Alternative Fuel Vehicles: Introduction

Article

Advanced Technologies currently available in the United States include:

Flex-fuel Vehicles

A flexible fueled vehicle (FFV) has a single fuel tank, fuel system, and engine. The vehicle is designed to run on unleaded gasoline and an alcohol fuel (usually ethanol) in any mixture -- for example, 100% gasoline, E85 (85% ethanol, 15% gasoline), or M85 (85% methanol, 15% gasoline) or any combination of these fuels. The engine and fuel system in a flex-fuel vehicle must be adapted slightly to run on alcohol fuels because they are corrosive. There must also be a special sensor in the fuel line to analyze the fuel mixture and control the fuel injection and timing to adjust for different fuel compositions. The flex-fuel vehicle offers its owner an environmentally beneficial option whenever the alternative fuel is available.

Flex-fuel technology was created by Ford Motor Company in the mid-1980s. Flexible fueled vehicles (also called variable fuel vehicles) have been produced by Ford (Ranger, Crown Victoria and Taurus), GM (Chevy S-10 and GMC Sonoma), and Daimler-Chrysler (Plymouth Voyager and Dodge Caravan).

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 order to assure a readily available fuel source. In currently available U.S. models, the other fuel system is usually designed to run on compressed natural gas (CNG) or propane (LPG).

CNG vehicle refueling stationCompressed Natural Gas (CNG) Gasoline powered vehicles can be modified to use compressed natural gas. Vehicles can be designed for the dedicated use of CNG, or more commonly as bi-fuel vehicles which can use either CNG or gasoline.
Liquified Petroleum Gas (LPG) Gasoline-powered vehicles can be modified to use LPG (more commonly known as propane). LPG has been used to provide energy for transportation for over 60 years, and LPG vehicles are the most common alternative fuel vehicles. Vehicles can be designed for the dedicated use of propane or as bi-fuel vehicles that can use either propane or gasoline.

Diesel Vehicles

Unlike diesel engines sold in this country during 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 and considerably cleaner.

The "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; the combustion chamber "swirls" the air and fuel; and a computerized electronic management system controls the engine operation and turbocharger, fine-tuning the entire process for fuel efficiency and emission control. This process eliminates heat loss, increases fuel economy by 20% over conventional diesels (40-50% over conventional gasoline engines), and softens the combustion process, making the ride seem more like a gasoline engine.

Electric Vehicles (EVs)

Some of the earliest automobiles were powered by electric motors driven by batteries. But rapid advances to internal combustion engines quickly drove the heavier, range-limited EVs from the market. The pressing need to reduce air pollution together with new advanced batteries and motors have allowed EVs to reappear as a clean alternative to internal combustion vehicles. Electric drive systems are virtually non-polluting and extremely energy efficient. Whereas only about 20% of the chemical energy in gasoline gets converted into useful work at the wheels of an internal combustion vehicle, 75% or more of the energy from a battery reaches its wheels.

Another advantage of electric motors is their ability to provide power at almost any engine speed. While internal combustion engines must be revved up to high rpm to achieve maximum power, electric motors provide nearly peak power even at low speeds. This gives electric vehicles strong acceleration performance from a stop.

Ultimately it's the batteries that will determine the cost and performance of EVs. There are several major types of automotive batteries available and under development, from advanced lead-acid batteries like those that start our internal combustion engine vehicles, to nickel-metal hydride, to lithium polymer batteries. Even the best of these, however can store only a few percent of the energy of a gallon of gasoline in the same volume. The greater efficiency of electric motors helps a lot, but the range of EVs is still limited. EV recharging StationRecharging is also a consideration. Home recharging systems are available, relatively simple and give EVs an added advantage. Recharging sites away from home are still scarce and the time required for a full charge can be substantial.

-FuelEconomy.gov-