Just the Facts Hybrid Electric Vehicles and Battery Electric Vehicles
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Hybrid Electric Vehicles
Hybrid electric vehicles started off slowly in acceptance from the American public. It was just a few short years ago that “hybrid” was an unfamiliar term. It seems now that most people who own a TV or a computer know what a hybrid is—or do they? When fuel prices are high, most commuters are looking to reduce their fuel costs; however, they see the word “hybrid” and assume that they are all the same. This is not true because there are several ways to categorize hybrid vehicles on the market. Within these types there are many different technologies and operation of the vehicle.

Ford Escape Hybrid. NAFTC Photo

There are some terms that need to be described before explaining the different hybrids:

• Belt alternator system (BAS) – A hybrid electric system that uses a motor/generator connected to the ICE through an accessory belt
• Start-stop technology - As of 2004, all hybrids must have start-stop technology that allows the engine to stop running when the vehicle is not moving. There are some situations where the engine will not shut off; example, if the AC is on, most hybrid engines will not shut off.
• Regenerative braking - Minimizes energy loss in an electric vehicle or hybrid electric vehicle by recovering kinetic energy that is normally wasted when slowing or stopping a vehicle. The kinetic energy is used to generate electricity stored in the battery pack.
• Motor/generator (MG) – Is a component of a hybrid electric vehicle that can be used to provide energy for propulsion, charging the batteries, or both, although never at the same time. Some full hybrids have two MGs.
• ICE – Internal combustion engine

(Hybrid Myths)

I have listed the hybrid technologies in five categories; there is no exact description industry wide as new technologies are arriving from manufacturers faster than terminology can be developed. These are just example categories:

1. Micro hybrid - A vehicle equipped with start-stop technology combined with regenerative braking. The electric motor/generator never drives the wheels or adds power to the drivetrain. This is known as the BAS (belt alternator system).
2. Mild hybrid - A vehicle equipped with stop-start technology combined with regenerative braking. The electric motor/generator never drives the wheels or adds power to the drivetrain. The MG is larger than on a micro hybrid and is usually located in the bell housing between the engine and transmission. These vehicles may have additional features to reduce fuel consumption such as electro-hydraulic power steering.
3. Power hybrid - A hybrid vehicle that utilizes an efficient ICE coupled with a MG that provides additional power to the drivetrain when needed. These hybrids do not have electric only mode.
4. Full hybrid - A hybrid vehicle that is able to run on the ICE, one or more motor/generators, or a combination of the two. Full hybrids also have many fuel saving features such as electric steering, water pump, air conditioning, etc. These hybrids are the only hybrid that is able to operate on electric only mode. These are the most efficient and complex hybrids available. This technology developed by Toyota has been on the roads for almost a decade and has been adopted by other manufacturers. It has proven to be reliable over the years.
5. Plug-in hybrid - Full hybrids with larger batteries and the ability to recharge from an electric power grid. They are equipped with a power socket that allows the batteries to be charged when the engine is not running. They have the ability to operate on electric only mode until the battery needs to be charged, usually at 20, 40, or 60 mile increments depending on the size of the larger battery pack.

Dodge Sprinter exemplifying plug-in hybrid electric technology. NAFTC Photo

All hybrids are beneficial in helping reduce greenhouse emissions and dependency on foreign oil, but there are many differences in their technologies. It wasn’t too long ago when consumers had the main option of standard or automatic transmission. Now it won’t be too long before all vehicles produced will have a hybrid drivetrain as an option.

Most consumers think of a hybrid as an ICE and MG by definition. However, there are other configurations that are classified as hybrids. The definition of a hybrid is a vehicle that has two or more sources of propulsion. When we look further into this definition, we have other technologies that fit this category.

Fuel Cell Vehicles (FCVs)
FCVs are hybrid vehicles as they use hydrogen to create electricity in a fuel cell stack and store the electricity in a battery pack. The stored electricity is used to power MGs. The fuel cell stack separates the electron and proton of the hydrogen molecule, and the protons are able to pass through the stack while the electron is not. The electron wants to meet back up with the proton so a conductor is provided with a path for the electron to travel. During the electron’s journey on the provided conductor, it is stored in the battery pack. The electron is then used to operate the MG to propel the vehicle. If you understand electron flow, you know that the motor will consume only voltage that is pushing the electron. The electrons flow freely back to the other side of the fuel cell stack to meet up with the proton. Oxygen is introduced to the electrons and protons to create water vapor as the only emission of a FCV. I have provided only a baseline explanation for understanding the operation of an FCV. The actual process is much more complicated.

General Motors (GM) Hydrogen Fuel Cell Vehicle. NAFTC Photo

Hybrid hydraulic vehicles are also being researched for automotive use. The idea is to have an efficient ICE operate at maximum efficiency and power output to run a hydraulic pump. The vehicle is propelled by hydraulic motors. The engine has no direct connection to the drivetrain. This technology has been used for years in off road equipment. It is just recently that advancements in technology have been available to utilize on automobiles.

Electric vehicle and hybrid electric vehicle technology are here to stay, and it can be confusing to understand because it is progressing very quickly. The best suggestion is to obtain some formal training on the basics of the systems, and as the technology progresses, you will be able to progress with the technology. The NAFTC offers courses and workshops on hybrid electric vehicles, battery electric vehicles, fuel cell vehicles, and other alternative fuel and advanced technology vehicles. More information can be found on them at www.naftc.wvu.edu.

Supplemental Links:

National Alternative Fuels Training Consortium (NAFTC) – http://www.naftc.wvu.edu
U.S. Department of Energy (DOE) – http://www.doe.gov
U.S. Environmental Protection Agency (EPA) – http://www.epa.gov
U.S. Department of Energy's Clean Cities Program – http://www.eere.energy.gov/cleancities
Alternative Fuels Data Center – http://www.eere.energy.gov/afdc/
Just the Facts on Natural Gas and Propane
Just the Facts on Biofuels

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