Electric cars are a pipe dream

[KitemanSA]

Super- Flywheels are a high energy density way, perhaps even soon and economical way, to store kinetic energy but getting huge power surges from them is much more costly than getting that power from a spinning generator as you still need that high power capacity generator to convert the stored KE into electric power. - Just let the generator be both the energy storage device and the converter of KE into electric power. - No need for two separate units of approximately equal cost.

The only way to store reasonable amounts of power in a generator is to make it essentially a flywheel. And if you are going to do that, might as well do it well. Both Beacon and Pentadyne seem to do it well in the 25kW range. The new EMALS for the new Ford Class supercarrier uses a flywheel WAY bigger that either of those. It is bloody HUGE.

 

[Billy T]

The only way to store reasonable amounts of power in a generator is to make it essentially a flywheel. And if you are going to do that, might as well do it well. Both Beacon and Pentadyne seem to do it well in the 25kW range. The new EMALS for the new Ford Class supercarrier uses a flywheel WAY bigger that either of those. It is bloody HUGE.

I don´t know about the EMALS. If you have a link please post it, or I will search if you don´t. Beacon was correcting the electrical 60 Hz phase and doing that requires much less energy than actually making the 60Hz power.

I.e. when a quasi-isolated AC generator is suddenly placed under increased load its rotation rate slow as it is using the "flywheel" stored energy to meet the larger demand. If the generator is driven by steam turbine as is typical, the turbine will in a few cycles get the rotation back up to restore the 60 hz. Because so many modern devices use that 60Hz as a "clock" that brief drop in frequency is no longer acceptable. - Why the new FERC Order 755 takes effect this October.

My point was that a separate flywheel is not required - a large generator IS an energy storage system and much cheaper than both it, which you must have, plus a separate or even common shaft Flywheel. This is mainly because the battery is charged with DC and it is of no importance (to the solid state rectifiers) in this application if the rotational speed of the generator drops from say 100 hz down to 50 Hz as the battery is charged. That drop would extract 75% of the rotationally stored energy. The battery re-charge problem is VERY different from the one Beacon units were designed for and much easier /cheaper as there is zero need for keeping rotation rates for 60Hz power generation.

As the stored energy goes as the square of the rotational speed, I would think rotation speeds should be higher than 1000 rpm. Car engine speeds would be fine and the units could be much samller and cheaper, if high rotation speeds were used. For example a unit running at 1000 rpm stores 100 times more energy than one running at 100 rpm. Thus, the 1000 rpm unit could have a moment of rotational inertia 100 times less and store the same energy. The cost of the unit scale crudely as it size. So a 1000 rpm unit storing the same energy as a 100 rpm uint would cost only ~1% as much.

I´m just guessing but with high speed rotation when full energy is stored, I think a unit about the size of a suitcase would be all that is required for most recharge centers, conveniently located only 15 or so blocks apart in a city. I.e. If someone was using the first you came to, just drive to the next. I bet it is even possible to spin up the generator with a gasoline motor quite like a lawn moyer motor! Fully automated units in which you stick a few dollar bills, should not be any bigger or more costly than the self-service pumps you get your gasoline from today! Many, if not most, parking lots would have one.

PS by edit: Also there is no large UGT that eventually often leaks gasoline into the ground water and is an explosion or at least fire hazard.

 

[John Connellan]

I heard that the Formula 1 governing body and many of the manufacturers are looking into electric cars as the future of the sport! Will never be the same again though - the engine noise was one of the defining and most exciting features of the sport!

