Electric cars are a pipe dream

[Billy T]

electric motors makes use of "counter EMF" in the armature. ...

I knew that and that transformers do too. The EMF is what limits the AC current in both cases. I have always heard it referred to as "back EMF" but perhaps "counter EMF" is more common nowdays.

I also know that DC motors have much better low rpm torque than common AC motors, but think some new version (forget the name)* of AC motors have very good low speed torque too. The car´s energy source will produce approximately constant voltage DC. Perhaps with the new high torque AC motors and modern efficient solid state DC to AC converters, the ability to make AC at frequency of the the turning rate of the wheels** (or some integer factor of that) may be better than DC motors. - Just guessing that may be possible.

* Electricfetus knows their name etc. as she told me of them many posts back.

** Perhase even a different frequency for each drive wheel to keep it just below slipping for max possible acceleration of the car, skid control, etc. A physics education opens a lot of ideas but tells little about what is most practical without some "hands-on" experience.

 

[leopold]

counter EMF and back EMF are the same things.
"Just to speak a little bit more about this subject, you know that when an electrical induction "squirrel" motor runs, you have a magnetic field that circulates around the squirrel. There is a speed difference between them, what in turn generates a voltage and a force appears, which drives the "squirrel". A back-emf also appears, which lowers the net electric electron flow. The current through a rotating electric motor is greatly reduced because of this back-emf and if you avoid the moviment of the rotor, the current should be so large that could damage the equipment."
http://www.newton.dep.anl.gov/askasci/phy00/phy00351.htm

 

[billvon]

Hmm.... looked up the theoretical efficiencies and you're right that otto/diesel should be better than GTE, but I'm wondering if it is easier to make more efficient GTEs than otto/diesels since typical car engines run considerably below their theoretical efficiencies: http://www.houseofdavid.ca/engine.htm

Both engines have the issue that they are most efficient in one operating regime. With turbines the problem is that the aerodynamics of their various stages are optimized for one pressure/flow rate, and with recips they do best at wide open throttle since that's where pumping losses are minimized. Both engines would do much better thermodynamically in a system (like an advanced hybrid) that could run constantly in these states. For turbines that would mean constant power and RPM, and for a recip that would mean constant WOT operation.

 

[billvon]

I am a physicist, without much practical knowledge of motors, but would bet that best designs for car motor spin the PM with drive coil on the outside as there is more space there for larger copper wire.

These are known as brushless DC motors and are the most efficient motors out there right now. However that doesn't mean everyone uses them due to cost, fragility and lifetime issues. (Good rare earth magnets operated at very high temperatures eventually lose magnetic field strength.) The Prius uses these.

There are some that are very close though. Induction AC motors are the mainstay of the EV world now since they are incredibly rugged and cheap, and still reasonably efficient. Since the stator field has to induce the rotor field some of that energy is lost creating the field on the lossy rotor structure. The Leaf uses these.

Note that there are an endless number of versions of the above. There are synchronous AC motors, which are very much like induction motors but always run at field speed. Induction motors always "lag" a bit. There are reluctance motors that operate very much like induction motors but use "poles" of magnetic material that allow synchronous operation.

Also note that all modern EV motors use external commutation as opposed to brushed commutators. This greatly reduces maintenance requirements. (And in some cases, like BLDC, you can't practically use brushed commutators anyway.)

I woud also guess that the motor shell is non-magnet material as a spining magnetic field would have losses in the shell if it is not - I bet shells are some aluminum alloy - Anyone know if my guesses are correct?

The stator is a magnetic structure intended to capture almost all the field from the field windings, so the motor casing isn't as important. Some are steel, some are aluminum. Some motor casings ARE the stator.

 

[MeNotYou]

This may already have been addressed sometime in the last 3084 posts, so forgive me if this has already been covered...

What about graphene batteries? It's clearly still in R&D, but the ability to store enormous amounts of energy with a very small footprint seems like the thing Electric Cars need. Wouldn't the extremely high electron mobility in graphene translate into fast recharge times?

