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Most of the high power consumers could run on DC power with only slight modifications (in design, not aftermarket). Heating elements can run on DC more or less

by andix 3y ago

Most of the high power consumers could run on DC power with only slight modifications (in design, not aftermarket). Heating elements can run on DC more or less unmodified. Also electric motors can run on DC efficiently (see electric cars). Back in the days 3-phase power was needed to run strong electric motors (very common in Europe, but i think it exists also in the US for factories and businesses). But there are many easy solutions nowadays to just run them on DC.

Liftyee 3y ago
> Heating elements can run on DC more or less unmodified. ..but to get the same power (heat) output you need more current in a low voltage DC system. And power loss in the supply cables scales with the square of current, so you'll need thick (expensive) wiring in the wall or you'll risk the walls becoming an equally effective heating element. Electric motors that run on DC are either brushed or have extra driver/conversion circuitry to pulse their coils in the right order. Both of these are not perfectly efficient.
eternityforest 3y ago
High voltage DC is hard to switch with mechanical switches, and you have to convert it back to AC to run motors(Unless you're willing to accept brushed motors), so it wouldn't be trivial.
- Scoundreller 3y ago
  A lotta motors are moving to variable drive to have a continuous duty cycle and do that by internally converting whatever is coming in into AC. They should happily accept DC since they're just rectifying the AC anyway. My fridge is "inverter drive" and just runs continuously at a low duty cycle all day. Most heat pumps are like this too to dial up and down instead of strictly being on or off. (Unsure what voltage the motors are running at though, so maybe AC-in is preferred to step it down before rectifying and chopping)
  - eternityforest 3y ago
    That's pretty neat! Nobody I know has many appliances from the last 20yrs so I'm a bit out of the loop on those... I guess all we'd really need is reliable switches and breakers that could be made affordably, and connectors that didn't create a huge arc every time someone unplugged a running space heater? Still a pretty big challenge, the lack of arcing seems like a really big advantage.
cesarb 3y ago
> Also electric motors can run on DC efficiently (see electric cars). It's quite likely that the motors on electric cars (and other efficient electric motors) are actually using an inverter to turn the DC into multi-phase AC and power an AC motor; this allows varying both the voltage and frequency of the AC fed into the motor.
- phkahler 3y ago
  Bingo. The frequency is proportional to motor/vehicle speed. The inverters are at least 98 percent efficient at high power, and a good EV motor is in the 90s at high power.
Scoundreller 3y ago
Increasingly, heat pump devices, like fridges, air conditioners, heat pumps, water heaters, are inverter drive, so they just rectify all the AC into DC and start chopping it to get to their desired frequency. (Also dumb that electric codes require dedicated circuits for many of these things, despite them not having the surge like they used to)

by andix 3y ago

Liftyee 3y ago

> Heating elements can run on DC more or less unmodified. ..but to get the same power (heat) output you need more current in a low voltage DC system. And power loss in the supply cables scales with the square of current, so you'll need thick (expensive) wiring in the wall or you'll risk the walls becoming an equally effective heating element. Electric motors that run on DC are either brushed or have extra driver/conversion circuitry to pulse their coils in the right order. Both of these are not perfectly efficient.

eternityforest 3y ago

High voltage DC is hard to switch with mechanical switches, and you have to convert it back to AC to run motors(Unless you're willing to accept brushed motors), so it wouldn't be trivial.

Scoundreller 3y ago
A lotta motors are moving to variable drive to have a continuous duty cycle and do that by internally converting whatever is coming in into AC. They should happily accept DC since they're just rectifying the AC anyway. My fridge is "inverter drive" and just runs continuously at a low duty cycle all day. Most heat pumps are like this too to dial up and down instead of strictly being on or off. (Unsure what voltage the motors are running at though, so maybe AC-in is preferred to step it down before rectifying and chopping)
- eternityforest 3y ago
  That's pretty neat! Nobody I know has many appliances from the last 20yrs so I'm a bit out of the loop on those... I guess all we'd really need is reliable switches and breakers that could be made affordably, and connectors that didn't create a huge arc every time someone unplugged a running space heater? Still a pretty big challenge, the lack of arcing seems like a really big advantage.

cesarb 3y ago

> Also electric motors can run on DC efficiently (see electric cars). It's quite likely that the motors on electric cars (and other efficient electric motors) are actually using an inverter to turn the DC into multi-phase AC and power an AC motor; this allows varying both the voltage and frequency of the AC fed into the motor.

phkahler 3y ago
Bingo. The frequency is proportional to motor/vehicle speed. The inverters are at least 98 percent efficient at high power, and a good EV motor is in the 90s at high power.

Scoundreller 3y ago

Increasingly, heat pump devices, like fridges, air conditioners, heat pumps, water heaters, are inverter drive, so they just rectify all the AC into DC and start chopping it to get to their desired frequency. (Also dumb that electric codes require dedicated circuits for many of these things, despite them not having the surge like they used to)