DC Home Power

Discussion in 'General Electronics Chat' started by tindel, Apr 21, 2013.

  1. tindel

    Thread Starter Active Member

    Sep 16, 2012
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    I've been thinking a bit about lighting, and the eventual change to LED lighting everywhere, and how to make this cost efficient. This has got me to thinking about weather it would be worth it to start converting to DC power inside home breaker boxes. - I'm thinking moderate voltage DC - like 12 or 15 volts. The cost of the LED bulbs seems to be in the converter, pwb, etc, so why not put the converter in the breaker box?

    Look around your house - almost everything has a AC-DC converter on it. TV, amplifiers, lighting (more prevalent as time goes on), computers, alarm clocks, you name it - only a few things run on AC power these days.

    Seems to me that to really get the cost down on lighting you have to have a converter in the breaker box. This would have the side effect of not needing converters in every single piece of equipment you buy, making things cheaper in the long run.

    There would be other challenges, like bus impedance, efficiency, cable loss, etc, but it seems to me like this is the direction we're headed. I have started to see wall outlets with USB outlets in them at the home depots. You could even have high efficiency POL converters in the wall outlets. It would also increase safety - I've never heard of anyone being seriously injured by 15VDC.

    Maybe I shouldn't be giving these ideas away for free on the internet?
     
  2. #12

    Expert

    Nov 30, 2010
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    LOL!

    It's not a secret:D

    The first problem is that AC is the ONLY way to deliver power across long distances. The second problem is that almost everything you can buy is internally adapted to use AC. The third thing is that the amperage is 8 times as high using 15 volts instead of 120 VAC.

    Now, because LEDs are about 8 times as efficient as incandescent light, you have a viable idea. I wonder: will the usual circuit breakers for AC work the same with DC? That would be soo convenient! Next, you have to install redundant wiring for the DC system. Is the capital investment worth the savings? I don't think so, considering the small fluorescent bulbs that are available.

    Next opinion?
     
  3. Brownout

    Well-Known Member

    Jan 10, 2012
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    FWIW, I live temporarily in a small travel trailer. All the lighting is 12VDC. Seems to work fine, no noticable loss in the wires. Of course, that means nothing to a larger family size home. One option is to not have one central place for DC access, but a distributed system at strategic places.
     
  4. killivolt

    Active Member

    Jan 10, 2010
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    If it's only for lighting purposes, they do have LED bulbs available.

    If you want to convert to DC elsewhere sounds expensive.
     
  5. tindel

    Thread Starter Active Member

    Sep 16, 2012
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    I realize that, but they typically convert to DC to provide constant power. Every single LED lightbulb has a AC/DC converter... that is where most of the expense comes from, I'm guessing... the other part of the expense is adequate heat syncing (aluminum). This way new bulbs would only need the LED's and heat syncing, not the converter.

    This may not be necessarily for older homes (without large expense), but new builds I think would benefit.

    I think this is the reason we don't already wire our houses with low voltage DC, as #12 alluded to:
    I did some quick calculations with typical 14AWG home wiring - it's rated for 5A, at 15V that's only 75W... that will power most lighting applications, but won't power a TV or a computer. You'd need 8AWG wire to deliver 20A (300W @ 15V) without much loss. 8AWG wire is pretty expensive for the average consumer and wiring lighting and power separately is going to cost even more.
     
  6. #12

    Expert

    Nov 30, 2010
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    Your wiring sizes are very wrong. For house wiring, the current allowed is rated to not heat the copper enough to degrade the insulation. Wiring for DC would allow exactly the same amps as for AC. 14Ga wire is rated for a 15 amp circuit breaker. 12Ga wire is rated for a 20 amp circuit breaker.

    ps, you don't synchronize the heat, you sink it.

    Edit: I did not consider that the voltage drop in the wires will mean 8 times as much to a 15 volt system. You can lose 7 volts on a 120V line and it doesn't mean much. On a 15 volt line, it will wreck the results. The whole system would have to be calculated for resistance losses in the wiring.
     
    Last edited: Apr 21, 2013
  7. killivolt

    Active Member

    Jan 10, 2010
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    I've thought about it myself, but what you need to do now is calculate the expense, like any other engineer would do.

    Get it into an exel doc or something, come up with a component pricing and installation.

    Then calculate the cost over time.

    You might have something. But, if it's a good idea. Don't post on the net, keep it under you hat;)
     
    #12 likes this.
  8. tindel

    Thread Starter Active Member

    Sep 16, 2012
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    Meh - I'm not paid for my grammar - I'm paid for my engineering - and I got the point across.

    I was guestimating at 100ft round trip... 15V line with less than 2.5V drop. Giving at least 12V at the load. I could have made a wrong calculation somewhere - like I said - it was just a quick estimate.

    Killivolt - I'm guessing that running two power lines is going to be cost prohibitive for at least a number of years.

    I see the U.S. going in this direction eventually (DC power at the box), but it will be a hard sell for most consumers for a while, I'd guess... although I'm betting you could light your entire typical residential home (~1500sqft) on about 3 15V@5A circuits, if designed correctly... what happens when one LED goes out though!? You could spend all day finding it! HA! :p:D;)

    I'm not really looking at designing anything right now - I'm just thinking about the logistics of making it happen, and if my hunch that we'll go in the direction of a AC/DC converter at the box is even feasible. The power transfer is the biggest issue, looking at it real quick here for a couple hours.

    I'm also curious about what is really going to make LED lighting affordable... right now it's incredibly expensive - I calculate 19 years at my house for it to break even, but 'breaking even' goes back and fourth based on when you most recently purchased your latest LED bulb. However, If you average the replacement cost over the years, then it takes 145 years to break even! I would love to see LED lighting take off, but I think the thing holding it back is the price of the converter. How do you take the converter out of the equation - that is the question. Whoever figures that out will make a lot of money.
     
  9. #12

    Expert

    Nov 30, 2010
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    Become an electronics hobbyist and build your own.
     
    PackratKing, tindel and killivolt like this.
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