Better Storage Through Chemistry

FEATURE FOCUS: Fluid Power and Processing
ON THE COVER

better storage through chemistry

One company has come up with another way of holding hydrogen.

by Paul Sharke, Associate Editor

Of the major markets anticipated for fuel cells, the largest one, the transportation sector, will be the slowest to emerge. So said Stephen Tang, president and CEO of Millennium Cell Inc., a developmental-stage company based in Eatontown, N.J. The company has produced a hydrogen fuel system for
a DaimlerChrysler fuel cell minivan. The vehicle is capable of driving up to 300 miles on a single fueling of chemically stored hydrogen.

Before fuel cell vehicles become commonplace, Tang expects that we'll see fuel cells making more progress in distributed generation, micro power, and portable appliances—areas in which Millennium Cell is also active.

What's holding back the acceptance of fuel cell automobiles is a lack of fueling infrastructure. All but possibly onboard reforming of gasoline will require some kind of change in the status quo, namely, the ubiquitous gas station. Even the infrastructure changes necessary to support Millennium Cell's ideas for fuel cell vehicles may be five to 10 years off, Tang said. Still, the company offers a fresh twist to a field flooded with great ideas and grand schemes.

Millennium Cell's hydrogen-on-demand system stores hydrogen in the form of sodium borohydride, a chemical whose chief use today is for bleaching paper. Mixed with water, the chemical makes a fuel that can be stored as a liquid in plastic vessels under ambient temperature and pressure. The mixture is neither flammable nor explosive. After catalysis
releases hydrogen from the mixture, only sodium meta-borate remains. The waste product is a common mineral known as borax.

A mirror below the Natrium reflected, from back to front, the fuel tank, fuel processor, air compressor, humidifier, heat exchanger, fuel cell stack, dc/dc converter, lithium ion battery pack, and electric drive.

The secret to the hydrogen-on-demand system lies in the company's proprietary catalyst and catalytic chamber. A solution of sodium borohydride pumped through the chamber liberates hydrogen at a rate equal to the demand of the fuel cell. No hydrogen storage is needed. Shutting off the pump stops the flow of sodium borohydride and water, and the release of hydrogen.

DaimlerChrysler unveiled the Town & Country Natrium fuel cell minivan at the Electric Vehicle Association of the Americas conference held in Sacramento, Calif., this past December. The minivan—which Thomas Moore, vice president of the company's Liberty and Technical Affairs research group, said was named after the Latin word for sodium—uses a Ballard/Xcellsis fuel cell and a Siemens motor in addition to the fuel processor supplied by Millennium Cell.

According to Chrysler's senior manager of fuel cell systems, Christian Mohrdieck, the vehicle will go from 0 to 60 mph in 16 seconds, hit a speed of 80 mph, and return the equivalent of 30 mpg in fuel economy. The car uses a 40-kilowatt Saft lithium ion battery pack.

Unless you crawl underneath, there's nothing visible inside or outside the vehicle that would distinguish it from any other minivan on the road today. Indeed, the entire fuel storage, processor, fuel cell, motor, and battery systems fit beneath or in front of occupied space.

If sodium borohydride were as readily available now as gasoline is, there might be very little about even fueling the Natrium that would tip off its operator that the car was a hydrogen vehicle. About the biggest difference in fueling the car is that the waste borax and water would have to be removed from the car after, or while, the fresh sodium borohydride solution was pumped in.

But that is a big difference. For Millennium Cell's technology to work on a grand scale, waste borax will have to be recycled back into sodium borohydride through the addition of hydrogen. This is an area the company is exploring through partnerships with companies like Rohm and Haas of Philadelphia, Air Products and Chemicals of Allentown, Pa., and System Consulting of Budapest.

It is likely that sodium borohydride could be trucked to filling stations as gasoline is today, and stored, similarly, in underground tanks. Tanker trucks that currently deadhead back to refineries could, in an NaBH₄ future, haul the spent product off to recycling facilities, Tang said.

The hydrogen-on-demand system stores fresh and depleted chemical in one tank. A flexible membrane inside the tank keeps the two from meeting. Hydrogen, produced as needed, feeds a fuel cell or an internal combustion engine.

Switching over existing gasoline-powered automobiles to operate on sodium borohydride would not present insurmountable obstacles either; in fact, internal combustion engines could be made to burn hydrogen. Tanks could be converted to vessels for storing sodium borohydride and borax.

