Hybrid Technologies
Diesel
A diesel automobile uses an engine that has a different combustion cycle than a traditional gasoline engine. In a traditional gasoline engine, fuel is mixed with air, drawn into a cylinder, and ignited by the spark plug. In a diesel, air is drawn into the cylinder and compressed first before the fuel is added. This compression heats the air to such a high temperature that when fuel is then injected into the cylinder, it combusts.
By using higher compression ratios and higher combustion temperatures, diesels operate more efficiently. As a result, diesel vehicles attain better fuel economy than their gasoline counterparts. In addition, a gallon of diesel fuel contains about 10 percent more energy than a gallon of gasoline. These two factors help modern diesels achieve roughly 50 percent higher fuel economy than their gasoline counterparts. Diesel vehicles now account for nearly half of all new vehicle sales in Europe, and a small but growing market share in the US.
Ethanol
Ethanol is a renewable fuel that comes from agricultural feedstocks, and thus can be produced domestically. Using ethanol—particularly E85, an 85-percent blend of ethanol—also results in less pollution, reducing smog-forming emissions by as much as 50 percent relative to gasoline. E85-powered vehicles contribute to global warming, although experts disagree about just how much greenhouse gas is emitted by using ethanol.
E85 may be better for the environment and the American farmer, but it has some drawbacks.
Ethanol can be more expensive than gasoline, depending on where you live.
Regardless of the price you pay for ethanol, it contains less energy than gasoline. This means that your car won’t go as far on a gallon of E85, and your fuel economy will decrease by 20-30 percent.
E85 is widely available only in the Midwest. The Department of Energy lists nearly 2,000 1,000 E85 stations in the United States, but most of those are in two states: Minnesota and Illinois. Other areas, even populous ones, have little E85 infrastructure.
Plug-in Hybrids
A plug-in hybrid car is similar to a conventional hybrid vehicle—both use a gasoline engine as well as an electric motor. However, a plug-in hybrid uses larger battery packs that can be recharged by connecting to common household electricity. Plug-in hybrids can be driven for long distances—from a few miles to as much as 40 miles—without using any gasoline.
Plug-in hybrids provide the benefits of an electric car, while maintaining the same driving range as conventional vehicles. Plug-in hybrid drivers travel in an all-electric mode for the vast majority of common local driving. When the battery’s electric charge is depleted, a downsized gas engine is used to either recharge the batteries (as the car moves), or as the primary source of propulsion until recharging the batteries via a plug.
Plug-in hybrid cars are also known as plug-in hybrid electric vehicles or PHEVs. Plug-in hybrid cars that use a gas engine exclusively for recharging batteries—rather than directly powering the wheels—are also called Extended-Range Electric Vehicles or E-REVs.
Electric
An electric car is powered by an electric motor instead of a gasoline engine. The electric motor gets energy from a controller, which regulates the amount of power—based on the driver’s use of an accelerator pedal. The electric car (also known as electric vehicle or EV) uses energy stored in its rechargeable batteries, which are recharged by common household electricity.
Unlike a hybrid car—which is fueled by gasoline and uses a battery and motor to improve efficiency—an electric car is powered exclusively by electricity. Historically, EVs have not been widely adopted because of limited driving range before needing to be recharged, long recharging times, and a lack of commitment by automakers to produce and market electric cars that have all the creature comforts of gas-powered cars. That’s changing. As battery technology improves—simultaneously increasing energy storage and reducing cost—major automakers are expected to begin introducing a new generation of electric cars.
Hydrogen
Hydrogen can be used to power vehicles in two ways. It can be burned using a hydrogen internal combustion engine (sometimes called an H2ICE), which is basically a modified gasoline engine. It can also be used in a fuel cell.
Unlike a traditional car engine, a fuel cell does not burn fuel and has few moving parts. Inside the fuel cell, a chemical reaction takes place that converts the chemical energy of a fuel into electricity. Fuel cells are a little bit like batteries, except that you never have to charge them. To keep them operating, all you do is provide a constant supply of fuel. For automobiles, that fuel is hydrogen.
Fuel cell cars can be refueled in about 5 minutes, just like today's cars. And just like a common hybrid, the fuel cell car stores energy captured during braking and deceleration in a battery to further improve efficiency.