Beta
×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

The Last DC Power Grid Shut Down in NYC

Zonk posted more than 6 years ago | from the edison-we-barely-knew-ye dept.

Power 533

cell-block-9 writes "Today the last section of the old Edison DC power grid will be shut down in Manhattan. 'The last snip of Con Ed's direct current system will take place at 10 East 40th Street, near the Mid-Manhattan Library. That building, like the thousands of other direct current users that have been transitioned over the last several years, now has a converter installed on the premises that can take alternating electricity from the Con Ed power grid and adapt it on premises.' I guess Tesla finally won the argument."

cancel ×

533 comments

Sorry! There are no comments related to the filter you selected.

Tesla won but... (4, Insightful)

Bryansix (761547) | more than 6 years ago | (#21385265)

most people don't even know who Tesla was or that he pushed for the system that we now use to distribute electricity.

Re:Tesla won but... (5, Informative)

Anonymous Coward | more than 6 years ago | (#21385277)

Re:Tesla won but... (4, Insightful)

oo7tushar (311912) | more than 6 years ago | (#21385315)

Just like most of us here on Slashdot don't know (without the assistance of a search engine) who won the 1982 Super Bowl. Different things matter to different people and most people have things to worry about rather than wondering who the proponents of power transport via AC were.

Most of us here on /. certainly know who Mr. Tesla is and what he pushed for and we should take pleasure in being in such distinct company...except for the trolls and turds.

Re:Tesla won but... (5, Funny)

Paul_Hindt (1129979) | more than 6 years ago | (#21385403)

Even trolls need electricity.

Scale.. (2, Insightful)

msimm (580077) | more than 6 years ago | (#21385459)

Without Tesla there's be nothing to watch the Super Bowl on. I'm pretty sure I could live without the Bengals or the 49ers (some might disagree with me).

DC vs AC (1)

falconwolf (725481) | more than 6 years ago | (#21385763)

Without Tesla there's be nothing to watch the Super Bowl on. I'm pretty sure I could live without the Bengals or the 49ers (some might disagree with me).

I'm pretty sure most if not all TVs the Super Bowl plays on convert the AC power they receive to DC. Most home and office appliances have to convert the AC power they're fed to DC before using it. This conversion introduces inefficiencies. Now is it more efficient to transmit high voltage DC then step down the voltage when it reaches the point of use, or convert at the transmission point?

Falcon

Re:DC vs AC (1, Informative)

peragrin (659227) | more than 6 years ago | (#21385817)

um the fact that we use AC for long distances means that it is in fact better to convert locally to DC, and transmit AC.

About the only time it isn't is in totally self contained systems such as ships, cars, and planes.

Re:Scale.. (1)

Achromatic1978 (916097) | more than 6 years ago | (#21385819)

Without Tesla there's be nothing to watch the Super Bowl on.

Except your eyes of course. You know, when it's there, in front of you?

1982 Super Bowl Champions (1)

sconeu (64226) | more than 6 years ago | (#21385467)

That would be the 49ers. The start of their dynasty that lasted nearly 20 years, but is now in ruins.

Re:Tesla won but... (5, Interesting)

MikeFM (12491) | more than 6 years ago | (#21385329)

Or that he died broke and alone because people like Edison stole his ideas and robbed him blind. Tesla was a genius and could have done so much more for the world if only things weren't controlled by rich people with no vision further than how much money they can make, right away, off an idea. Tesla's failure is a perfect example of capitalism at work.

uh (3, Insightful)

circletimessquare (444983) | more than 6 years ago | (#21385399)

do you have a superior system than capitalism in mind?

people are fond of pointing out democracy's many failures too

but the real overriding realization with democracy and capitalism is that however much you think they suck, and they do suck in many ways, they are still better than any other system we can think of and have tried

so please, criticize capitalism. but unless you can enunciate a superior alternative, your criticism means absolutely nothing

Re:uh (-1, Flamebait)

timmarhy (659436) | more than 6 years ago | (#21385489)

he's probably one of these leftist wankers who still thinks communism works. your beautifuly presented retort will be lost on the parent.

Re:uh (4, Insightful)

ResidntGeek (772730) | more than 6 years ago | (#21385529)

No. Capitalism is the best system available, but that doesn't make it fair. It is up to the people within the system to try to make it fair. That includes pointing out the problems with it. His criticism isn't meaningless, it's important.

no (-1, Redundant)

circletimessquare (444983) | more than 6 years ago | (#21385689)

enunciate a better system, or shut up

no one needs someone to tell them something sucks, that everyone knows sucks

crticism without a superior alternative is useless

Re:no (1)

cromar (1103585) | more than 6 years ago | (#21385789)

No it really isn't. There's a time to get off your ass and do something, but if it's not that time yet it is one of few ways to express such an idea. If shit gets rolling and you just sit there and complain, that's useless. Right now many could do with such an insight.

Re:uh (4, Funny)

sweatyboatman (457800) | more than 6 years ago | (#21385537)

do you have a superior system than capitalism in mind?


I'm sure Tesla wrote it down somewhere.

Re:uh (2, Insightful)

Adambomb (118938) | more than 6 years ago | (#21385543)

So shit does not stink in the absence of less fragrant shit.

