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.
Yep!
ReplyDeleteElectric motors are just about perfect for vehicle use, but the batteries kill you.
One of the guys I worked with at DirecTV was one of the anointed few who was able to get a GEN-II EV1 on lease. This guy was "Mr. Green", and was constantly telling people how the electric car was the future, and how lucky he was to have the honor of being able to leave this fantastic new technology.
For about a month......
Then the shortcomings of the car started to smack him over the head, and he refused to talk about it.
Since I was the FNG at our uplink about this time, and a confirmed gear head, I guess he looked at me and my questions differently, and when we talked about the car, he was pretty open about it.
It flat out SUCKED.
He was lucky to get 50 miles of range, and that was on level ground, no air-conditioning, and driving like there was an egg under his right foot. Oh, sure, it go like a scalded dog when you jumped on it, but one good burst of acceleration knocked 10% off your range!
I had a ride in it a few times, and it was all that you could imagine it to be. Stiff riding, mediocre handling, eerily quiet, and not too much fun to drive.
Electric cars have come a LONG way since then, but until somebody invents a battery with about 10x the energy density, they just aren't practical for most people.
As James Watt said "Electricity is just an easy way to move coal around" (or words to that effect).
ReplyDeleteBandy about all the efficiency figures for Electric motors all you like but you have still got to produce the electricity in the first place and except in a few instances (Hydro electric, nuclear) it means back to the burning of fuel of one sort or another and the attendant losses in conversion/transmission/reconversion.
Phil B
Interesting article from Australia on developments in battery technology:
ReplyDeletehttp://www.smh.com.au/technology/technology-news/inventors-race-to-breathe-extra-life-into-batteries-20120517-1ysqc.html
The shame is we could convert virtually all IC engine cars over to Natural Gas OR better yet, they could come right from the manufacture as a Natural Gas vehicle but NO, the green wieners have closed that off as well with regulations out of the EPA!! Such a shame, anyone is even considering Electric. And when you factor in all the subsidies that EV manufactures get their cars are a sad reflection vision and what is practical.
ReplyDeleteHydrogen is the way to go but GM turned that off when it was taken over by Big Brother and told to go with the Volt. So any speak of going green is pure BS. People have money to make and money is green, so they push that around at the expense of common sense.
BT: Jimmy T sends.
I've always been a fan of hydrogen. It has the disadvantage of less energy per volume than bigger molecules, but it burns in everything we've got now, with a change to the carburetor and timing.
DeleteThe fact it's the most abundant element in the universe can't hurt.
Many moons ago, when my slipstick was new, I was involved in a development project for a couple of reciprocating internal combustion engines. The goal was raise horsepower to the maximum point which would also allow the engine to successfully operate for at least 5 minutes longer than the duration of the race.
ReplyDeleteWe discovered, as had many before and many more since, that truly amazing horsepower could be coaxed out, as long as one disregarded longevity and power band width (what most people call "drivability"). We accepted those limitations and built some rather impressive grenades with 65-70 minute fuzes; if it was running at the end, it was usually in first place, and everything in it that moved was dumpster food immediately thereafter, including much of the drive mechanism which took a heck of a beating keeping the engine at peak HP RPM while applying the maximum possible load without dragging RPM down. The heat involved in that was fatal to a lot of components.
Anyway, thinking about that particular adventure got me to wondering about small, high-efficiency turbo diesels, alternators and electric motors. I'm wondering if a small, constant speed (and hence, as efficient as possible at that RPM - basically what one sometimes encounters as a "stationary powerplant") diesel driving an alternator which met 80-90% of normal vehicle load, with a small battery pack to temporarily bridge the gap between 80-90% and the occasional 105% needed might work well.
It's easier, and lighter, to run copper wire than driveshafts and differentials and electric motors, as you point out, have better power curves than internal combustion reciprocating engines, and diesel load - running the alternator - can be easily controlled with solid state electronics. Stored energy per pound is much higher in diesel fuel than in batteries, it's much more portable (and independent)than the coal-to-electron conversion process, and requires no new technology to implement. Diesel-electric submarines have done almost exactly the same thing for decades.
This isn't truly a hybrid, as the diesel provides the primary motive power, albeit more efficiently than a gasoline engine and 5-speed transmission.
I'm thinking, however, that if this were workable someone would be making one, (other than the non-nuclear subs).
So, where is it that this fails?
Thanks for the excellent comment.
DeleteI don't know if or where it fails. As you say, it's used in submarines and it's also the basic approach of modern trains. As you say, diesels are most efficient over a narrow range of RPMs, and this would be a better use than as an engine with a wide range transmission.
I haven't seen anything written on the approach. Perhaps Size/Weight?
It fails on 2 scores. 1 is scale and 2 is the American male.
Delete1. Most cruise ships today, as well as a lot tug boats, ice breakers, military vessels and the like, use gas turbines (jet engines) to generate electricity. They use the exhaust to generate steam and more electricity. And they use the electricity to run everything - including the motive power to the boat. Trains have been diesel-electric since the 50s. You run the ICE or the turbine at high-constant speed, you use electric power to maximum torque at minimum RPM, and everyone is happy. And locomotives use batteries for surges in power - but they are liquid-sulfur batteries. 250 degrees F. If they cool down and solidify it takes something like a week of intense effort to get them to liquify. This isn't going to go over well, for people who want to leave their cars at the airport for a week-long business trip.
