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Seems like a good idea. A new house should have both AC and DC available. Save us all the wasted power and effort converting AC to DC in most electronics. I j

by Fuxy 13y ago

Seems like a good idea. A new house should have both AC and DC available. Save us all the wasted power and effort converting AC to DC in most electronics. I just hope we don't go overboard removing AC. Some thing are just simpler using AC.

masklinn 13y ago
> I just hope we don't go overboard removing AC. I don't think builders will risk alienating users of non low-power appliances (a fridge, a hoover or an electric kettle). Plus it's not like drawing two cables (AC and DC) and installing mixed wall plugs (with both AC and DC/USB sockets) is more complex than just single cable and AC sockets.
- VLM 13y ago
  For several years you can buy COTS wall sockets with an embedded switching power supply squirting out USB power to a USB connector, so from an electrician's point of view its just a funny looking, somewhat large, extremely expensive standard wall socket.
  - seabrookmx 13y ago
    Except this completely defeats the purpose. You no longer have a central DC supply, but instead have a wall-wart converter build into the wall instead of hanging off the plug. This would actually be less efficient than the approach in the article, as you are increasing the number of idling DC supplies, not reducing them.
    - VLM 13y ago
      Ah. I was intending to comment more on the claim that electricans would install AC and DC runs (aside from most building codes and common sense requiring AC and low voltage unprotected DC to be run more or less physically separately) +5V switchers the size and shape of a light dimmer with a little USB port have been COTS for many years now, for dorms and hotels and stuff, so its more likely the electrician would run 120 AC to some convenient spot in the room where its converted to 12V at high(er) current rather than a parallel scheme where the electricians homerun both 120VAC and 12VDC to a combined circuit breaker panel or some such. Or in short (oh bad pun), DC power supplies are COTS and electricians know exactly what to do with them. It is inevitable if you had parallel wiring they'd mess it up. Wanna be home electricians are made fun of all the time for screwing up 3 simple obvious wires line neutral and ground, giving them +5 would just result in fireworks. Admittedly most of the electricians making fun of the home wiring guys are the same pros who blow up 3-phase machinery by swapping a phase on an occasional basis too...
      - seabrookmx 13y ago
        Oh god. There's electricians out there that don't even know what 3-phase is. It's scary. That and all the DIY guys building rotophases to power their cheap 3-phase equipment they got on auction, only to realize their 120/240 in their garage won't cut it.
- djrogers 13y ago
  Might not be more complex, but it'll be a long time before it's compliant with any building codes. You can't run LV anything in the same runs as your AC lines.
gph 13y ago
I'm far from an electrical expert, but I don't understand how this will save power for the majority of people. Won't we just be converting from AC to DC one step further up the electrical chain? It's not like the power company is going to start sending me DC. I get that it will benefit people with solar, which is nice. But that's far from the majority of people. Any electrician want to correct my ignorance on this?
- sp332 13y ago
  For large datacenters, DC can be a big improvement. http://gigaom.com/2012/01/13/the-next-big-thing-for-data-centers-dc-power/ http://gigaom.com/2012/01/13/the-next-big-thing-for-data-cen... But this is mainly where UPSes are involved, or solar power. That might not be relevant to a house, but it could have other advantages besides efficiency. Imagine all your computers had tiny DC-DC converters instead of heavy, hot bricks of inverters. Laptops would only need a cable to charge instead of a power brick.
- leoedin 13y ago
  I think the article puts forward one point - if the number of devices using DC is large enough, the load will become much less variable. Less variable loads mean one power supply can operate at peak efficiency rather than having many sitting idle most of the time. I'm not completely convinced that this makes sense though. Any low voltage DC distribution network will need fairly thick wires to distribute anything but trivial power levels. The power lost in the cables over tens or hundreds of feet would probably make any efficiency gains fairly moot. The efficiency of modern switched mode power supplies is fairly high, and my understanding is that the no-load power use is almost trivial (milliamps). One issue that seems to have surfaced recently is that there's loads of very, very cheap AC-DC power supplies which are awfully made. It would definitely make sense for a single high quality supply over a bunch of cheap, noisy and dangerous ones, but I think the best solution is investing slightly in wall-socket based power supplies of a known quality. As an aside, power transmission with DC is actually quite a lot more efficient than AC. The reason AC won the power race was the ease of voltage change with transformers. As solid state power electronics improves, we're going to see more and more DC based transmission lines. We're probably centuries away from a DC grid (if ever).

by Fuxy 13y ago

masklinn 13y ago

> I just hope we don't go overboard removing AC. I don't think builders will risk alienating users of non low-power appliances (a fridge, a hoover or an electric kettle). Plus it's not like drawing two cables (AC and DC) and installing mixed wall plugs (with both AC and DC/USB sockets) is more complex than just single cable and AC sockets.

