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Bringing Back DC Electricity

Discussion in 'Off Topic' started by dpeilow, Dec 16, 2008.

  1. stopcrazypp

    stopcrazypp Well-Known Member

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    Funny, I just finished helping someone with a paper on building a solar power inverter yesterday, so I do understand how it's annoying having to change the DC voltage to AC then to an adapter to a device that runs on DC.
     
  2. graham

    graham Active Member

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    Yes, I have thought about doing the same thing at my house, but thus far laziness and lack of funds have kept me from it.

    I think if I could tap DC pre-inverter from the solar panel/batteries if only for the refrigerator and the computers, I would see a marked improvement with my overall energy usage.
     
  3. deenko

    deenko Member

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    DC has its place and Power transmission is not one of them. As a result, if you want to put power on the grid, you need AC. There is no way around it.

    DC low voltage transmission is best when transmission lines are kept short. IF you have a high current (a couple of amps) low voltage line, the power loss getting the power from one point to another will easily be larger than the energy loss converting from AC to DC at the usage point.

    For Solar cells, there might be better uses for non converted DC, but that is a unique case for home solar applications.

    As for running DC in a whole building..... I do not think that it would be a good idea.
     
  4. graham

    graham Active Member

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    I don't think the article was recommending trying to do long distance haul transmission with DC. But as more people generate power locally (via solar or what have you) it would be nice to not convert it into AC and then convert it back to DC. Lots of inefficiency there.

    Telco data centers for years have been DC as it is more efficient to plug all the equipment in directly DC instead of each component having an AC-to-DC power supply. It would be nice if it were easier to do for home use as well.
     
  5. deenko

    deenko Member

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    Yea, DC distribution in data centers makes sense. There you can run Heavy current wires etc. with in the room. But if you think about it, Long Haul for DC can be as far as the next room depending on usage. That is unless you want to run extra, heavy gauge, wires along with your "thinner" AC wires.

    For Solar, it all depends if you want to be on the grid or not. Most solar installations (here in California) are done on the grid to take advantage of tiered energy prices. It is unfortunate, but that is the way the solar business works.

    OF course if you are into solar to be the best environmentalist, DC to DC conversions are generally more efficient.
     
  6. GSP

    GSP Member

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    I'm hugely impressed by Nikola Tesla's AC superpower system that powers today's world. However the advantage of AC was the ability to use transformers to step voltage up for long-haul transmission. Nowadays there is a high voltage DC alternative that is even more efficient:

    High-voltage direct current - Wikipedia, the free encyclopedia

    GSP
     
  7. graham

    graham Active Member

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    My California Solar system is grid tied, but also to a battery bank. I can't see running a DC line into my kitchen for the refrigerator is any worse than running it across the roof down to the garage in the first place. I am sure it is not for everybody, but it makes sense for me. Some day I shall get around to doing it if I can find a DC fridge that I like... and get the money... and become less lazy...
     
  8. AntronX

    AntronX Member

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    Thickness of wire has nothing to do with direct or alternating current. You don't need thicker wires to run 120V DC system, than what's used for traditional 120V AC. Are you thinking of 48V system when you say DC ?

    Actually, DC may be more efficient than AC for local power distribution with today's silicone power devices. You don't have to worry about poor power factor and can ditch lossy bridge rectifiers.
     
  9. TEG

    TEG TMC Moderator

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    One nice thing about AC is you don't have to worry as much about corrosion issues. (Even notice all the "gunk" that builds up on the negative terminal of your 12v car battery?)
    [​IMG]
    [​IMG]
    Welcome to IEEE Xplore 2.0: Corrosion Aspects of HV DC on Buried Telephone Plant
    High voltage DC power cable - Patent EP0938102
    Or the backup battery on your motherboard:
    [​IMG]

    Another good thing about AC is that shocks don't cause your muscles to tense up and clamp down on the wire leaving you unable to let go.

    I used to yearn for a DC powered house, but I learned to appreciate some of the benefits of AC.

    Regarding solar panels - the output is irregular - the voltage changes depending on how much light is hitting the panels. So you will need some sort of interface box that does "buck/boost" type things to equalize voltage. So you already have a big box full of electronics - inverting to AC is just another function to add.
     
  10. TEG

    TEG TMC Moderator

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    implants-medium.jpg :tongue:
     
  11. AntronX

    AntronX Member

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    Ok, ok, should have said semiconductor power devices.

    BTW about the HVDC, ABB got some interesting promo videos on their site: The ABB Group: Films
     
  12. graham

    graham Active Member

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    Yup - for my house, I would pull off the batteries instead of directly off the Solar for that reason.
     
  13. deenko

    deenko Member

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    For safety, the definition of high voltage for consumers is any thing greater than 50V. Saying low voltage implies 48 or lower.

    I just mean that to power most of anything in my house, the currents will be greater at lower voltages than standard 110. Especially considering the 100's of feet of wiring running in the walls. Higher currents, long distances (relatively), and at the same power usage means that I would need thicker wire than what is wired in the house.

    That is a good idea. especially since usage is also never constant.

    Having been shocked by many voltages, I definitely prefer AC.

    This looks promising. There is always a more ideal solution to any problem.
     
  14. TEG

    TEG TMC Moderator

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    Not sure you saw it, but I was baffled a bit by different versions of "high voltage" vs "low voltage".

    For instance, here they said:
    And here they say:
    (according to the NEC, "high voltage" is 600V+)
     
  15. deenko

    deenko Member

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    Well, it turn out that there are several definitions. Sorry about the confusion. My work place uses high voltage in terms of workplace safety. You are right that 600V+ is techinically high voltage, but

    High Voltage Definition, High Voltage Buying Guide, High Voltage Reference, High Voltage Articles

    defines that even 40V can be unsafe.
     
  16. TEG

    TEG TMC Moderator

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    As a kid I used to chain 9V batteries together until I could feel the shock... So yes, 40V is about right for jumping through skin...

    (A tongue conducts much more readily though) :tongue:

    And, yeah, I know what 40,000V feels like too. :frown:
    Laser tube power supply and automotive ignition system...
     
  17. malcolm

    malcolm Active Member

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    Now there's a signature if ever I saw one :biggrin:
     

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