Marginal power

[eledille]

I did, I just don't think it fits. If everyone is responsible for your emissions, does everyone get credit if you don't don't turn on your lights, don't turn your heat up, or don't plug in your EV? After all by not using your EV you reduce grid emissions.

When I bought a heat pump, Norway started buying a few less kWh per day of night-time coal power from Denmark. That would reduce the time coal is on the margin by a tiny amount. By your method of calculation, the next EV to plug in would get the credit of pushing coal up to the margin for a shorter amount of time. By my method, every consumer would share that benefit.

Should my energy saving be credited to somebody else's EV?

Am I emitting more CO[sup]2[/sup] *EDIT: per kWh consumed* if I plug in a new EV than if I fail to buy a heat pump or insulate my home properly?

 

[rabar10]

If the following assumptions are valid:

• Typical grid electrical usage over any 24-hour period has a 'hill-and-trough' pattern, with (in general) more usage during the day/evening and less usage during the night/early morning
• Grid producers have structured their supply to be compatible with this pattern, with 'base-load' generation as well as 'load-following' and 'peaking' plants, using whatever mix of sources is applicable for that country/region
• Most EV charging will be done overnight at the owners' residence

Then as more EVs come online, the overnight troughs will be raised. Therefore the base load value will rise, but the differential between base-load and peak load will shrink.

In the short-term (i.e. if this transition happens very suddenly, which I think is unrealistic), then existing load-following plants will run at a higher rate overnight.

But in the long-term, utilities can increase their base-load generation capacity in whatever way is most economical for them in that country/region, and potentially retire or upgrade some existing inefficient or uneconomical load-following or peaking plants.

So the answer to "what source of power is used to charge an EV" is dependent on whether you mean "my single EV today" vs. "some percentage of vehicles being EVs in 10 or 20 years"...

 

[Yggdrasill]

I agree that you need to take into account the mixed energy generation capacity. If you make the argument that a new load on the grid is responsible for the marginal generation capacity, you're assigning ownership of the initial power generation capacity to an older load. What's the point of doing that?

An analogy to show what you are in fact doing:

Imagine an island with a single waterfall. If you build a 100 MW hydropower plant there and a factory that needed 100 MW, this factory would use 100% clean energy. But suddenly, consumers need more stuff, and an additional factory is needed, and so a 900 MW coal power plant is built, as well as a new factory. Now you have a grid with 10% renewables and 90% non-renewables, and two factories using all the energy generated. Is it okay for the first factory to declare that their products use only clean energy in the production? Do they "own" the original hydropower until the end of time? What if both factories make the same exact product, let's say they produce paper. Can the first factory say that as long as they buy the paper from them, the customers can waste as much paper as they feel like, without having any effect on the environment? Do customers who reduce their paper consumption only help the environment if they bought from the second factory? If the island actually needs all the paper produced in the two factories, no amount of shifting the blame will actually reduce the paper consumption. The society on the island has been built up around the paper consumption, and it isn't the fault of the people buying the paper from the second factory, nor the factory owners. It is a systemic issue relating to how much paper the society needs. The society needs to cut paper consumption, period. They don't need to cut paper consumption originating the second factory, and keep the first factory out of it.

This sort of ownership of the clean energy sources is nonsensical. You need to consider the grid as a whole, where everyone has a responsibility to conserve energy. And buying clean energy certificates and the like is just a way of greenwashing ones energy consumption. (Unless that additional money goes into developing more clean energy capacity, rather than into the clean energy power plant owners' pockets.)

 

[eledille]

Yggdrasill: Great example, thank you.

rabar10: I agree 100%. That is one aspect of it. The other aspect is who owns the higher emissions of the instantaneous marginal power, which I'm arguing with JRP3 about

 

[JRP3]

Am I emitting more CO[SUP]2[/SUP] if I plug in a new EV than if I fail to buy a heat pump or insulate my home properly?

I don't know, but you are emitting more CO2 than if you bought the heat pump and insulation and did not buy an EV. Let's say you bought the heat pump and insulation, but instead of an EV you then bought a hot tub. Even if your overall load is lower than before that hot tub is still adding more load than would have existed without it.

 

[JRP3]

I think we all "own" any emissions above base load, but when we add even more load than exists above base load we are directly responsible for that. If I leave all my home lights on all the time and they are all 100 watt incandescents how is that anyone else's responsibility but my own?

 

[eledille]

I don't know, but you are emitting more CO2 than if you bought the heat pump and insulation and did not buy an EV. Let's say you bought the heat pump and insulation, but instead of an EV you then bought a hot tub. Even if your overall load is lower than before that hot tub is still adding more load than would have existed without it.

Sorry, let me rephrase.

Am I emitting more CO2 per kWh consumed if I plug in a new EV than if I fail to buy a heat pump or insulate my home properly?

 

[eledille]

I think we all "own" any emissions above base load, but when we add even more load than exists above base load we are directly responsible for that. If I leave all my home lights on all the time and they are all 100 watt incandescents how is that anyone else's responsibility but my own?

I should have specified that I'm thinking of emissions per unit of energy here.

