3 ms·

TBH, this article is full of weird quirks: > For instance, Marshall stated, it is not unusual for a 37.5 kilovolt-ampere transformer to support 15 households,

by _ea1k 4y ago

TBH, this article is full of weird quirks: > For instance, Marshall stated, it is not unusual for a 37.5 kilovolt-ampere transformer to support 15 households, as the distribution system was originally designed for each household to draw 2 kilowatts of power. It wasn't that long ago that 10 light bulbs would consume about half of that. So, lets assume 60 watt bulbs with 4 in the living room, 4 in the kitchen, and 4 in a bedroom all on. Now someone turns on a couple of floodlights outside. We are at ~1KW with no TVs, computers or air conditioners running. At that point, do we just hope noone turns on a hairdryer? :) Someone has messed up something fundamental in this article. Remember the early days of the internet when "experts" predicted it'd collapse as the user base grew? Much of this article reads like those.

mikeyouse 4y ago
The grid runs on averages.. If all 15 houses connected to that transformer were drawing 1kw for lighting, and it was spec'ed to allow for 2kw each, there are 15kw available for peak loads as people blow dry their hair or run their AC. It's not saying that houses are limited to 2kw, just that the system was designed for them to average 2kw. The article gets this right and it's a completely normal part of utility design and distribution, which is unsurprising because the person quoted is a PE-licensed electrical engineer with the title "Director of Utilities".
- _ea1k 4y ago
  No it doesn't, and you aren't think about it much at all if you think it does. 15kw gets real small when spread across 15 houses that each have 3kw air conditioners. It doesn't even take a hot day. The average oven can easily pull that too. Someone picked the wrong numbers. Even older homes tend to have 100A panels, in newer homes 150A and even 200A are more common. It sounds like he's presenting a real edge case but not making it clear that its an edge case.
  - mikeyouse 4y ago
    Of course nobody is using 1kw in lighting any more, so the contrived example is already out of date. I don't know what to tell you, the utility engineer is exactly right and 37.5kv transformers serving 15 houses was a completely standard amount of power to be delivered in the past -- which is exactly his point. All of the heat pumps and electric cars are going to require massive infrastructure upgrades because many neighborhoods are still served by the old infra.
    - _ea1k 4y ago
      I guess I wouldn't have had an issue if he had said these were tiny homes, with mostly gas appliances, gas heat (if any) and no air conditioner. That's a completely different world from most of the country. But to me the kicker is that he went into no further detail. Transformer setups like that are done with knowledge that overloading can happen. If your defending him, then you'd surely know all about how much and for how long, right? Instead, he just said 2kw per house, which is literally absurd.
ec109685 4y ago
AC uses 3kw’s and many homes have two, so during a heat wave, it seems like those transformers should already be severely overloaded. A clear saving grace of EVs is that there is a lot of hours during the evening to charge a car (and most aren’t going from zero). Coordination on when to start and trickle charging across the whole evening seems like a much cheaper way to stretch the grid’s capacity than mass upgrades.
- _ea1k 4y ago
  I agree. His wording is interesting though: "it is not unusual" - Maybe he means some case with exceptionally small houses in a climate where AC is not needed and not installed and noone uses electric heat? Coordination is an in interesting aspect. The nice thing is that these cars tend to have internet connections and the ability to remotely control charging. In my area, we are already seeing utilities experiment with offering incentives to allow remote control to improve load management. The technical solutions in many cases no longer require additional hardware.

by _ea1k 4y ago

mikeyouse 4y ago

The grid runs on averages.. If all 15 houses connected to that transformer were drawing 1kw for lighting, and it was spec'ed to allow for 2kw each, there are 15kw available for peak loads as people blow dry their hair or run their AC. It's not saying that houses are limited to 2kw, just that the system was designed for them to average 2kw. The article gets this right and it's a completely normal part of utility design and distribution, which is unsurprising because the person quoted is a PE-licensed electrical engineer with the title "Director of Utilities".

_ea1k 4y ago
No it doesn't, and you aren't think about it much at all if you think it does. 15kw gets real small when spread across 15 houses that each have 3kw air conditioners. It doesn't even take a hot day. The average oven can easily pull that too. Someone picked the wrong numbers. Even older homes tend to have 100A panels, in newer homes 150A and even 200A are more common. It sounds like he's presenting a real edge case but not making it clear that its an edge case.
- mikeyouse 4y ago
  Of course nobody is using 1kw in lighting any more, so the contrived example is already out of date. I don't know what to tell you, the utility engineer is exactly right and 37.5kv transformers serving 15 houses was a completely standard amount of power to be delivered in the past -- which is exactly his point. All of the heat pumps and electric cars are going to require massive infrastructure upgrades because many neighborhoods are still served by the old infra.
  - _ea1k 4y ago
    I guess I wouldn't have had an issue if he had said these were tiny homes, with mostly gas appliances, gas heat (if any) and no air conditioner. That's a completely different world from most of the country. But to me the kicker is that he went into no further detail. Transformer setups like that are done with knowledge that overloading can happen. If your defending him, then you'd surely know all about how much and for how long, right? Instead, he just said 2kw per house, which is literally absurd.

ec109685 4y ago

AC uses 3kw’s and many homes have two, so during a heat wave, it seems like those transformers should already be severely overloaded. A clear saving grace of EVs is that there is a lot of hours during the evening to charge a car (and most aren’t going from zero). Coordination on when to start and trickle charging across the whole evening seems like a much cheaper way to stretch the grid’s capacity than mass upgrades.

_ea1k 4y ago
I agree. His wording is interesting though: "it is not unusual" - Maybe he means some case with exceptionally small houses in a climate where AC is not needed and not installed and noone uses electric heat? Coordination is an in interesting aspect. The nice thing is that these cars tend to have internet connections and the ability to remotely control charging. In my area, we are already seeing utilities experiment with offering incentives to allow remote control to improve load management. The technical solutions in many cases no longer require additional hardware.