5 ms·

When you add load to a grid that's in the process of decarbonizing, you need to look at the marginal impact. Taking the average energy mix is bad math, because

When you add load to a grid that's in the process of decarbonizing, you need to look at the marginal impact. Taking the average energy mix is bad math, because you're delaying the shutdown of the dirtiest sources. This can get more complicated if you have excess renewable energy generation at times, where the use is essentially free. Not to mention demand dispatch to smooth intermittent renewables. I'm a big EV fan, but it's important to get the math right, because overstating the impact does disservice to other options. Especially in Germany. When I lived in Berlin for two years, not in the loop, I just used public transport. Most of my friends rode to work.

_ph_ 7y ago
The mix is the right math. After all, you cannot say, which electric device uses which power source. Or suddenly it might be your TV running on pure coal energy - this does not make much sense. The best approximation is, that you apply the average energy mix. Which might be even too pessimistic, as not only a lot of people do power their electric cars with their own solar energy but also it is easy to charge your electric cars especially in those times where the grid is on a relatively low carbon content and even surplus energy needs to be exported. Of course, there are plenty of better alternatives to cars in many places, especially city centers. But as long as there is a genuine need for cars, they better be electric than combustion engined.
- reitzensteinm 7y ago
  The question that needs to be answered is, what is the marginal impact of taking an ICE off the road and replacing it with a BEV? Using the current mix of renewables is a form of double counting. No more renewable energy is being fed in to the grid, however more is coming from dirty sources. Reductio ad absurdum, what happens if all of Germany's cars were BEV overnight? I've seen estimates that the load on the grid would be increased by 20%. Surely you'd agree that using the current mix of renewables would no longer make sense calculating their environmental impact. So why does that change at the margins? The answer is that it doesn't. The math is the same. With the exceptions we've both pointed out.
  - socialdemocrat 7y ago
    At the margins Germany is primarily adding solar and wind. And this solar and wind benefits from having BEVs which can suck up excess production when needed.
socialdemocrat 7y ago
If you look at marginal impact then BEVs have no emissions, because generating capacity is primarily growing in the renewable energy segment. In fact there is an even bigger benefits to BEVs: New BEVs are being made to allow sending current the opposite direction. Hence the BEV fleet can be used as a large battery for storing renewable in times of overproduction and selling it back when it is needed. In other words adopting renewable energy REQUIRES BEVs.
- reitzensteinm 7y ago
  > If you look at marginal impact then BEVs have no emissions, because generating capacity is primarily growing in the renewable energy segment. This is simply not true. You are tying them together incorrectly. BEVs cause growth in electricity demand, which keeps carbon sources around for longer. Renewable growth displaces carbon sources. The sum may be in the right direction, but it doesn't mean it wouldn't go faster if electricity consumption were lowered. It's also a bit beside the point, as BEVs are more environmentally friendly even when powered by coal plants. My argument is not at all anti BEV or pro ICE. > In other words adopting renewable energy REQUIRES BEVs. Yes, when renewables hit a point where you can't build more for reliability concerns, BEVs performing demand dispatch and even V2G will provide a ton of storage. This is the biggest reason I'm a BEV fan (although PHEVs can also provide much the same role), as dual use of batteries is the only real way to get remotely the storage we're going to need. But my point is that BEVs, while better than an ICE, shouldn't be thought of as equivalently clean to riding or taking public transport. This isn't a radical position, it's math.
hokkos 7y ago
It is more a philosophical question. If you add demand to a system should it be counted like a marginal addition, or as the same as the current demand. Most studies on the subject of the full cycle of CO2 emission of EV tend to use average carbon intensity of the electricity. The few studies that use marginal carbon intensity are from mostly biased anti EV, pro fossil fuel sources. Also it is not always the worse carbonated source that is added when demand surge, for example coal is rather slow to increase, so the grid operator probably kept some hydro power to the rescue, nuclear can ramp up rather quickly too. If you are really interested in minimizing the carbon intensity of the charge, you can use the api of ElectricityMap that gives you those numbers, and automatically charge your car based on a maximum carbon intensity and some fancy heuristics. They also have a good article on the marginal electricity of European countries : https://www.tmrow.com/blog/marginal-carbon-intensity-of-electricity-with-machine-learning https://www.tmrow.com/blog/marginal-carbon-intensity-of-elec... Also here is an article on the subject (in french) translated here : https://www.i-care-consult.com/opinions/contenu-co2-de-lelectricite-methodes-objectifs/ https://www.i-care-consult.com/opinions/contenu-co2-de-lelec... The so-called "average emission factor" method. This method is the existing and historical "default" method currently made available by ADEME: it consists in using a national average emission factor for electricity (this "average" factor also exists by use). This method makes it possible to "attribute" to each French actor its "share" of national emissions and to carry out a balance sheet (this is why it is the method used for regulatory GHG balances). However, this method is not suitable for properly assessing the impact of an action plan: it does not take into account the fact that changing the consumption curve or the production fleet modifies the structure of the energy mix itself, and therefore the average CO2 content per kWh. The so-called "marginal" method: this method was published in 2007 by ADEME-RTE but is no longer institutionally relevant, although it is still used by some independent actors. This method is based on the principles of optimizing the electricity production fleet (merit order principles): at each moment, an upward (or downward) change in consumption leads to an increase (decrease) in production from the so-called "marginal" means, i.e. from the means available at lower cost at that moment: the means of production can thus be classified from the least expensive to the most expensive (variable production cost), this is what is called the "merit order". If we consider the emission factor of the marginal means of production, we are talking about the marginal CO2 content of electricity. In 2007, RTE and ADEME reported marginal values ranging from 450 g CO2/kWh (for base uses) to 700g CO2/kWh (for peak uses). This method is adapted to the consequential reasoning of modifying production or consumption, and therefore to the evaluation of the impact of actions on the electricity system, but this reasoning is valid at the margin: actions that would have a very significant impact (e. g. significant modification of the nuclear fleet, new use such as the electric vehicle), and that would significantly modify the stack of means of production cannot be evaluated with this method. The so-called "incremental" method: this method has not been officially published by ADEME but has been the subject of various proposals from energy companies and professional associations. It is based on the idea that for some structuring actions, a "marginal" reasoning (mathematical notion of a value derived from the CO2 content of a kWh) is no longer valid, and that in this case it is necessary to use the comparison of 2 supply/demand balance scenarios (the no-action scenario and the action scenario) and to compare the GHG emissions associated with these 2 scenarios. The resulting value of this method depends on the extent of the system modification (upward or downward, in energy and power). This method, which is the most complex but also the most theoretically accurate, should therefore be used when the marginal method is outside its field of validity.