 

[ElectricFetus]

I don't see why there can't be hyrbids a gas turbine powering electric traction motors would be crazy powerful for sporting events. The gas turbine has more then double the power density of a IC engine, although that ratio might fall back to 1:1 or lower once you add in the weight of the generator and traction motors, unless you make them superconducting which is a awesome possibility. It would not be very efficient since the gas turbine would need to be run up to max before starting so there is no acceleration lag (if the gas turbine was driving the drive shaft directly the car would accelerate at a crawls pace, hence why electric in between is needed)

 

[John Connellan]

Not even a need for hybrids with todays technology:

http://www.youtube.com/watch?v=nDZ4VSFC6z0

View attachment 6218

 

[billvon]

I don't see why there can't be hyrbids a gas turbine powering electric traction motors would be crazy powerful for sporting events.

Sure, that could work. It would be noisy and inefficient but it would have a very high power/weight ratio.

(Keep in mind, though, that even regular Formula 1 race cars are not limited in power by how big an engine they can fit in the car - they are limited by strict limits in displacement, engine control etc to try to "level the playing field.")

 

[KitemanSA]

I don´t know about the EMALS. If you have a link please post it, or I will search if you don´t. Beacon was correcting the electrical 60 Hz phase and doing that requires much less energy than actually making the 60Hz power.

Type in EMALS into Wikipedia.
Beacon had other uses for their flywheel besides frequency maintanence.

I.e. when a quasi-isolated AC generator is suddenly placed under increased load its rotation rate slow as it is using the "flywheel" stored energy to meet the larger demand. If the generator is driven by steam turbine as is typical, the turbine will in a few cycles get the rotation back up to restore the 60 hz. Because so many modern devices use that 60Hz as a "clock" that brief drop in frequency is no longer acceptable. - Why the new FERC Order 755 takes effect this October.

I know about frequency regulation. Why are we talking about it here?

The subject was, AFAICT, the use of storage devices to allow rapid charging of a Tesla S (or maybe just EVs in general). The purpose of the storage device is to isolate the grid from the massive load. Seems that a set of flywheels would be just about optimum for that purpose.

My point was that a separate flywheel is not required - a large generator IS an energy storage system and much cheaper than both it, which you must have, plus a separate or even common shaft Flywheel. This is mainly because the battery is charged with DC and it is of no importance (to the solid state rectifiers) in this application if the rotational speed of the generator drops from say 100 hz down to 50 Hz as the battery is charged. That drop would extract 75% of the rotationally stored energy. The battery re-charge problem is VERY different from the one Beacon units were designed for and much easier /cheaper as there is zero need for keeping rotation rates for 60Hz power generation.

But that assumes that each gas station would have its own generator, not something that seems economic to me.

 

[Billy T]

Type in EMALS into Wikipedia.

I did and have posted else where some comments on the new Ford class of aircraftcarriers that will launch with them.

Beacon had other uses for their flywheel besides frequency maintanence.

AFAIK that was their only application, but they may have other ideas in mind before going bankrupt.

...The purpose of the storage device is to isolate the grid from the massive load. Seems that a set of flywheels would be just about optimum for that purpose.

Yes, but I call any spinning energy storage a "flywheel" and noted that to convert that stored energy into electic energy for charging a battery an electrical generator is ESSENTIAL. It can be the energy storage system by its self, especially as it can spin faster than 1000 rpm in this battery recharge application, where the AC frequency it produces can vary greatly. I.e. unlike an application not making DC (with rectifier of the variable frequency AC) one can extract at least 90% of the stored rotational energy. This makes very small systems possible - I guessed "suitcase" size would be adequate and very cheap. If these cheap recharge units are in most parking lots, probably they should have a red lght showing during their respin period that switches to green to show they are available for motorest driving by to recharge if his battery is getting low.

But that assumes that each gas station would have its own generator, not something that seems economic to me.

No, it doesn´t: If the recharge takes 5 seconds* and the re-spin up of the generator is done in 1000 seconds that is a 200 fold reduction in the power taken from the electic company - possibly less than gas station is using for it lights etc. The stations could turn off half their advertizing lights for 1000 seconds, but I doubt even that would be needed. Gas stations have already electric motors that can lift a heavy truck for an oil change in 5 seconds - that is much more power that the 1000 seconds recharger required. - Keep the advertizing light fully lit, just don´t give oil changes to heavy trucks for 1000 seconds. I.e. no need for a separate generator.