Is there potential here?

 

[billvon]

What about graphene batteries? It's clearly still in R&D, but the ability to store enormous amounts of energy with a very small footprint seems like the thing Electric Cars need. Wouldn't the extremely high electron mobility in graphene translate into fast recharge times?

There is a lot more than electron mobility when it comes to dealing with fast charge times.

Graphene batteries sound great, and is about the 34th amazing advance that will make it possible to store huge amounts of energy in a small footprint. It's the Holy Grail of EV batteries, and such a battery is announced, on average, about every four months. The only real advance I've seen to make it out the labs are silicon anode batteries, and even those have problems (swelling.)

 

[MeNotYou]

There is a lot more than electron mobility when it comes to dealing with fast charge times.

Graphene batteries sound great, and is about the 34th amazing advance that will make it possible to store huge amounts of energy in a small footprint. It's the Holy Grail of EV batteries, and such a battery is announced, on average, about every four months. The only real advance I've seen to make it out the labs are silicon anode batteries, and even those have problems (swelling.)

Yeah, for awhile you couldn't read sci/tech news without seeing at least one new "Major advancement" in graphene report every few days.

It seems like the questions regarding the possibility of mass market electric cars should be centered around supercapacitor research. Li-Ion alone isn't going to get us there.

 

[leopold]

in my opinion a brushless motor will have synchronizing problems because of the varying load and it will not have "fast throttle response".

here are 2 known disadvantages:
There are numerous applications using a Brush DC Motor that could instead utilize the Brushless DC Motor. However a few factors might prevent the changeover. The first factor is start-up cost. Although the Brushless DC Motor is lower-maintenance than the Brush DC Motor, initial cost is more expensive, due to its advantageous construction. Second is complexity. A controller is required in order to operate a Brushless DC Motor, and is usually more convoluted than most controllers. A Brushless DC Motor also requires additional system wiring, in order to power the electronic commutation circuitry.
http://www.anaheimautomation.com/manuals/forms/brushless-dc-motor-guide.php

i've used these types of motors as cooling fans for my bike with great success.
left out in the open, day after day, rain or shine, and it never failed to work.
it finally "quit" when a piece of road debris broke one of the blades.

 

[billvon]

in my opinion a brushless motor will have synchronizing problems because of the varying load and it will not have "fast throttle response".

A BLDC will have instant throttle response. Increase the throttle setting and you increase the current, which leads directly to increased torque. There are no "synchronizing problems."

The first factor is start-up cost. Although the Brushless DC Motor is lower-maintenance than the Brush DC Motor, initial cost is more expensive, due to its advantageous construction.

True.

Second is complexity. A controller is required in order to operate a Brushless DC Motor, and is usually more convoluted than most controllers.

Of all motors used in modern EV's a BLDC controller is the simplest*. You can either use an encoder for simpler control design or do a sensorless controller - fewer wires but more uncertainty on startup.

(* - even brushed DC motors. The brushes/commutators are inside the motor, but they still require design, maintenance, periodic cleanings etc)

 

[Billy T]

Interesting to note that tesla selling less than 5000 cars per quarter at price of $69,000 expects to make a profit (for first time) but;

Nearly two years after the introduction of the path-breaking plug-in hybrid, GM is still losing as much as $49,000 on each Volt it builds, according to estimates provided to Reuters by industry analysts and manufacturing experts. GM on Monday issued a statement disputing the estimates.

Cheap Volt lease offers meant to drive more customers to Chevy showrooms this summer may have pushed that loss even higher. There are some Americans paying just $5,050 to drive around for two years in a vehicle that cost as much as $89,000 to produce.

And while the loss per vehicle will shrink as more are built and sold, GM is still years away from making money on the Volt, which will soon face new competitors from Ford, Honda and others.

GM's basic problem is that "the Volt is over-engineered and over-priced," said Dennis Virag, president of the Michigan-based Automotive Consulting Group.

