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Introductory blog post here: http://electrichonda.blogspot.de/2011/05/introduction.html http://electrichonda.blogspot.de/2011/05/introduction.html Juan's proje
by Zak 14y ago
Introductory blog post here: http://electrichonda.blogspot.de/2011/05/introduction.html http://electrichonda.blogspot.de/2011/05/introduction.html
Juan's project is impressive, no doubt, but his analysis of the superiority of electric cars is suspect. He writes:
The average car uses about 20% of the potential energy of the fuel in useful motion while wasting the other energy as heat, noise and pollution. Electric cars use upwards of 80% of their 'fuel', a percentage which can be increased relatively easily as most of its losses are electrical.
The biggest problem is that he's treating the electricity in the battery as raw fuel. He does acknowledge that most electricity in the US comes from sources like coal, but ignores various losses between that coal and his car flying down the road. Let's add those in.
The best we can do from a coal plant is about 49%[0]. It may be possible to use the waste heat from such a plant for other purposes; I am not including such uses in this calculation as they do not have anything to do with powering the electric car.
The US power grid is around 93-94% efficient[1].
Electric cars don't get all the power from the grid in to the batteries as chemical energy. Charging batteries generates quite a bit of heat. The EPA estimates that the best electric cars are 62% efficient at converting power from the grid in to kinetic energy[2].
So we have 49% * 94% * 62% = 28.6% efficient at converting the chemical energy in coal to propelling the car. This is not a dramatic improvement over internal combustion. There is, of course the advantage of using power sources other than coal and oil, but the claimed efficiency is not quite what electric vehicle proponents would like it to be.
[0] http://en.wikipedia.org/wiki/Aved%C3%B8re_Power_Station http://en.wikipedia.org/wiki/Aved%C3%B8re_Power_Station
[1] http://en.wikipedia.org/wiki/Electric_power_transmission#Losses http://en.wikipedia.org/wiki/Electric_power_transmission#Los...
[2] http://www.fueleconomy.gov/feg/evtech.shtml http://www.fueleconomy.gov/feg/evtech.shtml
- JoeAltmaier 14y ago28% is absolutely a dramatic improvement, over 20%. It translates to a dramatic decrease in coal consumed to drive the vehicle - close to a third less.
- Zak 14y agoThe EPA says the best internal combustion cars are 26%: http://www.fueleconomy.gov/feg/atv.shtml http://www.fueleconomy.gov/feg/atv.shtml
- JoeAltmaier 14y agoAnd coal plants are about the worst yield of various energy plants. Anyway, the whole thing is moot. The article may as well say "High School Student crams stuff under hood of car, claims it will kick butt if he can get it to work". I predict we'll never know.
- Zak 14y agoCoal plants may be the least efficient, but they're the most common source of electricity in the US. To be fair, I picked the most optimistic efficiency I could find for a coal plant. I was trying to present a best-case scenario. It looks like the best case with natural gas is 60%, or 35% total system efficiency. Yes, that's a significant gain over 26%, but it's a best-case scenario. The real-world efficiency of the most efficient internal combustion cars is fairly similar to that of electric cars.
- JoeAltmaier 14y agoIt may be harder to measure 'efficiency' of nuclear (which we use here), solar and wind. Certainly they are more sustainable. Maybe we want the 'sustainability metric' instead.
- Zak 14y agoIt's not hard to measure the efficiency of nuclear or solar; it's just not as useful as directly comparing two systems that run on fossil fuels.
- JoeAltmaier 14y agoHm. How do you compare uranium fuel efficiency to coal? Chemical vs nuclear reactions - by weight? cost? heat?
- jsight 14y agoIf you want to include the efficiency of the entire electrical pipeline, then you need to do the same for the gasoline/diesel engine. How much energy is used for the extraction, refinery, transport, and distribution of gasoline/diesel fuel? I suspect 26% efficiency for gasoline would also be extremely high compared to reality if those costs were factored in.
- Retric 14y agoLast time I checked on average when you include extraction, refining, and transportation a higher % of coals energy ends up in the battery's than does Oil's in the gas tank. Initially, oil took little energy to refine etc, but we have started doing things like tar sands and cracking which take a lot more energy than earlier methods. While there is still some easy oil out there, Oil is worth 10x as much as coal vary energy expensive Oil starts to be worth extracting. PS: If you compare solar cells with Bio fuels it's vary one sided with electric cars far out in the lead.
- binarymax 14y agoSplitting hairs now, but coal for the grid also has extraction and delivery costs - probably not equal to that of oil, but if you start from the earth for one you need to start from the earth for the other.
- Zak 14y agoI'm talking about the efficiency of the pipeline starting with a fossil fuel and ending with a car moving down the road. It's also fair to start the comparison with a fossil fuel in the ground, but in that case you also have to start the electric pipeline at a coal mine. Electric might well win by a significant margin, but it isn't nearly the 85% to 20% claimed.
- jsight 14y agoWell, your car comparison started at electricity production. At the very least, your gasoline example should start at the refinery. Does anyone know the efficiency of the average refinery? Or distribution costs? My suspicion is that they are actually just as bad as the overhead of burning coal.