Wednesday, July 30, 2008

Automobiles and energy

Everyone and their brother is talking about hybrid vehicles. "They are amazing, I'm saving all this money." "They are so efficient," "they save all this carbon." Yadda, yadda, yadda.

Well I'm here to tell you that there is nothing miraculous or special about hybrid cars. Wanna know why they are so great? Regenerative breaking. Yep, that's it. Think about it for a little bit. The brakes on your average run of the mill car are just another type of engine. They convert one type of energy (kinetic) into another type of energy (heat). Friction brakes are actually very good at this. In fact, brakes are about 10 times more powerful than your actual gas engine. Generally speaking, an average car can stop 10 times faster than it can accelerate to a given speed. Now take city driving. One of the reasons cars are so terribly inefficient in the city is they have to start and stop a lot, and all that idling. Every time you stop, you just throw away all the kinetic energy (moving car) as heat produced by your breaks. If you could store all that kinetic energy somewhere when you stop, and then re-use it when you pull out, there would have to be some efficiency gain right?

Well, the answer to that is a simple yes. I won't belabor the point which is that it shouldn't be mystifying that hybrid cars are more efficient because they use regenerative breaking.

So, yeah, don't get all excited about it.