4 ms·

The problem is that the DC from the grid is going to be way higher voltage than the voltage to the house. There are lots of AC-AC transformers that would need t

The problem is that the DC from the grid is going to be way higher voltage than the voltage to the house. There are lots of AC-AC transformers that would need to be replaced to use DC for distribution and hard to switch incrementally without a dual converter in every house. Also, AC is better for medium distance transmission, DC can boosted to super high voltage for long distance but that isn't practical inside a city. Then, the house DC voltage is going to be higher than the electronics DC. So you'll need to have a box at every single outlet to convert DC-DC. The appliances are going to need the higher voltage house DC. And the house DC voltage is going to be more dangerous than AC. Also, there are no standards or even proposals for DC electrical system: no voltage and no outlets. The problem is that replacing DC-AC-DC with DC-DC-DC and there isn't much savings from all those conversions. Would you replace all of your appliances for 1% savings in electrical cost?

londons_explore 3y ago
And those reasons are why it'll take 100+ years... However, the AC-AC transformers currently use a lot of Steel+copper. That's expensive. New developments will be pushed towards solid state alternatives which are theoretically cheaper (and exist today, but aren't widely used). Outlets in your house I suspect will get replaced with super-USB-C. Ie. something which is 5 volts and then negotiates a higher voltage as needed. A future version I bet will support 3 kilowatts for hair dryers, etc. That will be safer. It'll also be pushed by device makers who currently hate the headache of making different versions of electrical devices for every country with different plugs. Fancy houses already have USB outlets in every socket. Cheapo devices like flashlights already use USB power input for worldwide universality. I could imagine rules might push people to super-USB-C too. Laying AC lines requires highly qualified labour, but plugging in super-USB-C cables into a super-USB-hub can be done by anyone - the safety is in the design, rather than requiring careful installation. When every outlet in your house is super-USB-C, it won't take much for newly built houses to instead use DC everywhere (maybe even negotiated voltages too - ie. your house only receives 5 volts until any device needs more power, and then it'll ramp up).
- Gare 3y ago
  > However, the AC-AC transformers currently use a lot of Steel+copper. That's expensive. New developments will be pushed towards solid state alternatives which are theoretically cheaper (and exist today, but aren't widely used). In what world is steel and copper more expensive than semiconductors?
  - londons_explore 3y ago
    A small CPU in 1974 cost $360. A functionally similar CPU today costs $0.03. Whereas a pound of copper went from $0.89 to $3.91 in the same time. Transformers of equal wattage cost more today than they did in 1974. Power electronics cost substantially less. I don't see this trend reversing.
- ianburrell 3y ago
  It is impossible for super-USB-C to carry that much power. The new 240V is at the limit of what USB-C can do and you are talking about order of magnitude difference. First, the wire thickness needs to be like regular wires to carry enough current. Changing the wiring in the walls is the hardest thing. Second, the voltage needs to be like regular service to carry enough power over regular sized wires. Higher voltages, like 500V, are better since DC loses more energy over distance than AC. Third, the plug needs to be similar size to power plugs to not arc, and DC arcs worse than AC. Is replacing everything worth the effort to increase efficiency by a little bit? You are optimizing for low-power DC devices at the expense of high-power AC appliances. The only way I can see DC power happening is in isolated community like the Moon or Mars.
  - londons_explore 3y ago
    > It is impossible for super-USB-C to carry that much power. 5 amps, 2000 volts. 10 kilowatts. Made safe by milliamp precision leakage detection (you won't manage to kill anything with a milliamp of current, and more than a milliamp of current will trigger the protection). 2000 volt insulation made of PVC needs to only be 0.1mm thick (say 0.5mm for a 5x safety factor). That can easily fit in plugs and sockets of the existing size. The leakage detection would also detect current leaked between the power conductors, so dielectric breakdown can be protected against. The cable would be designed to deliberately cause dielectric breakdown when heated before catching fire, so that in cases of a fatigued conductor or wire draped across a stovetop, a fire is impossible. This design is only safe if implemented correctly, so each end of the connection will frequently test the other end of the connection to ensure it is adhering to the spec. It would do this by sending an encrypted message saying "In 37 seconds I am about to cause what looks to you like a baby chewing through the insulation". Then, in 37 seconds, that happens, the power gets turned off, and a few microseconds later the encryption key is send over proving that it was a test and the power is turned back on again. Both sides would have capacitors so the user wouldn't notice the power going off for a few microseconds per minute.