Some people insist that when I charge my EV when coal is on the margin, I am responsible for a CO[sup]2[/sup] emission equal to the coal power emissions rate multiplied by consumption. I insist that I am only responsible for emissions equal to the grid average emissions rate multiplied by consumption. The difference can be enormous, in my case it is 1000 g/kWh vs 30 g/kWh.

I agree that you are responsible for your own consumption, and indeed I assume you are paying for it. However, you seem to think that when you are wasting energy your emissions per kWh is somehow lower than my emissions per kWh when I plug my EV in, simply because you have always been wasting energy, while my EV is new to the grid. That makes no sense whatsoever.

I agree that when I buy a new EV, more fuel will be burned than before and the margin will be pushed higher, but this does not remove your responsibility for not wasting energy - your consumption still counts just as much as mine in the new grid configuration. The proof of this is that if I buy a new EV using 5 kWh per day and you switch off resistive heating consuming 5 kWh per day, then total consumption is unaffected and emissions, emissions rate and marginal power is unchanged.

If you were right that I must be held accountable for emissions based on marginal generation because I have connected a previously nonexistent load, then:

• If you save energy, I pollute less per kWh
• If you waste energy, I pollute more per kWh
• A new paper mill pollutes more than an old paper mill even though they consume the same amount of energy
• If you built your own EV way back in the sixties you get the lower average emissions rate, while my new EV is burning coal.

Is it reasonable to credit me for your efforts to save energy, or to blame me for your waste? What about two identical factories producing identical products and being connected to the same grid having different carbon footprints because one was connected earlier than the other? Or that two EVs have different carbon footprints per kWh based on when they were registered?

This is nonsensical.

Every load has the same responsibility per kWh for the total consumption being what it is, and therefore for where the margin is, whether it is new or old. That implies that only the average grid emissions rate can be used to calculate the carbon footprint of any load, whether it is the last added or not.

 

[eledille]

The following statement sums up what happens instantaneously when loads are added or removed:

The emissions caused by the last added load can always be eliminated by disconnecting any equal load from the system, regardless of which power source satisfied that load when it was added.

This implies that any unit of load is as good or bad as any other, and the average is the correct value.

Example:

System load is initially zero. Load A of 1 kW is added to the system. This load is satisfied by hydro power at a CO[sup]2[/sup] rate of 0 g/kWh. Other loads are added until marginal emission rate is 1000 g/kWh, system load is 1 MW. Load B of 1 kW is then added, being satisfied with coal power at an increase of CO2 emission of 1000 g/h. Load A is then disconnected. System load goes back to 1 MW and the reduction of emissions is 1000 g/h.

Mr. Devil's Advocate (a.k.a. JRP3): This is bulletproof. The next time they try to blame you for charging with coal you can tell them that the grid unfortunately remembers neither sins nor virtues, and that marginality only concerns the next change. And thank you for playing devil's advocate

 

[Robert.Boston]

IMO, it's the marginal carbon intensity of the generation that matters.

Let's suppose that you have a carbon tax (and we actually do here in the Northeast). Every power plant has to pay this tax, in proportion to their carbon emissions. Power plant owners bid the cost of this tax into their generation offer price. The highest-priced offer sets the clearing price for all the electricity used in that interval. Therefore, if a high-emitting power plant is the marginal resource, its high carbon tax is setting a higher electricity price. Thus, all users are being assigned the cost of the high pollution.

 

[Yggdrasill]

If all users have to pay for the high pollution, isn't that really a way of saying that all users are assigned the blame for the high pollution?

I mean, the utility companies could assign electricity lot numbers to all customers, and then distribute the electricity out to customers according to the numbering. An electricity lot number might be good for 1 kWh per day, a customer could have any number of lot numbers, until the end of time, provided they were actually used, and any overshooting consumption ends up at the back of the line. And each electricity lot number would be priced according to the corresponding bid from the electricity producer. (Say you have lots 1, 2 and 3, and three electricity producers with bids of $0.01/kWh, $0.05/kWh and $0.15/kWh, all for 1 kWh/day each. The customer with lot 1 would pay $0.01/kWh, the customer with lot 2 would pay $0.05/kWh, and so forth.)

Then the blame for the pollution could be laid squarely at the feet of those customers with high electricity lot numbers. (People who increase their consumption and people who are selfish enough to move out of their parents' homes - those bastards!) Does this seem reasonable? It is in effect what you should be supporting when you say the marginal production emissions are what matter.

 

[Robert.Boston]

Your approach, Ygg, is not a market approach, inasmuch as people pay different prices for the same thing. The advantage of uniform pricing is that owners of clean generation get paid a premium, and therefore more suppliers want to build generators that have low carbon emissions (and therefore earn a premium).

Also remember that the Norwegian generation is a monopoly, whilst American generation is competitive. In a regulated monopoly, consumers will be charged an average rate for power but will also pay their share of the capital cost of the generation.

In any case, as an economist I always evaluate activity at the margin, not on average. If I work another hour, will I earn enough extra money to offset the lost enjoyment of the hour elsewhere? If I eat another doughnut, will that make me happier (or just fatter)? If I charge my EV at midnight tonight, how much more carbon will be emitted? This marginal thinking leads to right action in nearly all circumstances.

