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Electric vehicles don't add up..

by Pumblechook
Tags: electric, vehicles
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LURCH
#19
Dec29-08, 12:39 PM
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Quote Quote by Proton Soup View Post
i believe i've read the suggestion elsewhere that a quick charge of supercapacitor-fueled vehicles would be done thusly: at your residence, you keep a stationary capacitor bank. this capacitor bank is charged slowly throughout the day or night, even taking advantage of off-peak power rates. when you get the vehicle home, you can then do a quick charge from one capacitor bank to the other.

now, i ain't done the math, so i'm not sure what size conductor you'd need to keep the cables from fusing with a 5-min charge. the EEstor was around 3000V, so maybe not too big.
This is similar to what I heard, except that the large caps, which would be more expensive, would be stored underground at fuel stations. At home, the car would be plugged in overnight, and take 6-10 hrs to charge. On the road, one could pull into a fueling station and charge up in 5-10 minutes, and a slightly higher cost than charging at home.

Although I have met some people who think that EV's have no emissions, I have also met others who think that the emissions remain the same, and have merely been moved from the tailpipe to the smokestack. Both of these views display equally "poor technical/scientific knowledge." According to my math, if the only source of electricity in the whole world was coal burning power plants, the total emissions from an EV would be roughly one-half of what produced by an ICE.
mgb_phys
#20
Dec29-08, 02:21 PM
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Even if they did have the same overall efficiency, EVs would still be better for the local environment. It's a lot easier to deal with a single smoke stack at a power plant than 1000s of tailpipes at street level.
It's like dropping litter out of the car window compared to putting it in a trash can and then landfill - same total amount of litter, but easier to deal with.
Jreyes85
#21
Dec30-08, 02:22 AM
P: 1
I was having a discussion today in a class with my professor and classmates about electric cars, we talked about hte different models and someboyd mentioned hte tesla roadster. I got curious and started reading about it. I dont really see any reference to actual tesla experiments in the technology other than the name. Having heard about Tesla but not really knowing much about what he has done I decided to read up. After reading since it is late at night and the fact that I dont really know much yet, i started rambling in my head and thinking.

-quoted from wiki
"Ignoring earth currents and other natural electromagnetic phenomena the Tesla antenna can receive, atmospheric electricity's total power of only all the sky-to-ground lightning everywhere on Earth from moment to moment has been stated at 700 megawatts"

After reading that to the best of my understanding it seems that tesla implied that without wires he could send electricity or even use the one in the atmosphere for practical applications. Does it work two way? would a power plant be able to use another tesla antenna to transmit electric power to a recieving one from far away?

"The Tesla Antenna utilizes the effects or disturbances to charge a storage device with energy from an external source (natural or man-made) and controls the charging of said device by the actions of the effects or disturbances (during succeeding intervals of time determined by means of such effects and disturbances corresponding in succession and duration of the effects and disturbances).[35] The stored energy can also be used to operate the receiving device. The accumulated energy can, for example, operate a transformer by discharging through a primary circuit at predetermined times which, from the secondary currents, operate the receiving device.[36]"

If so wouldnt an electric car with a tesla antenna be able to power the electric motor by either using the energy in the atmosphere that it picks up, or from nearby power stations transmitting it? and can or would it be possible that such transmitted energy in an error or an overflow actually become dangerous?

Sorry if most or if all of this doesnt make sense, I just started learning about all this, but I thought, what better place to ask or say this than a forum where nobody knows me, or tomorrow in class and with my *** teacher, he will probably not just point out it is wrong, but make me a fool infront of everyone.
Proton Soup
#22
Dec30-08, 02:24 AM
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who is john galt?
Pumblechook
#23
Dec30-08, 02:55 AM
P: 359
Tesla was a crackpot who at one time claimed he was receiving signals from aliens.

All that about transmitting power wirelessly is utter nonsense.
montoyas7940
#24
Dec30-08, 07:53 AM
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Quote Quote by Pumblechook View Post
Tesla was a crackpot who at one time claimed he was receiving signals from aliens.