Gotcha.

close (0, Redundant)

circletimessquare (444983) | more than 6 years ago | (#21385665)

no one needs anyone to tell them that shit smells like shit

Reminds me of the quote (2, Insightful)

onion_joe (625886) | more than 6 years ago | (#21385639)

whether or not Churchill said it, "Democracy is the worst form of government imaginable. Except all the others."

One could easily apply this to economic systems as well. The only thing I could think of that would be better would be some Deus Ex-type computer-AI directing or at least regulating human activities. Self regulation seems to be one of our biggest difficulties.

Re:Reminds me of the quote (1)

cromar (1103585) | more than 6 years ago | (#21385811)

I know! If only computers never failed and were tamper proof.

Re:uh (3, Interesting)

vux984 (928602) | more than 6 years ago | (#21385649)

people are fond of pointing out democracy's many failures too

The failures of democracy aren't democracy itself, but rather of the fact that our implementation of democracy is poor in that it doesn't actually give people the representation in government that they should have. Its too easy to get re-elected, its too hard to break into politics without vast amounts of cash and/or support from existing politicians, its too hard to remove someone who is doing a shitty job, its not nearly transparent enough, the voters don't have more than a token say in most issues as elections are only 'big issue items', and too infrequent to give voters real voices in more mundane items, like patent reform, whether the RIAA should be allowed to sue children, etc. And its too hard to vote. (seriously, the cost and organization to run an election or referendum are an obstacle to effective democracy). First past the post elections wipe prevent minority views from having any voice at all.

There is nothing wrong with democracy. We just don't have a good implementation of one.

Capitalism on the other hand has many REAL flaws, even if implemented perfectly. And a hybrid of capitalism and something else is the only way of fixing it, short of a completely new paradigm like the star-trek-economy where scarcity of resources is pretty much a non-issue.

so please, criticize capitalism. but unless you can enunciate a superior alternative, your criticism means absolutely nothing

Bullshit. The first step in fixing a problem is to identify what the problem is.

But you want solutions to capitalism? Sure, close the borders with any other country that doesn't implement capitalism the same way we do, so that we can compete under a fair system. A great deal of capitalisms problems stem from the comparative advantages of -exploiting- foreign economies that don't have the level of protection of human rights, wages, environment, etc. Or alternatively to closing the borders, treat foreign assets and employees as local ones -- and ensure wages and working conditions and environmental practices are compliant with local standards regardless of where the plant is. Its one thing for there to be a competitive advantage by refining your oil closer to the source, or taking advantage of high unemployment and locating a call centre in its epicenter -- but its something else entirely to exploit a 2nd or 3rd world country to get labour at a fraction of its real value to you.

Second, re-design corporations - make directors accountable personally, make ceos accountable personally.

Third, re-design the stock market so that its focussed on serving INVESTORS not TRADERS. If corporations were interested in satisfying INVESTORS they would take a longer view, but right now all that matters is tomorrows share price and this quarters sales. Only traders care about that.

Third, institute separation of commerce and state. Business should have NO ability to affect or impact on government at all. The biggest problem of capitalism is that its a corrupting force on democracy. Separate them.

I could go on...

dude, calm down (3, Insightful)

circletimessquare (444983) | more than 6 years ago | (#21385753)

all you did is enunciate standard real world checks and balances on the ideas

no one expects pure capitalism or pure democracy to ever be able to exist

i'm taking umbrage with radical fundamental departures from the core concepts: communism instead of capitalism, for example, or theocracy versus democracy

not capitalism, tweaked, or democracy, tweaked

the core ideas are always tweaked in one way or another to fit in the real world

Re:uh (1)

mcarp (409487) | more than 6 years ago | (#21385797)

Except that your long post goes on about an entity that currently does not exist. The free industrialized world nations that you know today are representative republics. Democracy is where everyone votes and power and law are decided based on the outcome directly. A republic is where everyone votes but the power and law are implemented by representatives.

Re:Tesla won but... (4, Insightful)

Tablizer (95088) | more than 6 years ago | (#21385413)

Or that he died broke and alone because people like Edison stole his ideas ... Tesla's failure is a perfect example of capitalism at work.

Much of the good ideas that really propel technology are that way. Capitalism rewards manipulative wheeler-dealers far more than creativity. It rewards those who can best exploit creative ideas, not make them.
     

Re:Tesla won but... (0, Redundant)

Briden (1003105) | more than 6 years ago | (#21385581)

mod parent up, here is someone who understands capitalism!

Re:Tesla won but... (0)

Anonymous Coward | more than 6 years ago | (#21385433)

Capitalism and capitulationism.

Buck's the system.

Re:Tesla won but... (1, Troll)

Blakey Rat (99501) | more than 6 years ago | (#21385483)

Tesla died broke because he spent all his money trying to create a "wireless power distribution" that made no sense. If he had spent more time reading physics and less time building 100+ foot Tesla coils. Were some of his inventions stolen? Undoubtedly. But I think he has only himself to blame for losing all his money.

He went a bit wacko, also, Howard Hughes-style wacko.