Millennium Cell's approach might just offer a fairly painless way of shifting an economy from gasoline to hydrogen without requiring that every vehicle owner go out and buy a new car.
For readers interested in the chemistry, Rex Luzader, who heads up business development for the company's transportation program, explained: A salt, NaBH₄, is dissolved in water, where it remains until H₂ is needed. As NaBH₄ passes over the catalyst, H₂ comes out, leaving behind a solution of NaBO₂, another salt.

Half the hydrogen comes from sodium borohydride; the other half comes from water.

Two benefits of using sodium borohydride as an energy carrier for fuel cells are its ability to deliver hydrogen at 100 percent humidity and its freedom from carbon monoxide. Humidity levels matter a great deal to maintaining fuel cell health; minimizing carbon monoxide matters, too, in preventing a fuel cell's poisoning, Luzader explained.

According to Tang, it would take about 6 percent of the world's borax reserves to completely fill the recycling loop for what would be the equivalent of every new car on the road today. The United States holds big borax deposits that could be readily mined as demand grew. Right now, sodium borohydride is costly, owing to its limited demand. Increasing production would drive down the chemical's costs.

Back to the Future

Millennium Cell's niche provides a convenient ledge from which to peer in on some of the issues affecting the fuel cell industry. As an audience member asked during one of the EVAA plenary sessions in Sacramento, what's different this time from the discussions of a decade ago, when battery-electric vehicles were the rage? Conversations today are similar to what they were then, he said, except now they focus on fuel cells. How best to address infrastructure needs? How best to lower the cost of technology?

During the conference, Ballard Power Systems chairman and CEO Firoz Rasul said that a sparse 12,000 filling stations populated the United States in 1921; eight years later, that number had jumped 1,100 percent to 143,000. He said the figures demonstrate how fast an industry can respond when there are economic forces at work.

John Wallace, executive director of Ford Think, asked just what forces could help move the country from its reliance on petroleum for transportation. What he called the most successful product of the 20th century, the automobile, is so entrenched today that more vehicles are registered than there are licensed drivers to use them. Seventeen million new ones are sold each year, he said. Cheap gasoline prevails. Plus, "the automobile is a heavyweight in terms of its ability to offer value to a customer," he said.

Missing from this loop is the sodium borohydride filling station. It might use existing underground tanks for storing NaBH₄ and NaBO₂. Tanker trucks might be able to transport these chemicals as easily as they do gasoline today.

By means of comparison, Wallace cited the existence of some 4,500 battery-electric vehicles, 6,000 low-speed vehicles (that he said should triple in 2002 and double the following year), and 24,000 hybrids. He predicted that hybrids would reach annual volumes of 250,000 units in the next four to five years.

He couldn't say when, but predicted that one day fuel cell vehicles would rule the roost. "Almost every major automaker is involved," he said. "Nobody wants to be left out."

Fuel cells represent the only "credible" way of getting the nation to move away from its oil dependency, Wallace continued. "There really is no other major contender," he said.

No other technology offers the efficiency and cleanliness of fuel cells. No other will match its prowess at using hydrogen and renewable energy. But the potential of fuel cells is going to be difficult to realize, Wallace cautioned. He called for the government to continue its help by providing financial incentives and an "enabling infrastructure." A higher, stable gasoline price wouldn't hurt either, he said.

Environment and Security

"Why is fuel consumption such a big deal?" asked Thomas Gross, deputy assistant director of transportation technologies at the U.S. Department of Energy, during the conference. In the early 1990s, the petroleum used by highway vehicles in the United States surpassed the amount produced here. Since then, the oil gap has grown, a result of more miles driven and the increasing popularity of light and heavy trucks, Gross said.

The oil gap in the United States today exceeds 11 million barrels a day out of the country's overall daily diet of 18 million barrels. Two-thirds of that amount fuels transportation.
"Combusting all that oil affects our national security, pollutes our air, and has climate change implications," Gross said. When oil's price increases, so, too, does the cost of moving people and goods.

At the same time, OPEC controls most of the world's oil reserves, Gross said. "Not only that, but OPEC nations are producing a relatively smaller amount of oil in comparison to their reserves than is the rest of the world," he added.

The United States consumes 26 percent of the world's oil, yet harbors only 2 percent of its reserves. By 2020, predictions call for 60 percent of the world's oil to come from the Persian Gulf region, Gross continued. The United States currently gets about 24 percent of its oil from Middle Eastern countries.

Following September 11, energy security again became a manifold topic. In some circles, it seems to have surpassed concern over the environmental consequence of burning oil. The United States must work toward "assuring that the fuel we need is always there at a cost which is stable," Gross said. Hence, in a word, hydrogen.