To drive home that point, I even noted that a IC motor, much like a lawn moyer has, could do the re-spin job as it has wide range of RPMs, but some automatic gear shift might be usefully if one wants to drain 90% of the stored energy out during a battery recharge. I was not suggesting that a small IC engine be used - the power line would be the better energy source in almost all cases except at home with only 100 Amp or less service.

* Few batteries can full charge in 5 seconds but we were speaking of new types that makers of claim can.

 

[KitemanSA]

Your original response to me implied NOT a flywheel but just a generator. Now you are implying a flywheel IS a generator cuz it needs to generate the electricity. Well duh. Way to back track

 

[Billy T]

... you are implying a flywheel IS a generator cuz it needs to generate the electricity. ...

That is a little twisted from what I am saying:

Charging a battery equires a source of electrical energy. A local spinning AC generator with rectifiers is most efficient for that. All spinning generators do store energy so are a form of "flywheel energy storage." Compared to most such flywheel applications, almost all the stored energy can be extracted while the battery is charged as any AC frequency is OK for producing DC. For example, if the full stored energy spin rate is dropped down to only 0.1 of that spin rate, you have extracted 99% of the stored energy to charge the battery with.

 

[Billy T]

Tesla Motors Inc. (TSLA), the luxury battery-car company run by billionaire Elon Musk, is North America’s rechargeable auto sales leader so far this year as its Model S sedan passed General Motors Co. (GM)’s Chevrolet Volt.

Tesla expects to report at least 4,750 deliveries of the electric Model S in the U.S. and Canada when it releases first- quarter results on May 8, said Shanna Hendriks, a company spokeswoman, reiterating a March 31 estimate. That compares with 4,421 Volt sales in North America and 3,695 deliveries of Nissan Motor Co. (7201)’s Leaf, based on data provided by the carmakers. ... Tesla {is} saying it would report a first-quarter profit, the first in its 10-year history. The plug-in hybrid Volt, which uses both batteries and a gasoline engine, led regional sales in 2012.

Tesla began selling the Model S, with a $69,900 base price, in mid-2012 and hasn’t begun shipments beyond North America. It goes as far as 300 miles (483 kilometers) on a charge, according to Tesla. Musk has set a target of delivering 20,000 of the cars, built in Fremont, California, this year. (2013)

The rapidly growing wealth of the top 7% (Up 28% in 3 years) is good for sales of the Model S. The 93% of US population losing ground (4% drop in wealth, 2009 thru 2011) was not going to buy a Model S anyway. They do, however, get to pay taxes making Musk´s SpaceX profitable.

Musk really knows both the economy and high technology*, like few do. He will do well when he builds new factory in China - many very rich there already and status cars (almost all imported) are big sellers in China - world´s largest car market especially for top of the line luxury cars. Just in the US that top 7% with rapidly growing wealth total 8 million families, so China may need to wait a decade or so before musk builds a model S there. Musk may export Model S to a few Chinese paying more than $100,000 for each just to lay the ground works for a bigger factory there.

* Musk has explained why Boeing´s 787 battery catches fire (and an MIT electrical engineering professor said: "I would have used exacttly the same words."). If Musk and that professor are correct, the new FAA aproved version probably makes problem worse as now has less cooling inside the new box, especially for long, high-altitude flights with new vent to lower outside pressure.
Read Musk´s / MIT explaination/ here: http://www.sciforums.com/showthread...any-millions&p=3041392&viewfull=1#post3041392
I think they are right - i.e. more fires probably ahead for the 787 battery.

 

[Russ_Watters]

I don't see why there can't be hyrbids a gas turbine powering electric traction motors would be crazy powerful for sporting events. The gas turbine has more then double the power density of a IC engine...

