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When to Charge? Not at Night.

BillRadio

Member with an Altitude
Jan 2, 2022
122
222
Denver
A recent study about EV charging from Stanford University says we're doing it wrong. Most of us without our own solar are charging at night, but if an increasing number of EV's charge then, that eventually becomes the new "on-peak" period. Of course, we're charging at night because we're at home and the rates are lower. Our local utility co-op does not have "off-peak" rates, instead, we have a "penalty", based on our maximum kWh usage between 4 and 8pm.

One third of our utility's power comes from renewables, therefore, we should be charging when there is more renewable energy available. That means charging during the day. The study reports we should encourage more charging at work. Those of us who don't commute have more options. I have stopped charging at midnight, and started charging when the sun is up. This creates a new problem: when to start charging during the day? Certainly not near 4pm. The maximum solar available starts at about 11am, but what if I want to drive then? Instead of using START TIME at midnight, I program the LEAVE TIME for 12Noon, and charge more often. Shorter charge sessions allow for charging to occur closer to prime solar time, and a 12 Noon departure time leaves some flexibility should I want to leave in the morning. I want to make this as automatic as possible, so I may tweak the time, possibly earlier, then forget it.

Also, our utility is surveying EV owners on our usage and since we all have updated (AMI) meters, they know exactly when we charge. This might create new Time Of Use tiers, which may or may not be at night. If they offer a lower tier at night, I'll switch back.
 
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Sophias_dad

Active Member
Supporting Member
Jul 29, 2018
2,601
3,042
Massachusetts
I know EV usage will increase, but at the moment EV charging is a small sliver of our power usage in the US, and an even smaller sliver is those that charge at night in TOU areas.

The study is correct that there may be a bit of mayhem if a zillion EVs are set to start charging at the same moment. This would be easily fixed in software(at least by Tesla, maybe not by other manufacturers. I assume almost ANY charging station that allows one to set a time of charge could add a randomization factor of up to 15 minutes before it starts charging, or even add pauses or variations in the middle of charging so as to more closely mimic large power usage devices. I also know I've seen some charging stations that can be controlled by the utility, allowing them to dictate when the EV is charged.

The variation between peak load and night load in most of the US is enormous. Even now, in November in California, you can see that the low point in usage is from 10am to 1pm, and is about 25% less than the peak. For most of the night, its more like 20% less than peak. Repeat that exercise in July, and you lose the low in the AM, and its a more-expected low at around 4am, this time 37% off the peak. You can play with the data yourself at California ISO - Today's Outlook

Maybe by 2035 this will be an issue for SOME areas of the country, specifically those with enormous solar fields. At least one study I've seen says wind turbines produce MORE power at night, so that works against Stanford's study.
 

Missile Toad

MSLR Wht/Blk/19 | OD 6/10/21 | RN11512
Aug 30, 2016
709
841
30.04, -95.16
Maybe by 2035 this will be an issue for SOME areas of the country, specifically those with enormous solar fields. At least one study I've seen says wind turbines produce MORE power at night, so that works against Stanford's study.
The midwestern states all have surpluses of energy at night. The wind turbines are being put in at a pace that FAR exceeds the demands put on them by electric cars, recently added. This pattern will persist for at least the next 5 years. Accordingly, there are some nights in Texas and Kansas, where there is so much wind on the grid, that they have to turn off the wind turbines, an activity known as curtailment.

95% of the time, the curtailments happen at night, when wind tends to run stronger and demand is weaker. Denver is likely also drawing a lot of power from the midwestern wind farms. So as you travel East from the Rockies, night charging is best, until you reach Louisiana, Tennessee and Ohio.

Shoot, there are 2-3 nights in this second week of November, where wind generation, alone, is forecast to exceed all electricity demand in some Great Plains states: https://marketplace.spp.org/pages/forecast-vs-actual

1667788784698.png
 

BillRadio

Member with an Altitude
Jan 2, 2022
122
222
Denver
I agree completely with your replies. However, I am embarrassed to admit our local co-op (Core) gets 59% of its energy from coal. All their power but solar is purchased from other utilities, including wind. I really can't in good conscience charge at night when there is locally-produced solar available a few hours later.

That said, I hope our co-op establishes some kind of EV-friendly program. Surrounding utilities offer tertiary price tiers and free chargers. At least for now I'll feel better by charging in the daylight.
 

Missile Toad

MSLR Wht/Blk/19 | OD 6/10/21 | RN11512
Aug 30, 2016
709
841
30.04, -95.16
I agree completely with your replies. However, I am embarrassed to admit our local co-op (Core) gets 59% of its energy from coal. All their power but solar is purchased from other utilities, including wind. I really can't in good conscience charge at night when there is locally-produced solar available a few hours later.

That said, I hope our co-op establishes some kind of EV-friendly program. Surrounding utilities offer tertiary price tiers and free chargers. At least for now I'll feel better by charging in the daylight.
I think your Core Co-op is one of the utilities that trade and balance in the Western Area Power Administration. Although the Core website shows only 30% of the energy comes from renewables, if the WAPA generation mix is to be trusted, then the vast majority of that energy is from wind.

Real-time Operating Grid - U.S. Energy Information Administration (EIA)
This chart shows the absolute MW going into the system(s). If you consider that demand is lower at midnight (normally a good assumption most nights in the midwest), then, as a proportion, renewables (wind and solar) will be greater around midnight. Charging at noon, the sun offers a very modest bump to the already strong wind MW. (I try to show an average of winds, through those periods, with the red 'bars')

At best, the increase in solar, during the day, is tiny as compared to the winds at midnight.

4nights midnight is best.png
 

Rocky_H

Well-Known Member
Feb 19, 2015
8,825
11,535
Boise, ID
A recent study about EV charging from Stanford University says we're doing it wrong.
Oh jeez. I remember seeing that posted a couple of months ago when it came out, and the conclusion surprised a lot of people. But looking into it found very quickly why the study was such a misleading, ill-informed, steaming pile of hot garbage.

The "conclusion" is based on some assumed conditions:

Almost all electricity is solar generated, and almost all cars are electric.

It's asinine. It's such a California-centric set of blinders. Those conditions are a ridiculous hypothetical possible future, which probably won't happen for many decades yet, if ever at all. So as of now, and the foreseeable future for quite a while yet, its recommendation is blatantly wrong and harmful. Grid load is the main issue to be careful of, and in most areas, afternoons are still where we don't want to add extra load, and night time still usually has extra capacity.
 

Sophias_dad

Active Member
Supporting Member
Jul 29, 2018
2,601
3,042
Massachusetts
Oh jeez. I remember seeing that posted a couple of months ago when it came out, and the conclusion surprised a lot of people. But looking into it found very quickly why the study was such a misleading, ill-informed, steaming pile of hot garbage.

The "conclusion" is based on some assumed conditions:

Almost all electricity is solar generated, and almost all cars are electric.

It's asinine. It's such a California-centric set of blinders. Those conditions are a ridiculous hypothetical possible future, which probably won't happen for many decades yet, if ever at all. So as of now, and the foreseeable future for quite a while yet, its recommendation is blatantly wrong and harmful. Grid load is the main issue to be careful of, and in most areas, afternoons are still where we don't want to add extra load, and night time still usually has extra capacity.
I try not to think of how much our government paid for the 'study'....sigh
 
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