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A Closer Look at Alternative-fuel Vehicles

A Closer Look at Alternative-fuel Vehicles

By Jeff Youngs, February 24, 2012
Toyota PriusThe increase in popularity of hybrid-electric vehicles (HEVs) such as the gasoline-electric Toyota Prius, Nissan Altima Hybrid and Ford Fusion Hybrid is attributed to consumers seeking more fuel-efficient and environmentally friendly transportation. That same demand has pushed automotive engineers to explore other types of fuels-something besides petroleum-based gasoline and diesel-to burn during the internal combustion process (whereby fuel is exploded inside one or more cylinders). These so-called "alternative fuels" include hydrogen, compressed natural gas, liquefied natural gas, liquid petroleum gas, and ethanol. Each burns much cleaner than gasoline or diesel, but none are yet ready to replace traditional fuels.

Hydrogen-powered Vehicles
Hydrogen-powered vehicles operate by burning hydrogen in a traditional combustion powerplant (e.g., BMW Hydrogen 7) or by utilizing hydrogen in a fuel cell to generate electricity (e.g., Honda FCX Clarity). At first glance, hydrogen seems to be a perfect fit for both consumers and the environment, as the only "waste" out the exhaust pipe is pollutant-free water vapor. Unfortunately, hydrogen is not naturally occurring on earth-it has to be manufactured in special facilities that are currently limited in production.

In addition, vehicles must carry large pressurized tanks of hydrogen to equal the "cruising range" of today's gasoline-powered vehicles as hydrogen has much less "energy per unit of volume" than gasoline. Furthermore, widespread distribution for hydrogen doesn't exist-many consumers would run out of fuel before they could find a filling station. For these reasons, hydrogen remains much more of a future concept than a reality.

Honda Civic GXCompressed Natural Gas for Automotive Use
Compressed natural gas (CNG), liquefied natural gas (LNG), and liquid petroleum gas (LPG) are familiar to many homeowners; these common gasses are used to heat and cook. Although not widespread on a consumer level, they are also viable energy sources for automobiles. Best of all, in most cases existing gasoline-powered vehicles with internal combustion engines can be converted to run on these fuels-at a price.

While the exhaust from these vehicles isn't as clean as that from a hydrogen-powered car or truck, it is one of the cleanest-burning alternative fuels available today. As is the case with hydrogen, CNG, LNG and LPG are all stored in high-pressure cylinders within the vehicle (the size of the storage area is directly related to the vehicle's range). And, suffering from the same disadvantages as hydrogen, a small infrastructure of vehicle refueling stations limits widespread use. Nevertheless, many city and government-owned vehicles (city service trucks and mass transportation) are currently operating with this energy source. The only production vehicle available for consumers with this type of alternative fuel is the CNG-powered Honda Civic GX, and it is only sold in limited markets.

2010 Ford ExpeditionWhat about Ethanol?
Ethanol has been used for a vehicle fuel for more than a century (Henry Ford's first car, designed in 1896, ran on pure ethanol). Today, it is widely used as a blend with traditional gasoline to reduce emissions. In fact, many vehicles on the road today are able to burn ethanol-blended fuels. These are called Flexible Fuel Vehicles (FFVs).

While ethanol-based fuel is readily available, the blend has less energy than pure gasoline-meaning both horsepower and fuel economy decrease. Many who have the capability to run their vehicles on either fuel simply choose the more efficient (but less environmentally friendly) gasoline. Some FFVs available in showrooms today include the Pontiac G6 FFV, Nissan Armada 2WD FFV, and the Ford Expedition 4WD FFV.

While fuels such as hydrogen, compressed natural gas, liquefied natural gas, liquid petroleum gas, and ethanol show promise, they still don't deliver the energy level of traditional fuels-and their national distribution today is inadequate for public use. Nevertheless, consumers are very supportive of alternative sources of fuel. Automakers know this, and they continue to push to solve the deficiencies inherent in each option. While gasoline and diesel fuel aren't going to disappear in the near future, the future of environmentally friendly alternative fuels looks very promising.


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