There is a tremendous curiosity about hybrid vehicles that you only fully experience after driving one. Stop for fuel and people ask you what the economy is like. Stop at the grocery store and you may get asked if the batteries take up the room where you would want to put your groceries. Park it downtown and a passerby will undoubtedly ask how it accelerates on the highway. Every hybrid owner becomes a wealth of knowledge for others interested in the technology. So what is a hybrid?
A hybrid is a vehicle that is propelled by more than one power source. The most common application combines a gasoline engine with electric motors but there can be many other designs. You could combine a diesel engine with electric motors, or a fuel cell with either the gas or diesel engines. How about combining a fuel cell with batteries that can be charged by plugging the vehicle in to your house, or using solar power combined with a fuel cell? Even using ethanol and hydrogen as fuels for a vehicle with an internal combustion engine could technically be considered a hybrid, as energy is derived from two sources. Pure electric cars that run off battery power alone are not real hybrids, but because much of the electric motor technology is shared with hybrids, they are often included in hybrid discussions. Right now, when we look at production vehicles available to the public they are all gasoline and electric hybrids. You may hear several names when referring to these gas/electric hybrids: mild hybrids, full hybrids, two-mode hybrids, series hybrids and parallel hybrids. Each describes variations in the integration of the hybrid systems. Let's look at series and parallel systems first. Series systems may connect the two power systems in line. For example, the electric motor may assist the gas engine, but the vehicle can not operate on each independently. Another example of a series system can be found on locomotives and some city buses. Here, the diesel engine turns a generator, which provides power for the electric motors to move he vehicle. Most of the hybrid systems are parallel designs. Parallel designs allow the vehicle to be propelled by either of the power sources independently or in combination. For example, the vehicle can operate on the gasoline engine alone, or on electric motors alone, or both together. There are many advantages to this design including maximum fuel economy and no emissions when operating on electric motors alone. Much of the electrical power to charge the batteries on these systems comes from regenerative braking. When the vehicle decelerates, the force used to slow the vehicle is converted into electrical energy by generators. If the battery charge becomes too low, the gasoline engine can also turn the generator to charge the battery pack. The biggest disadvantage to these systems is the complexity and cost to integrate the two power sources. Two-mode hybrids are simply another term for parallel hybrid. The vehicle can operate in either of two modes - gasoline or electric or combine the two. Full hybrid also refers to a parallel system as opposed to a partial hybrid that only provides assist to the main propulsion system. Soon you will hear a lot about Mild hybrids. Last year General Motors introduced the hybrid Saturn Vue, and this year the Saturn Aura and Chevrolet Malibu hybrids enter the market. These vehicles use gasoline engines combined with a low voltage power system that operates a Motor/Generator Unit to move the vehicle. Typical voltage is in the 42-volt range for the battery pack and electric motor/generator system. This is much lower than the 300 volts or more used on other production hybrid systems, but the lower voltage can provide only "mild" propulsion compared to the much more powerful 300 volt systems. This mild hybrid will move the vehicle independently of the gas engine but only at a crawl. Its main purpose is to assist the gasoline engine and enable an autostop feature. Autostop is a mode of hybrid operation that turns off the gasoline engine when the vehicle is not moving, such as at a stoplight. As soon as the driver releases the brake pedal or steps on the gas, the hybrid electric motor instantly and smoothly starts the gasoline engine. This autostop feature can improve fuel economy by up to 15 per cent in stop and go driving. It doesn't matter if you are driving a distinctive Toyota Prius or the more conventional appearing Honda Civic hybrid. As soon as people see the hybrid emblem on the vehicle, there are questions to be answered. It's kind of fun!
