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Power United States Science

The Last DC Power Grid Shut Down in NYC 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."
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The Last DC Power Grid Shut Down in NYC

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

    by MikeFM ( 12491 ) on Friday November 16, 2007 @07:41PM (#21385329) Homepage Journal
    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.
  • by blind biker ( 1066130 ) on Friday November 16, 2007 @07:51PM (#21385431) Journal
    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:Advantages? (Score:5, Interesting)

    by Jerry Coffin ( 824726 ) on Friday November 16, 2007 @07:56PM (#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).
  • by HTH NE1 ( 675604 ) on Friday November 16, 2007 @07:56PM (#21385461)

    A non-American writes:

    What do they use in Washington?
    Wind power.
  • Re:Advantages? (Score:3, Interesting)

    by jumpingfred ( 244629 ) on Friday November 16, 2007 @07:57PM (#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:Tesla won but... (Score:3, Interesting)

    by Dr. Cody ( 554864 ) on Friday November 16, 2007 @07:59PM (#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:Advantages? (Score:4, Interesting)

    by vacantskies9 ( 1190171 ) on Friday November 16, 2007 @08:00PM (#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.
  • Progress. (Score:5, Interesting)

    by LoRdTAW ( 99712 ) on Friday November 16, 2007 @08:09PM (#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:uh (Score:3, Interesting)

    by vux984 ( 928602 ) on Friday November 16, 2007 @08:19PM (#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...
  • Re:Tesla won but... (Score:3, Interesting)

    by Rei ( 128717 ) on Friday November 16, 2007 @08:31PM (#21385767) Homepage

    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: []

    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.
  • Re:Advantages? (Score:3, Interesting)

    by evanbd ( 210358 ) on Friday November 16, 2007 @08:57PM (#21385955)

    Yep, for ever expanding definitions of "short distances." High voltage high power DC silicon is getting better and cheaper, so we're already seeing a few long-haul DC lines where the reduced radiative losses and increased carrying ability of the cables makes it more efficient. On the other end, DC converters are becoming ubiquitous inside electronics. Google wants to standardize on only one voltage (12V) coming from your computer's PSU, and anything that wants another voltage just has its own converter. All of this will make power distribution and conversion cheaper, smaller, and more efficient. And some places are already moving to distributing DC to the rack-mount cabinets, at (iirc) 48V, and converting DC-DC from there.

    On the flip side, I absolutely hate DC converters when trying to do analog work. If you buy a 16-bit analog to digital signal capture board, they run off a switching power supply -- a power supply that generates lots of high frequency noise. I've worked with ones that simply can't do better than about 12-13 bits -- the last 3-4 are basically worthless from the noise. I worked on a project that had need of a voltage monitor on a large battery-powered system involving a large number of sensors and controls. We installed a nice little digital LED voltmeter. It had a tiny, noisy switching converter in it. Not only did it dirty up all our data, it actually kicked back enough noise that it lit up LEDs that should have been electrically isolated from it (capacitative coupling through a long cable). Needless to say, we ripped it out and installed an analog (as in coil, magnet, needle) voltmeter.

    Even good (read: expensive, as in $1/W or more) sine wave inverters are a pain. One we worked with produced wonderfully clean AC output -- but also created significant radiated noise, and dirtied up the DC input! Capacitors and ferrite beads helped, but not enough -- we eventually just moved it far away and ran the AC through a long extension cord.

    So... DC/DC converters are wonderful for space, efficiency, and cost, but they can be quite the pain to work with if you actually care about having any sort of analog precision anywhere nearby. That sort of noise is amazingly hard to get rid of, and you often can't get rid of all the switching supplies these days.

  • Re:uh (Score:2, Interesting)

    by mcarp ( 409487 ) on Friday November 16, 2007 @08:59PM (#21385969)
    People are also fond of calling republics democracies.

    Democracy: people vote and the power and law are made directly (volatile)
    Republic: people vote and representatives implement the power and law (slow change over time, more stable)

    As for capitalism being fair (or not), my grandma always said, "If you dont work you dont eat."
    Fairness doesnt come from the marketting scheme per se, but from ethical practice. There are rich and poor, fair and unfair people. In theory those that do the most valuable work or inovate the most valuable products make the most money. In practice ethics can fail. Given this, capitalism already is the most fair possible marketting scheme avaiable. If you cant put forth the effort to provide a valuable product, you will be poor. In another point if you dont use your brain while practicing the system, you will fall victom to those practicing bad ethics. It is when large groups of people do not use their brains that large groups of people fall to even mediocre semi-fair but marginal ethics. Use your power to fire those companies who's products you dont like. Done in volume even large companies with bad ethics can be put down. It is the assumption of people who feel they have no power that keeps large unethical companies in business. However, lazy fat people rarely care if they are being screwed. Thus, everyone thinks capitalism is unfair.

    By contrast, socialism is a system where by many lazy uninventive people with voting power cry that no one has given them anything and politicians wanting power cater to that outcry. Thus the few earners and inovators are forced to support the masses.

    In essence, the definition of 'fair' has been skewed.
  • by WillRobinson ( 159226 ) on Friday November 16, 2007 @09:32PM (#21386197) Journal
    Tesla Man out of Time [] Which is a excellent book on what was going on then.
  • Re:Tesla won but... (Score:3, Interesting)

    by petermgreen ( 876956 ) <> on Friday November 16, 2007 @10:13PM (#21386531) Homepage
    wireless power transmission is possible but not at efficiancies that makes it usefull for anything more than extremely low power items (like your crystal radio). Teslas ideas of large scale wireless power distribution were a pipe dream.
  • by Wonko the Sane ( 25252 ) * on Friday November 16, 2007 @10:58PM (#21386811) Journal
    More and more industrial motors are being controlled by variable-frequency drives, which must internally convert incoming AC power to DC and then back to AC.