Reading physics? (2, Insightful)

Anonymous Coward | more than 6 years ago | (#21385545)

He was too busy DISCOVERING how these things worked to be able to "read" them all laid out nicely in some book. Yes, some of his inventions were a bit crazy, but we owe a lot of progress to the man. If it weren't for him, we'd be stuck with Edison's crappy DC systems and the modern electrical systems we have today would not exist. Edison helped ruin the poor man just to sell his crap and he did it via evil fearmongering, doing things like electrocuting an elephant with AC.

Also, the wireless power transfer IS possible. Too dangerous to actually use, but possible. And he left behind plenty of shocked people to prove it (literally...).

Re:Tesla won but... (1)

ackthpt (218170) | more than 6 years ago | (#21385553)

Or that he died broke and alone because people like Edison stole his ideas and robbed him blind. Tesla was a genius and could have done so much more for the world if only things weren't controlled by rich people with no vision further than how much money they can make, right away, off an idea. Tesla's failure is a perfect example of capitalism at work.

Edison called Alternating Current the devil's work, he was so certain of Direct Current. One glaring example of how stupid this view was happened when at a prison they tried to electrocute a prisoner. It took several tries, eventaully igniting the prisoner, before he died. This was a great embarrassment to Edison and contributed to his grudging acceptance of Alternating Current, along with the fact DC lines could only go so far, thanks to their DC resistance.

I'm a bit surprised there was still DC anywhere. Amazing.

Re:Tesla won but... (0)

Anonymous Coward | more than 6 years ago | (#21385679)

Er.......
Capitalism is simply the right to use ones OWN property as they see fit. What your talking about is more like piracy (stealing someone elses property and then doing with it as you see fit). I know the the terminology is often intermingled, but there really actually is a difference.

Re:Tesla won but... (2, Interesting)

Rei (128717) | more than 6 years ago | (#21385767)

And?

That's pretty typical. Example: who do you think of as the inventor of the telephone? Most people would say Alexander Graham Bell. But one could equally credit Antonio Meucci, Johann Philipp Reis, and Elisha Gray. Meucci especially. He beat Bell to it by over 20 years. But he was an Italian immigrant, spoke only poor English, and was effectively broke.

Example: A couple years ago, I independently came up with this:

http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=4&f=G&l=50&co1=AND&d=PG01&s1=blur&s2=camera&OS=blur+AND+camera&RS=blur+AND+camera [uspto.gov]

Did I patent it? Nope. Why? Because I have about as much ability to manufacture modern cameras as I have to get to the moon. I have no knowledge about how to market such things to other companies, to raise venture capital, or anything of the sort. My variant was actually a bit better than theirs (combining superresolution imaging with blur correction), but, well, too late.

And that's the way things go. It happens all the time, and you'd expect it to. If one person can come up with the idea, why not several people? As tech advancing opens up new possibilities, it's only a matter of time before novel applications of it are invented, independent of who reaches the patent office first.

ComEd not Con Ed (-1, Troll)

Anonymous Coward | more than 6 years ago | (#21385409)

Just so you idiots know....it is ComEd for Commonwealth Edison. Not Con Ed.

Re:ComEd not Con Ed (2, Informative)

Volante3192 (953645) | more than 6 years ago | (#21385441)

No, it's Con Ed for Consolidated Edison.

Idiot.

Re:ComEd not Con Ed (2, Informative)

PorkNutz (730601) | more than 6 years ago | (#21385513)

Com Ed is Illinois, Con Ed is New York.

I know an excellent surgeon who can remove that foot from your mouth.

Re:Tesla won but... (1)

Lisandro (799651) | more than 6 years ago | (#21385411)

Very true, and it's a crying shame. Tesla was one of the brightest men of his generation, and the number of inventions and research he left behind is beyond impressive [wikipedia.org] . That, and he had this crazy-scientist image thing going along aswell :)

Most people answer with a blank stare whenever in mention the work of Tesla. While Edison's contribution is undeniable, he was more of a salesman than a scientist.

Re:Tesla won but... (2, Informative)

urcreepyneighbor (1171755) | more than 6 years ago | (#21385427)

While the majority of people don't know who Tesla [wikipedia.org] was or what he contributed [wikipedia.org] to the modern world, it's safe to say that most of the people here on /. are - at least - aware of him.

If I ever make it to Belgrade, I'm planning to check out the Nikola Tesla Museum [tesla-museum.org] . :)

Re:Tesla won but... (2, Funny)

markbt73 (1032962) | more than 6 years ago | (#21385465)

I know who Tesla was. "Modern Day Cowboy" was an awesome song.

Re:Tesla won but... (2, Interesting)

Dr. Cody (554864) | more than 6 years ago | (#21385485)

Do to all the anti-gravity devices, free energy machines, and death rays which the Lovecraftian writhing of Tesla's decaying mind gave birth to--and to all the countless nuts propagating them--I would like to paraphrase a widely-attributed quote:

"When I hear the name 'Tesla,' I reach for my revolver."

Re:Tesla won but... (0)

SueAnnSueAnn (998877) | more than 6 years ago | (#21385507)

Hell we have a war in Iraq and most people can't find Iraq on a map.
Public schools like anything else that is public is of the lowest quality.

You all should thank the rest of us who went to real schools we are glad to
carry you on our backs.

