Environmental Engineering Reference
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But, natural gas may be the wrong fuel on which to base a hydrogen-
based transportation system. A large fraction of new U.S. natural gas con-
sumption will probably need to be supplied from overseas. While these
sources are more secure than the sources for oil, replacing one import with
another does not move us towards energy independence.
Natural gas can be used far more efficiently to generate electricity or
to cogenerate electricity and steam than it can be to generate hydrogen for
use in cars. Using natural gas to generate significant quantities of hydro-
gen for transportation would, for the foreseeable future, damage efforts to
battle CO 2 emissions.
In 1998 a report prepared for the California Air Resources Board
(CARB) called Status and Prospects of Fuel Cells as Automotive Engines
favored methanol fuel cell stacks in cars over a direct-hydrogen infrastruc-
ture. Hydrogen is not as ready for private automobiles because of the dif-
ficulties and costs of storing hydrogen on board and the large investments
that would be required to make hydrogen more available.
The report noted that the automotive fuel cell is being pushed along
due to the almost $2 billion international investment and that fuel cells
would provide an environmentally superior and more efficient automo-
bile engine.
The CARB report indicated that hydrogen would be produced at
large, central facilities similar to a gasoline refinery. But hydrogen could
also be made at neighborhood refueling stations or at renewable energy
farms. The report also stated that hydrogen compressed at 5,000 pounds
per square inch may not be able to supply the required range.
In a study by Ford with a fuel efficiency of 70 miles per gallon the
size of the tank needed for a 350-mile range would impact both the pas-
senger and cargo space. Some fuel cell prototype cars place the tank on the
roof, like the NECAR II van, but this is not acceptable for a passenger car.
Storing the fuel in special structures has been demonstrated by Toyota and
Honda, but the metals are costly. Ford's latest fuel cell cars use a long fuel
tank area under the passenger space.
Northeastern University has worked on a high-density storage sys-
tem based on the absorption powers of carbon nanofilters. This form of
storage could make direct-hydrogen cars practical. The National Univer-
sity in Singapore has had some encouraging results in this area.
Directed Technologies, a consultant to Ford, believes that hydrogen
could be delivered at around the same cost as its equivalent in gasoline,
but this compares a 24.5-miles-per-gallon gasoline car using taxed gas
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