| Amidst all the scientific studies, academic research and political rhetoric, the debate continues on how much effect converting to electric cars – powered from our existing electrical grid – will have on the emissions of greenhouse gasses – CO2. With the proliferation of these studies, some tracing CO2 contributions all the way back to the first exhalation of breath from the dinosaurs, it can be hard for the average rocket scientist, let alone mere mortal, to come to a conclusion. Therefore, I have decided to shun the scientific calculator, eliminate the variables, and do a simple, empirical analysis of their direct impact. |
First, the Coal burning Power Plants.
We are fortunate here in that someone, most likely math challenged, actually had the good sense to measure the CO2 output of power plants. It has been measured and confirmed many times since. Ends up the average Coal burning power plant emits 2.17 pounds of CO2 for every kilowatt-hour it produces. (EIA) Now, coal makes up only 48% of our electrical generation. Natural Gas produces 20% and it also emits CO2 (1.4 pounds per kWh). But, 30% comes from nuclear and renewable sources. So, taken together, our national electrical supply generates, on the high side, 1.51 pounds of CO2 per kWh.
Now for the Cars.
Basic Chemistry tells us that burning 1 gallon of gasoline emits 19.4 pounds of CO2. It also tells us, based on BTU content, there are 36 kWh of energy in that gallon of gas.
One place where all the research gets bogged down is trying to account for the varying efficiencies of our automotive contraptions. Automotive IC (Internal Combustion) engines are anywhere from 15 to 28% efficient in average driving. Well, for our worst case, empirical study, I am going to assume the most efficient – 28%. The most efficient means it is the most work we get for every globule of CO2 emitted. Indeed, the meaning is that 28% of the BTUs in that gallon of gas will get turned into useful, mechanical work. All the rest are wasted as heat. There are 124,000 BTU’s, give or take, in a gallon of gas, so at 28% efficiency 34,720 of them or 10.16 kWh, are actually used for something productive. Yet, we still created 19.4 pounds of CO2 burning that gasoline. A little math, and the emissions result for our car is 1.90 pounds of CO2 per kWh of work produced. Note that at the other end of the scale – at 15% efficiency - those numbers would be 5.4 kWh of useful work, and 3.59 pounds of CO2 per kWh.
Although this article is not about CO2 per mile (remember, simple), for the sake of reference, both the Chevy Volt, and my Chevy Malibu use approximately .240 kWh for each mile at a </i>steady<i> 60 Miles Per Hour. The Tesla Roadster claims to use .217. The Prius is about .220. Your dumptruck, I don't know. However, we do not need to factor in the relative mileage of different vehicles to determine the absolute CO2 emissions potential. Replacing a similar gasoline vehicle, with a similar electric vehicle will still result in similar energy needs.
The answer please!
The results show that burning gasoline in an ICE powered car creates anywhere from 21% to 58% more CO2 than getting the same amount of energy from our electric grid for the same size and shape car. And, that point is important.
The other way many of these studies tend to confuse the issue is trying to relate everything to mileage – like pounds per mile. That is truly putting oranges in an apple barrel. The matter of mileage is irrelevant when comparing similar size and shape vehicles where the only difference is the source of power. They will both use the same amount of energy, which here is expressed in Kilowatt-hours. Regardless of whether they are powered by electricity, gasoline, or soda pop. The difference lies in the source of the power.
Now granted, if you replace your dump truck with a compact car, you will be emitting less CO2, but that is true of either power source, because your small car uses less energy than a dump truck. The reverse would also be true, although good luck finding an electrically powered dump truck.
It should be clear by now that by replacing a gasoline powered ICE vehicle with an electric one, for the same amount of power at the wheels, we would reduce CO2 GHG emissions by anywhere from 21% to 58% - even with our existing electrical supply. And, in fact, those who have bothered to reduce some of the complex, often politically motivated and artistically spun, studies down to their basic conclusions have found exactly the same thing.