Sue

Re:Tesla won but... (2, Funny)

markov_chain (202465) | more than 6 years ago | (#21385521)

It's kinda funny that the Tesla Roadster runs off of DC batteries :)

Re:Tesla won but... (3, Funny)

vought (160908) | more than 6 years ago | (#21385599)

It's kinda funny that the Tesla Roadster runs off of DC batteries :)
Not when you consider that there are no such things as A/C storage batteries... :-)

yes... (0)

Anonymous Coward | more than 6 years ago | (#21385681)

But it uses AC electric motors. The best tech for the best uses. We don't have AC batteries yet!

Re:Tesla won but... (1)

segedunum (883035) | more than 6 years ago | (#21385691)

Everybody knows who Nikola Tesla was now, and he has been a character in many films, books, games and in the media. His name is synonymous with electricity. Let's face it, Tesla is a far cooler name than Edison. I know it shouldn't count, but it does.

Yes, he was screwed over a few times, but he formed his own company, filed many important and innovative patents, had money to follow his interests and different projects and he lived as he wanted. He certainly could have had very, very good money if he wanted. The guy was an undoubted genius (he was also a practical rather than a theoretical man as well, and very logical) and he will live on throughout history.

Re:Tesla won but... (0)

Anonymous Coward | more than 6 years ago | (#21385705)

Tesla was great. His songs rocked the 80s in a big way. Didn't know he also invented electricty. Cool.

Yeah Love is all around you
Love is knocking, outside the door
Waitin' for you, is this love made just for two
Keep an open heart and you'll find love again

Re:Tesla won but... (0)

Anonymous Coward | more than 6 years ago | (#21385725)

WOooooooHOoooo we won....

Serbs 1 - 0 USA

Advantages? (1)

segedunum (883035) | more than 6 years ago | (#21385293)

Are there any advantages to DC current?

Re:Advantages? (2, Funny)

Gregb05 (754217) | more than 6 years ago | (#21385313)

it makes math pretty easy, and your computer is currently running on it.

Re:Advantages? (2, Informative)

ChrisMounce (1096567) | more than 6 years ago | (#21385331)

The advantages of AC are mostly in transportation from the power station to the consumer. Internally, electronics use mostly DC, I think (correct me if I'm wrong here). Batteries store and release DC current, a computer's power supply converts to DC, etc.

Re:Advantages? (4, Funny)

jallen02 (124384) | more than 6 years ago | (#21385525)

You never, ever, have to say "correct me if I am wrong" on Slashdot. Someone will gleefully correct you if you are wrong.

Re:Advantages? (1)

hjf (703092) | more than 6 years ago | (#21385773)

The world is not all "electronics". There are "electrical" things all over the place, that run much better with AC, and that, I'm pretty sure, use the majority of electricity: motors. HVAC, fans, refrigerators, pumps, all those things work much better in AC than DC, especially when they're huge. Sure, the IGBT (insulated gate bipolar transistor) has helped bring the "brushless DC" motor to a scale larger than your average computer fan, but still today, a squirrel-cage 3-phase motor is the cheapest and most efficient way to make things spin. Followed by the 1-phase AC motor.

Also, it's really easy to make an AC-AC converter (a transformer!) that works with over 99% efficiency in hundreds of kilowatts, than to make a DC-DC converter that big. And, as an AC-DC converter can get 94% efficiency easily, there's no reason for changing things.

There's only one application of large scale DC nowadays and it's the HVDC transmission lines, which reduce power losses due to capacitance, among other things. But that was actually developed in the last few decades (with the help of power semiconductors and vacuum tubes), and they work in too high voltages to be practically deployed in cities.

Re:Advantages? (5, Funny)

irn_bru (209849) | more than 6 years ago | (#21385335)

Depends if you are an elephant or not.

Re:Advantages? (4, Informative)

oo7tushar (311912) | more than 6 years ago | (#21385345)

For short distances and for use within IC it's quite useful. The conversion from AC to DC at lower voltages for use within computers produces quite a bit of heat (hence the fan in your PSU, yes I realize that even DC from a higher voltage to DC at a lower voltage produces quite a bit of heat) and so you find that some data centers are moving to converting from AC to DC outside of the cases and transporting DC directly to the servers.

There was an article on /. about this a while back and perhaps somebody who'd like to be modded up a bit can post the link.

Re:Advantages? (5, Funny)

Four_One_Nine (997288) | more than 6 years ago | (#21385349)

Do ATM machines (where we enter our PIN numbers) run on DC current?

Re:Advantages? (1)

MikeFM (12491) | more than 6 years ago | (#21385365)

Most likely they convert from AC to DC internally just like the majority of other consumer electronics.

Re:Advantages? (1)

wesmills (18791) | more than 6 years ago | (#21385421)

Wow, that joke just went sailing right over your head...

Do you post from a DSL line?

Re:Advantages? (2, Funny)

clem (5683) | more than 6 years ago | (#21385549)

What's so funny about all the TLA acronyms?

Re:Advantages? (0)

Anonymous Coward | more than 6 years ago | (#21385559)

It was not funny. Quite stupid actually.

Re:Advantages? (1)

fm6 (162816) | more than 6 years ago | (#21385777)

Went sailing past mine too. ATM? DC?

