See also:

• Hydrogen Automobiles, Buses, Bicycles and Airplanes

While fuel cells themselves are potentially highly energy efficient, and working prototypes were made by Roger E. Billings in the 1960s, at least four technical obstacles and other political considerations exist regarding the development and use of a fuel cell-powered hydrogen car.

Fuel cell cost

Currently, hydrogen fuel cells are costly to produce and fragile. Engineers are studying how to produce inexpensive fuel cells that are robust enough to survive the bumps and vibrations that all automobiles experience. Also, many designs require rare substances such as platinum as a catalyst in order to work properly. Such a catalyst can also become contaminated by impurities in the hydrogen supply. In the past few years, however, a nickel-tin catalyst has been under development which may lower the cost of cells.^[15]

Fuel cells are generally priced in USD/kW, and data is scarce regarding costs. Ballard Power Systems is virtually alone in publishing such data. Their 2005 figure was $73 USD/kW (based on high volume manufacturing estimates), which they said was on track to achieve the U.S. DoE's 2010 goal of $30 USD/kW. This would achieve closer parity with internal combustion engines for automotive applications, allowing a 100 kW fuel cell to be produced for $3000. 100 kW is about 134 hp.^[16]

Freezing conditions

Freezing conditions are a major consideration because fuel cells produce water and utilize moist air with varying water content. Most fuel cell designs are fragile and cannot survive in such environments at startup but since heat is a byproduct of the fuel cell process, the major concern is startup capability. Ballard announced that it has already hit the U.S. DoE's 2010 target for cold weather starting which was 50% power achieved in 30 seconds at -20 °C.^[17] Although this is a good step, there still has to be many more improvements in that area for fuel cells to be strong enough to hold up to hard weather. Jackob Anderson estimates that 75% power should be generated within 25 seconds of startup at -15 °C.^[18]

Service life

Although service life is coupled to cost, fuel cells have to be compared to existing machines with a service life in excess of 5000 hours^[19] for stationary and light-duty. Marine PEM fuel cells reached the target in 2004^[20] Research is going on especially for heavy duty like in the bus trails which are targeted up to a service life of 30,000 hours.

Low volumetric energy

Hydrogen has a very low volumetric energy density at ambient conditions, equal to about one-third that of methane. Even when the fuel is stored as a liquid in a cryogenic tank or in a pressurized tank, the volumetric energy density (megajoules per liter) is small relative to that of gasoline. Because of the energy required to compress or liquefy the hydrogen gas, the supply chain for hydrogen has lower well-to-tank efficiency compared to gasoline.^[5] Some research has been done into using special crystalline materials to store hydrogen at greater densities and at lower pressures.

Hydrogen production cost

Molecular hydrogen can be derived chemically from a feed stock, such as methanol, but can also be produced electrochemically from water. Current technologies for manufacturing hydrogen use energy in various forms, totalling between 25 and 50 percent of the higher heating value of the hydrogen fuel, to produce, compress or liquefy, and transmit the hydrogen by pipeline or truck.^[21] Electrolysis, currently the most inefficient method of producing hydrogen, uses 65 percent to 112 percent of the higher heating value on a well-to-tank basis.^[22] Environmental consequences of the production of hydrogen from fossil energy resources include the emission of greenhouse gases, a consequence that would also proceed from the on-board reforming of methanol into hydrogen. Studies comparing the environmental consequences of hydrogen production and use in fuel cell vehicles to the refining of petroleum and combustion in conventional automobile engines find a net reduction of ozone and greenhouse gases in favor of hydrogen.^[1] Hydrogen production using renewable energy resources would not create such emissions or, in the case of biomass, would create near-zero net emissions assuming new biomass is grown in place of that converted to hydrogen. The scale of renewable energy use today is insufficient and would need to be greatly increased to meet demand for widespread use in transportation. For example, hydroelectricity accounts for approximately 6 percent of global energy use, whereas other renewable resources, such as geothermal, solar and wind comprise only about 1.4 percent of energy production as of 2004.^[23] Development of renewable sources faces barriers, and although the amount of energy produced from renewable sources is increasing, as a percentage of worldwide energy production, renewables decreased from 8.15% in 2000 to 7.64% of total energy production in 2004 due to the rapid increase in coal and natural gas production.^[23] However, in some countries, hydrogen is being produced using renewable sources. For example, Iceland is using geothermal power to produce hydrogen,^[24] and Denmark is using wind.^[25]

In addition to the inherent losses of energy in the conversion of feed stock to produce hydrogen which makes hydrogen less advantageous as an energy carrier, there are economic and energy penalties associated with packaging, distribution, storage and transfer of hydrogen.^[5]

