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0 pointsObi_Juan_Kenobi5y ago0 comments

Simple: most people charge at night.

Sure, fast charging will add some day-time demand, but it's not much. Cheap night-time pricing keeps the charging demand off-peak.

More even demand curves make generation more economical. It becomes trivial to upgrade distribution where needed.

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7 comments · 2 top-level

athms5y ago· 3 in thread

>Simple: most people charge at night.

Except the people that don't have a charging station in their garage or folks that have a power outage. Just this week, we had a heat wave (70-80F) and winds up to 90MPH across California that resulted in power outages throughout the state as well as several fires.

qndreoi5y ago

It seems that gas stations would not work during a power outage. Santa Ana winds cause lots of edge case problems.

erik_seaberg5y ago

“What if all the gas pumps go offline because of power or network outages” was a pretty scary failure mode they were thinking about before Y2K.

athms5y ago

You are right, but I have cans of gasoline as part of my emergency kit in case of an earthquake or fire.

tw045y ago· 2 in thread

I still don't see how that works when you're talking EVERYONE charging. Here's a quick example from New England in 2010:

https://www.eia.gov/todayinenergy/detail.php?id=830

During "peak" hours they're using roughly 17Gw total, and during off-peak, it's at 15Gw so we've only got 2Gw total to buffer electric cars charging.

Feel free to tell me how my math is wrong, but let's assume worst case scenario: a tesla charger lists 11.5kW max draw. There are roughly 14m people in New England, if we assume even half of them were charging overnight, that's 86Gw of power draw. Even if you back that off to 25% of the population and half the power draw from the charger, you're at 21.5Gw of power, which is 10x what is available, and more than the total power usage during peak hours.

If someone else has some different math I'm all ears but I don't know how we're going to more than double the total power capacity in 10 years - even if you assume we can get there with renewables, the backend infrastructure can't handle it.

yongjik5y ago

2021 Tesla Model S has a 100kW battery and 402-mi range. I searched for "average driving miles per year" and Google says 13,500 miles - assuming this, we have about 37 miles per day, which would mean our Tesla S only needs to charge 9.2kW every day. If they're sitting on a charger 10 hours per day, they can take a leisurely 920W per vehicle (less than a good hair dryer), not 11.5kW.

tw045y ago

I'm not sure I agree with that math for a number of reasons. For starters if you want to go strictly by averages, the average household has two cars, so your 9.2kW goes to 18.4kW out of the gate. Additionally that average includes teenagers which drives the mileage down, but households with teens tend to have more cars, so that means either they come out of the average or the 18.4 jumps to 27.6kW/day.

The average household uses <1200kWh per month. Adding another 18kW per day increases power usage by almost 50%, which goes back to: the national power grid doesn't have anywhere near 50% spare capacity.

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