Re:Advantages? (0)

Anonymous Coward | more than 6 years ago | (#21385823)

In his defense it wasn't a very good joke. AC/DC current is useful for being different then AC/DC voltage. Unlike the ATM and your PIN.

Re:Advantages? (1)

orionop (1139819) | more than 6 years ago | (#21385373)

There are indeed some advantages to direct current. Most electronics use direct current and have to convert from ac to dc between the device and the outlet, this causes some inefficiencies. The main problem with dc current is that it can not be transmitted over long distances without a lot of power loss, which is why our grid is in ac, despite the fact that everything runs on dc. If you had an in-house generator then dc power might be the way to go.

Re:Advantages? (3, Informative)

TigerNut (718742) | more than 6 years ago | (#21385463)

As related here [wikipedia.org] high-voltage DC transmission is more efficient than high voltage AC transmission for a number of reasons, and it has other benefits as well in allowing potentially unsynchronized AC systems to transfer power. The main problem is efficient voltage conversion, which requires more infrastructure than an AC system with equivalent power transfer capability.

Re:Advantages? (4, Interesting)

vacantskies9 (1190171) | more than 6 years ago | (#21385493)

Actually DC current is more efficient than AC in transmitting power due to there being no reactive component of the power. The main problem with DC is that it cannot be transformed to higher voltages which save a lot of energy losses. There is actually a very long DC transmission line to California that uses DC power. They convert to AC at the end of the line. AC is also a much safer means for transmitting power. It is nearly impossible to extinquish a fault on a DC line because the voltage never reaches a zero point. Protection devices on AC lines rely upon the zero point to extinquish faults.

Re:Advantages? (4, Interesting)

Jerry Coffin (824726) | more than 6 years ago | (#21385457)

A few, but not very many. The main one is that many power uses require DC in the end, so AC has to be rectified and filtered before it's used -- and in doing so, some power is lost. When/where you're using a lot of power in a relatively restricted area, that can make a meaningful difference. Automobiles, for one obvious example, mostly use 12V DC systems (nominally 12V -- really around 14V). Aircraft, for another example, mostly run on 48V DC (IIRC). Some data centers have also gone to having a single big power supply, and then piping DC around to the individual computers. I haven't measured it personally, but they claim this can cut power usage by around 30% in some cases.

Another difference is that getting shocked by DC tends to be slightly less dangerous than the same shock from AC. A 110V DC shock to bare (unbroken) skin is is quite mild feeling, where most people in the US have found (sometime or other) than 110V AC is fairly uncomfortable, though usually not particularly dangerous (i.e. for every person who dies of electrocution, an unknown but certainly large number of others are shocked with no real consequence beyond surprise and discomfort).

Re:Advantages? (2, Interesting)

jumpingfred (244629) | more than 6 years ago | (#21385471)

DC power has many advantages over AC. Lower peak voltages for the same power delivered. No reactive losses. You don't need to synchronize generators feeding the system.

AC power has one HUGE advantage and maybe other smaller ones. You can cheaply and easily step the voltage up and down. Stepping A DC voltage up and down is much more complex. DC to DC converters are getting cheaper and better to the point that people are proposing and building high voltage DC power distribution systems.

Re:Advantages? (1)

rrkap (634128) | more than 6 years ago | (#21385473)

Are there any advantages to DC current?

AC is a bunch more convenient for distributing power on a citywide scale because, unlike with DC, it's cheap and easy to transmit power at high voltage (to cut resistive loses) and then drop it down to a lower voltage (so you don't need really thick insulation to have a wire that can be safely touched) for use. However, DC is still useful for very long high voltage transmission cables (say between Utah and Los Angeles) and for links between unsynchronized power grids.

Re:Advantages? (1)

byrnespd (531460) | more than 6 years ago | (#21385657)

Yes, DC is better for power transmission at high levels of voltage and current. Why exactly? I would have to bust out some old power electronics texts.

Side note, Tesla pretty much won the argument before he made it.
DC voltage can't be transformed (well, technically it can, for a microsecond or so... after that transformer cores saturate and you get lots of foul smelling smoke and poof, no more transformer). Can anyone name more than a handful of items in the house that doesn't have a transformer associated with it.

Now, yes, you could make a power supply to provide different voltages for devices based on DC supply; however, back in those days you had only linear power supplies. Linear power supplies basically hold back the excess voltage across a resistor. That is a huge waste of power. We didn't have switching power supplies until very recently. Obvious solution is to use a transformer to get a desired voltage before heading to the linear power supply.

Additionally, when you transform, you are magnetically coupled to the line, not physically through a wire. This prevents any direct connection to the gazillion volts of the main power grid.

Re:Advantages? (1)

OrangeTide (124937) | more than 6 years ago | (#21385669)

DC motors are easier to design for self start than single-phase AC (induction) motors.

Re:Advantages? (1)

dextromulous (627459) | more than 6 years ago | (#21385775)

Yes, besides the plethora of stupid responses to your question, DC power transmission has a major advantage of not losing as much power into its surroundings when submerged underwater (long lines = high capacitance, which causes the AC power loss.)

