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Fuel Cells: Coming Sooner Than You Think
by Alan R. Earls
Alan R. Earls is a freelance writer based in Franklin, Massachusetts, who specializes in business, technology, and property issues. This article is reprinted with permission of NFPA Journal Online.
Fuel-cell technology for motor vehicles is a little bit like the fable of the tortoise and the hare. Proponents predict that fuel cells, which promise to reduce direct vehicle emissions and work smoothly with a range of renewable energy sources, are about to race to the finish line, only to have that success remain out of reach.
Meanwhile, the real work of perfecting fuel cells and making them practical has proceeded slowly —yielding results, gathering experience, and demonstrating feasibility. And the finish line—practical, reliable, affordable fuel-cell technology—does seem to be slowly and steadily getting closer. But the safety, design, and performance standards that will be needed if fuel cells are eventually to become a mainstream vehicle power source remain unresolved.
While many of the needed fuel-cell fixes are on the cutting edge of technology, fuel cells have been around as laboratory curiosities at least since 1839. However, they weren’t used in any practical application until the U.S. space program installed them to provide onboard electric power for Project Gemini in the 1960s.
In theory, fuel cells should be winners for fueling cars and trucks. That's because they efficiently create electricity directly from chemicals, usually hydrogen and oxygen, in such a way that the surface of an anode supports catalysis and isn’t itself consumed. Fuel cells are potentially 40 to 60 percent efficient in converting fuel to electricity, compared with about 20 to 30 percent for a typical turbine-based process.
Still, says Dr. Ravindra Datta, professor of chemical engineering at Worcester Polytechnic Institute, Worcester, Massachusetts, and director of its co-located Fuel Cell Center, the nature of hydrogen poses broad challenges in handling.
Among the safety concerns associated with hydrogen is asphyxiation and flammability. Nature’s lightest element, hydrogen has a relatively high auto-ignition point, Professor Datta says. While methane’s auto-ignition point is 813º Kelvin and gasoline’s is 500º to 700º Kelvin, hydrogen’s auto-ignition point is about 858º Kelvin. However, hydrogen also has an extremely wide flammability limit of 4 percent to 75 percent, compared to gasoline’s flammability limit of 1 percent to 7 percent. Fortunately, hydrogen is so light it tends to disperse more quickly than other volatile substances.
Hydrogen also has a low energy density compared to gasoline and most other fuels. Whether liquefied or compressed, like natural gas, or even stored in a solid adsorbent, Datta says there’s no way to store enough fuel to provide 300 miles (483 kilometers) of driving distance in a storage-tank volume similar to that found in a typical internal-combustion car. And the storage will be neither simple nor compact.
Professor Datta says several approaches are being considered. One alternative is creating hydrogen within the vehicle from familiar liquid fuels, such as gasoline, methanol, or ethanol, a process called “reformation.” But that approach comes with further weight, space, and cost penalties.
Obviously, any approach must make allowances for the peculiar characteristics of hydrogen. For instance, hydrogen, though non-toxic, can embrittle metals, meaning that storage tanks would have to have non-metallic liners. Some research has pointed to the possibility of storing hydrogen in porous materials, such as metal hydrides or carbon nanotubes, but this technology isn’t yet mature.
Fortunately, neither its flammability nor its density is fatal to the adoption of hydrogen as a motor vehicle fuel.
“It’s currently handled and produced in large volumes commercially,” Datta says. The key issue, he says is that the consumer hasn’t used it. And counterbalancing its potential problems are the clean-burning characteristics of hydrogen, which normally produces just water as a byproduct.
The Different Meanings of Safety
“The issue of safety has different meanings based on the interested parties,” says Neil P. Rossmeissl, technical manager of the Hydrogen Sub-Program of the Office of Hydrogen, Fuel Cells, and Infrastructure Technologies at the U.S. Department of Energy (DOE).
Like Datta, Rossmeissl says that the unknowns facing hydrogen fuel cells have to do with fundamental issues such as hydrogen’s wide flammability limits, “since the range is so great anything can ignite the fuel.”
