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The hydrogen economy reconsidered
STANFORD -- It's time to revisit the idea of creating a hydrogen economy.
Paul Kruger, professor emeritus of civil engineering at Stanford University, will deliver that message Feb. 20 at an energy conference in Tokyo.
The last time the idea of weaning the world economy from its fundamental dependence on oil was discussed seriously was during the energy crisis of the mid-to-late 1970s. The Arab oil embargo caused severe gasoline shortages in many parts of the country, and spurred major investments in energy research and development. The use of hydrogen fuel was considered, but political, technical and economic problems kept the idea from becoming a reality.
This time around, Kruger is pushing the idea on environmental, rather than energy supply, grounds. The primary byproduct of hydrogen combustion is water. Unlike burning gasoline, which produces a wide variety of pollutants - including carbon monoxide, nitrogen oxides and a variety of hydrocarbons - an auto that is powered by a hydrogen fuel cell has extremely low emissions. More than 1,000 hydrogen-powered cars could operate without producing as much air pollution as one gas-powered auto.
Kruger has not been able to attract much attention in the United States, despite the number of cities with serious air pollution problems and the fact that the country is more dependent on imported oil today than it was in 1972. But he has found an audience in Japan, which has embarked on a 28-year, joint industry/government/university effort called the world energy network (WE-NET) project. The project is designed to produce the technical and economic advances necessary to replace fossil fuels with hydrogen fuel, particularly for transportation. At a WE-NET meeting in Tokyo, Kruger will deliver a progress report on his study of the potential improvements in air quality in that city that would result from a shift to hydrogen-powered vehicles. "There is no doubt that the use of hydrogen fuel could substantially improve air quality in cities like Tokyo, Los Angeles and Mexico City," Kruger said. "If the savings that result from the improved health of people in these areas can be credited to hydrogen use, then hydrogen could be produced at a cost more competitive with gasoline," he said, adding that studies have indicated that the epidemiological value of reducing air pollution from autos could amount to about 2.2 cents per mile.
To produce hydrogen economically, however, would require a fundamental change in the way that electric utilities around the world operate.
Currently, generation of electricity is considerably more expensive than it might be because of the daily variation in demand. Electric utilities meet the lowest, or baseload, demand level with large nuclear, coal or hydroelectric generators that produce the same amount of electricity every day. During periods of peak demand, the utility must turn on smaller, more expensive generators that add disproportionately to the overall cost.
Kruger suggests replacing these more expensive, intermittent generators with enough additional larger plants that utilities can use them to generate power above peak demand. Then, during periods of lower electricity demand, the excess power could be used to produce hydrogen by the electrolysis of water. Using this method, it should be possible to produce hydrogen at a cost competitive with gasoline, he said.
Since the 1970s, development work on hydrogen-powered vehicles has continued at a modest level. The favored method is to use hydrogen in a fuel cell, a device first used in the Apollo spacecraft, to produce electricity. The fuel cell replaces the battery of an electric vehicle. Currently 30 hydrogen buses are being built for use in the Munich airport and three hydrogen buses will begin testing shortly on Chicago streets, Kruger reported.
Tokyo plans to take various measures to reduce traffic volume during periods when smog levels reach regulatory limits. Officials there also plan to require technology to reduce vehicle emissions. When factors such as continued growth in population and car ownership are taken into account these measures will reduce nitrous oxide pollution - the key ingredient in smog - by 8 percent. Doubling planned restrictions would push the level down by about 24 percent, Kruger estimates. By comparison, a 25 percent reduction in these pollutants could be obtained by replacing roughly one million gasoline-powered or liquid propane-powered autos with hydrogen-powered ones.
"There are two basic approaches to reduce vehicle emissions. One is the 'do without' philosophy. The other is the 'do better' philosophy. I prefer the latter," Kruger said.
He began studying the potential of hydrogen fuel as a result of his research on geothermal energy. In 1992, he was involved in a joint study with the Mexican Federal Electricity Commission (CFE) and the U.S. Department of Energy to study the feasibility of increasing the productivity of geothermal power plants by having them generate hydrogen and electricity. Geothermal plants are particularly suited for this because it takes less electricity to break water down into hydrogen and oxygen when it has been preheated with geothermal liquid.
The study concluded that the plan was feasible and that a moderate-sized power station - 100 Megawatts of available capacity - could produce enough hydrogen fuel to run about 100,000 vehicles. Mexico has an estimated capability of producing about 1,200 Megawatts of electricity by the year 2005. If all this geothermal power could be converted to hydrogen fuel and used to power vehicles in Mexico City, it potentially could reduce auto exhaust emissions by 20 to 24 percent.
This is particularly significant because Kruger projects that a recent Mexican measure to increase the number of driveless days from one to two per week will decrease the nitrous oxide levels by 31 percent, but will have little effect on hydrocarbon levels, which will jump by 85 percent by the end of the century.
Kruger initiated a similar study for the Los Angeles basin. He and a student estimated that the potential air quality benefit of using hydrogen amounts to about 2.2 cents per mile. By comparison, gasoline at $1.30 per gallon is the equivalent of about 4.7 cents per mile. "Thus, the health potential of hydrogen represents about half the cost of gasoline fuel," Kruger said.
The civil engineer admits that this is a long term project. It will take 20 to 30 years to build enough hydrogen-powered vehicles to see the resulting improvement in air quality statistically in major urban areas like Tokyo, Los Angeles and Mexico City. It will take even longer - 50 to 60 years - to build up a complete hydrogen fuel infrastructure, including generators, service stations and vehicles.
"Whether current governments have the perseverance to continue the development over such a time span remains the critical test of hydrogen's potential," he said.
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