When Mike and I wrote our review of the 2011 Chevy Volt, and when I drafted my rebuttal to George Will’s editorial on the car, one thing became clear: the majority of American consumers have no idea that there are different kinds of hybrids. Thanks to ineffective marketing campaigns from automakers and the short attention span of the average consumer, they’re completely unaware that a Toyota Prius differs from a Chevy Volt.
I’m going to attempt to clear things up, in language that even the most sound-bite-addicted car buyer can understand. I won’t discuss electric cars here, nor will I discuss the uber-efficient gasoline powered or diesel powered cars that are coming over the next few years. Instead, this is all about the hybrids on the market or under development.
First, lets start with a definition of a hybrid. The the Society of Automotive Engineers (SAE) considers any vehicle with two or more distinct power sources to be a hybrid. By loose definition, that includes the cars we assume would be covered, like the Toyota Prius or the Honda Insight. Strangely enough, it would also include a Honda Goldwing motorcycle, which uses a six cylinder engine to produce forward motion, but uses an electric motor (the starter, actually) to produce reverse. Hybrids, by definition at least, are more common than you may have thought.
As the term hybrid relates to the automobile, there are five basic types: parallel hybrid, series-parallel hybrid, series hybrid, plug-in hybrid, and fuel cell electric hybrid. Let’s jump right in to the differences.
A parallel hybrid uses an electric motor and an internal combustion engine, both coupled to a mechanical transmission. A significant feature of a parallel hybrid is that it can be driven by either electric power (usually for short distances at low speeds), gasoline power or a combination of both. A subset of the parallel hybrid is called the “mild parallel hybrid”; these use a small, low capacity electric motor to provide supplemental power under acceleration and regenerative braking under deceleration. The electric motor of a mild parallel hybrid can also be used to provide an effective stop / start mechanism for fuel savings at traffic lights. Examples of the parallel or mild parallel hybrid class include the Honda Insight and Honda CR-Z, as well as BMW’s 7 Series Hybrids.
A series-parallel hybrid is, first and foremost, a parallel hybrid. Its more complex series-parallel drive can vary the amount of power derived from the electric motor or the gasoline engine; both can be used sequentially (in series mode) or together (in parallel mode) depending on the demands placed on the vehicle. Most series-parallel hybrids are primarily gasoline powered with an electric motor assist to help with acceleration or to boost fuel economy. This is the most common type of hybrid, and examples include the Toyota Prius, the Lexus HS 250h and the Ford Fusion Hybrid.
A series hybrid can also be called an extended range electric vehicle, since it is powered by electric motors which derive electricity from battery power. A gasoline or diesel engine is used to power a generator, which produces electricity to charge the batteries and extend the range of the vehicle. Diesel submarines use similar technology, as do diesel-electric locomotives. The Chevy Volt is the first commercially produced series hybrid vehicle, and the upcoming Fisker Karma will use series hybrid power as well.
A plug-in hybrid is simply a parallel or series parallel hybrid that has additional battery capacity to extend the range possible in electric vehicle mode. Toyota is currently market testing a plug-in hybrid version of the Prius, which they hope to bring to market at the end of 2012. The goal is a range of approximately 15 miles on battery power alone, which Toyota feels is adequate for most urban commuters.
Fuel cell electric hybrid
Welcome to the future: a fuel cell electric hybrid will use battery power and fuel cell power to drive the vehicle’s electric motor or motors. There are no internal combustion engines used, so fuel cell hybrids are the cleanest of the lot. Unfortunately, fuel cell technology is not yet at maturity in regards to functionality and price point. Until a hydrogen fueled infrastructure can be developed, and until the cost of implementing fuel cell technology comes down to compete with fossil fuels, fuel cell electric hybrids will exist as test mules only. The Honda FCX Clarity is a fuel cell electric hybrid concept.
So what does all this mean? If you drive a parallel or series parallel hybrid, you’re really using a gasoline engine with a supplemental assist from battery power. If you drive a series hybrid, you’re relying on battery power, supplemented by a gasoline motor to produce additional electricity as needed. If you drive a plug in hybrid and have a very short commute, you’ll probably exist somewhere between the other two worlds. If you drive a fuel cell electric hybrid, you’ve probably got a PhD and wear pocket protectors, and will send me a list of two dozen things that I over-simplified in this brief article.
If there’s good news for the future, it’s this: in order to meet the upcoming CAFE standards, electric motors and gasoline motors will need to peacefully coexist for some time. As a car enthusiast, I’ve yet to drive a parallel hybrid that I’ve found satisfying, since none function particularly well as an electric car or as an enthusiast-oriented gasoline car. That will change, and I see a day in the not-too-distant future where muscle cars still make 400 horsepower, but with two-liter, four banger engines supplemented by big electric motors and lots of battery capacity. Whether you love hybrids or hate them, maximum torque from zero RPM is something any gearhead can embrace.