AC vs. DC fast charge

[Kane]

Things Take Time.

On which side is time? AC or DC? :wink:

BTW in Norway DC is growing 10-times faster then AC (by 222% year-on-year for DC vs. 19% for AC).

 

[eledille]

On which side is time? AC or DC? :wink:

BTW in Norway DC is growing 10-times faster then AC (by 222% year-on-year for DC vs. 19% for AC).

If you want a quick solution that we will regret in ten years, then sure, go ahead and push for DC only. My opinion is that that would be dumb in a market flooded with medium power three phase connections.

I don't care how much each is growing. ATM was growing like crazy for years, but now it's dead. Medium power AC has a future because the AC infrastructure is mostly there already, and it can be converted to DC by rearranging existing equipment that the cars contain anyway. This year there is probably only one car model that can take advantage of the last point. Probably next year too. But if Renault isn't flat out lying when they say their cost increase for 43 kW AC is 150 euros compared to a standard 3.6 kW charger plus a DC charge port, then everyone will in time have to follow.

 

[Kane]

This year there is probably only one car model that can take advantage of the last point. Probably next year too. But if Renault isn't flat out lying when they say their cost increase for 43 kW AC is 150 euros compared to a standard 3.6 kW charger plus a DC charge port, then everyone will in time have to follow.

We will see, but I have something else to think about.

In France Nissan Leaf cost 32990 EUR (current version, not 2013). Zoe cost 20700 EUR. Both without 7000 EUR subsidies.
But Leaf have 24 kWh pack, Zoe not (You must rent it 79 EUR/month).

So we can assume some battery price (for final consumer) and see difference. If battery price is:
600 EUR/kWh: Leaf pack will cost 14400 EUR and rest of the Leaf 18590 EUR (less then Zoe)
500 EUR/kWh: Leaf pack will cost 12000 EUR and rest of the Leaf 20990 EUR (almost same as Zoe)
400 EUR/kWh: Leaf pack will cost 9600 EUR and rest of the Leaf 23390 EUR (more then Zoe)
300 EUR/kWh: Leaf pack will cost 7200 EUR and rest of the Leaf 25790 EUR (much more then Zoe)

Leaf is bigger, have 80 kW motor and power electronic (Zoe 65 kW) and onboard charger 3,3 kW. So without battery should cost more than Zoe. It means that AESC battery cost now less then 400 EUR/kWh?

 

[Eberhard]

Lets see what may be in 5 years time, when thousand of EV-Cars like Models S are on the road. I will still charge my car at home, maybe from my solar-panels. But for long distance trip, i will see service stations for EV like those today for ICE. But what happens if you want to charge 10 Models S with 43kW AC or 90kW DC. For AC-charging you need an transformer to step down down the 20kV voltage down to 230V/400V. The Transformer has losses (92-95% efficiency) Transformer are expensive too 600KVA around 30.000-40.000 Euro. To this add the losses for the on-board charger. Other scenery: on big rectifier transforms 20kV AC direct into 500V DC which are distributed to each DC charging station. No transformer losses, higher efficiency as single charger. The conclusion, if you want to charge more cars at the same time quickly, advanced DC charger are the solution. A single CHAdeMO is a nutshell an while disappear because being to slow and to expensive to produce.

 

[eledille]

Lets see what may be in 5 years time, when thousand of EV-Cars like Models S are on the road. I will still charge my car at home, maybe from my solar-panels. But for long distance trip, i will see service stations for EV like those today for ICE.

I usually will not. My longest trips are around 500 km, and then I will usually have a lunch/rest break of about 45 to 60 minutes. With 22 kW, that will give me about 100 km extra, which is what I need. If I was zipping along a motorway at 140 km/h, I would need more power.

But what happens if you want to charge 10 Models S with 43kW AC or 90kW DC. For AC-charging you need an transformer to step down down the 20kV voltage down to 230V/400V. The Transformer has losses (92-95% efficiency).

I believe 98 % is more correct for a large power distribution transformer (around 500 kVA).

Transformer are expensive too 600KVA around 30.000-40.000 Euro.

That's WAY too high. Search for "transformer price" in this link, 400 kVA is 7000 euro in 2011: Price Of A Transformer | EEP

Other scenery: on big rectifier transforms 20kV AC direct into 500V DC which are distributed to each DC charging station. No transformer losses, higher efficiency as single charger.

If it was that easy to convert 20 kV AC to 500 V DC without losses, then I would expect to see this kind of technology elsewhere too, or what?

You can create a more efficient switched transformer than an iron/copper one, but it's more expensive. If it wasn't, then the utilities would be using them already. This might change in the future, but you'll never get rid of conversion losses anyway. You could get around it by using a 20 kilovolt battery, of course...

The conclusion, if you want to charge more cars at the same time quickly, advanced DC charger are the solution. A single CHAdeMO is a nutshell an while disappear because being to slow and to expensive to produce.

I agree that advanced DC looks promising, but there are at least two good reasons why we need primarily AC with some support from DC: First, right now we don't have anything at all, and AC is easier to implement. Second, I want to be reasonably confident that I'll find a reasonably powerful charge pole in the vicinity wherever I feel like stopping. If I have to go out of my way to find those super-powerful DC chargers, then any gain is lost very quickly - first you have to navigate to it, then you very likely have to queue (or else utilization factor drops like a rock and cost rises like Apollo 11), and finally you have to wait in a place you did not choose to go to while your car charges. That charger has to be insanely powerful to make up for those disadvantages. Now if it was at a rest stop along the motorway I was driving on, two of the disadvantages would disappear. I would be there already and wouldn't have to waste time going out of my way to get to it, and if I'm running out of electrons on the motorway, we can't do any better than high power DC anyway.

 

[GSP]

Lets see what may be in 5 years time, when thousand of EV-Cars like Models S are on the road. I will still charge my car at home, maybe from my solar-panels. But for long distance trip, i will see service stations for EV like those today for ICE. But what happens if you want to charge 10 Models S with 43kW AC or 90kW DC. For AC-charging you need an transformer to step down down the 20kV voltage down to 230V/400V. The Transformer has losses (92-95% efficiency) Transformer are expensive too 600KVA around 30.000-40.000 Euro. To this add the losses for the on-board charger. Other scenery: on big rectifier transforms 20kV AC direct into 500V DC which are distributed to each DC charging station. No transformer losses, higher efficiency as single charger. The conclusion, if you want to charge more cars at the same time quickly, advanced DC charger are the solution. A single CHAdeMO is a nutshell an while disappear because being to slow and to expensive to produce.

Exactly This.

See page 2 of this document for info on EPRI's work on this subject:

http://mydocs.epri.com/docs/CorporateDocuments/EPRI_Journal/2012-Spring/1025049_InDevelopment.pdf

This seems like a compelling method of providing fast charging, with lower installation cost, lower energy costs, and lower demand charges.

GSP

PS. EPRI's 31 Dec 2012 update:

Update