2. American men are fixated on horsepower. And noise. They might talk about torque, when someone pointed out that the acceleration they get is more a function of torque than HP. But really. The original Honda Accord debuted with 91 horses. Today, it has more than 200. Because even a car that spends most of its life idling in rush-hour traffic needs to be sold to men who only one one gauge for cars. HP numbers and then MAYBE how loud the exhaust is.
two more things: Internal Combustion Engines HP numbers are maximum HP that can be generated for 15 minutes without overheating. That means at 16 minutes you have steam and red lights and buzzers. Electric motors are rated at continuous output. And since industrial applications often have them running for weeks or months without shutting down this is important.
DeleteBut try convincing the average American than his 200 HP ICE gas-guzzler really can be replaced by a 20HP or 30HP electric motor. (At highway speeds, you need about 18HP to maintain speed in an average car. The rest is wasted as heat.) You might need more if you are going to be doing a lot of towing, but you don't need 100HP electric motor.
Two excellent comments, Zendo Deb. More reasons why it's just hard to replace the ICE in a car for everyday use. The system (car with ICE) and the way people live with it have been evolving for a hundred years. They're very highly tuned to each other.
DeleteLiquid sulfur batteries could probably be replaced with something more friendly to consumer use, but the concept of a turbo diesel running an electrical system that really runs everything sounds like it's worth another look.
I'm pretty sure I've mentioned this before, but for a couple of years around '04 I received an auto industry trade magazine, probably by mistake. There was an article in there on how the Detroit auto makers had missed the boat on hybrids. They had studied the possible approaches and decided the platform just wasn't practical. Way too expensive for a regular consumer to justify. What they missed was that most buyers don't buy a hybrid because it makes sense, they buy it "because it says something about me" - that is, to impress random strangers in traffic.
But can we substitute "uneducated American males" for your second reason? The knowledge about torque and HP is pretty widespread. Not just the techno-geeks I work with and but guys who tweak cars for fun.
One thing I forgot to include in my original comment - an odd thing we noticed was that as HP went up and the powerband narrowed (they go hand in hand), fuel consumption did not rise as much as expected, which surprised us. There is only so much energy per unit in any fuel, and our projections on energy conversion per fuel unit turned out wrong, indicating that efficiency went up along with horsepower. Not a great deal, but some. Now, everything from the before the start of the intake (meaning we looked at airflow dynamics around the intake area at speed in an attempt to take advantage of higher air pressure as vehicle velocity increased, which we wore out a couple of slide rules figuring out all the ramifications of), to beyond the exhaust outlet, also at speed, was calculated and engineered to maximize HP within the extremely narrow RPM range we wound up working in. The lack of substantial fuel consumption increase for the HP gain achieved is really what's kept me curious all these years and wondering about powering cars with high efficiency narrow RPM band reciprocating engines.
DeleteZendo Deb mentioned gas turbines - you see some of the same efficiency gains with turbine-powered aircraft; engineers, and hence the airlines, are aware that each turbine is different, and that each "likes" a certain altitude (meaning air density), a certain throttle setting, and a certain velocity of air coming in. The Air Force has achieved some impressive fuel consumption results under specific operating conditions with specific aircraft by staying within a narrow set of operating conditions. Airlines have gotten pretty good at stretching a gallon as well as fuel costs have risen.
At ground level between our garage and the supermarket we have to deal with widely varying conditions, so "drivability" is engineered in to make the driving task more pleasant, and that, through engine and transmission design, carries a certain cost in fuel economy.
And, Deb, I won't challenge your assertion that many men enjoy horsepower and the noise that comes with it; I'm one of those, assuming that I can find a way to keep the horsepower glued to the racing surface where it's usable. As we used to say back in the day when asked "how much horsepower is enough," the answer was always "I dunno, how much horsepower is there? Can we get it all?"
Batteries; exotic materials used in; end of life.
ReplyDeleteNow what?
Q
Sounds like a business opportunity to me, reclaiming those exotic materials.
DeleteThat would be the kind of thing I would expect...I just wonder if the proponents of electric cars think of such things: disposal and replacement - wouldn't want to buy a new car because the battery died.
DeleteOr maybe the car part will be disposable and the battery itself is where the major part of the cost resides. Battery dies; cheaper to buy a new car.
I see electric cars possibly being feasible in places like San Francisco or New York (recharging load on grid?) but just for a niche market nationwide
Q
Oh, those electric vehicles have been around for quite some time. We used to call them golf carts.
ReplyDeleteMy oh so liberal and green (but i repeat myself) SIL will rant on about how electric cars don't pollute, and are therefore the savior of civilization. Conveniently ignoring or shouting down any mention that electrics simply displace the point of pollution to somewhere else.
My work commute has always been short, however i seriosly doubt that i could make do with 40 miles of range on a charge. And what of driving vacations? Perhaps that is the intent - take public transport for distance, or 10 days to drive 400 miles.
There probably is a place for such technology - Catalina island comes to mind. Propane or LNG would seem to be a good fit for many delivery vehicles.
A better approach IMO would be avoiding commuting altogether - I imagine that would be doable for perhaps 50% of the working population.
itor
This stuff is very exciting. It seems it's only a matter of time before a truly viable alternative to the internal combustion engine will be upon us. I can only see it as a win win situation. Even if it means we burn more coal initially to "charge" our cars. The resulting lower price for oil will make processing natural gas cheaper too.
ReplyDeletere-involt