Alternative Fuel Vehicles

Virtually all cars, trucks, and buses on the road today are designed to operate using gasoline or diesel fuel. These are nonrenewable fossil fuels that won’t last forever. Finding alternatives is a sensible way to plan for future transportation needs.

Alternative fuel vehicles are designed to run on fuels other than gasoline or diesel fuel. Some of these vehicles are already on the road. Others are still in the research and development stage.

Battery Electric Vehicles

Electric vehicles (EVs) run on electrical energy instead of gasoline or diesel fuel. Instead of a fuel tank, batteries store the electricity that is used to operate an EV. These batteries can be charged by plugging the vehicle into a charging station or a 220 V outlet at a home or office. The batteries store the electricity until the vehicle is driven.

Examples of battery EVs include golf carts, scooters, and other personal vehicles used for short trips at low speeds. Some automakers have recently introduced very compact, two-passenger EVs for use in urban areas. These cars have a top speed of 25 mph and can travel a little over 50 miles per charge—perfect for short trips in the stop-and-go traffic of a large city.

Under the hood, an EV consists of an electric motor, one or more controllers, and batteries. The controller governs the amount of electricity that flows from the batteries to the motor when the driver steps on the accelerator. The motor changes electrical energy from the batteries to mechanical energy, which makes the vehicle move.

Driving an EV down the road produces no pollution at all. Even when pollution related to power plant electricity production is factored in, EVs produce less pollution than gasoline or diesel vehicles. EVs are also twice as efficient as gasoline or diesel vehicles, if you compare the energy used in creating gasoline at a refinery or producing electricity in a power plant.

When an EV is stopped in traffic, it doesn’t have to use fuel to keep the motor running like a gasoline engine does. Added efficiency is created by something called “regenerative braking.” When an EV slows down, the motor continues to turn, but the power no longer flows to the wheels. Instead, the power is fed back to the batteries, giving them a small charge every time the driver stops or goes downhill.

Hybrid Electric Vehicles

A hybrid vehicle is any vehicle that uses two or more power sources. The most common hybrids on the road today are gasoline-electric hybrids, also called hybrid EVs. A gasoline engine and an electric motor power these vehicles.

Between 1999 and 2003, more than 100,000 gasoline-electric hybrids were sold in the United States. Sales in 2004 could rival sales of the previous four years combined. The popularity of hybrid EVs is on the increase, and automakers are busy designing and building new models.

The major components of a hybrid EV include a gasoline engine, an electric motor, a transmission, and, in some models, a generator. A fuel tank stores gasoline for the engine, and a battery pack stores electricity for the motor. The transmission moves, or transmits, mechanical energy from the engine or motor to the vehicle’s wheels.

Hybrid EVs use smaller, more efficient gasoline engines than conventional gasoline or diesel vehicles. Hybrid EVs also produce less tailpipe emissions and provide much better gas mileage—today’s models get up to 60 mpg. Burning less fuel means producing fewer pollutants. Hybrid EVs also release less carbon dioxide into the air. Carbon dioxide is a greenhouse gas that contributes to global warming.

Current hybrid EV models are similar in size and comfort level to the most popular gasoline-powered automobiles. Unlike battery EVs, hybrids don’t have to be plugged in. Their batteries are charged by the gasoline engine and by the electric motor or generator during normal operation. Regenerative braking charges the batteries slightly when the car slows down, recovering some of the energy that’s usually lost when brakes are applied.

Natural Gas Vehicles

Vehicles that run on natural gas instead of gasoline are called natural gas vehicles (NGVs). Natural gas that has been compressed into special high-pressure cylinders to get more volume into a smaller amount of space is called compressed natural gas, or CNG. Some NGVs run on CNG only, and others can run on either CNG or gasoline. Some long-haul trucks and transit buses run on liquefied natural gas, or LNG, which is made by refrigerating natural gas to condense it into a liquid.

When the engine of an NGV is started, natural gas flows into a fuel line, then enters a regulator where the gas pressure is reduced. A fuel injection system mixes the gas with air and feeds the mixture into the engine. The fuel/air mixture is adjusted to burn efficiently and with the least possible emissions. Natural gas burns in the engine just like gasoline.

NGVs produce fewer pollutants than gasoline or diesel vehicles and cost less to maintain. The tanks used to store natural gas can withstand crashes and heat far better than most gasoline tanks can. In the event of a crash, natural gas disperses into the air, whereas gasoline pools on the ground, creating a fire hazard.

Fuel-Cell Vehicles

Fuel-cell vehicles (FCVs) are powered by hydrogen fuel cells. Fuel cells produce electricity by combining oxygen with hydrogen. FCVs aren’t on the road yet, but automakers and other companies are working hard to develop them. A fuel-cell car would operate much like an EV, except that it would depend on a supply of hydrogen, rather than a battery pack, for power.

The components of one prototype FCV now under development include three stacks of fuel cells, a tank of hydrogen, an electric motor, and an inverter. The fuel cells operate something like batteries in reverse. Inside each fuel cell, hydrogen and oxygen from the air are combined in a reaction that splits the molecules into protons and electrons and produces electric current. The inverter changes the direct current produced by the fuel cell into alternating current that powers the electric motor, which turns the vehicle’s wheels. The electric current also charges a conventional car battery that powers the car’s lights, radio, air conditioning, and so on.

FCVs are twice as efficient as gasoline or diesel engines, and they produce no pollutants or carbon dioxide. The only tailpipe emission is water vapor. The biggest challenge now facing the developers of FCVs is where to get the hydrogen.

Hydrogen is plentiful in fossil fuels such as methane and natural gas. At the present time, fossil fuels are the most convenient source of hydrogen. But using fossil fuels to produce hydrogen creates pollution and adds to the consumption of nonrenewable resources.

Alternative sources of hydrogen include plant crops, agricultural waste, and wastewater from food processing plants. But, at least so far, so much energy is required to extract hydrogen from these sources that it becomes too expensive to use as a vehicle fuel. FCVs that arrive on the market in the next few years probably will use hydrogen derived from fossil fuels. But the long-term goal is to find efficient, inexpensive ways to extract hydrogen from alternative sources.

Biodiesel Vehicles

Biodiesel is a fuel that can be made from vegetable oils, recycled cooking oils from fast food restaurants, and certain animal fats, such as fish oil or beef tallow. Biodiesel can be used in any diesel engine in place of diesel fuel. No engine modification is necessary, because diesel engines were originally designed to run on a variety of fuels, including vegetable oils.

Biodiesel is easy to make and store, and is safer to transport than diesel fuel. It helps increase engine life. Using it reduces the consumption of fossil fuels. Compared to diesel fuel, biodiesel produces almost no pollutants and significantly reduces carbon dioxide emissions. It’s also more pleasant to use—the exhaust from a biodiesel vehicle often smells like popcorn or French fries! In some regions of the U.S., biodiesel is becoming popular as a fuel for agricultural equipment, such as tractors and trucks, as well as for passenger vehicles.

People-Powered Vehicles

Some vehicles run solely on people power. Wheelbarrows, rickshaws, and bicycles are just a few examples of transportation devices powered by people. In many parts of the world, especially in places where vehicles and fuel are expensive and difficult to obtain, people depend on their own two feet for transportation.

Using people power whenever possible makes a lot of sense. Walking and bicycling produce no pollutants and help keep the environment healthy. They also contribute to personal health—getting plenty of exercise can lengthen a person’s life span and help avoid health problems like obesity and heart disease. And people are easy to fuel—all it takes is food!

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