One prediction, which Gross said would make automakers happy, brought the environment quickly back into focus. The world's population of automobiles is expected to grow from today's 700 million to an eventual 3 billion. He cited two examples of per capita automotive use today as an indicator of what's coming: China is now about where the United States was in 1913; Latin America is where the U.S. was in 1922.

"The trick is to handle the projected growth, while simultaneously achieving cleaner air, reducing greenhouse gas emissions, and decreasing economic vulnerability," Gross said. "Accomplishing this is going to take a substantial investment in new technologies and a whole lot more investment in actually commercializing those technologies."

Closing the oil gap is easy, Gross suggested: Increase supply and decrease demand. At the Office of Transportation Technologies, the mission was to "help get demand reduction without giving up mobility, safety, vehicle performance, consumer choice, near-zero emissions," he said.

Gross outlined the office's budget: Of an annual $300 million, more than half went to research and development work in electric, hybrid, and fuel-cell vehicles. Other amounts went toward deploying such technologies, toward increasing vehicular fuel economy, and toward the stimulation of alternative fuel use. Smaller amounts went to such programs as testing vehicles under standardized procedures.

Gross said he expected a soon-to-be-public strategic program review to recommend that federal funding for fuel cell development and hydrogen research increase from current expenditures.

Big Hand on the Wheel

Few fuel cell companies share Ballard's name recognition. The company has business relationships with many major automakers. So, when Firoz Rasul said that enthusiasm wouldn't be enough to commercialize fuel cells and bring them to the fore, an audience of enthusiasts listened.

Instead, complexity and cost must be engineered from fuel cells, he said. One way of achieving that was by "putting fuel cells in the hands of our customers," through field trials, demonstrations, and the like.

Also, technology and infrastructure had to develop concurrently. The California Air Resources Board, a conference sponsor, had been demonstrating this kind of progress by bringing together partnerships among oil and technology companies, Rasul said.

The government would be needed to prepare the market for fuel cell acceptance, he said. One way, of course, is through financial incentive programs. Another important way is by developing codes and standards. Clear rules would speed technologies to commercialization. Lacking them, manufacturers might have to comply with an entire batch of standards and end up deciding for themselves which rules truly apply.

"No industry moves as fast as when economic choices are clear and have long-term horizons," Rasul said, offering his example of gas station development in the 1920s. He also pointed to the aircraft industry, which adopted jet engines for 80 percent of its planes in about 15 years. That move, too, required changes to both the fueling infrastructure and the craft.

Government entities like CARB and the Department of Energy go a long way in providing an environment of certainty, he said.

Finally, the automakers themselves would need to add value to their products over and above the qualities of efficiency and environmental cleanliness. Qualities like smooth and quiet rides would be tangible reasons for buyers to want fuel cell cars.

The life cycle efficiency of delivering hydrogen by way of sodium borohydride is projected by Millennium Cell at 20 to 30 percent based on steam methane reforming and the use of proton-exchange membrane fuel cells.

The fuel cell industry was changing—maturing, Rasul said. In the past two months, Ballard had consolidated Xcellsis and Ecostar beneath a single roof. Such structural changes would enable his organization to build entire power trains, not only for DaimlerChrysler and Ford, but for all fuel cell automakers.

It is among this elaborate mix of players big and small that Millennium Cell's engineers and scientists must work. Despite its roster heavy with Ph.D.s, the company, like many in the industry, owes its continued survival in some ways to CARB, which last year upheld its zero-emission-vehicle mandate.

"Industry responds when given a kick," said CARB chairman Alan Lloyd. And certainty: By reaffirming its ZEV mandate, the board had provided the certainty that industry needs to pursue risky technology, Lloyd said. "Conventional technologies and fuels are not enough" to bring about a cleaner environment, he said. About 90 percent of Californians are breathing dirty air, he added.

But the mandate had been changed to recognize the need for flexibility when it comes to ZEVs—acknowledging that battery-electric vehicles could enjoy only limited markets. Through loan and educational programs, the board was nudging ZEVs closer to public acceptance.

Meanwhile, Millennium Cell continues its research. There's more it must learn about heat management, Rex Luzader said. It is attempting to drive down catalyst costs, Stephen Tang explained. Improving catalyst durability is another constant challenge. The company continues making key changes in the packaging of its hydrogen-on-demand technology to reduce the space it occupies.

As for Millennium Cell's researchers, their desks filled with abundant technical challenges, they undoubtedly have plenty to do besides worrying about the future.