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Transportation accounts for 65 percent
of all oil consumption in the United States, according to the U.S.
Department of Energy’s (DOE) Energy Efficiency and Renewable
Energy division. It is also the predominant source of air pollution.
Yet, new transportation technologies under development are intended
to reverse this consumption pattern by improving the efficiency
and emissions of vehicles using petroleum-based fuels, as well as
provide cleaner-burning alternative fuels altogether.
Which alternative fuel will predominate in the future remains to
be seen; each fuel’s pros and cons is under considerable debate,
constant scrutiny—and continuous development. For example,
at the 2003 Challenge Bibendum, the distribution of technologies
was markedly different than the previous year. Hydrogen powered
cars (fuel cells and ICEs), diesels and several hybrid technologies
dominated the field this year, yet in 2002 it was compressed natural
gas (CNG), liquid natural gas (LNG) and electric vehicles that were
in the majority.
One thing is certain: alternative fuel options are both varied and
complex. For those without a chemistry degree, the following is
a brief overview of some of the most common alternative fuel options
along with their characteristics and uses:
* Biodiesel
Biodiesel is promoted as a low-polluting diesel alternative that
can be made from vegetable oils, rapeseed oil, animal fats and even
recycled cooking greases. Available in liquid form, it can be used
in any vehicle that currently runs on diesel fuel with no modifications
for up to five percent blends. Many engines also are compatible
with blends up to 20 percent. Proponents say biodiesel reduces particulate
matter and global warming gas emissions compared to conventional
diesel; opponents claim that NOx emissions may be increased. Biodiesel
is domestically produced and has a fossil energy ratio of 3.3:1,
which means that its fossil energy inputs are similar to those of
petroleum. Currently, there are approximately 25 states that have
biodiesel stations available to the public.
* Electricity
Electricity is considered a fuel when used in electric vehicles
because it shifts the burden of pollution control to the electrical
supply systems, resulting in much lower emissions per mile traveled.
Coal, however, is electricity’s main fuel source; however nuclear,
natural gas, hydroelectric and renewable resources also can be used.
Electricity is currently used to power neighborhood electric vehicles,
bicycles, light-duty vehicles as well as medium and heavy-duty trucks
and buses. Proponents of electric vehicles (EVs) cite zero tailpipe
emissions; yet some amount of emissions can be contributed to power
generation. Most homes, government facilities, fleet garages and
businesses have adequate electrical capacity for charging, but special
hookups or upgrades may be required. It is estimated that more than
600 electric charging stations are available in California and Arizona.
* Ethanol
Mainly used today as a liquid fuel additive, ethanol is also used
in an 85-percent-ethanol/15-percent-gasoline blend called E85. The
main technical goals are to lower the cost of ethanol while expanding
the ethanol infrastructure. Currently, the industry is supported
by various fuel standards, codes and legislation. Ethanol proponents
say E85 vehicles can demonstrate a 25 percent reduction in ozone-forming
emissions compared to reformulated gasoline. It is produced domestically
and it is renewable. Most E85 fueling stations are located in the
Midwest; however there are approximately 175 stations available
in 23 states.
* Hydrogen
Available in compressed gas or liquid form, proponents look to hydrogen
as the best option for reducing U.S. dependence on foreign oil.
Although hydrogen can fuel an engine directly, or serve as a fuel
additive, the current emphasis is on the use of hydrogen to supply
fuel cells, which power electric vehicles. Hydrogen has also been
blended with methane to form a fuel called hythane. Pros include
zero regulated emissions for fuel cell-powered vehicles, and only
NOx emissions possible for internal combustion engines operating
on hydrogen. Relatively few hydrogen stations operate across the
country and most are privately owned.
* Methanol
Like ethanol, liquid methanol is blended with gasoline in a ratio
of 85 to 15 to form M85. When burned in an engine, methanol produces
low emissions; estimates show that M85 vehicles can demonstrate
a 40 percent reduction in ozone-forming emissions compared to reformulated
gasoline. It can be produced at prices comparable to gasoline from
natural gas as well as coal and wood. Methanol is also the fuel
for the direct-methanol fuel cell. Cars that burn pure methanol
offer much greater air quality and efficiency advantages. Many automakers
have developed advanced M100 prototypes and it has long been the
fuel of choice for race cars because of its superior performance
and fire safety characteristics. Developing a methanol refueling
infrastructure is essential to expand its use.
* Natural Gas
Natural gas is a clean-air alternative to conventional fuels. It
is used in vehicles as compressed natural gas (CNG) or liquefied
natural gas (LNG). Natural gas is sourced from underground reserves
and can be used to fuel many types of vehicle classes including
medium and heavy-duty trucks and buses. Both CNG and LNG vehicles
demonstrate a reduction in CO2 and NOX emissions compared with conventional
fuels, however hydrocarbon emissions may be increased. Also at issue
is the availability of refueling sites for vehicles that run on
these fuels. While an estimated 1,200 CNG stations operate nationwide,
the highest concentration is located in California. Home fueling
options also have recently been made available. Public LNG stations,
however, are more limited—estimates show that less than 50
are available nationally. LNG is available, though, through several
suppliers of cryogenic liquids.
* Propane
Propane is usually used in the form of liquefied petroleum gas (LPG).
