JRP3
Hyperactive Member
Glenn Doty thinks the low NG prices are a temporary event from over production. NG pricing does seem to be volatile so he could be correct.
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Marginal power
- Thread starter eledille
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Norbert
TSLA will win
If otherwise NG has a higher cost, then that should mean that NG would be used for marginal power, not coal.
None, your water heater is in the base load - on average, when you turn your water heater on, someone, somewhere has just turned theirs off.
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JRP3
Hyperactive Member
So compare that to a fleet of EV's, all turning on around the same time over night, if we assume a large percentage of night time charging.
JRP3
Hyperactive Member
Glenn addresses this study and points out it's not actually marginal emissions at all: Recent Analysis From The Union Of Concerned Scientist Is Garbage. - Glenn Doty - Seeking Alpha
Norbert
TSLA will win
He claims they don't understand the definition of "marginal", and he is wrong. This is even more obvious when you look at all the graphs of a previous incarnation of that study. They examine in detail which power plants are used to address incremental load, additional load. They go as far as examining this for different times in the day, and different months. That is the meaning of the table I posted: It describes the CO2 emission specifically of that power which is used to address marginal load.
Here, as I already posted, is how they describe what they do:
And you haven't answered this yet, which may be a crucial point:
If otherwise NG has a higher cost, then that should mean that NG would be used for marginal power, not coal.
Norbert
TSLA will win
Not if EVs are charged during the the period of lowest consumption in the night. Then they smooth out the demand curve, and replace power [EDIT: power consumption] that is turned off.
When using Vehicle-to-Grid communication, they can increase the continuity of demand, and reduce the need for dispatchable power generation.
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JRP3
Hyperactive Member
I think he objects to the inclusion of hydro power which is base load and load following, not marginal, and if used at night instead of being backed up it's not available during the day.
Except at night, when there is excess coal capacity. Why power up a more expensive NG plant if there is cheaper coal capacity available?
JRP3
Hyperactive Member
How does extra demand "replace" power? Coal and NG plants reduce output at night, increased demand means they reduce output less.
Again, future projections, which I do expect to happen, but not currently relevant. Until it's proven cost effective it's just speculation.
Norbert
TSLA will win
That was a typo, it should have said "power consumption", instead of "power". The point is that less dispatchable power is needed, which is more or less the point MPT was making: that things may "average" out.
If you expect it to happen, why do you call it "speculation"? It's not a major point in any case, I just mentioned it because I also expect it to happen.
Norbert
TSLA will win
I wouldn't be sure that is what he meant, but that would be just as wrong. The study mainly finds that, to a large part, specific flavors of NG are used for marginal load. However, for example, which flavors, depends on how much hydro is available, not only on where the demand curve is at a specific time of day. Sometimes, when less hydro is available, different plants are used for marginal load than when more hydro is available.
He wrote:
That's not true. He might assume they merely look at the different average mix being used at different times. But they actually determine which specific kind of plants are used for marginal load. For example, consider this sentence:
(NGCT is a specific flavor of natural gas power plants).
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Yes , you'd power down all NG available first, until you powered down NG as much as you can. So if the nighttime demand goes below that, you power down the next most-expensive source, which might be coal. That might in fact happen when you bring coal back online, as then NG might be powered down already during the day, and the total availability of power plants exceeds even day time demand. Or it could happen when there is less NG than the difference between day and night demand.
And the same can happen to coal once the even-less expensive sources increase in capacity to the degree where coal isn't needed, for example in states with a lot of hydro.
I think, this shows once more that these factors depend only on the peculiarities of the grid at each location. One needs to distinguish "individual responsibility" and "effect on the whole system at some specific point".
And the fact that coal is chosen in such cases (as above) is because utilities decide without regard for the external costs of CO2. That would need to be changed at the political level, from the outside. And this is what currently the EPA makes happen: increase the requirements on coal such that either CO2 is reduced to about NG level, or such that coal is taken off-line because that would be too expensive. And clean energy is being added in amounts larger than the EV consumption increases.
The net result is that CO2 (and other GHG) production is reduced, and that EVs will have effective CO2 emissions lower than the best hybrids.
Of course, the final destination of EVs is to be used with a clean, sustainable grid where they produce zero emissions. And we are currently doing everything that leads in this direction, even though it could and should be more.