And much higher efficiency. But it runs hotter so it takes longer to start and warm up and runs at very high rpm so it would likely be more maintenance intensive. Now with a hybrid engine the longer warm-up may not be an issue though (just run on battery for a couple of minutes), so I'd like to see it happen. And throttling wouldn't need to be fast if it is a hybrid either.

 

[Russ_Watters]

Not even a need for hybrids with todays technology:

http://www.youtube.com/watch?v=nDZ4VSFC6z0

View attachment 6218

I assume it has about a 3 mile range...?

 

[Billy T]

General Motors Co. (GM), the largest carmaker in the U.S., is shifting its center of gravity to China, where it sells more cars and now invests more money.
GM’s announcement at the Shanghai auto show this month that it is spending $11 billion by 2016 on new plants, products and people in China demonstrates a change in priorities. GM is investing $1.5 billion in North America this year, where it has a more modest factory footprint.

Money follows the market demand and it ain´t just GM building in China.

 

[KitemanSA]

That is a little twisted from what I am saying:

Charging a battery equires a source of electrical energy. A local spinning AC generator with rectifiers is most efficient for that. All spinning generators do store energy so are a form of "flywheel energy storage." Compared to most such flywheel applications, almost all the stored energy can be extracted while the battery is charged as any AC frequency is OK for producing DC. For example, if the full stored energy spin rate is dropped down to only 0.1 of that spin rate, you have extracted 99% of the stored energy to charge the battery with.

But at a typical generator spin rate, the energy stored is quite small. You either need a VERY high spin rate to store significant energy (which is basically the flywheel I was talking about) or enormous otherwise unneeded mass (not very efficient).

 

[billvon]

And much higher efficiency.

They're actually less efficient on a kwhr per unit of fuel measure. But they are simple and have a very high power to weight ratio, making them very attractive for things like aviation. In some applications (power plants) their inefficiency is overcome by a second stage Rankine cycle engine (i.e. a modern combined cycle natural gas power plant.)

 

[Russ_Watters]

They're actually less efficient on a kwhr per unit of fuel measure. But they are simple and have a very high power to weight ratio, making them very attractive for things like aviation.

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

 

[leopold]

http://www.houseofdavid.ca/engine.htm

i noticed the efficiencies of the wankel and electric motors aren't listed.
not sure about the wankel but most electric motors attain efficiencies greater than about 75%
http://www.engineeringtoolbox.com/electrical-motor-efficiency-d_655.html

 

[Billy T]

... most electric motors attain efficiencies greater than about 75%
http://www.engineeringtoolbox.com/electrical-motor-efficiency-d_655.html

Nice link. They certainly can and most are in the low 90% range. Only applications like a hair dryer where motor losses as heat are not really loses would drop below 75%. Also things that make the motor more efficient like larger diameter copper wires add weight, which makes the hair drier less competitive in the market place.

Even low hysterisis iron is cheaper than modern rare earth magnets which can reduce magnetic losses (and of course eliminate the "copper loses" with the elimination of the field coils). These compact high quality magnetes are mainly used in moderater power motors, such as in wheel motors for electric vehicles where the compact size helps too. It would be too costly to use them as main motor of an electric train, which does not much mind the extra weight of heavy copper wires.

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. 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?

For this thread focused on electric cars, I think you can safely assume that 90% or more the electric energy delivered to the drive motors is converted into mechanical energy.

 

[leopold]

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.Anyone know if my guesses are correct?

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

with regards to DC motors:
"the starting of fairly large DC motors REQUIRES that the current be increased gradually or that resistance be inserted in series with the armature"
http://books.google.com/books?id=Yx...esult&resnum=1&ved=0CDIQ6AEwAA#v=onepage&q=dc motor reduced voltage starting&f=false

i know that an alternator with a PM armature and field coils are not very efficient.
in order to regulate the output the excess is shunted to ground.
with field and armature both made of coils the field strength is reduced to lower the output.