DC power being turned off in New York

The design of the V-2 rocket that terrorized London in the last days of WWII was, in substantial part, determined by Roman legislators around 450 BC. The V-2 rocket was designed to be transported on the back of a truck for launch. The width of the Meillerwagen was determined, of course, by the width of the roads available, many of which dated to Roman times. Roman roads were designated by law to be 2.45 metres wide. The V-2 therefore had to be built to comply with a 2500-year-old engineering standard! (This isn’t my original insight, by the way, I just can’t find the source).

A much younger, but perhaps even more anachronistic engineering standard just passed into history a couple of days ago: the last remnants of the DC power grid in New York City.

Thomas Edison, the famous inventor, was the first to start selling grid electricity to customers. His system transmitted power at 110 volts, using Direct Current (DC). This worked quite well – provided the generator was within a kilometre or so of the customer. In an electrical distribution system, voltage is the rough equivalent of water pressure – it’s the amount of energy transferred by a unit of electricity (such as the charge carried by a single electron) as it travels from place to place. The higher the voltage, the more energy carried by each electron. If you want to transmit electricity a long way across a small cable, you need to use a high voltage to minimise the loss of energy. However – like high-pressure water – high-voltage electricity will also escape through the wire and travel through other things very easily – including humans. That’s why long-distance electrical cables have to be separated such a long way from people, and from each other. And that’s not practical in home appliances. So, what was required was a way to change the voltage – make it high for long-distance transmission, and drop it down again for the end use. But – at least with the technology of the time – DC voltage couldn’t be changed – high voltage for long-distance transmission, low voltage for in the home.

Several engineers and businesspeople – chief amongst them George Westinghouse and Edison’s former assistant Nikola Tesla – gradually developed a different transmission system called Alternating Current, or AC for short. In AC transmission, the voltage increased and decreased in a regular pattern, depending on the system somewhere between 25 and 100 times per second – and the current flow actually reversed direction, hence the name AC. The advantage of AC distribution was that by the use of a gadget known as a transformer, the voltage (technically, the size of the peaks and troughs, thus increasing the “average” voltage) could be increased as much as desirable for long-distance transmission, and decreased closer to the end user.

The competition between the two competing standards became known as the War of Currents. Edison resorted to marketing stunts that would make the most ruthless contemporary CEO think twice, even constructing the first electric chair to promote the view that AC was unacceptably dangerous. Like all good scare campaigns, there is a certain element of truth to this – at the same (averaged-out) voltage level, AC is indeed more dangerous than DC. Any practical distribution voltage, however, will be dangerous whether it’s DC or AC, and the massive efficiency advantages of the AC system won out. Edison started selling AC equipment within a decade.

However, the existing DC grid in New York didn’t shut down. DC had some advantages for some customers; notably, DC motor technology was more advanced than AC motors. But by 1928, plans were being made to phase out the DC grid. On-site AC-DC converters – a scaled-up version of the gadgets that supply DC power to all your electronics – were gradually installed. And, 79 years later, that process is complete.

It’s fascinating to think how things might have turned out if DC had have been the standard power transmission technology. Edison’s scheme relied on having power generation close to where it is consumed to avoid excessive transmission losses. Essentially, that’s what the various proponents of distributed electricity generation are arguing for right now. Or would high-voltage DC power transmission – which, if you can efficiently increase voltages to similar levels as AC, is actually slightly more efficient – have become commonplace?

But there’s one last thing to take out of this tale. It will take a really long time to change the architecture of our energy supply systems. If I may again get on my hobby horse for a moment, that makes drop-in replacements for coal-fired power stations – large-scale energy sources that run reliably – that don’t emit CO2 rather useful things.

The link about DC power was originally from Slashdot, arguably the mother of all blogs

Posted in science
21 comments on “DC power being turned off in New York
  1. wilful says:

    The rocket story I heard related to the Space Shuttle boosters, and included a note about horses arses. True, but trivial. http://www.straightdope.com/columns/000218.html

  2. Yeah,I remember something about that too.

    And, while the specific example is trivial, the point – that engineering decisions can have implications for a very, very, very long time afterwards – isn’t.

  3. silkworm says:

    Tesla also wanted to build a tower on Long Island that would transmit electricity wirelessly to any part of the world. The source of the energy was going to be the vibrations of the Earth itself. The project was financed by Pierpont Morgan, the richest man in the world at that time. The project was stopped, not for technical reasons, but for political reasons – Morgan realized as the project neared completion that there was no practical way to charge end-users. Anyone with a conversion device could capture this energy for free. The tower was eventually pulled down.