londons_explore 3y ago

And those reasons are why it'll take 100+ years... However, the AC-AC transformers currently use a lot of Steel+copper. That's expensive. New developments will be pushed towards solid state alternatives which are theoretically cheaper (and exist today, but aren't widely used). Outlets in your house I suspect will get replaced with super-USB-C. Ie. something which is 5 volts and then negotiates a higher voltage as needed. A future version I bet will support 3 kilowatts for hair dryers, etc. That will be safer. It'll also be pushed by device makers who currently hate the headache of making different versions of electrical devices for every country with different plugs. Fancy houses already have USB outlets in every socket. Cheapo devices like flashlights already use USB power input for worldwide universality. I could imagine rules might push people to super-USB-C too. Laying AC lines requires highly qualified labour, but plugging in super-USB-C cables into a super-USB-hub can be done by anyone - the safety is in the design, rather than requiring careful installation. When every outlet in your house is super-USB-C, it won't take much for newly built houses to instead use DC everywhere (maybe even negotiated voltages too - ie. your house only receives 5 volts until any device needs more power, and then it'll ramp up).

Gare 3y ago
> However, the AC-AC transformers currently use a lot of Steel+copper. That's expensive. New developments will be pushed towards solid state alternatives which are theoretically cheaper (and exist today, but aren't widely used). In what world is steel and copper more expensive than semiconductors?
- londons_explore 3y ago
  A small CPU in 1974 cost $360. A functionally similar CPU today costs $0.03. Whereas a pound of copper went from $0.89 to $3.91 in the same time. Transformers of equal wattage cost more today than they did in 1974. Power electronics cost substantially less. I don't see this trend reversing.
ianburrell 3y ago
It is impossible for super-USB-C to carry that much power. The new 240V is at the limit of what USB-C can do and you are talking about order of magnitude difference. First, the wire thickness needs to be like regular wires to carry enough current. Changing the wiring in the walls is the hardest thing. Second, the voltage needs to be like regular service to carry enough power over regular sized wires. Higher voltages, like 500V, are better since DC loses more energy over distance than AC. Third, the plug needs to be similar size to power plugs to not arc, and DC arcs worse than AC. Is replacing everything worth the effort to increase efficiency by a little bit? You are optimizing for low-power DC devices at the expense of high-power AC appliances. The only way I can see DC power happening is in isolated community like the Moon or Mars.
- londons_explore 3y ago
  > It is impossible for super-USB-C to carry that much power. 5 amps, 2000 volts. 10 kilowatts. Made safe by milliamp precision leakage detection (you won't manage to kill anything with a milliamp of current, and more than a milliamp of current will trigger the protection). 2000 volt insulation made of PVC needs to only be 0.1mm thick (say 0.5mm for a 5x safety factor). That can easily fit in plugs and sockets of the existing size. The leakage detection would also detect current leaked between the power conductors, so dielectric breakdown can be protected against. The cable would be designed to deliberately cause dielectric breakdown when heated before catching fire, so that in cases of a fatigued conductor or wire draped across a stovetop, a fire is impossible. This design is only safe if implemented correctly, so each end of the connection will frequently test the other end of the connection to ensure it is adhering to the spec. It would do this by sending an encrypted message saying "In 37 seconds I am about to cause what looks to you like a baby chewing through the insulation". Then, in 37 seconds, that happens, the power gets turned off, and a few microseconds later the encryption key is send over proving that it was a test and the power is turned back on again. Both sides would have capacitors so the user wouldn't notice the power going off for a few microseconds per minute.