is the company that has been putting fuel cell vehicles in customers’ hands, GM remains the industry leader in fuel cell know-how, as measured by the number of patents filed each year and the critical technologies it commands, according to Pivovar. GM built its first FCV in the 1960s.

Toyota, however, has been catching up, so GM’s partnership with Honda is a good match. That’s because freezing a fuel cell specification for production means that resources are no longer used to improve, refine and reduce the cost of the fuel cell system and instead get focused on the practical matter of building the cars, according to Charlie Freese, GM’s Executive Director of Fuel Cell Activities.

With this partnership, Honda can take care of building Clarity FCVs and learning production lessons, while GM engineers toil on the Gen 3 fuel cell the companies will use in their 2020 products.

“By teaming up with Honda, Honda was already locked in on a production program they are rolling out,” said Freese. “They are able to remain focused on that while we remain focused on this next generation technology.”

GM's development of proton-exchange membrane (PEM) fuel cells took on a new dimension in 2011, when the automaker began working with U.S. Navy researchers to develop a fuel-cell power unit for an unmanned undersea vehicle—essentially a robotic mini-submarine. The UUV is powered by an automotive fuel-cell stack similar to those used GM's fleet of 118 Equinox FCV test vehicles. When submerged the UUV's fuel cell “breathes” through a sophisticated closed-loop oxygen storage system (see http://articles.sae.org/13909/).

Today’s fuel cells have already conquered the most significant issues. The Clarity’s fuel cell fits entirely under the car’s hood, so spending additional resources to shrink the size of the next iteration wouldn’t provide any discernible benefit.

Similarly, the amount of platinum used has already been successfully reduced to nearly the benchmark level of that used in the catalytic converters for internal combustion engines. GM’s Equinox fuel cells used 80 gm (2.8 oz) of platinum and the 2011 Clarity FCV used 30 gm (1.05 oz). Catalytic converters typically use 10 gm (.35 oz), according to Pivovar.

Catalysts can work with less than that, but for the sake of longevity and to provide a margin of safety, manufacturers tend to err on the side of caution by using an extra couple grams in their catalysts, he said.

So with the new Clarity FCV using less than 12 gm (.42 oz), according to the company, the precious metals battle is also nearly won.

Next stop: mass production

That means that Freese’s GM team is focused on designing to reduce the cost of manufacturing in volume. One thing they can do is to simplify the cars’ systems. The Clarity Fuel Cell has a pair of cylindrical hydrogen tanks because the ideal design, a sphere, would intrude unacceptably on passenger space.

Using a pair of cylinders in place of a single sphere lets the tanks fit under the car’s floor, but it requires more complex and costly assembly and adds valves and lines that contribute additional cost.

A better solution would be a new tank that doesn't have the packaging compromises of a cylinder or sphere, and holds enough hydrogen in a single tank to provide the requisite 300-400 mi (482-643 km) driving range. The industry’s engineers are scrambling to solve this technical challenge.

“Conventional vehicles have a plastic tank molded to any shape available,” Freese told Automotive Engineering. “That would be the thing you’d aspire to get closest to.”

Toyota had been working with pressure-tank specialists Quantum Technologies on a new high-pressure hydrogen storage solution, but the automaker brought development back in house, said a source involved with the program.

A big challenge to cost reduction is that production volumes will be low by industry standards, even with both Honda and GM selling cars, because the market for the cars will still be immature in 2020. But even with relatively low-unit production, it is possible for some components to enjoy high enough volumes to exploit economies of scale because many of them are used in each car.

With 330 layers of carbon paper for gas diffusion in the cell, it creates the opportunity for 3.3 million of those layers in a production year of 10,000 cars, Freese pointed out.

Another area where there is the potential to benefit from production scale is in the production of components that, while they are unique to fuel cell vehicles, are similar to those used in high-volume internal combustion vehicles. For example, the compressors used in fuel cells are similar to turbochargers, and so they may be able to benefit from the higher production volumes of turbos, Freese said.

“There is a lot of knowledge that can be brought over,” he said. “It is the same thing on injectors. There are unique requirements, but it is not unlike other injectors that inject gaseous fuels like CNG. So they are not entirely foreign to the rest of the industry.”

The supply base that can provide these components is another area Freese points to as a benefit of GM’s joint effort with Honda.

“In some cases there are not a lot of suppliers out there who can do the things we need,” he explained. “We were working with some of the same suppliers but some were different. So we not only get exposure to other ideas, we also got exposure to other supply base players.”

As automakers find the path from today’s low-volume, hand-built production to more affordable mass-produced fuel cell vehicles, the cars will be able to attract customers and manufacturers can stop losing money on them.

“Everybody loses money on the way through just to get us to a better place,” Pivovar reflected. “From a technological perspective, it is clear: fuel cell vehicles are here.”

Maybe fusion is next.

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