_ph_ 7y ago

The mix is the right math. After all, you cannot say, which electric device uses which power source. Or suddenly it might be your TV running on pure coal energy - this does not make much sense. The best approximation is, that you apply the average energy mix. Which might be even too pessimistic, as not only a lot of people do power their electric cars with their own solar energy but also it is easy to charge your electric cars especially in those times where the grid is on a relatively low carbon content and even surplus energy needs to be exported. Of course, there are plenty of better alternatives to cars in many places, especially city centers. But as long as there is a genuine need for cars, they better be electric than combustion engined.

reitzensteinm 7y ago
The question that needs to be answered is, what is the marginal impact of taking an ICE off the road and replacing it with a BEV? Using the current mix of renewables is a form of double counting. No more renewable energy is being fed in to the grid, however more is coming from dirty sources. Reductio ad absurdum, what happens if all of Germany's cars were BEV overnight? I've seen estimates that the load on the grid would be increased by 20%. Surely you'd agree that using the current mix of renewables would no longer make sense calculating their environmental impact. So why does that change at the margins? The answer is that it doesn't. The math is the same. With the exceptions we've both pointed out.
- socialdemocrat 7y ago
  At the margins Germany is primarily adding solar and wind. And this solar and wind benefits from having BEVs which can suck up excess production when needed.

socialdemocrat 7y ago

If you look at marginal impact then BEVs have no emissions, because generating capacity is primarily growing in the renewable energy segment. In fact there is an even bigger benefits to BEVs: New BEVs are being made to allow sending current the opposite direction. Hence the BEV fleet can be used as a large battery for storing renewable in times of overproduction and selling it back when it is needed. In other words adopting renewable energy REQUIRES BEVs.