He’s also concerned about the issue of permeation from high-pressure tanks. In response to problems such as metal embrittlement, Rossmeissl believes U.S. and Canadian tanks will probably be composite tanks made of carbon fiber with nonmetallic liners, which will permit some permeation of hydrogen.
“This amount will be extremely small, lower than the lean flammability limits, but must be taken into account using passive ventilation,” Rossmeissl says.
Because hydrogen is colorless, odorless, and tasteless, we can’t detect its presence. Abandoning a traditional human-based approach to leak detection, Rossmeissl says, DOE has taken a position that odorants aren’t appropriate for hydrogen because they contaminate the catalysts that are a key to fuel-cell operation.
“Due to the millions spent on developing sensors,” he says, “we want the person taken out of the safety equation—all of our designs incorporate sensors and controls to determine if any leak is present.”
Another unresolved technical issue is “fuel-cell blowdown.” “Some of the manufacturers require fuel to be vented unreacted from the stack,” Rossmeissl says. “This amount hasn’t been quantified but, based on modeling, should be handled with passive ventilation.”
Another technological area where challenges remain is instruments and controls.
“Due to the buoyancy of hydrogen, all of the instruments must be mounted in elevated positions,” he says, limiting the flexibility of the final design. Although a number of technologies have been developed to master this challenge, Rossmeissl says they aren’t yet commercially available.
Complete Revision of NFPA 52
NFPA is just starting to deal with safety standards for fuel-cell motor vehicles. A complete revision of NFPA 52, Compressed Natural Gas (CNG) Vehicular Fuel Systems, in 2005 would consolidate NFPA 52 and NFPA 57, Liquefied Natural Gas (LNG) Vehicular Fuel Systems, and add requirements for the vehicular use of hydrogen.
The NFPA Technical Committee on Vehicular Alternative Fuel Systems, responsible for the revision of NFPA 52 that would cover hydrogen vehicle applications, will request proposals in August 2003.
Ralph Rackham, vice president of Toronto-based Fuel Maker Corporation, which has been selling natural-gas-refueling gear for more than a decade and now develops technology for hydrogen fuel handling, serves on the NFPA committee.
Rackham says the committee is working with a number of NFPA documents, consolidating existing standards and developing new ones for all gaseous fuels in public fueling stations that will eventually be consolidated into one document.
“There aren’t any huge issues,” he says. “It’s really that a standard hasn’t been written before for hydrogen vehicular use. There’s currently a debate regarding whether we should confine ourselves to the refueling systems or also look at the vehicle itself.”
The committee is also coordinating its activities with similar groups at the Society of Automotive Engineers (SAE) to ensure "that nothing is left out," Rackham says.
Automakers’ Initiatives
With all the safety issues added to daunting economic hurdles, fuel-cell motor vehicle technology seems destined to be very expensive, even if produced in commercial quantities. We’re looking at 10 to 15 years before fuel cells are cost-competitive for cars, a DOE technology-development manager predicts.
Despite that, some vehicle manufacturers have stepped to the plate. Earlier this year, the hydrogen-powered Honda FCX concept car became the first fuel-cell vehicle in the world to receive U.S. government environmental certification. The California Air Resources Board (CARB) has certified the FCX as a Zero Emission Vehicle, and the U.S. Environmental Protection Agency (EPA) has certified it as a National Low Emission Vehicle.
The two-door, four-passenger FCX also meets applicable U.S. safety and occupant protection standards. Its electric motor has a top speed of 87 miles (140 kilometers) per hour, with a maximum power output of 80 horsepower, and it has a driving range of approximately 220 miles (355 kilometers). Honda hasn’t released a price. Still, the FCX is simply a real-world demonstration vehicle.
As part of that demonstration, Honda will start a lease program for a limited number of FCXs in the United States and Japan by the end of this year. During the first two- to three-year period, Honda plans to lease about 30 fuel-cell vehicles in California and the Tokyo metropolitan area, two locations with access to what’s currently a very limited hydrogen fuel-supply infrastructure.
Honda is a member of the California Fuel Cell Partnership (CaFCP) based in Sacramento, California.
