4 ms·

I'm not a pro in these systems (yet, I hope), but my understanding is that, beside lack of demand, HVDC is a safety nightmare compared to AC, and inverters are

by ansgri 2y ago

I'm not a pro in these systems (yet, I hope), but my understanding is that, beside lack of demand, HVDC is a safety nightmare compared to AC, and inverters are getting more efficient each year. So, even given the choice, I'd keep AC home-wide distribution and set up inverters in key places, with exactly the highest required voltage.

kkfx 2y ago
Well, yes DC is unsafe because if you get electrocuted instead of being "pushed out" you get "attached" to the conductors, but if you have a p.v. inverter at home you already have a 400V DC line from the module to the inverter, how different can be having the same to the garage? The same to an exterior heat-pump unit (where the DC compressor it's typically located) witch is also insulated by the mere fact you drive it via a remote? Aside I'm not much an expert as well but, from DC to AC we are pretty efficient, around 98% of energy get converted. But the other way round it's pretty inefficient, meaning a loss around 30%. So while your p.v. it's pretty efficient in generating AC, your car it's pretty inefficient generating DC from AC to recharge. You heat pump would gain as well. To be clear I do not advocate DC for any DC home appliance like washing machines or dishwashers, just for energy intensive appliances like big heat pumps and car chargers. Not more.
- ansgri 2y ago
  Valid points, though for safety I thought less about shock and more about fire: the DC arc is much more stable, thus the switches, breakers and relays have to be more robust. The rated DC voltage of magnetic relays is about 1/10 of AC.
  - kkfx 2y ago
    Well... I'm ready to pay 10-time the price of an AC breaker to recharge regularly DC-to-DC and since that's the very same link than stationary 400V LFP batteries being able to use the car battery as a home one when I'm at home. Try to imaging how well you could run if you have a small battery, as an expensive UPS for the home when you are not there (ventilation, homeservers, fridge(s)/freezer(s) etc) and when you are at home, thanks to a let's say 70kWh battery you can also run your heating in winter in case of a blackout... In the end it's the very same power circuit, why not? 300€ extras in breakers to run my heat pumps more efficiently? No issue, they'll pay back countless more.

by ansgri 2y ago

kkfx 2y ago

Well, yes DC is unsafe because if you get electrocuted instead of being "pushed out" you get "attached" to the conductors, but if you have a p.v. inverter at home you already have a 400V DC line from the module to the inverter, how different can be having the same to the garage? The same to an exterior heat-pump unit (where the DC compressor it's typically located) witch is also insulated by the mere fact you drive it via a remote? Aside I'm not much an expert as well but, from DC to AC we are pretty efficient, around 98% of energy get converted. But the other way round it's pretty inefficient, meaning a loss around 30%. So while your p.v. it's pretty efficient in generating AC, your car it's pretty inefficient generating DC from AC to recharge. You heat pump would gain as well. To be clear I do not advocate DC for any DC home appliance like washing machines or dishwashers, just for energy intensive appliances like big heat pumps and car chargers. Not more.

ansgri 2y ago
Valid points, though for safety I thought less about shock and more about fire: the DC arc is much more stable, thus the switches, breakers and relays have to be more robust. The rated DC voltage of magnetic relays is about 1/10 of AC.
- kkfx 2y ago
  Well... I'm ready to pay 10-time the price of an AC breaker to recharge regularly DC-to-DC and since that's the very same link than stationary 400V LFP batteries being able to use the car battery as a home one when I'm at home. Try to imaging how well you could run if you have a small battery, as an expensive UPS for the home when you are not there (ventilation, homeservers, fridge(s)/freezer(s) etc) and when you are at home, thanks to a let's say 70kWh battery you can also run your heating in winter in case of a blackout... In the end it's the very same power circuit, why not? 300€ extras in breakers to run my heat pumps more efficiently? No issue, they'll pay back countless more.