    While there is no reason to replace a three phase AC motor with a DC motor, You might start powering variable-frequency drives directly from a DC distribution system.
  • Re:DC vs AC (Score:3, Interesting)

    by hedwards ( 940851 ) on Friday November 16, 2007 @11:01PM (#21386837)
    The big issue I have with DC is that its a potential safety hazard. Unlike AC which you'll feel if you touch one of the wires, with DC you don't feel it unless you are grounded or touching both wires of the circuit. The problem is that when you're grounded is the worst time to just realize that you're holding a live wire.

    With AC, the biggest concern is that you get it through either the heart or the brain, in most cases if you just touch the live wire in your house, you're most likely just going to get a tingle. Without any lasting consequences, worst case, your heart has a wrong rhythm to it. Except for the heart rhythm, that all applies to DC as well.

    And for many years that's how electricians figured out if a wire was hot, they'd touch it, ensuring that they weren't grounded, if they got a jolt it was live, and if not it wasn't. That doesn't work with DC, by the time you realize you've hit a live wire, you're probably already badly burned or worse.

    In practical terms, the problem is that you don't get that additional chance to avoid the more serious injury with DC. You accidentally put your hand on a cord with a subtly damaged cord, and you don't know it until its too late, with AC, you do that and you'll feel it.
  • by sentientbrendan ( 316150 ) on Friday November 16, 2007 @11:53PM (#21387123)
    What sort of electric devices even come with DC input? Most everything has a AC/DC converter built into it. Does that mean that every electronic device on the premises needs both a DC/AC converter and a AC/DC converter chained together? Wow...
  • Re:DC vs AC (Score:3, Interesting)

    by porkThreeWays ( 895269 ) on Saturday November 17, 2007 @12:28AM (#21387277)
    Pain to convert doesn't even begin to describe it. AC can be both stepped up and stepped down with transformers. What are transformers? Basically coils of wire. You can step up and step down voltages HUGE amounts with basically more wire. Stepping up and stepping down DC are two different processes. Stepping down is really inefficient and stepping up requires caps (and caps don't really scale to voltages that high well). Also, it's waaay easier to turn AC into DC than the other way around. You can pretty easily turn AC into DC with a full wave rectifier. I can turn 120VAC at the wall to 12VDC for electronics with about 1 dollar in supplies. Try going the other way for that cheap.
  • by bitrex ( 859228 ) on Saturday November 17, 2007 @12:35AM (#21387319)

    I think the most beautiful piece of old AC to DC conversion technology was the mercury arc rectifier...apparently these devices were still used on some branches of the NYC subway until late in the 20th century. A video of one in operation can be seen at []

    A center-tapped transformer was connected to two anodes to form a full-wave rectifier(some had more anodes and were used for 3 phase power), and a pool of liquid mercury was used as the cathode material which would form an arc only if the anode was positive. A keep-alive electrode kept the interior full of vaporized mercury to facilitate the discharge. I'd sure like to have my own. Unfortunately an average sized mercury arc rectifier contains around 2 pounds of liquid mercury, so if it ever broke, my neighborhood would have to be decontaminated, my home razed to the ground, and the rubble buried in a concrete encasement.

  • Re:DC vs AC (Score:3, Interesting)

    by MechaStreisand ( 585905 ) on Saturday November 17, 2007 @01:05AM (#21387457)
    It's true that AC is much easier to step up and down. However, DC isn't stepped the way you are thinking. There are switching DC-DC converters that can step DC up or down with high efficiencies and don't need any particularly large capacitors, as they use inductors. They are far more complex, expensive, and failure-prone than transformers for high power, and don't work at all beyond a few thousand volts or so, but they exist.
  • Re:Tesla won but... (Score:3, Interesting)

    by ScrewMaster ( 602015 ) on Saturday November 17, 2007 @02:25AM (#21387755)
    Not at all. He died broke because he was as inept financially as he was brilliant scientifically. He tore up a contract that would probably have made him a billionaire because he didn't want to bankrupt Westinghouse. Capitalism has its faults but Tesla's financial state upon his death is not one of them.

    That's not to say that Edison cheating Tesla out of tens of thousands of dollars was a good thing, but Tesla survived that and ultimately ended up working with George Westinghouse. You seem to forget that it was that partnership with Westinghouse which broke the impending Edison DC power monopoly and resulted in the modern power distribution system that we have today. Let's also not forget that it was Tesla who invented the polyphase induction motor, the workhorse of modern industry. Westinghouse recognized the value of that invention early on, and it's what originally brought them together.

    All in all, a perfect example of a genius working hand-in-hand with a capitalist to bring something good into the world (although Westinghouse was something of an engineering genius in his own right, with some 360-odd patents to his name.) Edison was a jerk who screwed over one of the world's greatest minds for a few bucks, and who shortly before his death admitted that he was wrong about A.C., and the power system which Tesla had put within his grasp. However, he wasn't the reason that Tesla died broke ... Tesla did that to himself.
  • Re:Tesla won but... (Score:3, Interesting)

    by GooberToo ( 74388 ) on Saturday November 17, 2007 @10:37AM (#21389617)
    Good to see Wikipedia hold up under the mad scramble of 10,000 Slashdotters

    Shesh...they have real servers and it's only read-only activity. As they are using MySQL, it's likely all cached hits to boot. As long as they have the bandwidth, it's likely a trivial load. It's not like /. has the hitting power it did five or six years ago.

Loose bits sink chips.