California is a global hotspot for fuel-cell development because of its pollution challenges. To date, 16 fuel-cell-powered vehicles produced by the eight automotive partners participating in the CaFCP are operating in West Sacramento. This year, another refueling station opened at the CaFCP’s West Sacramento fuel-cell vehicle-demonstration center, providing fuel for methanol-fueled fuel-cell vehicles. The estimated cost of each hydrogen gas pump is $500,000.
Although there are several competing fuel-cell technologies, all automakers in the partnership have agreed that the first fuel-cell vehicles to be demonstrated in the marketplace will use hydrogen as their fuel source. However, CaFCP says its members believe it’s important to continue researching all fuel sources, including those that extract hydrogen from methanol or petroleum.
Joe Irvin, a spokesperson for CaFCP, says the organization expects to find more answers to issues such as safety and best practices from a Hydrogen Vehicle Facilities Study that Parsons-Brinckerhoff is conducting. The study is expected to be completed by June 2003.
“It will include examining such facilities as a commercial servicing and repair station, a commercial multi-story parking garage, and a residential garage,” Irvin says.
“Industry members of CaFCP are targeting as early as 2008 for initial market introductions of passenger cars,” Irvin says. However, he admits, it may be until 2020 before there’s any significant penetration.
“In that time-frame, though, prospects for developing significant fleets of buses—and development of fuel cells as auxiliary power units for trucks—are very bright,” he says.
In Germany, officials at the Munich Airport use liquid hydrogen to power a four-door BMW sedan that whisks VIPs between the terminal and aircraft. The car is fueled using a fully automated robot system, and the hydrogen delivered to the station is stored in a 12,000-liter (3,170-gallon) tank.
The automated fueling system, which pulls up to the robot, recognizes and authorizes it with a magnetic-stripe ID card, docks and refuels, and undocks after issuing a receipt—is quick. Docking and undocking take only a few seconds, and refueling takes 10 minutes.
Munich Airport also uses gaseous hydrogen to run three articulated vehicles ferrying other less exalted passengers to and from planes.
At the beginning of October, the European Union (EU) said it would spend $2.09 billion between 2003 and 2006 on renewable energy development, mostly related to hydrogen. Over the past three years, the EU has spent $125 million on the project. In the United States, DOE is seeking $125 million in 2003 to help automakers with hydrogen power research.
While California has so far been the locus of fuel-cell activity, its successes are spawning efforts to further support a market for fuel cells. For instance, the U.S. Air Force is also looking at the potential for fuel-cell-powered vehicles. John Williams, a chemical and electrical engineer with the Advanced Power Technology Office at Robins Air Force Base in Georgia, says that, as they experiment with fuel-cell vehicles, they, too, are reviewing the current industry safety standards and evaluating the standards being developed.
“The Air Force will be accepting industry standards for most of our applications,” he says, “but there will be situations that will call for a more stringent policy” because Air Force vehicles and equipment are exposed to a more-hostile environment than the common commercial vehicle.
Meanwhile, the National Hydrogen Association (NHA), an industry trade group, is working with DOE to create a hydrogen infrastructure in the rest of the United States. To make that infrastructure a reality, though, may require development of safety codes and standards to which the industry can agree.
Even though there are a number of competing fuel-cell schemes, there has been support and continued movement toward starting with a hydrogen-based infrastructure, says Karen Miller, NHA vice president. Miller speculates that the infrastructure might first be built around hydrogen refueling stations for fleet vehicles with centralized refueling needs. On-site reformation of existing fuels, such as natural gas, propane, or gasoline, to create hydrogen could be a way to expand this infrastructure. Even portable electrolyzers, which split water into hydrogen and oxygen, could be used for local refueling, she says.
Standards Development
For its part, the DOE hydrogen program is focusing on the practical issues of developing technology for hydrogen production, storage, and use, as well as the necessary work of code development.