 

[Yggdrasill]

Our approach is basically that everyone pays according to the spot prices on the common Scandinavian Nord Pool Spot. I would say that places like California are a lot more regulated when it comes to electricity sales. (My brother who partly lives in SF keeps telling me about how the utility company paid for their washer/dryer because the utility company get paid based on how little electricity people use. That wouldn't happen here.) Nord Pool is by no means a monopoly - we have some electricity companies that are owned by specific cities and municipalities, but pretty much all the electricity companies compete on Nord Pool on equal terms.

I would agree that evaluating the margin makes sense when considering circumstances that you are in control of, such as whether to work an extra hour, because one can assume that you will add activity to the margin according to your priorities. However, you are not in control of other people's electricity consumption, and the grid as a whole will not add loads to the grid according to how rational each lead is, unless the cost is based on the last load added. I'm sure you know, but it is worth saying out loud; how the system works is that if I buy an EV and add it to the grid, the price for electricity will go slightly up, and this increased price leads to everyone else cutting their consumption a bit, according to how much there is to cut in their consumption. This demand is not completely flexible, so you end up with a bit higher total consumption, but not as much as the electricity consumption added by the EV, either, as the demand is not completely inflexible. This system treats all consumption equally, and ensures that you get a homogenization in the priorities in the grid. For all intents and purposes, each customer needs the power equally, as the higher price point does not cause them to cut consumption.

When everyone needs the power they consume equally, why should one lay the blame for the pollution at the margin at the feet of anyone in particular? I don't have any extraneous consumption to cut, and no one else has either.

This is what my earlier examples try to show. If, and only if, you had a system that distributed electricity unequally, it might make sense to blame the pollution on the marginal loads, but no electricity grid that I know of works that way. Mostly because it would be ridiculous. Electricity consumption would be much higher than in the current system, and you would have new customers suffering on the margin while the earlier customers waste electricity precipitously.

 

[Robert.Boston]

When everyone needs the power they consume equally, why should one lay the blame for the pollution at the margin at the feet of anyone in particular? I don't have any extraneous consumption to cut, and no one else has either.

Because if anyone took the step to reduce their consumption, it would have the effect of reducing emissions by the marginal amount.

 

[Yggdrasill]

Exactly, and that makes it anyone's fault, not just EV drivers.

 

[neroden]

A lot depends on your local grid characteristics. If you add gobs more night time EV charging in Ontario it will actually help Hydro One with their excess nighttime generation problem. Normally none of the carbon generators are running at night, because they are used for peak load.

This is probably true in the portions of upstate NY which buy great hunks of Niagara Falls energy, as well.

But anyway, analyzing marginally, I'm replacing the burning of premium gasoline in a car with 20 mpg, and of ordinary gasoline in a car with 40 mpg, with extra load on the electric grid. This is *clearly* an improvement to the overall carbon profile, unless you assume that I then resell the cars to someone who wasn't driving a car before.

 

[Dave EV]

Exactly, and that makes it anyone's fault, not just EV drivers.

Yep. Unfortunately, some people would rather argue that your EV is responsible for all the marginal emissions rather than the big-screen TV they leave on Fox News 24/7.

 

[JRP3]

Fox News 24/7

Wouldn't that be base load then? :wink:

 

[Norbert]

In a situation where you unexpectedly add more consumption during the night, the utility/power provider may have a limited choice about which power plant to use. But if you add a regular consumption, especially with the possibility to distribute it over night as is most suitable, then all current choices are available. IIRC previous discussions resulted in the conclusion that the inertia in powering down specific power plants over night is not really a problem.

So I think the real problem here is the decision process of the utilities. They currently often favor coal even if it is cheaper only by a small amount, ignoring the CO2 output. So this scenario exposes a problem in the energy system, not in EVs themselves.

The blame should go to the current system of choosing the cheapest power even if differences are small, ignoring CO2. Now, all over the planet, governments (and voters) are becoming aware of this, and start to change this system through political action. For example, as R.B described, by stopping more coal plants from being built. The movement towards renewables, and towards EVs, go together, and support each other very strongly. I think buying an EV has a much stronger positive effect on this process than buying a hybrid, exactly as it does use electricity and thereby "demands" renewable electricity, politically. Long term, it is more effective to even out power consumption over 24h, and to support a political process which encourages low CO2 generation also during the night.

If utilities were successfully encouraged to use the same (or perhaps even better) energy mix during night, then nighttime charging would, without producing more CO2, *lower* overall-cost, as it allows covering a larger electricity consumption with a comparatively smaller number of power plants. Blaming EVs/nighttime-charging for a malfunctioning decision process seems to me to only make things more complicated to solve properly.

 

[Robert.Boston]

@Norbert: I agree, and there's an elegant, simple solution: a carbon tax. Unless one makes the choice affect the bottom line, one can't expect the utility to make any other choice. In fact, in most parts of the U.S., it would be a tariff violation for the system dispatcher to take any action other than to dispatch the least-cost available resource.