JRP3
Hyperactive Member
A fleet of EV's charging at night is a large load on the grid that will increase emissions. Yes it may even out the day/night ratio somewhat, but emissions will increase. Unlike MPT's water heater scenario there probably won't be a bunch of EV's turning on and off over night to compensate and average out, they'll all come on around the same time and all shut off around the same time.
Because I can't tell the future? It's going to cost a lot to implement, and from what some people in the industry say the current grid technology is based in the 1960's. Being able to "throttle" a fleet of plugged in EV's could be a game changer, but we aren't there by a long shot.
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I guess I don't understand what is being argued. Should we not be getting EVs then? While in the short term people buying EVs and charging at night may increase emissions, so would new subdivisions, new factories would all increase emissions...etc
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I got lost too.
It seems to me that having more EVs charge at night--or other nighttime electricity use--would put pressure on the utility companies to increase the base load. This would result in a higher base load output during the day so there would be less demand for marginal power overall. Naturally, the utility companies aren't going to do this before there is a load, but it won't take them too long once a permanent load becomes permanent. IF there is in increase in CO2, and some utilities have said there won't be any additional power needed before half the cars are electric, then it's only for a short time until new base load plants are built. I have a hard time seeing the problem.
Norbert
TSLA will win
And to be clear for other readers, his article is not about this study:
ftp://ftp.dvrpc.org/dvrpc_misc/SMegillLegendre_DOEEVActionPlanLibrary_Asof03-01-2012/JournalofPowerResources_MarginalElectricityforPHEVsandFuelCellEVs_2009.pdf
This study, which I have been referring to, is only mentioned in the comment section, and as I showed above, not addressed correctly (merely done away with, in error).
To make the point clearer: There are no coal-fired units in California, and the last one in Oregon is closing soon. So there's no doubt that EVs on the US west coast are less polluting than ICEs.
JRP3
Hyperactive Member
Last I knew LA imported a huge amount of coal power from out of state, something around 40% of usage. So if you are part of the LA grid you may very well be charging from coal. Saying there are no coal plants in CA doesn't provide the whole picture. That's my main point of this whole exercise, that we have solid factual data to use.
stopcrazypp
Well-Known Member
You are mixing two things. Installation order and operation order. In this example you are making the assumption that what matters is what is turned on first (your water heater was turned on at a time when all the nuclear capacity was already assigned), not what is installed first. There's a major difference. To make it clear, here's an illustration.
power plant mix at a certain point in time (using an arbitrary one as an example):
base plant | peaking plant
xMW nuclear | xMW wind | xMW coal | xMW natural gas
installation order:
xkW 20 year old heater | xkW 19 year old water heater | ...| xkW 10 year old water heater | ... | xkW 1 year old EVSE | ... | completely new appliance
operation order:
xkW heater turned on 2 hours earlier | xkW water heater turned on 1.9 hours earlier | ... | xkW water heater turned on just now
If you are making the assumption what matters (in terms of counting as marginal demand) is installation order, then any newly installed appliance is disadvantaged, since it will likely be at the end of the list and not be able to fall under baseload (with the caveut about load replacement I will mention near the end of this post). If what matters is operation order, then what is turned on first will get assigned to the baseload, so the "newness" of the EVSE is irrelevant, and all you have to do is turn it on as early as possible if you want it to be assigned to baseload.
The key thing you have to keep in mind is there is ALWAYS something using the base powerplants in both cases, so you can't make the assumption that everything is marginal at a certain point in time, without being inconsistent.
And back to the installation order, you are still operating under the assumption (as are most studies on this) that nothing gets replaced or retired.
Here's how the profile would look like:
old load retired | old capacity retired | current baseload capacity/current load | new capacity added | new load added
(by load what matters is kW, so if an appliance gets replaced with a more efficient one, then the load is reduced).
As long as the old load being retired is retired at the same rate new loads are added, the baseload is in equilibrium (using the assumption every thing is follows an "established" schedule so the load profiles are the same every night). Even if the rate new loads are added is faster, there's going to be a certain amount of time that a new load being added to the list will fall under the current capacity as old loads are continuously being retired (the line keeps moving, even if it's growing). Then once you factor in new capacity that is being added (and old capacity being retired), which in general is in response to new loads being added faster than old loads retired, then it appears likely there will be enough baseload to cover new EVSEs being installed. Without data on this, you can't really say an EVSE won't be covered by baseload plants without making a huge assumption.
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