reitzensteinm 7y ago
> If you look at marginal impact then BEVs have no emissions, because generating capacity is primarily growing in the renewable energy segment. This is simply not true. You are tying them together incorrectly. BEVs cause growth in electricity demand, which keeps carbon sources around for longer. Renewable growth displaces carbon sources. The sum may be in the right direction, but it doesn't mean it wouldn't go faster if electricity consumption were lowered. It's also a bit beside the point, as BEVs are more environmentally friendly even when powered by coal plants. My argument is not at all anti BEV or pro ICE. > In other words adopting renewable energy REQUIRES BEVs. Yes, when renewables hit a point where you can't build more for reliability concerns, BEVs performing demand dispatch and even V2G will provide a ton of storage. This is the biggest reason I'm a BEV fan (although PHEVs can also provide much the same role), as dual use of batteries is the only real way to get remotely the storage we're going to need. But my point is that BEVs, while better than an ICE, shouldn't be thought of as equivalently clean to riding or taking public transport. This isn't a radical position, it's math.

hokkos 7y ago

It is more a philosophical question. If you add demand to a system should it be counted like a marginal addition, or as the same as the current demand. Most studies on the subject of the full cycle of CO2 emission of EV tend to use average carbon intensity of the electricity. The few studies that use marginal carbon intensity are from mostly biased anti EV, pro fossil fuel sources. Also it is not always the worse carbonated source that is added when demand surge, for example coal is rather slow to increase, so the grid operator probably kept some hydro power to the rescue, nuclear can ramp up rather quickly too. If you are really interested in minimizing the carbon intensity of the charge, you can use the api of ElectricityMap that gives you those numbers, and automatically charge your car based on a maximum carbon intensity and some fancy heuristics. They also have a good article on the marginal electricity of European countries : https://www.tmrow.com/blog/marginal-carbon-intensity-of-electricity-with-machine-learning https://www.tmrow.com/blog/marginal-carbon-intensity-of-elec... Also here is an article on the subject (in french) translated here : https://www.i-care-consult.com/opinions/contenu-co2-de-lelectricite-methodes-objectifs/ https://www.i-care-consult.com/opinions/contenu-co2-de-lelec... The so-called "average emission factor" method. This method is the existing and historical "default" method currently made available by ADEME: it consists in using a national average emission factor for electricity (this "average" factor also exists by use). This method makes it possible to "attribute" to each French actor its "share" of national emissions and to carry out a balance sheet (this is why it is the method used for regulatory GHG balances). However, this method is not suitable for properly assessing the impact of an action plan: it does not take into account the fact that changing the consumption curve or the production fleet modifies the structure of the energy mix itself, and therefore the average CO2 content per kWh. The so-called "marginal" method: this method was published in 2007 by ADEME-RTE but is no longer institutionally relevant, although it is still used by some independent actors. This method is based on the principles of optimizing the electricity production fleet (merit order principles): at each moment, an upward (or downward) change in consumption leads to an increase (decrease) in production from the so-called "marginal" means, i.e. from the means available at lower cost at that moment: the means of production can thus be classified from the least expensive to the most expensive (variable production cost), this is what is called the "merit order". If we consider the emission factor of the marginal means of production, we are talking about the marginal CO2 content of electricity. In 2007, RTE and ADEME reported marginal values ranging from 450 g CO2/kWh (for base uses) to 700g CO2/kWh (for peak uses). This method is adapted to the consequential reasoning of modifying production or consumption, and therefore to the evaluation of the impact of actions on the electricity system, but this reasoning is valid at the margin: actions that would have a very significant impact (e. g. significant modification of the nuclear fleet, new use such as the electric vehicle), and that would significantly modify the stack of means of production cannot be evaluated with this method. The so-called "incremental" method: this method has not been officially published by ADEME but has been the subject of various proposals from energy companies and professional associations. It is based on the idea that for some structuring actions, a "marginal" reasoning (mathematical notion of a value derived from the CO2 content of a kWh) is no longer valid, and that in this case it is necessary to use the comparison of 2 supply/demand balance scenarios (the no-action scenario and the action scenario) and to compare the GHG emissions associated with these 2 scenarios. The resulting value of this method depends on the extent of the system modification (upward or downward, in energy and power). This method, which is the most complex but also the most theoretically accurate, should therefore be used when the marginal method is outside its field of validity.