I.e. GM´s complex machine, the Volt, needs at current volume to be priced at $20,000 MORE than the Tesla just to break even, yet Tesla will make a profit at that volume!

 

[Billy T]

Tesla reports earning. If you were among the many who were short, the 24% surge up in share price must really hurt, but take your loss and get out before it gets worse.

Old saying: "He who sells what isn´t "hissen" must buy it back or go to prison."

Heavily shorted Tesla Motors (TSLA) delivered on its promise to log the first quarterly profit in company history Wednesday, as the electric vehicle maker reported adjusted EPS of $0.12 per share for Q1 (triple analysts' estimates) on revenue of $562M. Moreover, gross margins doubled sequentially as the company beat its early production estimate, producing 5K Model S vehicles. The company also said it will beat its FY13 vehicle delivery estimate of 20K. The stock raced 24% higher

 

[theDoctor]

the future is not in battery powered electric cars, but it is in hydrogen powered electric cars. They are extremely efficient and they dont have the strong limitations that bettery electric cars do. Not to mention that it will be our only option once we run out of oil, so either no one drives cars or we have electric cars. I dont think i really need to provide a source to prove that we will eventually run out of gasoline to fuel cars and ethanol is dreadfully inconvenient much more than electric. SO either we figure out the electric car or we get happy with trains really.

 

[Billy T]

... ethanol is dreadfully inconvenient much more than electric. ...

You are very mis-informed. I fill up with cheaper per mile driven ethanol in 3 minutes or usually less instead of 2 or more HOURS for a battery recharge.* It is just like filling up with gasoline. Brailians have been doing this for 30+years! At least 40, perhaps 50 million "flex-fuel" cars do this now in Brazil where I live. In Brazil, labor is cheap so "self-serve" filling station essentially do not exist. Instead usually some young lady fills my car, and if station is not busy, another cleans the front window.

Why would you say such a silly thing?

the future is not in battery powered electric cars, but it is in hydrogen powered electric cars.

That is just as silly. Hydrogen is very hard to store and not even an energy source but electric energy of electrolysis transformed. You either store it in a heavy steel tank as a compressed gas (weight and energy density worse than a Li-ion Battery) and need compressor somewhere to get the gas compressed, OR you store it in a heavy metal hydride, which is very heavy and at best stores only one atom of hydrogen per heavy metal atom - why it is again with worse weight and energy density worse than a Li-ion Battery.

Ethanol, from sugarcane, is renewal, sustainable, slightly carbon negative, slightly more powerful and much cleaner buring than gasoline, but does only take you 70% as far as same volume of gasoline would.

* As there are so few stations (less than 20 in all of USA) where you can buy hydrogen, I don´t know how much time is needed to fill up of H-fuel cell´s tank, but would guess that takes more than 10 minutes, probably less than 20 minutes, to compress a tank full or be absorbed in the metal hydride lattice. I am almost sure part of the energy stored in the hydrogen must heat the metal hydride to dirve the H2 out of the storage tank - that lowers the efficiency.

 

[theDoctor]

Because ethanol take a significant amount of energy and scientific efforts to produce not to mention the total cost in taking the resources from agricultural needs, we would never be able to meet the full demand of gasoline with ethanol because of the fact that we would need to take all of the food away from cows. SO while it is not inconvenient for you in how long it takes to fill your tank, it is however on the price of a cheese burger and the amount of community energy it takes to actually create ethanol.

 

[KitemanSA]

the future is not in battery powered electric cars, but it is in hydrogen powered electric cars. They are extremely efficient and they dont have the strong limitations that bettery electric cars do. Not to mention that it will be our only option once we run out of oil, so either no one drives cars or we have electric cars. I dont think i really need to provide a source to prove that we will eventually run out of gasoline to fuel cars and ethanol is dreadfully inconvenient much more than electric. SO either we figure out the electric car or we get happy with trains really.

The best hydrogen carrier is not hydrogen but ammonia. The best source for ammonia? Liquid Fluoride Thorium Recyclers.

