In die ou dae op die plaas -----
1. DC distribution WAS quite common.
2. The wiring was critical for good performance
3. There were applicable standards -- where are they, all withdrawn and now no longer there to be used?
4. DC distribution is NOT all that foreign to many of us coming out of the telecommunications industries. We know how to do this and it is NOT to try and use the existing wiring and conduits.
5. Yes there is lots to think about --- not the least of which is the design of so-called "modern housing", which frankly, has forgotten many things the old timers knew and provided for.
I wouldn't contest that DC may be efficient in a house, but 12VDC would be. At low voltages with high amperage, the resistance from the wire would be greater than the loss from transforming therefore negating any benefits from using DC directly.
Furthermore, there would be a lot of challenges. Firstly, the industry would need to come up with a common plug standard for DC that is different from AC so that there is no risk of the 2 being interchanged.
Then there would need to be a standard voltage and it needs to be high enough to ensure a low enough current to ensure efficiency from the wires.
At least then, a standard transformer could be used which could have the standard DC plug with a standard voltage.
Many devices would still need a step down transformer to change the voltage for the various electronic circuits. This would probably be more efficient than an AC to DC transformer, but not by much.
I'm no expert, but we have always learnt that AC is more efficient in transmitting electricity over long distances and the switch to AC meant that you didn't have to be within 10kms of a power station. Also, all grid distribution is currently AC and the costs to change this to DC would be immense. Grid power would likely remain AC then so for houses that are solely on grid power to have DC circuits, they would have to have an AC to DC transformer.
There may be some benefits for people running battery banks, but as most DC appliances are electrical circuits that don't use a lot of power, I can't see the efficiency gains being worth the cost of a second electrical circuit. Saving 10% efficiency on a 9W LED globe or 70W TV isn't really a major saving.
On the other side, you will still need AC circuits for heavy duty appliances like vacuum cleaners, pool pumps, washing machines, dishwashers, etc. These appliances draw in excess of 1000W and are more efficient on AC.
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