[lucid]

Originally Posted by jm1234

Speaking of being clear, this analysis mix and matches terms and is only partially clarifying from an ignoramus' (not you, the people you try to educate) perspective of pollution. A fuel source's "energy efficiency" (lumping thermal and process efficiencies) does not correlate to pollution levels. There are situations where falling thermal efficiencies have a positive correlation to lower pollution levels. An example automobile aficionados are familiar with is the catalytic converter which lowers pollutants but decreases thermal efficiency. By including processes that likely utilize other fuel sources (mining and transportation processes for a coal plant) you potentially have an alternate pollution source that should be separately evaluated from a pollution (not energy efficiency) standpoint. So, you've introduced a number to help educate the ignorant but understanding what that number means isn't trivial and even a lower number doesn't necessarily imply more pollution.

The overall energy efficiency indeed does not pinpoint the extent to which pollution is produced, especially when different types of power generation methods are used. That is the common criticism against this particular metric. The problem is that you will run into that issue with any metric. No single metric will reveal the entire environmental impact of electricity generation, and different metrics are more descriptive of different processes. That is why I actually brought up CO2 emissions at the end of my previous post. Overall energy efficiency and CO2 emissions are the most commonly used metrics that I am aware of, and as I mentioned earlier, there are various composite metrics that reflect a broader understanding. And, just to clarify, I did not estimate that CO2 emissions would be halved in the Tesla vs Civic example just because the overall energy efficiency is doubled (as stated by Tesla). Tesla also states that the operation of its product results in a third of the CO2 emissions caused by a Civic. They based that on what seems to be a rather optimistic scenario of natural gas driven electricity production process (I say optimistic because they quote a 52.5% "well-to-station" efficiency--I assume by station they mean socket--which is technically possible as a plant thermal efficiency figure with the state of the art combined cycle natural gas power plants, but that is far from the status quo as the current norm for natural gas power plant thermal efficiency in the US seems to be below 40%). My understanding is that burning coal results in about 60% more CO2 emissions than natural gas in power plants, and hence the "half the CO2 emissions" statement (0.33/0.60~1/2) if the Tesla is pluged into a coal based process (and if we accept Tesla's numbers). Clearly, if it is plugged into a natural gas based process, then it is 1/3 the CO2 emissions of the Civic.

Anyway, the "overall" energy efficiency metric is indeed not straightforward to interpret, but it is being commonly used to get a very simple concept across: how much energy was released into the environment as heat that was not used to do useful work. That does not nail down how much pollution was created in the process of releasing the non-useful energy into environment, but it is still a relevant thing to consider, especially when dealing with fossil fuels. I could have mentioned CO2 emissions or another metric in my original post, and we would most likely be having a similar discussion about CO2 emissions being far from telling the whole story. I just picked one to make a very simple point, that when the system boundary around the consideration is expanded in a relevant manner, our understanding of the true environmental impact deepens and becomes more meaningful, and that focusing entirely on narrowed down system boundaries can be misleading, which is what the video does. The video failed to make a single reference to how the electricity the car used was produced. Completely ignored it.

To illustrate my point further, I’m posting a link to a DOE study of life cycle analysis of coal powered electricity production:

http://www.nrel.gov/docs/fy99osti/25119.pdf

Skim through the exec summary if you have time. The “Average” category represents the current status quo in the US. Plant efficiency is 32%. When the entire “system” is considered (mining, transportation, and generation), the efficiency drops to 29%. When the upstream processes associated with the system processes are considered, the efficiency drops to 24%. Section 6 reports the findings in specific impact categories. It would be interesting to see a similar analysis for natural gas powered production. The overall efficiency should be higher, but I doubt it will be too much higher than 30%, and there will still be very significant emissions.

Originally Posted by jm1234

In addition, the number quoted is apparently for the most inefficient process in the US and yet you know that it accounts for only 50% of the electricity generated in the US. The final thought in this quote that "one can argue" doesn't convey the truth (stated clearly later in the thread) that any reasonably efficient electric car will pollute less per unit of performance. It's funny that my definition of a system boundary clearly delineated in the words I use (car) is "irrelevant", suggesting the power could come from solar energy is unrealistic but you quote figures for the worst case power production scenario in the US and lump in the inefficiencies of household appliances and somehow that's not worthy of an apology?

"Only" 50%??? So, you don't think 50% is a significant number? You can't be serious.

