Efficiency can be stated as power delivered divided by power supplied; in the electric motor, you supply voltage and current to the motor and get RPMs and Torque at the shaft. 90% of the power you supply to the motor can come out on the rotating shaft. Internal combustion engines, perhaps best called internal explosion engines, turn the chemical energy of exploding fuel air mixtures into rotating mechanical parts. Turning intermittent explosions into smooth rotation involves a lot of moving parts, each with their own losses. In addition, the explosions cause a mess of heat to be released. Every place your car looses heat, such as the radiator, and especially the exhaust, is a loss. To be truly efficient, your engine would be silent, and the exhaust would be a mixture of liquid air and carbon dioxide ice. But there is no good technology for sucking that much heat out of an explosion and turning it into rotary motion.
I won't get into it here, but engine efficiency is a long way from the total system efficiency, which depends on aerodynamic drag (block-y vs. "slippery"), tire losses and transmission losses.
The problem with electric cars is the batteries. There's a simple inescapable fact that has to be faced: there is no battery that can store the amount of energy that a liquid fuel can. Think of it this way: the electrical discharge of the battery is really a slower form of the combustion in the IC engine; electrons move back and forth between different compounds, what chemists call a Redox (reduction - oxidation) reaction. The battery has to carry around its own oxidizer; the IC engine gets to suck its oxidizer in from the environment.
What prompts this diatribe is some recent information I've come across on hybrids and electric cars. First, a recent study that shows most people who own hybrids are not likely to buy another.
A new study by R.L. Polk & Co. shows that the overall percentage of hybrids sold into the new vehicle market has fallen from 2.9 percent to 2.4 percent over the past three years. Moreover, approximately two-thirds of hybrid owners who returned to the market in 2011 did not buy another hybrid.The 33% who did buy a second hybrid ends up being a smaller number - 25% - if you take out the Toyota Prius. Either the Prius is the best hybrid on the market, or they simply have the best brand loyalty. Or both.
The market problem is that many people think that electric cars are trivial technology, and they're being killed off by greedy car companies who just want to keep selling the same old junk. Witness the conspiratorial documentary "Who Killed the Electric Car", which has that tone. The same team has released a sequel to that one, "Revenge of the Electric Car".
Design News magazine looks at the movie as less of an exploration of the cars as of the people behind the technology. Charles Murray, Senior Technical Editor, Electronics & Test, writes:
There's a moment in the movie Revenge of the Electric Car when a Popular Mechanics magazine editor says, "The scariest part is, can they get the cost of the batteries down?" If you watch the movie, that's about as close as you'll get to a real technical debate on the future of electric cars.And that's the problem. There are two sides: engineers trying to bend the problem enough to come up with good solutions, and consumers who think the companies are holding back solutions.
At the film's end, we see a "good news" montage of successes for GM, Tesla, Nissan, and Abbott (the EV converter). Tesla's stock soars, and its massive DOE loan comes through. GM rolls out the Volt. Nissan gets a $1.4 billion loan to build Leafs, and Abbott's business recovers from a devastating fire.Battery research is slow compared to the semiconductor "internet speed" we're used to. Think of how a battery works: two different materials give and take electrons at a voltage potential determined by the way the universe was put together. All of the simple combinations have been tried and new ones are being researched daily. The limits, though, are imposed by the universe. In semiconductor work, the same materials are always worked on, the techniques for putting down dopants and photoresistive masks is all that changes.
Danny DeVito joins the montage long enough to remind us that we've left the Dark Ages. Another actor, Adrian Grenier, tells us that he can't wait for the electric car era. "The innovations are here now," Grenier says, smiling brightly. "Bring them to me. I want to play." The viewer is left to wonder what Grenier might think of today's paltry electric car sales figures.
Battery development is hard, slow work. Throwing loads of money at it will help, but it will not make it happen overnight, as so many EV proponents have predicted. "There are no specific moving parts in a battery, but it's one of the most complicated things to develop, in terms of all the things happening inside," Luis Ortiz, chief operating officer of Liquid Metal Battery Corp., told us. "You've got multiple materials trying to come together in one place. It's volatile. And there are a lot of opportunities for things to go wrong." Liquid Metal Battery, an MIT spinoff, builds grid storage systems.One of the conclusions of the Revenge of the Electric Car is that we are heading in that direction. Like it or not; ready or not, we're moving. The first ones are likely to be, honestly, crap. Those are on the road now and will be for some time to come. They're the ones spontaneously catching fire that you read about. Even if perfect batteries were available now, the conversion will take time, because the power grid will need to be expanded and industries adapt (as they always do).
If you drive less than 40 miles a day, and just carry yourself or a small family, "someday" can be today. If you just go to the local supermarket two miles away once or twice a week, heck, buy a golf cart. If you need to haul a half ton, like an F-150 class pickup truck, or if you tow a moderate sized boat, or a camper, electric alternatives are probably more than 10 years out.