this post was submitted on 26 Dec 2023
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An EV running on a coal fired grid still has less emissions that a prius. Facts dont care about your feelings.
Could you please run us through your maths? I'm legit curious.
An ICE is only, at most, 35% efficient. In contrast to lithium batteries and electric motors, which is more like 90% efficient. Electricity produced from the dirtiest coal plants that exist, used in an EV, is more efficient and, thus, more environmentally conscious, than burning gasoline in an ICE.
Coal power plant efficiency is less than 40%. You'd also not get 90% of the outlet on the wheels. There is also a lot of loss on the grid, but there is also on the production of fuel. The two pollute almost the same.
Burning coal however is a lot worse for the air quality.
I'd like to prefix this all by pointing out that coal is absolutely terrible to use in several ways.
However: most thermal plants get about 45% efficiency, based on using very high steam temperatures. We all know that the theoretical max efficiency for a thermal process is limited by the Carnot cycle, which explicitly depends on the difference in temperature between the working fluid and the surroundings.
I'd also like to point out an important point: carbon plants are not constricted by the need to keep the engine lightweight, we can capture most fly ash and other process exhaust.
I again, do not care to bring such an arcane tech back online, it's terrible to mine, process and use. Just remember there's a bit more to all of this that engineers have indeed thought of.
E: https://www.sciencedirect.com/science/article/abs/pii/S0196890415007657
It's the put the pollution somewhere else policy so that cities are more liveable. It was hurting China's reputation and too many rich Chinese were going overseas and siphoning away the economy (and still are).
The coal plants are not 100% efficient though. In fact they're probably in the realm of 40%
Yup, and that's ignoring the loss in transforming and transporting the energy across the grid, and in the chemistry of the battery itself through charges and discharges. Energy density of batteries is also a fraction of that of petrol, so every EV is also carrying around a lot of extra weight.
What about the billions of cells that must be produced and replaced as the scale grown unto millions and millions of cars? And all the mining of rare earth elements it requires?
It turns out that the lithium is very recyclable. The process of disassembly is what's tricky, but one of Tesla's pre-musk founders is working specifically on this problem.
We can already do it. Mining is (for now) cheaper. Something legislation, applied carefully, can resolve.
I don't know if their statement is universally true, but the EPA's fuel economy / total emissions calculator seems to show it for what I've put in. You can put in a Prius or random EV and see how they compare.
https://www.epa.gov/greenvehicles/electric-vehicle-myths#Myth1
https://www.fueleconomy.gov/feg/Find.do?action=bt2
My guess would be the efficiency of coal power plants (35%) and electricity transmission (90%) + battery charging of an EV (80%) would be more than efficiency of transporting oil in ships (50%) , then in an ICE truck (40%) to fuel pumps and then finally the efficiency of the ICE car (40%).
I picked the numbers from internet, but they seem plausible.
A Prius will definitely pollute less than the typical SUV electric cars on a coal grid.
Cause:
Efficiency of coal power plant and all losses are as bad as ICE cars. The EVs do thermal->mechanical->electrical->grid->battery->wheels and if you count them all up, is not better than an EV
Prius is designed for low drag unlike an SUV
Prius had regenerative braking like an EV
But just the numbers:
Prius is rated at 94g/kg
Coal 950g/kwh
Volvo c40 0.2kwh/km or 190g/km even without losses
I took Volvo cause they published a report with a good compare ev and ICE https://www.volvocars.com/images/v/-/media/market-assets/intl/applications/dotcom/pdf/c40/volvo-c40-recharge-lca-report.pdf
Even with the current EU energy mix, it takes 77'000 km to be better than ICE, so arguably better. On coal electricity, they are worse. And this is comparing equally sized cars, a Prius will do better.
Regardless of the accuracy of your numbers - If you fix the ICE cars as they wear out, replacing them with BEV as the energy grid retires coal plants or goes to a higher percentage of renewables, they get cleaner. ICE cars will be as dirty tomorrow as they are today.
That is true. I do think we should retire pure ICE cars as soon as possible. If you need to do long distances, a hybrid that could be converted might be a good intermediate solution. If you only need a car sporadically, a car sharing platform with electric cars is a good solution. These already exist in big eu cities. Ofc good and adorable public transport is nr 1.
Decreasing the amount of cars would decrease emissions short and long term more than the current shift to EV and would make shifting easier as there are just fewer to replace.
Sorry sorry. Where are you getting the "all losses are equivalent to ice engine inefficiency"?
I don't expect you to be an ME/EE, but there's a lot of variables in that calculation, I'd just like to clarify for everyone here what you mean.
I put very minimal calculation which at least puts it around the same order and linked a report by Volvo where they try to count the whole cycle of a car with the emissions of the production and transport of used parts and fuels.
On current electricity mix, an electric car is only slightly better on a CO2 emissions. With only renewables, it can be 2x better.
But the statement that in China it's at least better than a Prius is just wrong. Until renewables take a serious share of the grid, a smaller well engineered hybrid is not worse.