It is a by-product of petroleum refining or natural gas processing.
Available in liquid form, it can be used to fuel light-duty vehicles,
as well as some medium and heavy-duty trucks and buses. LPG vehicles
can demonstrate a 60 percent reduction in ozone-forming emissions
compared to reformulated gasoline. It is widely available with an
estimated 3,500 refueling sites nationwide. The disadvantage is
that 45 percent of the propane fuel in the U.S. is derived from
oil.
* P-series
P-series fuels are new fuels that have recently been classified
as alternative fuels. These fuels are blends of methyltetrahydrofuran
(MTHF), ethanol and hydrocarbons. The fuels contain at least 60
percent non-petroleum energy content derived from MTHF (manufactured
solely from biomass feedstocks) and ethanol.
Additional Considerations
To further complicate the debate about alternative fuel type is
the subject of energy and propulsion systems. The two topics are
inexplicably linked, says Mark Gainsborough, head of Fuels at Shell
and its representative on environmental issues. “We have seen
over the past few years that while new technological developments
are possible in motor vehicles, we can also develop new types of
fuels. The two go hand in hand. We must therefore think in terms
of the vehicle-fuel pairing; this will be all the more true in the
near future.”
What are some of the newer car technologies that could impact the
future direction of fuel sources?
* Hybrids
A hybrid vehicle combines two or more sources of power. Hybrid cars
run off a rechargeable battery and gasoline. Hybrid engines use
the battery to provide extra acceleration power when needed. When
the car is stopped, hybrid gasoline motors can shut off and run
off their electric motor and battery. They can recover braking energy
and use it to charge the battery; no plug-in or long extension cords
are necessary.
* Fuel Cells
A fuel cell is an electrochemical device that produces electricity
from the reaction of hydrogen and oxygen. Its only byproduct is
water. Fuel cell vehicles are similar to battery-powered electric
cars in that the fuel cell produces electricity that powers motors
at the wheels. But while a battery must be recharged, a fuel cell
is “refillable” in the sense that recharging the vehicle
only requires refilling the fuel tank. The hydrogen fuel required
to power it can be stored directly on the vehicle in tanks or extracted
from a secondary fuel, like methanol or ethanol, that carries oxygen.
* Bi-fuel Vehicles
A bi-fuel vehicle has two separate fuel systems with the capability
to easily switch from one to the other. The vehicle can be powered
by either system. One fuel system is usually designed to run on
gasoline or diesel. In currently available U.S. models, the other
fuel system is usually designed to run on compressed natural gas
or propane. The need for two separate fuel systems and a storage
tank for a gaseous fuel increases the cost of bi-fuel vehicles and
reduces cargo space.
* Turbocharged, Direct-Injection (TDI) Diesel Engines
Unlike the diesel engines of the 1970s and ‘80s, modern passenger
car diesels are quieter, smoother, more responsive and almost entirely
free of diesel odor. They are also substantially more energy efficient.
Today’s “new” diesel engines directly inject fuel
into the combustion chamber rather than having part of the combustion
occur in a prechamber (indirect injection). The advanced fuel injectors
atomize the fuel into a fine mist in two stages, a process that
advocates claim eliminates heat loss and increases fuel economy
by 20 percent over conventional diesels (40 to 50 percent over conventional
gasoline engines).
* Electric Vehicles (EVs)
The only vehicles to meet California’s Zero Emission Vehicle
requirement, battery electric vehicles offer quiet, pollution-free
operation. However, electricity generation is not pollution free
so EVs produce indirect environmental impacts, but are still far
cleaner than gasoline-powered vehicles. Though still range limited,
recent advances in battery and electric motor technologies have
made EVs more practical than ever before.
The Future for Fuels
Few involved in the research of alternative fuels will predict with
any degree of certainty where developments may lead in the next
few years, yet they remain cautiously optimistic about progress.
The bottom line, though: it’s simply too soon to tell, they
say.
“It’s far too early yet to pick a winner,” said Dr
Ferdinand Panik, former head of Daimler-Chrysler’s Fuel-Cell
Project and co-founder of the California Fuel Cell Partnership,
during an interview at Challenge Bibendum. “We have to tackle
clean technologies step by step, and not decide before having solved
the key problems necessary to achieve a realistic and reliable roadmap
or plan toward commercialization. We should avoid promoting innovations
over-hastily. Creating public interest and demand that we won’t
be able to satisfy could spell the death of these new technologies.”
What seems to be a sure bet, though, is that the general public
is starting to pay more interest. According to the J.D. Power and
Associates 2003 Escaped Shopper StudySM, gas mileage is now fifth
on the list of reasons that new vehicle buyers reject one model
over another—a sharp jump up from 13th place in 2002.
“Between the concerns over the Middle East, high gas prices
and the growing trend toward larger and more powerful engines, it
is not surprising that 15 percent of new vehicle buyers cite gas
mileage as a reason for rejecting a vehicle they once considered
buying,” said Chris Denove, partner at J.D. Power.
As research and development in alternative fuels continues and availability
increases, new vehicle buyers may soon have many more options to
satisfy their concerns about energy efficiency—concerns they
will be able to act on at something other than the conventional
gas pump.
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