Online Nova Info

Background
The United States consumes 25 percent of worldwide oil production, with passenger vehicles accounting for about 40 percent of that. Those same vehicles emit an estimated 400 metric tons of greenhouse gases each year that pollute the air and the environment, and that affect human health. Concerns about air pollution, carbon-dioxide emission, and U.S. dependence on imported oil, along with record-high gasoline prices, are driving research into non-petroleum-based fuels and technology. Currently, some of the most promising alternatives include hydrogen fuel cells, ethanol fuel, and electricity from batteries. In addition, car manufacturers are investigating modifications to existing gasoline-powered cars that can increase energy efficiency and reduce gasoline use.

A hydrogen fuel cell is a device that turns the chemical energy in a fuel directly into electricity. The waste product is water. A single cell consists of a sandwich of two metallic plates with a plastic membrane between them. Hydrogen-rich fuel (derived from gasoline, natural gas, propane, or methanol) is fed to one side of the cell, where it combines with atmospheric oxygen to produce electricity and water. Numerous cells are packed together into a “stack” that can generate enough voltage to power a vehicle or some other electric device. Hydrogen fuel cell vehicles are more efficient than conventional internal combustion engine vehicles and produce no harmful tailpipe exhaust. However, extremely high manufacturing costs, fuel-supply problems, fuel storage problems, limited mileage ability, and cold-temperature sensitivity mean that a mass-market fuel cell vehicle probably won’t be available for at least 10–20 years—perhaps much longer.

Ethanol fuel is an alcohol (ethyl alcohol) fuel that can be made from very common renewable materials, such as sugar cane, corn, and cellulose, and is currently the most widely used alternative to gasoline. Ethanol has long been used in motor fuel, usually as an oxygenate additive or blended with gasoline, because ethanol emits less harmful air pollutants than gasoline does. The standard ethanol fuel is called E85, which is a blend of 85 percent ethanol and 15 percent gasoline. However, ethanol contains less energy per gallon than gasoline, so E85-powered vehicles get roughly 30 percent fewer miles per tankful than equivalent gasoline-powered vehicles. In addition, ethanol’s lower fuel economy results in more carbon dioxide (CO2) emissions than a similar gasoline vehicle gives off.

Electricity can be used to power electric and hybrid electric vehicles. Vehicles that run solely on electricity produce no tailpipe emissions. (The only emissions that can be attributed to electricity are those generated in the production process at the power plant.) Electric vehicles operate with electricity that is stored in a battery that must be recharged. They can be plugged into an electricity source wherever there is a suitable outlet. One of the disadvantages of an all-electric vehicle is that it has limited range (about 40–80 miles between charges). Hybrid electric vehicles typically combine the internal combustion engine of a conventional vehicle with the battery and electric motor of an electric vehicle. The combination offers low emissions, with the power, range, and convenient fueling of conventional (gasoline and diesel) vehicles. Unlike electric vehicles, hybrids don’t need to be plugged in. Instead, the engine charges the battery while the vehicle is in use.

Energy-efficient technologies include such innovations as new engine technologies, new transmission technologies, and using new materials to create lighter vehicles, all of which increase efficiency and reduce fuel consumption.

 

LINKS:

Video NOVA Program Clips
QuickTime or Windows Media Video (4 segments, 8-10 minutes each)
Website Team 1: Hydrogen Fuel
Web Resources
Website Team 2: Ethanol Fuel
Web Resources
Website Team 3: Vehicle Engineering
Web Resources
Website Team 4: Hybrid and Electric Cars
Web Resources
Website URLs Used in This Lesson
HTML Document
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