Are hydrogen vehicles set to take over as the 'green' car of choice?

by Melody M. Bomgardner. Published Wed 19 Nov 2014 19:11
The Toyota FCV runs on hydrogen and emits only water vapour
The Toyota FCV runs on hydrogen and emits only water vapour

California and Japan are places where the future arrives a bit early. And so it goes with the hydrogen economy. They are where hydrogen fuel stations are being built and where consumers will soon have the opportunity to purchase fuel-cell cars to use for personal transportation.

For a cool 7 million yen, or approximately $70,000, early adopters will be able to drive more than 400 miles on one fill-up of hydrogen and emit only water vapour.

Toyota Motor will be first out of the gate with its FCV model, which is expected to go on sale in April 2016 in Japan and in the summer of 2016 in California. Hyundai, General Motors, Honda, and Daimler all plan to offer fuel-cell vehicles for consumers in the near future.

Putting a fuel cell and hydrogen tank in a consumer sedan is the culmination of decades of research and development by automakers. GM powered its first hydrogen vehicle, called the Electrovan, in 1966 using fuel-cell technology borrowed from the space program. Toyota’s effort began in 1992, the same year it started developing the Prius gas-electric hybrid.

Serious consumer road testing began in 2007, when a small number of sports utility vehicles powered by fuel cells were introduced for lease. Back then, which is not so long ago, the SUVs cost about $1 million apiece.

A lot has happened since. The cost of fuel cells has come down, vehicle range has gone up, and performance goals, such as the ability to start up in frigid weather, have been met. Future hydrogen-powered drivers can thank innovations in chemistry and materials science for some of the most critical improvements, particularly inside the fuel cell itself.

Reaching the mass market still requires additional cost reductions of around 50%. And before fuel-cell cars can make a real impact on consumer transportation, infrastructure for hydrogen fuel stations must be built, and car buyers must switch to the technology in large numbers.

“I can’t say that the technology will become popular until at least 2025,” predicts Toru Hatano, an analyst at the consulting firm IHS Automotive. “As long as we can use other fuels—whether it’s gasoline, diesel, ethanol, or natural gas—consumers will not choose fuel-cell vehicles.”

Toyota and GM are taking different approaches to the adoption problem, while both firms actively work to make fuel cells less expensive. Toyota’s plan is focused on gaining consumer acceptance; it is even helping to finance the installment of hydrogen fuel stations. GM, for its part, has teamed up with Honda to make fuel-cell cars more cost-competitive.

The early generation of fuel-cell vehicles will compete with hybrid- and all-electric vehicles for the hearts and minds of low- or zero-emission car buyers. Although Toyota has had success with the Prius and other hybrid vehicles, it is now betting on a fuel-cell future, rather than an all-electric one.

“Battery-electric vehicles are limited in a lot of ways,” says Jana Hartline, environmental communications manager for Toyota Motor Sales U.S.A. The lithium-ion battery packs are too large and heavy to power efficient, convenient, and reliable vehicles. Future battery chemistries will make only an “incremental” difference, she argues. “Over the last decade, improvements in fuel-cell technology have lapped battery technology three or four times.”

Toyota points out that the convenience factor tilts heavily in favour of fuel-cell vehicles. The driving range is greater than what’s provided by all-electric and even many gas-powered vehicles. And a fill-up of hydrogen takes only three minutes, compared with overnight for a full battery charge in an all-electric car.

Since 2008, Toyota scientists and engineers have more than doubled the power density of the firm’s fuel cells. The smaller footprint means the automaker can fit a fuel cell under the seats of a regular-sized car, rather than under the hood of a hulking SUV. More strikingly, the cost of the fuel- cell system has been reduced by 95%.

The main reason for the cost breakthrough is a better catalyst that uses significantly less platinum. The catalyst enables a fuel cell to transform the energy in chemical bonds into electrical power. When hydrogen from a fuel tank flows to the anode side of the cell, it meets a platinum catalyst that splits it into two protons, leaving electrons that can be harnessed to both charge a vehicle battery and run an electric motor.

Like Toyota, GM has been busily removing platinum from its catalysts. In 2007, GM’s test model, called Project Driveway, used 80 g of platinum in its stack of fuel cells. “My workhorse system now is using below 30 g,” says Charles E. Freese, executive director of GM’s global fuel-cell activities. In development, Freese adds, is a stack that uses less than 10 g of the precious metal.

