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I used to work for Reykjavik Energy as a junior analyst about 12 years ago. One of my tasks was using their geo database to pull out cable and transformer data

I used to work for Reykjavik Energy as a junior analyst about 12 years ago. One of my tasks was using their geo database to pull out cable and transformer data for every neighbourhood and use it to generate load models (using Siemens PSS mostly). We knew the high voltage system (100kv+) was fine as there are quite a few big power hungry users on the network. We focused our research on the "neighbourhood transformers" - These are the transformers that take you from 11kv to 400v (3 phase, of which one leg is connected to a consumer fuseboard). They're generally sized so that each transformer can service a small neighborhood, but power can be routed through less efficient ways in case they break. We combined all the electrical data with traffic data to estimate when people finish work and would likely be plugging their cars in at home. The conclusion we came to was that if only 15 percent of homes wanted fast charge ability (which at the time was a lot less than what testa offers today) the majority of the city's transformers would be over their current limit. Iceland has a pretty decent and modern power infrastructure so this was a bit of a shock to everyone. I think my research was even presented to parliament :)

jaclaz 4y ago
Happy to see that someone actually did make some accurate calculations and found out with actual data that - even in a country where the main distribution lines are just fine and the "local" transformers and lines are modern/recent - the "last km" is/will be an issue. Now imagine what would be the results of similar analysis in European cities (relatively densely inhabited, with an aged/aging infrastructure, a number of limitations for new lines and what not). I mean, if you live in a solo or bifamily (or even very small condo's) house somewhere outside the city, or in a village, there will probably be less issues with upgrading the lines and transformers (at a cost), but for medium or large condo's in or near the city centre it will be impossible to provide enough power even for 7kW chargers when there will be many of them. AFAIK here (Italy) a typical "local" transformer 20,000 to 380 V or 10,000 to 380V, it depends on the specific areas, is usually within the 300/400 kW range and serves 50-100 houses/apartments, each one having 3-4.5-6 kW contracts, and it is already near 100% use. When/if each house (or anyway a recharge column for 1 car each) will want (or need) some 7 kW available, even if only at night, the amount of 380V electricity will be at the very least twice the current one. Very likely the current infrastructure can bear an increase of 5-10%, maybe 15%, and as said this with only "slow" chargers.
cm2187 4y ago
But why do you need fast charge ability at home? I thought it only made sense on the go.
- yakak 4y ago
  It seems more like convenience to me as long as you can charge overnight and have a high enough range per charge. There could be households with complex lifestyles that share one car though. I would still worry about this indicator for capacity though, if 100% of people were heavily overlapping on 8 hour of charging at night that seems like hours of the same draw as 15% of people who all fast charge at the same time for some reason. Whole neighborhoods might be 100% electric within a couple years of no longer selling new ICE vehicles.
  - turtlebits 4y ago
    A level 2 charger even at 3000w (2 space heaters) will give you 140 miles overnight (12 hours), which should be enough for most drivers.
    - deleted 4y ago
      [deleted]
Gravityloss 4y ago
Build a 800V DC neighborhood fast charging spot at the 11 kV access point. Maybe have a cafe there as well... Some of these are quite nice I would say. https://www.vastavalo.net/albums/userpics/12399/normal_Kulttuurimaisema_Tuusulasta-0.jpg https://www.vastavalo.net/albums/userpics/12399/normal_Kultt...

jaclaz 4y ago

Happy to see that someone actually did make some accurate calculations and found out with actual data that - even in a country where the main distribution lines are just fine and the "local" transformers and lines are modern/recent - the "last km" is/will be an issue. Now imagine what would be the results of similar analysis in European cities (relatively densely inhabited, with an aged/aging infrastructure, a number of limitations for new lines and what not). I mean, if you live in a solo or bifamily (or even very small condo's) house somewhere outside the city, or in a village, there will probably be less issues with upgrading the lines and transformers (at a cost), but for medium or large condo's in or near the city centre it will be impossible to provide enough power even for 7kW chargers when there will be many of them. AFAIK here (Italy) a typical "local" transformer 20,000 to 380 V or 10,000 to 380V, it depends on the specific areas, is usually within the 300/400 kW range and serves 50-100 houses/apartments, each one having 3-4.5-6 kW contracts, and it is already near 100% use. When/if each house (or anyway a recharge column for 1 car each) will want (or need) some 7 kW available, even if only at night, the amount of 380V electricity will be at the very least twice the current one. Very likely the current infrastructure can bear an increase of 5-10%, maybe 15%, and as said this with only "slow" chargers.

cm2187 4y ago

But why do you need fast charge ability at home? I thought it only made sense on the go.

yakak 4y ago
It seems more like convenience to me as long as you can charge overnight and have a high enough range per charge. There could be households with complex lifestyles that share one car though. I would still worry about this indicator for capacity though, if 100% of people were heavily overlapping on 8 hour of charging at night that seems like hours of the same draw as 15% of people who all fast charge at the same time for some reason. Whole neighborhoods might be 100% electric within a couple years of no longer selling new ICE vehicles.
- turtlebits 4y ago
  A level 2 charger even at 3000w (2 space heaters) will give you 140 miles overnight (12 hours), which should be enough for most drivers.
  - deleted 4y ago
    [deleted]

Gravityloss 4y ago

Build a 800V DC neighborhood fast charging spot at the 11 kV access point. Maybe have a cafe there as well... Some of these are quite nice I would say. https://www.vastavalo.net/albums/userpics/12399/normal_Kulttuurimaisema_Tuusulasta-0.jpg https://www.vastavalo.net/albums/userpics/12399/normal_Kultt...