Some reading:
http://en.wikipedia.org/wiki/HVDC [wikipedia.org] (Several more advantages listed under heading: 'Advantages of HVDC over AC transmission')
http://w1.siemens.com/en/whats_new/features/expert_feature_new_york.htm [siemens.com]
http://www.electricalportal.co.uk/electrical_article292.html [electricalportal.co.uk]

Re:Advantages? (1)

Technician (215283) | more than 6 years ago | (#21385783)

Are there any advantages to DC current?

Yes. In long runs, the line capacitance and inductance don't create reactive power problems. Among the problems are high reactive currents causing more line heating and loss as well as problems with voltage regulation along the length of the line. DC can be stored in batteries.

With the lines being an inductor and providing inductive reluctance and the conductors being capacitive along their length, a long line where only one end of the line opens, but not the other can cause extreme voltages on the end that opened due to approaching resonance. Long lines must be tripped off line at both ends at the same time. The failure of one substation breaker to open when the other end tripped is the cause of the great East Coast blackout.

http://en.wikipedia.org/wiki/2003_North_America_blackout [wikipedia.org]

http://en.wikipedia.org/wiki/Electric_power_transmission [wikipedia.org]

Inductive coupling to fences and other conductors is lessened. Corona discharge is lessened.

The big downside is the cost of the converter stations needed to change the voltage at all the local distribution points. On the West coast in the US, is the DC intertie. It starts near the Columbia River, crosses Oregon into California and Nevada and ends about 60 miles North of LA in California. There is a total of 2 converter stations along it's entire length. There are no substations in-between.

http://en.wikipedia.org/wiki/Pacific_DC_Intertie [wikipedia.org]

Edison's DC is not dead yet, at least for long haul power transmission.

That's as maybe (4, Funny)

JamesRose (1062530) | more than 6 years ago | (#21385305)

But Edison electrocuted an elephant, which quite frankly is just an awesome smear campaign.

Re:That's as maybe (0)

Anonymous Coward | more than 6 years ago | (#21385369)

He pulled a Michael Vick on more than a few dogs too.

Electrocuted (1)

Dr. Cody (554864) | more than 6 years ago | (#21385531)

What's this "electrocuted" you're talking about? He was westinghoused!

What about local (solar/wind/geothermal) power? (1)

TigerNut (718742) | more than 6 years ago | (#21385325)

How long until a significant proportion of local users have a hybrid AC/DC system to manage power distribution from power generated on site? Tesla certainly won the medium power, wide area power distribution battle, but there are a lot of developments taking place that will increase the visibility of DC power generation.

A powerful, electrifying news story (5, Funny)

Phat_Tony (661117) | more than 6 years ago | (#21385357)

Frankly, I'm shocked that there was still a DC power system in use in the US.

Re:A powerful, electrifying news story (0)

Anonymous Coward | more than 6 years ago | (#21385385)

A non-American writes:

What do they use in Washington?

Re:A powerful, electrifying news story (2, Interesting)

HTH NE1 (675604) | more than 6 years ago | (#21385461)

A non-American writes:

What do they use in Washington?
Wind power.

MOD PARENT "FUNNY"! (1)

onion_joe (625886) | more than 6 years ago | (#21385673)

Who the hell modded this "insightful"? Oh hell, I'm off to meta-moderate, get these fools the heck out of MY slashdot.

DC still in use (3, Informative)

TobinFricke (1190177) | more than 6 years ago | (#21385701)

DC is actually used extensively in modern power grids, the main advantage being that there is no need to synchronize the phase from different generating stations or subgrids. For example, the Pacific Intertie [wikipedia.org] transmits three gigawatts of direct current between Los Angeles and eastern Washington state. (Power is sent from LA to Washington in the winter, covering the demand of electric heating in the pacific northwest; and from Washington to LA in the summer to power our air conditioners.)

DC to AC converter inside? (3, Insightful)

themushroom (197365) | more than 6 years ago | (#21385361)

Okay, so if the building was running DC, what did the electronics and appliances inside plug into?

Re:DC to AC converter inside? (1)

SeaFox (739806) | more than 6 years ago | (#21385827)

Okay, so if the building was running DC, what did the electronics and appliances inside plug into?

Well, electronics run on DC power to begin with. With a minimal "power supply" that just branches off different voltages, they could plug the electronics right in to the wall.

Kinda ironic, Tesla's AC system is supposedly the "winner" here but arguably there would be greater use for a DC power system inside homes (except for most major appliances they came with).

Do CFL bulbs even use AC power? or does the base convert to DC before the tubes?

a few blocks from where tesla lost the argument (1)

circletimessquare (444983) | more than 6 years ago | (#21385363)

not with edison, but with death [wikipedia.org]

the new yorker hotel is on 34th and 8th. the final dc site near the midtown library is on 40th and 5th

unfortunately, business acumen and scientific genius do not necessarily go hand in hand

sad [wikipedia.org]

The inventor Nikola Tesla spent the last ten years of his life in near-seclusion in Suite 3327 (where he also died), largely devoting his time to feeding pigeons while occasionally meeting dignitaries.

