Marginal power

[stopcrazypp]

That is not exactly correct. For the most part nuclear never ramps down, yes some hydro does get backed up, for daytime use. Coal and NG do ramp down, but they don't produce unused electricity, what they produce is used. If there is more night time demand then they won't ramp down as far. Glenn is essentially correct that marginal load at this point is met with coal or NG.

I think that way of looking at things is completely BS and is essentially just a very contrived way to assign the worse plants to EVs. What you really care about is the amount of CO2 emitted during the period your EV is charging. That means when you calculate emissions, what you have to look at is the average CO2/kWh emitted by your utility during your charging session and then adjust that by the amount of kWh you used. To be extremely accurate, if you have an instantenous graph of CO2/kWh during the day for your utility, and the kW profile that your charger draws, then you can calculate how much CO2 can be attributed to your charging session. All the talk about baseload and peaking is a just a proxy way (that may or may not be accurate) of trying to figure out this number.

This electricity demand is shared equally among ALL your appliances and ALL the households powered by your utility. Unless the utility has a direct connection to your EV charger, it's not responding to your EV specifically, it's responding to the entire load as a whole. It doesn't make any sense to only assign the coal/NG plants to EVs and then the rest of the cleaner ones to non-EVs.

For example, if you run your heater at the same time that you charge your EV, why should the EV be assigned as the "marginal load" and the heater not. If the only thing running in your house is your EV charger, then why should YOUR household be the only one assigned as a "marginal load" and not other households that may be running other appliances. What's so special about EVs chargers that they HAVE to be the "marginal load" no matter what (and 100% at that), and why do we ignore all other appliances?

 

[rolosrevenge]

I completely agree with you.

 

[dsm363]

Yes, excellent argument. I'll have to use that one in the future. Thanks.

 

[JRP3]

Any new load has to be from dispatchable generation. Yes technically your heater demand is probably going to be met with NG or coal, just as your EV is.

 

[JRP3]

The ideal situation would be to run nuclear, wind, and hydro at capacity and supplement it with solar/NG/coal when needed

Nuclear and hydro are run pretty much at capacity, with some hydro held back for peaking and FR. Solar is not dispatchable, you get what you get, and curtail probably NG if there is a lot, and increase NG if there is not. During the day coal is pretty much flat out I think in most cases, so if you want to avoid coal use, daytime EV charging is probably the way to do it since the extra demand will be met with NG.
I think we've pretty much beat this one to death. I'm not a grid expert but I think I have a pretty clear picture of how the grid works. Obviously many of you don't agree, which is fine, but we are arguing in circles and I find myself repeating things that have been already covered, so I'm going to let it go.

 

[rolosrevenge]

All of this discussion makes me want to develop an online power engineering course that covers these topics. Maybe if I ever get a professor job.

 

[Norbert]

During the day coal is pretty much flat out I think in most cases, so if you want to avoid coal use, daytime EV charging is probably the way to do it since the extra demand will be met with NG.

Not for California (where currently most of EVs are), according to this 2009 report: (Note these are marginal emissions)

ftp://ftp.dvrpc.org/dvrpc_misc/SMegillLegendre_DOEEVActionPlanLibrary_Asof03-01-2012/JournalofPowerResources_MarginalElectricityforPHEVsandFuelCellEVs_2009.pdf

This means the best charging times are 2am - 4am.

Furthermore, a value of 568 g/kWh is a bit better than average grid at that time, and good even for NG.

This means in CA, night time charging is not coal level, it is NG level.

 

[Norbert]

It also means that solar power produces the most power at the time when it helps the most to reduce CO2 !

 

[JRP3]

Of course I was not speaking about specific areas since each will be different. Yes solar produces during peak times, but as I said it's not dispatchable, so if a new load is placed on the grid during peak solar that load is going to be met with dispatchable supply, which means NG or coal.

 

[Norbert]

Of course I was not speaking about specific areas since each will be different. Yes solar produces during peak times, but as I said it's not dispatchable, so if a new load is placed on the grid during peak solar that load is going to be met with dispatchable supply, which means NG or coal.