 

[Billy T]

Because ethanol take a significant amount of energy and scientific efforts to produce not to mention the total cost in taking the resources from agricultural needs, we would never be able to meet the full demand of gasoline with ethanol. ...

Still posting from great ignorance. All the worlds car´s* that need liquid fuel a decade hence, can be supplied with ethanol fuel using no more than 1% of the world´s arable land. The yield of food and fiber from the remaining 99% can easily be boosted by 10% with better agricultural practices (and some GM seeds) If this were done, it would reduce the release of CO2 from burning petroleum by 93%. - Go a long way to keep the Earth from over heating.

* Assumed here is that the increase in cars in Asia, is offset by the decrease in cars everywhere that need liquid fuel. I.e. assumes that the world´s current number of gasoline cars is to be fueled with alcohol from sugarcane. It would take about a decade to increase the production of sugarcane to met the demand for ethanol and also at least a decade to convert the cars needing liquid fuel to ethanol (cars on the road using gasoline typically are not scrapped for about 12 years.)

BTW, KitemanSA is correct, liquid ammonia is the best way to transport hydrogen. Only a very modest pressure keeps it liquid and in a gallon of room temperature ammonia there is ~30% more hydrogen than in a gallon of liquid hydrogen, which needs to be no more than a few degrees above absolute zero (-273 degees C)

It is not easy to do, as air ammonia mix must be set within a narrow range, but you can run slightly modified IC engine directly on ammonia - 20 or so years ago some Canadian did this. Google and you can find, I bet.

I forgot to mention that sugarcane ethanol has twice the RoE that shale oil does. - An 8 fold increase on the energy used for fertilizer, planting, harvesting and transport to the distillation plant. There the crushed cane not only supplies all the heat needed for distillation but an excess of heat that currently generates 4% of Brazil´s electrical energy! (and that electric energy is not even counted in the 8 fold energy gain - that counts only the energy in the ethanol produced!) Ethanol from Iowa´s corn has an RoE greater than 1 but less than 2 mainly as much more fertilizer is needed to compensate for the shorter growing season and fact that the distillation heat is almost always supplied by natural gas. That greater use of nitrogen fertilizer is very damaging to the environment as most of it is converted by soil bacteria into NOx.

 

[theDoctor]

I see what you are saying but, in truth we do not need the hydrogen to be liquid and if we are going off of what is possible, the best thing is indeed electric simply because if we begin to use geothermal and Solar power we would be able to meet any imaginable energy need to the point that we would be able to simply take water out of the ocean and break it down electrically so that we have hydrogen that is easier to transport than batteries. It does not need to be liquid hydrogen simply compressed hydrogen. Compressed hydrogen can provide a range of 650 miles per tank which is very good for a renewable energy source. (I would provide source but i cannot post links the easiest way to find the information would be to look up hydrogen storage, or cryocompressed hydrogen in wikipedia or google)

 

[billvon]

the future is not in battery powered electric cars, but it is in hydrogen powered electric cars. They are extremely efficient and they dont have the strong limitations that bettery electric cars do.

1) We don't have any hydrogen
2) We can make it but it takes a lot of energy
3) Hydrogen is among the most dangerous fuels out there
4) Hydrogen cars have very limited range due to the low energy density of hydrogen

Not to mention that it will be our only option once we run out of oil

If you can make hydrogen you can make almost any fuel, including methane - and methane is a lot easier to store.

and ethanol is dreadfully inconvenient much more than electric.

How is ethanol inconvenient? You pump it into a tank. Just like gasoline.

the best thing is indeed electric simply because if we begin to use geothermal and Solar power

We've "used up" most of the good geothermal sites already.

to the point that we would be able to simply take water out of the ocean and break it down electrically so that we have hydrogen that is easier to transport than batteries.

If you have the extra energy, use it to put into the grid - then save the natural gas you would have burned and use it to power our cars. We have enough natural gas to power all our cars and trucks if we could shut down our current natural gas generators.

If you don't have the extra energy then you can't make hydrogen.

