Fuel Cells in Transportation

The requirements of fuel cells to be used in transportation are drastically different from its requirements for other applications. Mobile fuel cells for vehicles have the following requirements:

  • Energy dense fuel – The fuel that powers the cell must contain enough energy to provide the power needed to propel vehicles as large as buses and for extended periods of time.
  • Portable fuel – The fuel source must be safe, simple, and inexpensive to transport
  • Quick access – The system must provide quick, reliable access to energy. It cannot have long start-up times or delayed responsiveness.
  • Cost – The cost of running such fuel systems must be competitive with standard internal combustion engines.

Market

The transportation sector is the largest consumer of fuel in most industrialized nations, using up to 70% of all petroleum fuel. Estimates from the United States Department of Transportation find that 75% of all fuel used for vehicles is used to power highway transport. Furthermore, highway transportation is responsible for over 60% of carbon monoxide emissions and 20% of greenhouse gas emissions. All of these factors make the transportation segment strongly attractive to fuel cell manufacturers.

Prior to August 2004, the department of energy invested significant resources into fuel cell systems that supported onboard vehicle fuel processing. In other words, the previous approach was to utilize standard fuels such as gasoline, methanol, ethanol, and other hydrocarbons to produce hydrogen on the vehicle just before its use by the fuel cell. A report in that year found that the technology for onboard fuel processing was likely to not improve significantly enough to support the transition to widespread commercialization of hydrogen fuel cell technology. As a result, the department of energy decided to invest research and development resources into direct hydrogen fuel systems for transportation.

Current Vehicles

Current fuel cell vehicles are considered to be pre-prototype vehicles. This means very few of them exist and they are all used for testing purposes. Most car manufacturers have produced demonstration models capable of speeds of over 90 miles per hour and of traveling distances up 280 miles without refueling. In 2003, a joint venture between the United States Environmental Protection Agency and the United Parcel Service (UPS) produced a hydrogen fuel delivery vehicle that logged over 12,000 miles in routine package delivery. The joint venture was considered a success.

While some manufacturers claim that they will have fuel cell vehicles available for public consumption within the next 10 years, most experts believe it will be at least 2020 if not later before fuel cell vehicles are economically viable.

Forays into internal combustion vehicles capable of running on either hydrogen or standard gasoline were initially undertaken in an effort to ease the transition to the “hydrogen economy.” However, these vehicles were found to be impractical on many levels, including cost, and most efforts were abandoned in favor of fuel cells.

Hydrogen Storage

The major drawback to the utilization of fuel cells in transportation is the storage of fuel. While onboard storage of gasoline and other hydrocarbon fuels is relatively simple and has been accomplished for well over 100 years, converting those fuels to hydrogen onboard a vehicle is relatively inefficient and still produces substantial unwanted emissions of carbon dioxide.

The alternative to converting hydrocarbon fuels onboard is to carry pure hydrogen. As discussed in other locations in more detail, carrying pure hydrogen represents several obstacles, including its flammability, low power density, and the fact that it is a gas at standard temperature and pressure. If the problem of transporting and storing hydrogen fuel can be overcome, hydrogen fuel cells will become a reality almost overnight.

Refueling Stations

The joint program between the EPA and UPS was partially successful because the EPA, in conjunction with Air Products and Chemicals, installed a hydrogen refueling station at its National Vehicle and Fuel Emissions Laboratory in Ann Arbor Michigan. The facility was capable of storing up to 1500 gallons of liquid hydrogen which was compressed and dispensed as a liquid at around 400 times that of standard atmospheric pressure. This system was considered a success, even though it required high quantities of energy to compress the hydrogen.

The installation of a hydrogen infrastructure for delivery of fuel is critical to the success of the widespread commercialization of hydrogen fuel cells. The U.S. government has estimated that it infrastructure large enough to support 10,000,000 vehicles powered by hydrogen fuel cells would cost approximately eight billion USD. When scaled up to the approximately 300,000,000 vehicles in the United States alone, this translates to a cost of approximately $240 billion.

Conclusion

The primary impediment to the widespread adoption of hydrogen fuel cells for transportation purposes is the hydrogen fuel itself. A safe, practical, and reliable means of storing, transporting, and utilizing hydrogen would make fuel cells commercially viable.