It doesn't need to be dispatchable because it comes in at the right time. That's the point. Adding solar replaces marginal power at that specific time.

 

[JRP3]

Tell me this, is the demand on the grid the same if you don't plug in an EV? No, it's lower. So if plugging in an EV increases demand on the grid, what meets that added demand? It has to be dispatchable power, and that is not solar.

 

[jcstp]

an EV charging, is petrol not being used (produced)
as we know, producing petrol demands more energy than just getting an EV driving with same energy
so at the end refinerys must produce less petrol, so less energy
this is replaced by an ev charging less energy then the refinery would demand
so less demand on the grid

 

[jcstp]

Tell me this, is the demand on the grid the same if you don't plug in an EV? No, it's lower. So if plugging in an EV increases demand on the grid, what meets that added demand? It has to be dispatchable power, and that is not solar.

More anti-ev gibberish

on this post it shows Texas will be very happy it can charge EV's at night
no mather if it's part of baseload or marginal load
else they would have wastedload

 

[Norbert]

Tell me this, is the demand on the grid the same if you don't plug in an EV? No, it's lower. So if plugging in an EV increases demand on the grid, what meets that added demand? It has to be dispatchable power, and that is not solar.

You are confusing several things.

The study above showed that EVs are best charged at night, in CA.

Solar, during the day, produces electricity, so the marginal generation at that time (which is dispatchable) can be reduced. (It's as if removing EV charging, the opposite of adding EV charging).

 

[jcstp]

this video tells why the grid is happy with EV charging at night

 

[JRP3]

The ability of the grid to supply power has nothing to do with increased emissions that come from increased demand.

 

[JRP3]

an EV charging, is petrol not being used (produced)
as we know, producing petrol demands more energy than just getting an EV driving with same energy
so at the end refinerys must produce less petrol, so less energy
this is replaced by an ev charging less energy then the refinery would demand
so less demand on the grid

It has been well established that petroleum production is self sufficient and even provides some extra power to the grid. In any case full well to wheel analysis already takes all that into account. It's all been covered in this thread and elsewhere so I'm not going to go over it all again.

 

[JRP3]

You are confusing several things.

The study above showed that EVs are best charged at night, in CA.

Solar, during the day, produces electricity, so the marginal generation at that time (which is dispatchable) can be reduced. (It's as if removing EV charging, the opposite of adding EV charging).

I'm not confusing anything. As you state solar during the day is the same as removing EV charging, which reduces dispatchable generation, which is NG, or coal. That means plugging in an EV, at any time, increases dispatchable generation, which is NG, or coal. You seem not to understand that you've just made my point.

 

[Norbert]

I'm not confusing anything. As you state solar during the day is the same as removing EV charging, which reduces dispatchable generation, which is NG, or coal. That means plugging in an EV, at any time, increases dispatchable generation, which is NG, or coal. You seem not to understand that you've just made my point.

First, in CA, coal is not used dispatch (according to the study, which understands very well "marginal cost"). Specific flavors of NG, and other sources, are used. The flavors at night are better for EV charging.

Then, what you are confusing is that I am not talking about plugging in an EV during the day at all. I'm merely talking about using solar to produce electricity, independent of EV charging (which happens at a different time). I'm saying that the fact that solar peaks during the day is great, because the generation it replaces at that time has a higher gCO2/kWh.

 

[JRP3]

Here are some samples:
FirstEnergy, Citing Impact of Environmental Regulations, Will Retire Six Coal-Fired Power Plants
FirstEnergy, Citing Impact of Environmental Regulations, Will Retire Three Coal-Fired Power Plants in West Virginia

GenOn Energy - A Leading Energy Producer - News Release


http://www.duke-energy.com/news/releases/2011071501.asp


The full list of PJM deactivations is HERE. >16,000 MW of units, mostly coal. Median age of the units is 53 years!

Taking a closer look at the PJM shutdowns, it looks as if most of them are simply temporary closings to allow upgrades to be done to them, not actual permanent shut downs.