Hydrogen infrastructure

In order to distribute hydrogen to cars, the current gasoline fueling system would need to be replaced, or at least significantly supplemented with hydrogen fuel stations. Hydrogen stations are being built in various places around the world.^[26] Private and state initiatives like California's "California Hydrogen Highway" are already starting the infrastructure transition in advance of any manufacturers mass producing hydrogen cars.^[27] Replacement of the existing extensive gasoline fuel station infrastructure would cost a half trillion U.S. dollars in the United States alone.^[28]

The UK has opened its first hydrogen filling station.^[29]

Political considerations

Most of today's hydrogen is produced using fossil energy resources.^[30] While some advocate hydrogen produced from non-fossil resources, there could be public resistance or technological barriers to the implementation of such methods. For example, the United States Department of Energy currently supports research and development aimed at producing hydrogen utilizing heat from generation IV reactors. Such nuclear power plants could be configured to cogenerate hydrogen and electricity. Hydrogen produced in this fashion would still incur the costs associated with transportation and compression or liquefaction assuming direct (molecular) hydrogen is the on-board fuel. Recently, alternative methods of creating hydrogen directly from sunlight and water through a metallic catalyst have been announced. This may eventually provide an economical, direct conversion of solar energy into hydrogen a very clean solution for hydrogen production.^[31]

Some in Washington advocate schemes^[32] other than hydrogen vehicles to replace the petroleum-based internal combustion engine vehicles. Plug-in hybrids, for example, would augment today's hybrid gasoline-electric vehicles with greater battery capacity to enable increased use of the vehicle's electric traction motor and reduced reliance on the combustion engine. The batteries would be charged via the electric grid when the vehicle is parked. Electric power transmission is about 95 percent efficient and the infrastructure is already in place[3]. Tackling the current drawbacks of electric cars or plug-in hybrid electric vehicles is believed by some to be easier than developing a whole new hydrogen infrastructure that mimics the obsolete model of oil distribution. A plug-in hybrid transportation system would face the same thermodynamic hurdles as would a system of hydrogen vehicles relying on electrolysis for its molecular hydrogen. The current electric grid, which is dominated by fossil energy resources in the United States, has a fuel-to-power efficiency of roughly 40 percent. Both the plug-in hybrids and the electrolytic hydrogen system would be subject to these comparative inefficiencies.

United States President George W. Bush was optimistic that these problems could be overcome with research. In his 2003 State of the Union address, he announced the U.S. government's hydrogen fuel initiative,^[33] which complements the President's existing FreedomCAR initiative for safe and cheap hydrogen fuel cell vehicles. Critics charge that focus on the use of the hydrogen car is a dangerous detour from more readily available solutions to reducing the use of fossil fuels in vehicles. K.G. Duleep speculates that "a strong case exists for continuing fuel-efficiency improvements from conventional technology at relatively low cost."^[4] Challenging perspectives to many such critics of hydrogen vehicles in particular and of a hydrogen economy in general were presented in the 2006 documentary, Who Killed the Electric Car?

President Bush's hydrogen car goals, in the opinion of some writers, are slipping away because "there are quicker, cleaner, safer and cheaper ways to reduce the tail-pipe emissions from cars and trucks that pollute the air and contribute to global warming." According to physicist and former U.S. Department of Energy official Joseph Romm, "A hydrogen car is one of the least efficient, most expensive ways to reduce greenhouse gases." Asked when hydrogen cars will be broadly available, Romm replied: "Not in our lifetime, and very possibly never."^[4] As an article published in the March/April 2007 issue of Technology Review argued,

In the context of the overall energy economy, a car like the BMW Hydrogen 7 would proba­bly produce far more carbon dioxide emissions than gasoline-powered cars available today. And changing this calculation would take multiple breakthroughs--which study after study has predicted will take decades, if they arrive at all. In fact, the Hydrogen 7 and its hydrogen-fuel-cell cousins are, in many ways, simply flashy distractions produced by automakers who should be taking stronger immediate action to reduce the greenhouse-gas emissions of their cars.^[2]

Alternatives

Electric cars, such as the General Motors EV1 are typically more efficient than fuel cell-powered vehicles on a well-to-wheel basis. As Technology Review noted in June 2008, "Electric cars—and plug-in hybrid cars—have an enormous advantage over hydrogen fuel-cell vehicles in utilizing low-carbon electricity. That is because of the inherent inefficiency of the entire hydrogen fueling process, from generating the hydrogen with that electricity to transporting this diffuse gas long distances, getting the hydrogen in the car, and then running it through a fuel cell—all for the purpose of converting the hydrogen back into electricity to drive the same exact electric motor you'll find in an electric car.^[35][36] For this reason, battery powered vehicles are gaining popularity, particularly with the introduction of new models like the Tesla Roadster.^[37]

References