Is there 600VDC in Boston? (3, Informative)

leighklotz (192300) | more than 6 years ago | (#21385381)

When I lived in Cambridge, I sometimes visited friends in Boston who had 600VDC elevators using power from the city.
Later elevators still used 600VDC but used a dynamotor; that whine you used to hear when you pressed an elevator button elsewhere was the dynamotor starting, to convert to 600VDC from the 120VAC line current. Eventually, elevator manufacturers stopped using it, but when you hear that whine in a medium-old elevator, you know what is is.

Re:Is there 600VDC in Boston? (4, Insightful)

Animats (122034) | more than 6 years ago | (#21385707)

Later elevators still used 600VDC but used a dynamotor

What you're hearing is not a dynamotor, but something called a Ward Leonard drive. It's a fixed-speed motor driving a generator, but its purpose is speed control. The field current of the generator, which is small, is adjusted to control the larger output of the generator. The variable output of the generator then drives the elevator motor. The Ward Leonard drive is thus a big power amplifier. Until power semiconductors got big enough, which wasn't really until the 1980s, this was the most effective way to smoothly speed-control large motors.

A dynamotor has a common field for the input and output sides, but a Ward Leonard drive does not.

Incidentally, the Wikipedia article in Ward Leonard drives is bogus. Here's a better reference. [google.com]

The article was wrong about subways (4, Informative)

IvyKing (732111) | more than 6 years ago | (#21385389)

The reason the subways use DC was that at the time the subways were developed, DC motors were smaller, lighter, cheaper and more efficient than variable speed AC motors. AC series motors were developed for railway service (e.g. the New Haven electrification between NYC and New Haven), but those required lower frequency (typically 25 Hz in the US, one exception was the Visalia Electric at 15 Hz and 16 2/3Hz in Europe). Commercial frequency electrification didn't become practical until the 1950's with the development of ignitron and silicon rectifiers.


AC's advantage of high voltage transmission doesn't apply to subways as 1200V seems to be the limit for third rail. 2400VDC was tried in 1915 on the Michigan Railways (an electric interurban in central Michigan) with abysmal results - the voltage was changed to 1200V within a year of the initial installation.

Re:The article was wrong about subways (1)

westlake (615356) | more than 6 years ago | (#21385595)

The reason the subways use DC was that at the time the subways were developed, DC motors were smaller, lighter, cheaper and more efficient than variable speed AC motors.

In 1900 that would seem to make DC the choice for anything other than long distance transmission. What else would you be using electricity for but a light, a motor, or a radiant heater?

HIP HIP HURRAY (0)

Anonymous Coward | more than 6 years ago | (#21385401)

Thomas Edison is a hack. He didn't invent anything, he just used work-for-hire technicians and inventors then slapped the Edison label on them before marching off to the patent office. Had there been a Steamdot back in the late 19th century and early 20th century I'm certain nerds back then would be decrying Edison's ethics and business practices. Of course old Tommy would've been literally and figureatively deaf to their criticisms.
The most charitable description of Edison's oeuvre is improving something that's already been invented. How can anyone consider Edison to be a legitimate scientist if he actually pursued technology that communicates with the dead?
Nikola Tesla may be considered obscure to Joe Sixpack and the mythical GNU/Linux-using Grandma but every generation will learn that efficient alternating current, those ubiquitous fluorescent lights and wireless broadcasting which form the backbone of Earth society and culture were the brainchild of a humble yet eccentric Serbo-Croatian. Someday soon Edison will become a footnote in history while Tesla will stand as an example of creativity and inspiration tempered with a rational mind seeking to contribute to humanity rather than to one's personal savings account.

DC, actually, nowadays makes a lot of sense. (4, Interesting)

blind biker (1066130) | more than 6 years ago | (#21385431)

First of all, let me tell you that Tesla is one of my role models. He is one of the reasons I studied electrical engineering - with a passion. And AC, if you want, is the "winner" for all intents and purposes. The future really validated Tesla's AC system. There have been other folks that helped the adoption of the AC system, like Proteus, another role model for me.

Said all that however, high-voltage DC, a transport technology that starts to make sense nowadays, thanks to high-power solid-state switching elements, has many advantages over AC in terms of losses and cable utilization. You can transport more energy via DC than AC, across the same thickness cable. And you have practically no losses due to parasitic capacitances and inductances. The corona effect is much easier to control, too.

So, if I was forced at gunpoint to make a prediction for the electricity transportation in 150 years from now, I'd say hihg-voltage DC.

Re:DC, actually, nowadays makes a lot of sense. (0)

Anonymous Coward | more than 6 years ago | (#21385583)

but I thought there is a greater loss due to resistance of the conductor, which is why AC goes farther.

Re:DC, actually, nowadays makes a lot of sense. (2, Informative)

blind biker (1066130) | more than 6 years ago | (#21385647)

The loss is due to low voltage/high current --> high joule loss.

So what you need to achieve is high voltage. But in the past, that wasn't possible with DC, because there was no _efficient_ way to transform the voltage/current aspect of the power line for DC, only for AC.

Re:DC, actually, nowadays makes a lot of sense. (0)

Anonymous Coward | more than 6 years ago | (#21385611)

By the gods, even TESLA and EDISON got us stuck on an upgrade treadmill!

