One of the nice things about analyses you can do on the back of an envelope is that they are easier to understand and lend themselves to settling issues. It occurred to me that a comparison of US LDV carbon emissions to the EV-related emissions from a nuclearized grid would be just one of those things.
First off, gasoline. Motor gasoline forms about 20 pounds of CO2 per gallon burned. In 2012, US LDVs burned 137 billion gallons of the stuff
for total emissions around 2.74 trillion pounds or 1.24 billion metric tons. At a guesstimated average fuel economy of 24.6 MPG, that same 137 billion gallons powered 3.37 trillion vehicle-miles travelled (VMT). Dividing miles by tons and moving the decimal point 6 places to the right to get grams, this comes out to 368 gCO2/mi or 229 gCO2/km.
Suppose that the average US vehicle did not have the characteristics of an ICE-powered light truck, but a Tesla Model S. Its energy consumption from the wall is 380 Wh/mi. Dividing by average transmission efficiency of 93%, this would be 409 Wh/mile at the generator. If it was charging off the French grid, with its net emissions of 77 gCO2/kWh, the vehicle's net emissions would be 31 gCO2/mi or 19.5 gCO2/km.
Things would not be so clean in "renewable" Denmark. The emissions from the Danish grid, at 385 gCO2/kWh, would result in 155 gCO2/mi or 97 gCO2/km. Some ICE-powered vehicles already emit less than this. And of course in coal-fired Australia, at 850 gCO2/kWh...
Climate scientists claim that we need no less than an 80% reduction in CO2 emissions to stabilize the atmosphere. This brief analysis shows that "renewables" will not get us there, even with electric vehicles. However, the combination of EVs and nuclear energy can achieve a reduction of around 92% even given a rather large and powerful EV, assuming French levels of carbon emission from generation. This is a pessimistic analysis in some ways; I've not assumed any reduction in per-kWh emissions due to increased base-load generation made possible by electrification and demand-side management of vehicle charging. Filling in the overnight demand trough and serving it with nuclear would reduce emissions at all times of day.
Another angle: supposedly there's room for about 1 ton/capita/year of carbon emissions. At 31 grams/mile, the 13,000 miles/yr travelled by the average US vehicle would emit just 400 kg of CO2. That leaves plenty of room for other things.
The bottom line? There's no existence proof that renewables can save the climate (and plenty of reasons to believe the job is far more difficult than claimed). Nuclear energy can.
Labels: carbon budget, carbon emissions, EVs, nuclear power, transport