What Is "Hybrid-Drive" Anyway?

By Mark Forsythe The Kansas City Post I've been using the phrase "hybrid-drive" figuring anybody that hasn't lived in a cave for the last five years has at least seen a Toyota Prius or Ford Escape Hybrid and developed a small understanding of the technology. Apparently that is not the case. While pitching my idea of Ultra Light Rail, I'm finding some community leaders don't understand what hybrid-drive actually is. So today I decided to forgo a preachy editorial and give a little primer on hybrid-drive. Simply defined, hybrid-drive uses a combination of an internal combustion engine and electric motors to propel a vehicle. This is hardly new. Railroad locomotives have essentially been hybrid-drive for years. The railroad hybrid-drive system is not for fuel economy or environmental friendliness. It's for reliability. Electric motors are extremely efficient, generate massive amounts of torque (that's the pulling power that pickup commercials are always talking about) and don't require a transmission. Can you imagine what the maintenance would be on a railroad locomotive if it had a transmission like an automobile? So the diesel engine drives an electric generator which in turn provides current to the electric motors that drive the wheels. Simple, powerful and reliable. With me so far? Somewhere along the way, engineers figured out that the diesel engines in buses worked the hardest, and produced the most pollution when the vehicle was accelerating from a standstill. If only there were some way to power the electric motors during that time without using the internal combustion engine. Hmmmm. How about a battery? Battery technology hadn't come far enough along to drive a railroad locomotive, but it could certainly propel a bus. When pulling away from a stop, a bus uses its banked battery power to drive the electric motors. Once the bus gets rolling, the diesel engine takes back over and also recharges the batteries. Once again, this system wasn't really pursued for environmental reasons, but it was marketed that way. The real impetus was for reliability. It's easier and much cheaper to swap out a simple electric motor than it is a complicated transmission. Now enter the automotive sector. Looking for ways to up their fleet average MPG and appease the growing environmental concerns, the car makers sized this bus technology down even further and added a new twist. Regenerative braking. Fancy term, but anybody who has ever driven a standard transmission car and down shifted to slow the vehicle understands the concept. All that drag and energy in slowing a vehicle could be recaptured and used to charge the batteries. As little energy as possible goes to waste. That's the hybrid-drive system you see on the road today. Interestingly enough, the concept trickled down from giant locomotives, to buses, to automobiles. Now the concept of regenerative braking is trickling back up and most new hybrid-drive systems for buses have the same form of energy recapturing that your run-of-the-mill Ford Escape Hybrid has. So buses run cleaner, are cheaper to maintain and are more reliable. New technology? Hardly. Just a new marketing spin on an old idea. Hopefully this clears things up a bit. Maybe? Clear as mud? Go ahead and ask questions if you like. I'll answer what I can!