Easier to feed back into? (2, Insightful)

Roadkills-R-Us (122219) | more than 6 years ago | (#21385617)

Seems like a DC grid would be a lot easier to have people feed surplus power into from solar cells.

DC transmission lines (1)

phasm42 (588479) | more than 6 years ago | (#21385515)

DC has become feasible and possibly advantageous for long-distance transmission lines now, thanks to better technology. The trouble was that there wasn't a good way to alter DC voltage, something trivial with AC using transformers. Now that DC can be pumped up to high voltages like AC, it's easier to transmit due to fewer losses and less stress on the lines.

It still may not be economical beyond transmission lines though.

Mandatory bad joke (0)

Anonymous Coward | more than 6 years ago | (#21385533)

So... the capital city of the U.S. is now Washington, A.C.?

Progress. (5, Interesting)

LoRdTAW (99712) | more than 6 years ago | (#21385571)

Kinda sad to me but it was in the way of progress. Lots and lots of buildings still use the old DC elevators here in New York City. Just yesterday I loaded in to Bayard's in downtown Manhattan into a 4x4 foot elevator that I swear Otis himself must have installed. I love how you have to hold the lever to go up and down and manually align the elevator to the floor. The elevator lights are powered by the DC current as well. At Pratt Institute they used to have those old DC elevators that were powered by an ancient motor generator set that was dated back to the 30's. Hell up until 1999 the MTA still had an old DC substation that had Rotary converters for the subway. ConEd also kept the 25 cycle plants running to feed those substations until the early 90's.

If you want a feel of old DC equipment from the days when if you wanted power you had to make your own, head down to Pratt Institute (located in Brooklyn on Willoughby ave. and Hall st.). They still have 3 steam driven reciprocating piston dynamos built by Ames Iron Works. They work but are only for show. And to top it off they also have a steam turbine dynamo all of which is hooked to a large open marble panel board with knife switches, carbon arc circuit breakers and blade fuses. The panel is still live on the AC side. The Motor generator I mentioned is still there. You can go down to the Pratt engine room and get a tour from Conrad Milster, the Chief engineer who keeps the place running. The large 1930's brick steam boiler still heats the campus and the surrounding neighborhood. The site is an IEEE land mark and walking down there is like going back in time, a real treat.

Re:Progress. (0)

Anonymous Coward | more than 6 years ago | (#21385687)

25Hz power is still used by MTA for all the signals, they just have to covert it themselves since ConEd stopped providing it, as you mentioned.

I guess Tesla finally won the argument (1)

falconwolf (725481) | more than 6 years ago | (#21385597)

Not quite yet. While AC has an advantage over DC transmitting long distance at low voltages, at high voltages DC has the advantage. There are discussions in Europe to use high voltage CD current long distances. By stringing up all of Europe with these power lines it would make it easier for Europe to develop alternative energy sources. For instance while it may not always be windy in Spain it may be in Germany or Poland, and Turkey could provide solar power part of the tyme. Some months back I think IEEE's "Spectrum" had an article of this, here's one from the "Economist", "Where the wind blows" [economist.com] .

Falcon

He won that battle (0)

Anonymous Coward | more than 6 years ago | (#21385667)

But not the war. In the end DC will win

DC is far more useful then AC especially now with the drive for efficieny
When efficieny/cost wasn't an issue then Direct-on-line AC machines (a.k.a Induction machine) were best (and their construction is easy). HOWEVER they are very inneficient and the drive to variable-speed drives using sync-machine has been going on for the last decade and they all need a DC-link to operate.

TV? run on DC. phone chargers? DC, vacuum some run on DC... infact there is hardly anything that actually requires AC to work now that electronics is everywhere, it exists for practicality

Power demands are going up and central Power stations just can't cut it. More and more homes are getting local generation (The full war of current was: AC & few,large central plants vs DC and many,small community plants) and such generation generates DC (which needs to be inverted to AC just cause the house is AC). Not only that but power needs to be moved around and to move vast quantities of it requires HVDC. China are building the highest voltage/power link from N->S atm (they are also builting the highest voltage AC as well in parallel) to shift vast quantiites of power. Europe will soon be inter-connected by a grid of HVDC networks under the sea linking all the wind-farms and networks together.

IF houses had a 42Vdc ring as well as the 230Vac ring it would make more sense from electronics and efficiency POF (no rectifier or low-freq transformer). Keep the AC for the high-power stuff (space-heating,oven...) and had the low-voltage DC for the entertainment stuff. This will cutdown on all the bulky power-bricks and small bricks can exist.

Tesla won the battle back then due to practical reasons, but the war will be won by Edison

Yep, Tesla won alright (1)

a_nonamiss (743253) | more than 6 years ago | (#21385793)

He sure did, and Edison's company clearly lost and has faded into historical obscurity. What was that company called again? Electric... General... General... something...

I know everything technically is DC.. (2, Insightful)

BlueshiftVFX (1158033) | more than 6 years ago | (#21385807)

but I didn't realise that anything was still being served anything other then AC out of the wall. I guess in the New york area was some of the original electrical installations. It is a shame that Tesla's lab was destroyed because I would bet that he could have come up with some more stuff that even today would make peoples jaws drop.
Load More Comments
Slashdot Login

Need an Account?

Forgot your password?

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>