The secret has been to use much more surface and much less platinum to get the same catalytic power, Freese explains. It requires depositing a thin layer of catalyst on a carbon support structure. To further increase the surface area, GM is working on techniques including hollow-shelled metal particles and special layering of the atomic-scale shells. Alloys of platinum and cobalt are also being tested.

Not all of the combinations of surface modification and catalyst work in real-life conditions, Freese acknowledges. The carbon support may oxidize, and the platinum can migrate and form clumps, which changes its catalytic properties. “These things don’t go right by accident,” Freese says. The goal: a catalyst that maintains its activity over at least a 10-year, 150,000-mile vehicle life span.

Durability is also key to the performance of another important part of the fuel cell, the proton exchange membrane. The PEM conducts protons—the result of splitting hydrogen—from the anode side of the fuel cell to the cathode side.

DuPont has been making PEMs for fuel cells for more than 40 years. Its leading contender, called Nafion, is a sulfonated tetrafluoroethylene-based copolymer.

The membrane can shuttle protons only when it has absorbed water, explains Randy Perry, a principal investigator at DuPont. The addition of water makes Nafion ionic—it contains both positive and negative ions. The negative ions are attached to the membrane, whereas the positive ions are mobile. “They come in one side, and other protons go out the other side,” Perry says. In contrast, electrons don’t move well through water, so they stay behind.

One good way to make a fuel cell more powerful is to increase the number of protons that can move through the polymer membrane. And proton conductivity has improved dramatically since the late 1990s, thanks to experiment and design work conducted under actual driving conditions, according to Perry.

Matthias Gebert, product manager for fuel-cell membranes at chemical maker Solvay, says his firm likewise has made strides in maximizing the ion-exchange capability of its Aquivion fluoropolymer. Thinner structures have reduced raw material costs, he says, and composite blends with dedicated additives impart robustness. Further improvements are coming, Gebert adds, “but you will be surprised how the 2020 car will already be very much like what we are used to today.”

Back at Toyota, another material win was to store onboard hydrogen in a smaller space. The company is weaving its own carbon fiber tanks that compress the gas to 70 megapascals. The resulting 20% increase in density means the FCV model coming out next year will have only two tanks versus its predecessor’s four.

It may seem strange that automakers are doing so much of their own development work rather than outsourcing to suppliers such as Ballard Power Systems, a large fuel-cell maker. Indeed, each major automaker will likely spend around $5 billion on fuel-cell vehicle programs, estimates Cosmin Laslau, an analyst at Lux Research.

Cars are much different from the stationary generators for which many commercial fuel cells were designed. “The fuel-cell-making companies did not develop their products for automotive use but rather tried to adapt them for that use,” GM’s Freese explains. “But the requirements are very demanding; you can’t just take an off-the-shelf product and have it work without compromising the functionality of the vehicle.” Even purchasing raw materials is tricky, he adds. “You can get the very best of everything and get a very poor fuel cell.”

Currently, Ballard does not manufacture fuel cells for use in consumer automobiles. Instead, it lends its expertise to automakers via partnerships; Ballard has such an arrangement with Volkswagen, Laslau says.

It’s not clear when or if carmakers will see a return on their fuel-cell investments. “In the long term, the question is: ‘Are we really going to go away from combustion engines for serious environmental reasons?’ ” Laslau says. “In 20 to 40 years’ time, we might see the extinction of the combustion engine. But that’s fuzzy.”

In the near term, the new technology will do a great deal to help manufacturers meet fleetwide emissions reduction targets, particularly in California, which gives extra credit for long-range, zero-emission vehicles.

Crafting fuel-cell vehicles that suit the average consumer may take a decade or more, and Toyota, at least, is okay with that. “We’ve always been a much-longer-term-planning manufacturer,” Hartline says. “With the Prius, people told us we were insane, but 6 million units later, hybrids are now in every manufacturer’s lineup.”

This article was first published in Chemical Engineering News and was reprinted with the kind permission of the American Chemical Society.



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Comments about Are hydrogen vehicles set to take over as the 'green' car of choice?

Can you explain how H2 cars are zero emissions? Doesn't H2 production require natural gas?
Bryan, USA around 4 months, 1 week ago


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