All that about transmitting power wirelessly is utter nonsense.
Sacrilege!

http://www.engadget.com/2007/06/07/m...bed-witricity/

How many years later?
Pumblechook
#25
Dec30-08, 08:31 AM
P: 359
That MIT thing is a bit of a joke.

The overall efficiency must be pretty poor. I think they claim 45% coupling efficiency. So 55% of the transmitted power is wasted. A lot will be wasted converting AC to RF and if you converted the received RF to DC and them maybe to AC there would be more hefty losses. They would be lucky to get around 20% AC in to AC out.

The coils are enormous just to bridge a 2 metre gap. Try and bridge a 20 metre gap they might have to be as big as the side of a house. Bigger gaps are not even worth thinking about.


Make more sense to just run a wire and get near 100% transmission.
mgb_phys
#26
Dec30-08, 08:50 AM
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Tesla was a genius that invented a lot of the electrical technology you use today.
He was also a bit 'eccentric' and rather poorer at PR than Edison so history has been less kind to him.

Quote Quote by Pumblechook View Post
Make more sense to just run a wire and get near 100% transmission.
It's useful for some applications, were you have to get power into moving equipment or have high potential differences, there are a bunch of problems powering some lab experiments that this would solve - but for general applications it's not going to fly.

You CAN efficiently transmit power over very much shorter distance using induction, so charging ipods/cellphones etc by placing them on a charging pad is practical.
Pumblechook
#27
Dec30-08, 09:09 AM
P: 359
That sums it up well I think.. OK for short distances but inefficient for anything over 1 metre or so.

I you consider a TV or radio transmitter. They shove 10kW or more into an aerial and a total of less than 1 microwatt ends up being picked up by all the viewers or listeners. 99.999999% does not get from A to B.

Not so sure Tesla invented very much. 3 phase AC was patented and first tested out in Britain in 1882 I think.. John Hopkinson before Tesla had even arrived in the USA.



I find the idea that Tesla had a model boat that could steer by radio in about 1896 a bit far fetched when many of the components required to do it didn't exist. It would have been tricky 20 later.



I also think that Marconi's claim that he bridged the Atlantic in 1901 (Cornwall to Newfoundland) on what we now call the AM band (medium wave) to be highly dubious as do many radio engineers. Actually about now 15:15 pm in Britain would be the time Marconi, also in December, claims to have done it. See if you can receive Station VOCM (if you were in Britain....or a British station going the other way) from Newfoundland on 590 kHz with your modern highy sensitive radio. Marconi had a receiver which was very crude and a million times less sensitive.
russ_watters
#28
Dec30-08, 04:34 PM
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I haven't seen much evidence that Tesla is a crackpot: what I've seen, rather, is that crackpots have picked up on his more obscure/wilder inventions (and attempted inventions) and let their own imaginations run away with the possibilities of what they may be capable of.

Rest assured, there is no large quantity of electricity to be pulled from the ground or air and wireless transmission of electricity is impractical for large quantities of power and large distances. Radio: yes. Wireless toothbrush charging station: yes. Wireless electric car: no.

Also note that discussions of crackpottery are not allowed here.
Pumblechook
#29
Dec30-08, 05:15 PM
P: 359
It is hard to sort out what Tesla did or didn't do or claimed to have done. He certainly does seem to have attracked some strange followers who claim he did some weird things. Just take a look at some websites. It is claimed his papers were burnt by vested interests or a government agency in order to suppress his techology. I don't think many serious scientists/engineers swallow that one.
Proton Soup
#30
Dec30-08, 06:55 PM
P: 1,070
i think Tesla was a genius who was way ahead of his time. even if he did have a few crazy ideas, i don't think it diminishes his accomplishments. that's just par for the course, it happens with lots of brilliant people.

you've also got to consider that Edison hated the guy, and spent money discrediting him. in the end, Tesla's power technology won, but Edison won the public relations war.


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