For at least one hundred years, there has been steady progress in increasing energy efficiency. The amount of energy needed to produce a unit of economic output has been declining and that has produced what is known as the “decarbonization” trend that characterizes the U. S. economy as well as the economies of other developed nations.
Progress in technology, research, and President Bush’s State of the Union address have created a vision of a future where the hydrocarbon economy is some day replaced by hydrogen economy. The prospect of a carbon-free economy and zero-emission transportation has tremendous appeal and undoubtedly will further stimulate increases in research and development.
While the potential of a hydrogen economy and zero emission vehicles may seem boundless, there are many technical and practical challenges that must be dealt with between where we are and where we hope to be in the decades ahead. As with all potential technology achievements, it is important that the rhetoric not get ahead of the reality and economics. In addition, it also is important that fuel cells not get politicized to the point where resources are wasted on pork-barrel projects and competitors use the regulatory system to get a competitive advantage.
Since the State of the Union address, there have been claims made about fuel cell progress and potential that are troublesome. The “irrational exuberance” that produced the stock market bubble should not now create the Holy Grail, hydrogen bubble. A perception that fuel cell technology could solve air quality problems, eliminate our reliance on imported oil and make a major reduction in greenhouse gas emissions, and do all of this in a little over a decade will lead to expectations that cannot be realized.
Perceptions borne of wishful thinking have a way of taking on a life of their own. In the energy area, Project Independence and the Synfuel Corporation had us chasing illusionary and impractical goals. They misled and wasted resources that could have been used productively for the real benefit of society. We should not make the same mistake with fuel cells and the long-term vision of a hydrogen economy.
Over the past decade, there has been significant progress in advancing fuel cell technology. As a result, their cost and size have been reduced. But many challenges remain before we can realistically see widespread use in the automobile fleet.
Fuel cells combine hydrogen and oxygen – both abundant elements – in a chemical reaction that produces electricity. In an automobile that electricity would power an electric engine. Fuel cells are about 60% efficient in using energy; gasoline engines about 25%. Unlike battery powered electric vehicles, fuel cells do not need periodic recharging. And, unlike gasoline engines, the tailpipe emissions are water, not regulated pollutants.
Although the potential for fuel cells appears significant, they must first overcome a number of practical and technological challenges. These include cost, size, fuel production and distribution, and vehicle safety. Although many proponents believe that fuel cells could be commercially viable in ten to twenty years, the reality is that no one knows with confidence how fast technology can and will advance. The pursuit of new technology always has it share of surprises and setbacks. Clear-eyed realism is needed in judging the near-term potential of fuel cells for automobiles. Wishful thinking will only lead to problems and disappointment.
Although fuel cells for vehicles are lighter and cheaper than just a few years ago, their cost is still ten times greater than that of gasoline engines. But, fuel cell cost is not the only, or perhaps the major, challenge. Hydrogen exists in almost unlimited abundance but only in combination with other chemical elements. So, it has to be extracted from a source to be used in a fuel cell. That can take place centrally or through a chemical process on board vehicles, using gasoline or some other liquid hydrocarbon as the basic fuel source.
For a central production facility, it would be necessary to greatly expand today’s production levels. Meeting today’s gasoline demand would require that hydrogen production increase by a factor of 17. It is not clear how easy it would be to permit and build new capacity. Once the central production issue is addressed, the issue of distribution is next on the list of challenges. There are two options. Specially designed, very low temperature tankers and pipelines. Current-technology high-pressure tankers are limited in their energy transporting volume. Since hydrogen has a much lower energy density than gasoline, there would be a significant increase in on-road tanker traffic. On the order of 19 special hydrogen tankers would be needed to replace the energy value of 1 gasoline tanker. Pipelines could move much greater volumes, but existing pipelines are not suited for hydrogen.
Developing the distribution infrastructure for hydrogen to be used directly as a fuel will be costly and could face prolonged delays as a result of potential permitting and legal challenges. The alternative is to use the existing liquid fuels infrastructure and extract the hydrogen with a vehicle on-board system. Such a system would also be safer but more expensive and complex. Vehicle safety is a major challenge in the direct use of hydrogen, which requires a high-pressure vehicle storage tank. Pressures as much as 10,000 psi would be necessary for enough fuel to equal current range of gasoline engines. Such high-pressure tanks pose serious explosive risks in collisions.
So, production, distribution and operating challenges must be overcome along with advancing fuel cell technology.
While the progress takes place, there are near-term options for increasing fuel use efficiency and reducing carbon dioxide emissions. Those alternatives are hybrid engine systems – a combination of an electric motor and gasoline or diesel engine – and advanced diesel engine technology.
When viewed from a total systems perspective – well to wheels – a diesel hybrid’s efficiency is either comparable or superior to some fuel cell systems. In addition, while fuel cell vehicles do not produce CO2 emissions, production of hydrogen or liquid fuels for on-board conversion is energy intensive and that production process does produce carbon dioxide emissions. On a systems basis these emissions are less than those of conventional automobile fuel systems but they are not zero. Continued progress in automotive technology can further reduce all emissions, including carbon dioxide, but a zero emissions system is not a reality.
The purpose of making these points is not to discredit fuel cells as a long-term replacement for the internal combustion engine. Rather, it is to urge that the potential of fuel cells be evaluated from a systems perspective [well to wheels] so that expectations do not exceed current realities. It is almost certain that fuel cells will play a role in our future transportation system. The pursuit of this technology will be well served by a healthy dose of realism-realism about challenges, about the speed of progress and about expectations. The future of fuel cells is closer than it was a decade ago but it is not tomorrow.
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