Some propose to substitute hydrogen for gasoline as the fuel source for automobiles. Hydrogen powered fuel cells are clean power sources but they may be too costly.
With concerns about global warming, many environmentalists suggest that we need a wholesale change from a carbon economy to a hydrogen economy. Instead of internal combustion engines, automobiles would use hydrogen fuel cells to produce the electricity to power electric motors. Opponents say that costs and safety concerns make the fuel cell an unlikely substitute for the internal combustion engine.
Opponents Say Hydrogen Is Too Costly
Unfortunately there is no readily available source of molecular hydrogen (H2) to be found on our planet. There is lots of hydrogen, but it is found as part of larger molecules, most commonly water or hydrocarbons. To be able to use hydrogen in a fuel cell, those hydrogen atoms must be stripped from hydrocarbons and reformed into H2 or electrically disassociated from oxygen in water.
According to Frank Kreith (J. of Energy Resources Technology, December 2004) more energy is required to produce the hydrogen fuel than is available from 'burning' that hydrogen in a fuel cell. Substantially more electricity could be produced by burning the hydrocarbon in a conventional electric utility than could be produced in a fuel cell from the same material converted to hydrogen; too many conversion steps in the hydrogen production process.
Similar objections are raised about using electricity to disassociate hydrogen from water. The electricity would still have to come from some source, most probably the burning of fossil fuels for the fore seeable future. Opponents say that it would be more efficient to burn hydrocarbons in an internal combustion engine (Wald, Scientific American, May 2004).
Hydrogen is Carbon Neutral
While fossil fuels might be burned to produce much of the energy required for hydrogen production, some electricity would also come from burning biomass or from solar, wind and hydroelectric generation. Generally, these non-fossil fuel power sources are becoming a larger part of the electrical power generation grid and should eventually supplant fossil fuels.
Additionally, according to Gene Berry and Salvador Aceves (J. of Energy Resources Technology, June 2005), carbon dioxide sequestration is possible in a fixed facility, but next to impossible in an automobile. This sequestration would make the fossil fuel electric generation carbon neutral and the bio-mass generation carbon negative.
Hydrogen is a Very Flammable Gas
Hydrogen is a light, very flammable gas. It burns at a much wider range of concentrations in the atmosphere than propane (Wald), and requires less energy to ignite. This means that hydrogen is much more likely to catch fire than are hydrocarbon fuels currently in use.
At the same pressure hydrogen has less than half the energy available from the same volume of methane (Avogadro's Law); meaning that hydrogen must be stored at very high pressures. Hydrogen is odorless and colorless, so a dangerous leak would be hard to detect. All of this makes hydrogen hard to safely use in a personal vehicle.
Do Not Use Hydrogen Gas for Hydrogen
Fuel cell proponents suggest using alternative sources for hydrogen instead of hydrogen gas. David Morgenstern (Energy & Fuels, 2005) points out that newer technology allows for the reforming of H2 from ethanol in the vehicle in a duel cycle system. And Millennium Cell (Eatonton, NJ) has developed a system that uses a recyclable sodium borohydride solution to produce H2 inside the fuel cell (Wakefield, Scientific American, May 2002). Both of these systems provide ways around the hydrogen storage problem.
Conclusion
The debate continues as researchers continue to work the bugs out of the various fuel cell systems. Fuel cells are starting to provide energy to some bus fleets. Only time will tell if they will be the replacement for gasoline engines in the family car.
