Cold weather charging / battery heating / loss of range (THEORY INSIDE!)

[digitaltim]

OK, so I know you work in the electric industry...I don't remember where I read it or which power source it was (maybe nuclear?), but I remember reading that some power stations actually end up dumping (wasting) power at night because they're unable to taper back to the low nighttime levels quickly enough. Does that ring any bells? In that case, for now anyway it would seem that you're not really being any better to the grid by charging at 20A vs. 80A in the middle of the night.

Not lost...

The biggest issue with low load on the grid at night is it drives generators to their minimums...too low and they have to shutdown. If they shutdown, it could take them offline for days as things have to cool before heating back up (minimum down times...and they also have minimum run times). The cycling on/off is stressful to the generator as it is ramping up and down. The baseload units as mknox notes just want to run at a constant output with very little oscillation.

BTW, nukes can stay online at full output for a year plus depending on design (BWR vs PWR). Once they go down for a refueling outage (RFO), it generally takes 20-30 days before they are back online. A lot of maintenance activities are taken care of during the RFO.

 

[jerry33]

The biggest issue with low load on the grid at night is it drives generators to their minimums...too low and they have to shutdown. If they shutdown, it could take them offline for days as things have to cool before heating back up (minimum down times...and they also have minimum run times). The cycling on/off is stressful to the generator as it is ramping up and down. The baseload units as mknox notes just want to run at a constant output with very little oscillation.

My understanding is:

Base load generators are low cost per energy unit but because they are limited in power output flexibility, they can't be sized much larger than the minimum load (typically at night). Charging EVs at night allows the base load to be increased because the low is higher. In an ideal world EVs would only charge at night and rooftop solar would take care of most of the a/c requirements. This would drastically reduce the need for peakers and should also lower the electricity rates.

 

[mknox]

Base load generators are low cost per energy unit but because they are limited in power output flexibility, they can't be sized much larger than the minimum load (typically at night). Charging EVs at night allows the base load to be increased because the low is higher. In an ideal world EVs would only charge at night and rooftop solar would take care of most of the a/c requirements. This would drastically reduce the need for peakers and should also lower the electricity rates.

Baseload is that level of demand that you would never go below even under the lightest system loading scenario (i.e. middle of a calm spring night during a holiday). Generators that supply baseload can run continuously, although some baseload generators may be dispatched in and out for various reasons (like scheduled maintenance). Baseload is ideally suited to nuclear and, in some cases, hydro. Peaking (gas) plants can step in to supply higher demands during the day and, increasingly, to pick up the slack when renewables like wind or solar go down due to lack of wind or sun.

EV charging is an ideal off-peak load. Here in Ontario, Canada we're seeing a lot of large scale wind turbines come and operators (unfortunately for grid operators) are given guarantees for the purchase of the power they produce. It seems around here the wind blows best over night and sometimes that extra capacity forces the hourly price so low that it can sometimes go into negative pricing (crazy market rules). This is because the grid operator is forced to purchase the wind, but you can't effectively spool the nukes up and down fast enough to compensate. When this happens, other jurisdictions we're tied to (New York, Minnesota, Manitoba, Quebec) can actually import our power and be paid for doing so! I believe this presents an excellent opportunity for some sort of overnight EV rate. Why pay people to take our power, or export it at low prices when we can use it to create and foster an EV market right here at home?

 

[digitaltim]

My understanding is:

Base load generators are low cost per energy unit but because they are limited in power output flexibility, they can't be sized much larger than the minimum load (typically at night). Charging EVs at night allows the base load to be increased because the low is higher. In an ideal world EVs would only charge at night and rooftop solar would take care of most of the a/c requirements. This would drastically reduce the need for peakers and should also lower the electricity rates.

Baseload gen is less expensive because of size/scale of the unit, design and fuel type (which is the biggest factor)...

Gen output has to match the connected load - regionally and in aggregated for the connected grid. If it doesn't, you end up with a frequency imbalance. The grid is designed to protect itself - underfrequency relays will trip shedding (disconnecting) load and/or generators will trip to create smaller islands where the gen=load balance can be restored.

The price incentives given to encourage night time usage is done for a variety of reasons, but the basic concept is to flatten the load/demand curve so that the "peak" usage is not so high. It saves capital investment on the transmission/distribution grids (they don't need to be sized as large) and allows baseload gen units to handle the load versus the expensive peakers you mentioned.