A couple more points on EVs - one positive/negative depending on your starting viewpoint, the other positive.
The first gets back to my aggravation at labeling EVs as "Zero Pollution". They get their power from the grid, and that is
not pollution free.
Some rough numbers, then some DOE and EPA numbers...
OK, so the battery charge/discharge might be ~ 90% eff, and the motor ~ 90% eff - so say 80% overall. Pretty darn good.
An ICE in a vehicle is ~ 20% eff - hmmm, pretty awful in comparison. But....
ROUGH NUMBERS: A typical power plant is 36-40% eff, some newer designs 48%, and a *single* cogeneration plant listed as near 60%. (source:
Fossil fuel power plant - Wikipedia, the free encyclopedia ). So, let's go with the upper end of typical - 40%. Eight % transmission losses and you are at ~ 37% eff (.92*40). 37% * the 80% of the EV and you are at ~ 29.6%. Hmmm, good, but not so much greater than the 20% for ICE.
So if we converted
every vehicle in the US to EV, we could say that instead of burning 100 bazillion units of fossil fuel over X time period, we only burnt 68 bazillion units of fossil fuel. OK, that's better, but it sure isn't zero - not even close.
OK, my rough numbers assume all fossil fuel generation - the US has some nuclear and hydro and renewable - but it gives a ballpark view.
DOE/EPA NUMBERS: Electric Vehicle Efficiency Analysis
In 2007, a DOE-sponsored analysis found that there is enough excess off-peak capacity in today's electrical grid to power the conversion of "up to 84% of U.S. cars, pickup trucks, and sport utility vehicles (SUVs)" to plug-in hybrids with a 33-mile pure electric range.
That same study found that under that scenario overall greenhouse emissions would decrease by up to 27%. .... particulate and SOx emissions would increase
Hey, I was pretty darn close at 32% reduction! Wait a minute, I assumed 100% EV, they assumed 84% on the present grid, hmmmm.... .84*32 = 26.88% versus their "up to 27%". I bet they spent a lot more money than a short #2 pencil and a (literally) back of an envelope (and wikipedia)!
And the EPA says (in a table):
If your electric power source is coal,
a 30mpg car will emit LESS CO2 than an EV! (and even less particulates and SOx). I guess I won't feel too guilty while getting 27mpg highway in my 1900's technology ICE that can actually make the occasional 300 mile trip I need to make on that highway
OK, so coal is bad - but the numbers aren't all that much better for the US grid average. It takes a 45 mpg car to do better than an EV. So that is good, but it just ain't zero. As good as EVs may be, they are not some panacea to pollution and CO2 emissions. And remember - future advances in EVs won't change these numbers much. Efficiencies are already near the max, only range and costs have the room to improve markedly. That affects adoption rates, not these efficiencies.
THE POSITIVE: OK, the above is actually good news for EVs overall, just not the "great" news that I think most people expect. But there is more good news. EVs don't care how the electrical power is generated - unlike "flex fuel" cars, you don't do anything to your EV to change it to charge from Nuclear generated electricity, or wind, or solar, or biomass, or any power that someone might dream up in the future. If it makes electricity, your EV will eat it. That's good, but only meaningful if we come up with low cost sources for that power.
I was actually surprised at these numbers. I thought that EVs would look better than that.
-ERD50