With the ultimate goal of making hydrogen a cost-effective energy source for transportation applications, as well as for utilities and other stationary applications, DOE has sponsored work in codes and standards since 1995. According to DOE, the initial efforts included providing support for NHA to conduct national codes and standards workshops. DOE credits these efforts with encouraging organizations such as NFPA, SAE, Underwriters Laboratories, and the Compressed Gas Association to get involved. Federal agencies such as the Department of Transportation, the National Aeronautics and Space Administration, and the National Institute of Standards and Technology also have regulatory or mission-related interests in hydrogen regulations, codes, and standards.
According to DOE, the NHA workshops helped spawn further efforts to develop hydrogen standards under the International Organization for Standards (ISO) Technical Committee 197. These proposed standards are in various stages of completion under the ISO process, though Anthony Androsky, director of the Fuel Cell Initiative for SAE International and deputy executive director of the U.S. Fuel Cell Council, warns that the international process, in particular, can be time-consuming.
Androsky says that SAE has been very active in developing fuel-cell-related vehicle standards. The SAE Fuel Cell Standards Committee meets monthly, and six working groups sometimes meet more frequently to address subjects such as performance, emissions, recyclability, terminology, safety, and interconnection/interfaces. To date, the SAE effort has yielded about 10 to 12 draft documents.
SAE draft documents include Recommended Practices for General Fuel Cell Vehicle Safety and Recommended Practices for Hazardous Fluid Systems in Fuel Cell Vehicles.
“If you develop the right recommended practices, it will get embraced by the companies, institutionalized within their own standards, and, eventually become industrywide in its impact,” Androsky says. “This kind of consensus-driven, freedom-of-design process will produce the safe, reliable, environmentally friendly protocols required to make fuel cells a reality.”
NFPA’s Carl Rivkin, senior chemical engineer, says that, although NFPA doesn’t yet have a standard dealing with mobile fuel cells, it does have one for stationary fuel cells, NFPA 853, Installation of Stationary Fuel Cell Power Plants, and several that relate to mobile fuel cells. NFPA 50A, Gaseous Hydrogen Systems at Consumer Sites, and NFPA 50B, Liquefied Hydrogen Systems at Consumer Sites, provide requirements for hydrogen storage.
NFPA 30A, Flammable and Combustible Liquids, gives requirements for service stations and garages. Although this document doesn’t have specific requirements for hydrogen usage, it would apply to facilities where fuel-cell-powered vehicles are repaired.
Besides the complete revision of NFPA 52, NFPA 50A and 50B are being consolidated into a revised edition of NFPA 55, Storage, Use, and Handling of Compressed and Liquefied Gases in Portable Cylinders, which will extend coverage from consumer sites to manufacturer sites. NFPA 853 is also being revised to address small residential fuel cells.
Even without outside safety standards specific to motor vehicle fuel cells, Ford Motor Company has implemented many safety systems in its demonstration fuel-cell-powered vehicles. The hydrogen-detection system consists of four sensors, two in the trunk, one under the hood, and another in the passenger compartment. Eight small fans continuously vent the vehicle during operation and fueling. Although hydrogen is nontoxic, it can cause asphyxiation when it displaces the normal 21 percent of oxygen in the air in a confined area without adequate ventilation.
BMW conducted numerous crash tests to see what would happen if the hydrogen tank on its vehicles was punctured or damaged. Its engineers report the liquid hydrogen dissipated harmlessly into the air.
NFPA 50A and 50B provide requirements for fire protection at facilities storing liquid and gaseous forms of hydrogen. Both standards state that “personnel shall be cautioned that hydrogen flames are practically invisible,” and that hydrogen fires aren’t normally extinguished until the hydrogen supply has been shut off because of the danger of reignition or explosion.
Combination fog and solid stream nozzles are preferred for the widest adaptability in fire control. Small hydrogen fires can be extinguished with portable dry-chemical extinguishers or with carbon dioxide, nitrogen, and steam. Reignition may occur if a metal surface adjacent to the flame isn’t cooled with water or some other means.
The safety-standards effort seems set to keep pace with whatever technological breakthroughs come about. SAE's Androsky stresses that NFPA’s role in developing standards is very important.
“The more we talk, the better we can harmonize, and that's good for the public and the industry,” he says.
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