The controversy in fast charging for electric vehicles

[zack]

If motion-sensing street lights (a great idea, btw) are used, they most certainly will have to be LED. I have a friend who builds LED streetlights and they're pretty amazing. Once we have a lot of batteries being taken out of electric cars we'll be able to install them at charge points for fast-charging (and charge a premium to fast-charge) to reduce stress on the grid. If a present-day Tesla pack was used at a charge point, wouldn't the cost be only about $12K, based on what Tesla charges us to pre-order a replacement? Or is that a projected price? I did a quick lookup of bulk-priced batteries and found one type for $3.70 each, and quantity pricing would certainly bring that down below half. If you double the price of a charging station but then double the price to fast-charge, it seems like a viable option to have on-site storage.

 

[Norbert]

OK, to see the possible power consumption of DC fast charging in relation to US electricity generation, I made this back-of-the-napkin calculation:

According to this doc (from a gov site, US Energy Information Agency, which I found starting with DOE): http://www.eia.gov/totalenergy/data/monthly/pdf/sec7_19.pdf
(Overview page: http://www.eia.gov/totalenergy/data/monthly/index.cfm)

In 2010, the total "Electricity Net Generation" was 4,120,028 Million kWh.

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If there were as many as 100,000 DC fast chargers (almost as many as gas stations, which is probably more than enough, given that most charging will be done at home), and each would operate an average of 10 hours each day with 100 kW (twice the amount used by the Leaf), then they would use 100 kW * 10 hours * 100,000 * 365 days = 36,500 Million kWh.

That would be 0.89 % of the total electricity generated in the US, and sufficient to provide about 4% of all charging if *all* vehicles in the US were EVs.

(I'd think that by the time that EVs reach such a large percentage, the average range of a battery will be several hundred miles, and so the need to fast charge will be lower than 4%.)

I welcome suggestions to improve this calculation, in fact that is a reason I am posting it.

 

[zack]

Which only goes to show that it's the oil companies that are spreading lies about electric cars.

 

[dmckinstry]

OK, to see the possible power consumption of DC fast charging in relation to US electricity generation, I made this back-of-the-napkin calculation:

According to this doc (from a gov site, US Energy Information Agency, which I found starting with DOE): http://www.eia.gov/totalenergy/data/monthly/pdf/sec7_19.pdf
(Overview page: http://www.eia.gov/totalenergy/data/monthly/index.cfm)

In 2010, the total "Electricity Net Generation" was 4,120,028 Million kWh.

---

If there were as many as 100,000 DC fast chargers (almost as many as gas stations, which is probably more than enough, given that most charging will be done at home), and each would operate an average of 10 hours each day with 100 kW (twice the amount used by the Leaf), then they would use 100 kW * 10 hours * 100,000 * 365 days = 36,500 Million kWh.

That would be 0.89 % of the total electricity generated in the US, and sufficient to provide about 4% of all charging if *all* vehicles in the US were EVs.

(I'd think that by the time that EVs reach such a large percentage, the average range of a battery will be several hundred miles, and so the need to fast charge will be lower than 4%.)

I welcome suggestions to improve this calculation, in fact that is a reason I am posting it.

I wouldn't worry about any improvements in calculations. Without even using a napkin it's apparent that your projected EV use is less than 40 in 4000 (< 1%). The only possible concern would be momentary "spiking" from every charger in the country starting at the same time. How often do you see every car at a gas station starting to fill at exactly the same time?

 

[Adm]

Also, I never saw the fact included that every time an EV charges means less gas needs to be refined and thus less energy is used. This must compensate a part of the energy used to charge. I believe I once saw 6kWh needed to refine 1 gallon of gas??

 

[TEG]

...The only possible concern would be momentary "spiking" from every charger in the country starting at the same time. How often do you see every car at a gas station starting to fill at exactly the same time?

Some of the new generation of charging stations have delayed start provisions. The scenario you described could happen if there was a broad power failure, then the power was restored but a lot of EVs reactivated their charging all at once. I have seen indications that the Blink chargers can delay charging restart after a power cycle.

 

[Norbert]

Since fast chargers are able to limit the power, they also should be able to slowly increase the power gradually, instead of generating a spike, in so far as that is a concern.

 

[Norbert]

Don't have exact numbers yet, but it seems the power consumption of a fast-charger is about that of a fast-food restaurant.