A reader asked about the Chevy Volt in comparison to the Honda Civic, which is a wonderful question. The Volt people claim that it can go 40 miles on just batteries, which is perfect for most people’s commutes provided they can plug in at work (or not for the really lucky ones). So, it’s obvious that there is no fuel consumed by the vehicle in these first few miles of driving, but I’m going to look at how much fuel is consumed to create those 8.8 kilowatts of electricity it takes to go 40 miles. First, the 8.8 number comes from Chevy’s claim that the gas engine kicks in at 30% battery charge, and the battery will only charge to 85% from the wall outlet, meaning it goes 40 miles on 55% of the battery capacity (16 KW), which equals 8.8 KW.
Energy in Maryland comes from many sources, as talked about here:
When it comes to electricity in Maryland today, coal is king. It fuels 58 percent of our needs and is used at plants such as Constellation Energy’s Brandon Shores and H.A. Wagner plants in Pasadena. Behind coal is nuclear power from Calvert Cliffs in Lusby, which satisfies another 26 percent of the state’s needs. Oil is used to generate 7 percent, natural gas just 2 percent. The rest comes from minor alternative sources.
So, getting some more data from here, we end up with this:
|Fuel||CO2 emissions (g/kWh)||Average||Maryland Power (g of CO2/kWh)|
|Gas||389 – 511g||450 g/kWh||8.99|
|Coal||790 – 1182g||986 g/kWh||571.88|
|Nuclear||2 – 59g||30.5 g/kWh||7.93|
|Oil||744 – 1126g||935 g/kWh||65.45|
There’s an extra 7% from “minor alternative sources” that I’m just going to estimate is an average of 100g/kWh of CO2, coming out to 7g/kWh contribution to the whole. That means for Maryland, for every kWh of power produced there are CO2 emissions of 661.25g. That’s actually really good compared to the 8,788g of CO2 per gallon of gasoline, as calculated here.
Another point to take into account is the Transmission and Distribution losses in the power grid, which are substantial:
The transmission and distribution, or “T&D” system includes everything between a generation plant and an end-use site, i.e. a residential home or commercial business. Along the way, some of the energy supplied by the generator is lost due to the resistance of the wires and equipment that the electricity passes through. Most of this energy is converted to heat. Just how much energy is taken up as losses in the T&D system depends greatly on the physical characteristics of the system in question as well as how it is operated. Generally speaking, T&D losses between 6% and 8% are considered normal.
We’ll stick with 6% in this article (look on the bright side). This means that rather than our original figure of 661.25g/kWh, we have to adjust for 94% efficiency, which means we need an extra 6.38% (100/94 because we cut into our principle…) emissions to get the power to the customer. This makes for a total of 703.46g/kWh.
So, in the Volt, that’s 6,190.43g of CO2 per 40 miles. Now, remember a gallon of gas is 8,788g of CO2. That means that in 30 miles my Civic creates 8,788g of CO2. That’s 292.93g/mile. The Volt comes out to 154.76g/mile.
So, even today, on mostly coal power, you can cut your CO2 emissions basically in half with a Chevy Volt provided you don’t use the gas part of the engine. That’s a larger margin than I was expecting, and it’s actually quite impressive. Of course, as I discuss at length in the previous article, the initial production cost of the Volt makes it a worse choice than a used Civic initially, but the Volt would have a much lower angle for BTU production than the Prius, so I assume it would become worth it in quite a few less miles (maybe like 50,000, but I don’t know). When it comes down to cost, forgetting the initial cost of the Chevy Volt, let’s see what happens.
A gallon of gas is right around $2 right now, which gets me 30 miles. That’s 6.66 cents/mile. Power from the grid is 11.82 cents/kWh. So, to go 40 miles, I pay $2.66 in gas. I would only pay $1.04 for that distance with the Volt.
All in all, it’s a very impressive vehicle, and it and other electric cars like it seem like a very viable option for the future. The biggest problem is cost, at about $32,500 in the US after subsidies. You’d have to drive it 679,012.35 miles to make up for the fuel price difference vs. a 2000 Honda Civic. If you want to feel good about carbon emissions, and you’re rich or ready to be in debt, get one. If not, get a Civic and save money.
Now if we just make more of the grid nuclear, we’d have a pretty tight infrastructure.