Just saw this recently...a EV leaving both Ferrari and Carerra GT in the dust... If you download the video, it's pretty interesting... to see potentials of full electric vehicles. http://www.wrightspeed.com/pages/1/index.htm Efficiency quoted by the EV builder...
"Faster acceleration than a supercar, 1/3 the energy consumption of a hybrid" Since the conditions of this claim are not identified, and WHICH hybrid is also not described, I have serious doubts that this venture capitalists behind this are not being quite frank with us. I rather doubt they get 180 MPG City on the EPA run in a car the size of a Prius...
1/3 the energy usage of a hybrid is misleading. If you measure the electrical energy COMING OUT OF THE BATTERIES, which I think they are, then you have the efficiency of the motor, the rolling resistance of the tires and friction in the bearings and gears. This makes it look very efficient. But that electricity had to come from somewhere and a lot was lost along the way. When you put electrical energy into a battery, you don't get it all back out. The exact losses depend on the battery technology and condition and how you charge it (in that regard a "plug in" has an advantage that it can charge slower). Figure 15-30% loss in the battery. Then there is the efficiency losses in generating the electrical energy and getting it to the batteries. A pure hybrid converts gasoline to electricity, which is about 30-35% efficient (70% loss). For a plug in, it depends on how the electricity is generated. If it is coal of natural gas, then the efficiency is only a little better than a gasoline engine, about 40% if you include transmission losses. Some people might argue that efficiency is irrelevent for Hydro-electric or nuclear, but they have other issues that make it even harder to compare to hybrids. If someone make an argument on the basis of efficiency, I want to know the the full cycle efficiency from start to finish, not just one piece. BTW, this is not a slam of EV's. I like them and think they make sense for a lot of the driving we do. I would love to have one. However, the engineer in me hates misleading statistics. Steve T