    Here is a potential solution to the greenhouse problem – the generation of unlimited energy with zero carbon emissions, distributed freely to all places in the world.

    The major problem in the implementation is American capitalism, which is based principally on the model that Morgan set up. The project needs to be developed outside the US. South America may be the best place for development due to its political climate. Plans for the conversion device could be posted on the Internet. Locally based “Tesla industries” could flourish.

  4. feral sparrowhawk says:

    I’ve heard various conspiracy theorists going on about various inventions Tesla was supposed to have made that got shut down because they offended capitalism. Trouble is, I can’t imagine how these things were supposed to work without violating some pretty fundamental laws – of physics not economics.

    Transmitting the energy wirelessly should be possible, although there would be some difficulties, but I’m at a loss to understand how one can produce that much energy from “vibrations of the Earth itself”. Do you actually have a credible source?

  5. pablo says:

    Speaking about anachronistic engineering, I can recall an international gathering at Sydney Uni a decade or two ago where the perennial topic of standardising domestic electrical connections was on the agenda. Users might relate to advice on how they had to carry adapters for any plug in electrical stuff if they were planning an overseas trip. I guess they’re still at it.

  6. Sir Henry Casingbroke says:

    The Tesla conspiracy is of current (he, he) interest because the greenhouse effect/peak oil/pollution have made energy and power generation topic de jour. On top of that there is the perennial conspiracy of patents for great inventions that would ameliorate pollution and make life better, etc. etc, except that the patents are bought up by evil capitalists who then secrete them away in a vault because that would make obsolete their old tech and stop making them fabulous fortunes.

    Apart from Tesla’s myriad of strange devices, two inventions come immediately to mind: (1) Jean Bertin’s Aerotrain, a rapid transit system that is cheap to build and cheap to maintain, and would be able to whisk passengers from Sydney to Melbourne in a couple of hours and could be updated to run on solar power; (2) Maria Skyllas-Kazacos and her vanadium Redox battery, which promised to revolutionise cars by allowing them to be filled with recharged electrolyte fluid from service stations like petrol; thus allowing the recharge time of less than a minute and cars would then run purely on electricity, the electrolyte fluid can then be recharged when there is sun and or wind. By so doing it would make the internal combustion engine obsolete and petrol ditto, something GM, Ford and Mr Shell would not like one bit.

  7. Andyc says:

    Tesla’s plans for long-distance, high-power wireless electricity transmission still spook me a bit. I suspect that the ‘vibrations of the Earth itself’ might be what we’d now call Extremely Low Frequency Radio Waves, like what we currently use for long-distance submarine detection, etc, but much higher in power.

    I have a feeling that such a scheme might indeed have tranferred a lot of power over long distances, but I am glad that it never got tried, just in case it worked. There is a lot that they didn’t know about the cooking efficiency of long wavelength electromagnetic radiation, back then.

    More OT:
    “It will take a really long time to change the architecture of our energy supply systems.”

    This statement is neither accurate nor apposite. We can set up many local (house- or block-level) power generation systems as we like: solar, fuel cell, biofuel generator, whatever, as the will and wealth become available. Since these are local, no concerted architecture change is needed. As these come online, dependency on the Big Grid gradually fades.

  8. Nabakov says:

    Ooo, a Tesla thread.


    That should put the cats among the inonospheric pigeons.

  9. Sir Henry Casingbroke says:

    That comment is a bit on the heaviside Nabakov. HAARP does not rely on the Tesla grounded circuits. “Everything You Know is Wrong”.

  10. High-power wireless electricity transmission, otherwise known as radio.

    Andyc: and if you start taking less energy out of the grid, the electrical utilities will increase their rates to compensate for the fact that the connection costs pretty much the same to maintain whether you’re buying 1 or 100 kwh per day.

    In any case, if we go big-time for solar and wind, the Big Grid will probably end up even bigger to cope with intermittancy.

  11. Andyc says:

    Robert Merkel:

    1. The intermittency problem is a furphy, if we use intermittent sources for energy storage by heating or pumping water, charging batteries, etc.

    2. How much of the cost of grid electricity is running the connection, rather than the power stations (which could be gradually decommissioned)? Is there any reason why fixed, consumption-independent costs could not be borne via government rather than individuals, so as to give consumers more of an incentive (albeit psychological) in the form of reduced bill to move off the grid?