VLM 13y ago
For several years you can buy COTS wall sockets with an embedded switching power supply squirting out USB power to a USB connector, so from an electrician's point of view its just a funny looking, somewhat large, extremely expensive standard wall socket.
- seabrookmx 13y ago
  Except this completely defeats the purpose. You no longer have a central DC supply, but instead have a wall-wart converter build into the wall instead of hanging off the plug. This would actually be less efficient than the approach in the article, as you are increasing the number of idling DC supplies, not reducing them.
  - VLM 13y ago
    Ah. I was intending to comment more on the claim that electricans would install AC and DC runs (aside from most building codes and common sense requiring AC and low voltage unprotected DC to be run more or less physically separately) +5V switchers the size and shape of a light dimmer with a little USB port have been COTS for many years now, for dorms and hotels and stuff, so its more likely the electrician would run 120 AC to some convenient spot in the room where its converted to 12V at high(er) current rather than a parallel scheme where the electricians homerun both 120VAC and 12VDC to a combined circuit breaker panel or some such. Or in short (oh bad pun), DC power supplies are COTS and electricians know exactly what to do with them. It is inevitable if you had parallel wiring they'd mess it up. Wanna be home electricians are made fun of all the time for screwing up 3 simple obvious wires line neutral and ground, giving them +5 would just result in fireworks. Admittedly most of the electricians making fun of the home wiring guys are the same pros who blow up 3-phase machinery by swapping a phase on an occasional basis too...
    - seabrookmx 13y ago
      Oh god. There's electricians out there that don't even know what 3-phase is. It's scary. That and all the DIY guys building rotophases to power their cheap 3-phase equipment they got on auction, only to realize their 120/240 in their garage won't cut it.
djrogers 13y ago
Might not be more complex, but it'll be a long time before it's compliant with any building codes. You can't run LV anything in the same runs as your AC lines.

gph 13y ago

I'm far from an electrical expert, but I don't understand how this will save power for the majority of people. Won't we just be converting from AC to DC one step further up the electrical chain? It's not like the power company is going to start sending me DC. I get that it will benefit people with solar, which is nice. But that's far from the majority of people. Any electrician want to correct my ignorance on this?

sp332 13y ago
For large datacenters, DC can be a big improvement. http://gigaom.com/2012/01/13/the-next-big-thing-for-data-centers-dc-power/ http://gigaom.com/2012/01/13/the-next-big-thing-for-data-cen... But this is mainly where UPSes are involved, or solar power. That might not be relevant to a house, but it could have other advantages besides efficiency. Imagine all your computers had tiny DC-DC converters instead of heavy, hot bricks of inverters. Laptops would only need a cable to charge instead of a power brick.
leoedin 13y ago
I think the article puts forward one point - if the number of devices using DC is large enough, the load will become much less variable. Less variable loads mean one power supply can operate at peak efficiency rather than having many sitting idle most of the time. I'm not completely convinced that this makes sense though. Any low voltage DC distribution network will need fairly thick wires to distribute anything but trivial power levels. The power lost in the cables over tens or hundreds of feet would probably make any efficiency gains fairly moot. The efficiency of modern switched mode power supplies is fairly high, and my understanding is that the no-load power use is almost trivial (milliamps). One issue that seems to have surfaced recently is that there's loads of very, very cheap AC-DC power supplies which are awfully made. It would definitely make sense for a single high quality supply over a bunch of cheap, noisy and dangerous ones, but I think the best solution is investing slightly in wall-socket based power supplies of a known quality. As an aside, power transmission with DC is actually quite a lot more efficient than AC. The reason AC won the power race was the ease of voltage change with transformers. As solid state power electronics improves, we're going to see more and more DC based transmission lines. We're probably centuries away from a DC grid (if ever).