Here are the stats on how we currently produce electricity:

http://www.eia.doe.gov/cneaf/electri...m/epm_sum.html

The largest slice in that pie is coal, by over a factor of two. And you claim I deceptively picked a scenario that is misleading? Coal IS the dominant scenario and that's why it was used in the example.

Moreover, fossil fuel based electricity generation as a whole accounts for 71% and the overall energy efficiencies of the natural gas and oil driven process in the US are currently not that far from to the energy efficiencies of coal driven processes although I don't have the exact figures. And burning fossils fuels, regardless of how efficiently and "cleanly" done, results in significant emissions. Finally, coal alone accounts for 2/3 or more of electricity generation in China (and their power plant and mining operations are significantly less efficient as far as I can tell). So, using a coal driven electricity generation process in the example is appropriate.

I don't see the need for an "apology". Yes, the overall efficiency figure I remembered was not accurate, and I corrected that, but it's not as if what I remembered was 10% efficiency where the actual figure is 50%. My point, which is explained in the first part of this post, stands.

This perhaps illustrates the key issue in our exchange. Rather than responding to the point I was trying to make--and I agree that I did not do a good job in articulating the point in that original post--you started accusing me of intentionally bending and twisting the truth in pursuit of some anti-green agenda. Ironically, I am very much on the "green" side of things. I elected to pay more for electricity in my residence, and if you believe the power company, the electricity I use originates from a wind mill in upstate New York (not literally of course). I donate to other renewable energy causes. I would be happy to pay a substantial gasoline tax provided it would be used to generate energy from renewable sources. I put on another sweater as opposed to turning the heat up during winter (oil furnace) although my landlord pays for it, don't use the AC system during summer unless I absolutely have to (5-6 days in a year), etc. The M3 is pretty much the only luxury in my life that stands out from that norm, and like you, I would be willing to give it up for an electric version (the Tesla is not it for various reasons). The position I took was against equating electricity usage to no pollution. Again, currently in this country, that is very far from the truth, and statements such as my plug-in electric car does not pollute should always be carefully qualified until we stop producing electricity by burning fossil fuels. You can chose to narrowly delineate the boundaries of what you are talking about, but that doesn’t make what you are saying relevant or meaningful.

Originally Posted by jm1234

As to what people "do not get" that is not at all clear to me...

I simply stated that as an opinion (and I said “many” people not all people). I don't know of any generalizable study that proves or disproves it. However, there are some relevant points and observations. First of all, of course people will say they support renewable energy in a survey. What does it cost them to say so? Nothing. What are people actually willing to do about it? Not much apparently since we still rely on fossil fuels to an overwhelming extent. If people’s primary sensitivity was pollution, we would have done something about renewal energy a long time ago; pollution has been around. We only start seeing the public “express” significant sensitivity toward pollution when the price of oil goes up. The SUV market crashed when gas hit $4/gallon (before the entire automotive market crashed). To the best of my knowledge, people started driving less and gasoline consumption dropped when the price of oil went up (as basic economics would suggest). So, people, in general, are primarily price sensitive. Of course, there are groups of people who are primarily pollution sensitive and are willing to put their money where their mouth is, but they don’t seem to be in the majority here. Moreover, even those people might or might not be cognizant of the upstream environmental impact of plugging an electric car into the grid. Anecdotally, I’ve met many such people, whose understandings of the upstream effects were very limited. They either did not know the extent to which we rely on fossil fuels to generate electricity, or were ignorant of the information life cycle analysis such as the one disseminated in the DOE report reveals. Again, the video in question unfortunately reinforces that type of thinking by ignoring those key issues. (You are saying I did something similar by not discussing the efficiency or pollution dimensions of IC engine operation, but does that really need to be established? Doesn’t the population already know that gasoline powered cars are inefficient and polluting? Yes it would be useful to consider them as a benchmark if you really wanted to be specific, which is what I eventually did, but I didn’t think it was necessary at the beginning.) Then you have the general public, who is even less informed about those issues…

I will move this thread to the off-topic section soon since there has not be a single track driving specific post.


EDIT: I just ran into the LCA for a combined cycle natural gas power plant done by DOE. Plant efficiency is 48.8%. Efficiency of the entire system (pipeline construction, natural gas production and distribution, ammonia production and distribution for NOx removal, and power plant operation) drops down to 40%. When all upstream process are accounted for, the efficiency drops down to 29.9%, which is not far from the external efficiency of the coal plant as I said above (5.9% difference). CO2 emmissions seem to be ~50% of the coal plant.

http://www.nrel.gov/docs/fy00osti/27715.pdf