    3. I note that point (2) contradicts my usual hardcore stance of “no subsidy for private industry”. But then, I do not believe that gridded power generation should be in the private sphere, in the first place.

  12. wilful says:

    By the way, a ‘nanosolar’ factory is breaking ground soon. When up and running it will produce ~430 MW of ultracheap solar panels a year. Maybe a drop in the ocean, but in five years I could see 200 of these plants in China. That would not be a drop in the ocean.

    This is not vapourware.

  13. Andyc: wholesale power from coal-fired power stations costs about 4 cents per kwh. Retail power, about 13c.

  14. Graham Bell says:

    Robert Merkel;
    So AC has finally won the battle that was still being fought when I was a kid.

    What about that other standard – railway gauges? 3’6″ in undeveloped parts of the British Empire. Standard Gauge 4’8.25″ in England, Scotland, continental Europe, U.S.A. and civilized parts of the world such as the Colony of New South Wales. The Russian Empire’s very own gauge. And, of course, the 5’3″ of Ireland, Victoria and South Australia.

    Wonder how many standards adopted in our time will bring down on us the well-deserved curses of future generations?

  15. Zarquon says:

    Basslink is 400KV DC. If they find more high-temperature superconductors then cables and everything will be DC again.

  16. Jacques Chester says:

    Good of you to point this out for a wider crowd, Robert. However, as many comments at Slashdot pointed out, AC won because DC is not a good fit for how we generate and distribute electricity. In particular, DC requires much more complicated equipment to step up and step down voltage — it only becomes attractive for HVDC where you can bury the cable (my old man tried to explain it to me and I failed to understand). Otherwise AC has the edge.

    I think that nanotechnologies such as solar paint, solar roads etc will reduce the need for central plants but it cannot eliminate them. What you get from a large central plant is better reliability of supply. The economics still dictate central generation.

    That might change in time according to technologies. Maybe central generation will disappar, maybe it will continue to dominate. More likely it will be like the PC revolution, with central generation’s niche (like the mainframe’s) shrinking but continuing to exist. My point would be to let it happen on demand and supply, rather than trying to pick winners.

  17. Peter Kemp says:

    Love that DC, as an automotive electrician in a former life. Was always amused by seeing the driving lights installed by house electricians on their cars, requiring 30 amp cable to the relay and 15 amp wire to each 100 watt lamp to allow for long term degradation of connections, (particularly the use of crimp terminals in a 12 volt environment–which I used to solder anyway for the perfect job)). Usually they used 2.5 mil wire for everything and wondered why the lights were so dull. A lot of difference in cabling between 240v AC and 12v DC.

    Panels on the roof and DC, that’s the way of the future. (Well OK, an inverter for the whitegoods, TV etc but looking good for charging the electric car!)

  18. Pablo, one issue you’ve got is that voltages and AC frequencies aren’t standardised either.

    Australia, the UK, the rest of the EU, and China have sufficiently similar voltage standards that it’d be safe to make a universal plug to fit everything. In practice, we’d probably be forced to adopt the EU standard plug. Our standard is actually one of the more elegant, because it supports a range of carrying capacities by altering the size and shape of the earth pin.

  19. silkworm says:

    My golly gosh, there was a Teslaesque item on the 7.30 report tonight, and it involved my old mate Malcolm Turnbull. Turnbull has given? promised? $10 million to Australian Rain Corp to test a Russian rain-making scheme that involves negatively charging up the ionosphere. Scalar perhaps? Besides the scientific doubts that surround the project, the ABC reported that Turnbull had breached the bipartisanship convention of the pre-election period, and that Rain Corp, while claiming to be 100% Australian-owned, was in fact 75% Swiss-owned.

  20. silkworm says:

    Australian Rain Corporation is run by Matt Handbury, whose uncle is Rupert Murdoch. If the technology works, why was it necessary to get the $$$ from the government, when uncle Rupert, who is apparently keen on the project, could give it away as loose change.

    Here’s a link to a good article on the affair.


    The scientific reputation of Dr Jurg Keller of UQ is also on the line.

  21. Graham Bell says:

    Silkworm [19 & 20]:
    I myself would normally be rather sceptical of any rainmaking claims …. except that I have a vague impression, from way back in the late 50s ~ early 60s, of the USSR tinkering with rainmaking and climate control.

    Apparently, those commenting in the news media today about this latest barrel [pork- or rain-] neither spoke nor read Russian nor were they familiar with Soviet-era or current Russian science.

    Anybody got any corrections or more reliable information?

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