It does not need to be liquid hydrogen simply compressed hydrogen. Compressed hydrogen can provide a range of 650 miles per tank

Sure, if you pull a trailer with a hydrogen tank on board. (I wouldn't want to be anywhere near it if you ever get into a fender bender though.)

 

[theDoctor]

1) We don't have any hydrogen
2) We can make it but it takes a lot of energy
3) Hydrogen is among the most dangerous fuels out there

Actually that is not true Gasoline is atually more dangerous than hudrogen, the technology we have for using, storing and transporting it to the point that any sort of dangerous situation is far and few between.

4) Hydrogen cars have very limited range due to the low energy density of hydrogen

If you look at one of my earlier posts I explain tat we ave the technology to make a car that uses compressed hydrogen and has range of 650 miles, that is definitely a decent range compared to that of a internal combustion powered car.

If you can make hydrogen you can make almost any fuel, including methane - and methane is a lot easier to store.

Yes but the chemical resources are more available for hydrogen, it is literally the most common element in the entire universe and also on this planet.

How is ethanol inconvenient? You pump it into a tank. Just like gasoline.

If you read my earlier post you would have seen that I continued to explain that it may not be inconvenient for you as an individual but the process of getting ethanol is exremely costly compared to hydrogen.

We've "used up" most of the good geothermal sites already.

Actually we have barley used any of our geothermal resources to the point where if we simply used all of the readily available geothermal power in the US we would able to power the Entire Earth. the only country that really uses geothermal power to any sort of high degree is Iceland. I would recommend that you look at a geological map of all of the geothermal power hot spots.

If you have the extra energy, use it to put into the grid - then save the natural gas you would have burned and use it to power our cars. We have enough natural gas to power all our cars and trucks if we could shut down our current natural gas generators.

If you don't have the extra energy then you can't make hydrogen.

Natural Gas is Finite, electricity is not, why would we even bother repeating this whole petroleum thing. It is much more simple to move to something renewable to start off with.

Sure, if you pull a trailer with a hydrogen tank on board. (I wouldn't want to be anywhere near it if you ever get into a fender bender though.)

Actually the tank fits comfortably inside a normal sized vehicle there is no need for a trailer.

 

[Billy T]

... Solar power we would be able to meet any imaginable energy need to the point that we would be able to simply take water out of the ocean and break it down electrically so that we have hydrogen that is easier to transport than batteries...

Certainly there is more than enough solar energy, but it is the economic cost of electrolysis added on to the cost of Hydrogen fuel cells that makes one of two main reasons why hydrogen fuel cell powered car is not used - no technical problems - just too costly compared to several alterantives.

The second main reason is the added weight of the heavy thick walled tank storing H2 for your 650 mile driving range. You can keep the weight lower by not making the presure dozens of atmopheres but then the volume of the 650 mile tank is more than 30% of the car volume. I cann´t be more specific until you indicate what presure you want your tank to hold, but one or more of these three factors (weight, volume, & cost) is why H2 is not attractive vs. some of the alternaive. Get specific and we can discuss more, but just your hand waving claims are exactly that.

... the process of getting ethanol is exremely costly compared to hydrogen.

Give some real world dollar / joule (or Wh) data trying to support that nonsense. Waving your hands is not very persuasive, especially when you have the realtive cost backwards. Note ethanol made from sugarcane is cheaper per unit energy contained than gasoline! (and the IC engine that uses it is also much cheaper than the fuel cell with its precious metals etc. NASA can afford them - you can´t.)

Because the cost of a fuel cell large enough to give the power output needed for passing on the highway is so great, there would need to be a li-ion battery in the "Hydrogen powered" car too. I.e. the battery gives the high power level needed to accelerate the car going 50mph to 70mph in < 7 seconds while passing the car going 55mph in a 60mph zone. After the passing is done, the H2 fuel cell recharges the the Li-ion battery. Note this car is extra heavy with both the battery and the heavy steel tank hold the H2, so takes more energy to do that common passing job.

Summary: Get realistic. Stop with the hand waving nonsense.