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Autonomous Cars Could Be Worse For Carbon Emissions
HughPickens.com writes: David Roberts writes at VOX that it stands to reason that vehicle automation could save energy and reduce emissions in some ways. Cars will be able to chain together more aerodynamically, drive at more consistent speeds, and perhaps serve as shared vehicles in lieu of individual vehicle ownership. But it also stands to reason that automation could increase energy use and emissions in some ways. If driving is easier and more pleasant, people will do it more. Automation will open up car travel to populations (the young, the elderly, the visually or otherwise impaired) who did not previously have access. Self-driving cars could increase the overall amount of vehicle miles traveled. (Read more, below.)
Hugh Pickens continues: A new study: "Help or hindrance? The travel, energy and carbon impacts of highly automated vehicles," suggests that the big swing factor is travel cost reduction — in other words, how cheap and easy driving gets. If that stays at the low end, then the effects of self-driving cars on energy use are almost certain to be a substantial net positive. However if it reaches the high end, a 60 percent boost in energy consumption for transportation, all the energy-saving benefits could be wiped out, for a net increase in energy and emissions. "This leads to somewhat surprising policy implications It may be that the socially optimal outcome, at least for now, is partial, not full, automation. That way the energy and emissions benefits of smarter driving practices can be fully captured, without allowing drivers to tune entirely out — without making it too easy," concludes Roberts. "Perhaps when we get farther down the road (ahem) — when more vehicles are electrified, when car sharing is more firmly established, when the benefits of automation have proven out — we can move to full automation without the risk of carbon blowback."
See Jevons Paradox.
Truth. Vox dot com is a garbage media source. They specialize in these "hot takes" that always end up to be shallow Freakonomics horseshit. "Gee, some studies suggest smoking may actually be good for you!" or "Why do so many successful people drink water?"
I'm not saying it's because Vox is made up of a bunch of 20-something journo students who couldn't find jobs anywhere else, or that it's because Ezra Klein was one of the founders. It might be something else.
Vox likes to set up their stories as "explainer cardstacks" (yes, this is a term of art). It means basically great big graphics with no indication of data sources and video. And they wrap it all up in ugly typography and web design that makes it one of the least pleasurable spots on the Internet. Don't believe me? See for yourself. But wait: it's also one of those sites that if you happen to use adblock or a script blocker, just turns to a long, ugly list of links, looking like something circa 1993.
I hate Vox. It's Forbes, except run by a bunch of 20-somethings with associates degrees in art & design.
You are welcome on my lawn.
It's important to understand that the cost advantage of operating an electric car is only slightly due to improved energy efficiency. The vast majority of the price differential is due to the extremely low price of coal and natural gas relative to gasoline.
An ICE engine can hit about 30% efficiency. An automatic transmission is about 90%-95% efficient (pretty impressive considering it's just squirting fluid at a turbine).
Newer coal plants are about 40% efficient. Natural gas plants are about 60% efficient. Split the difference and go with 50%. Power lines are about 98% efficient. Real-world charging efficiency of the Tesla is about 80% (1/1.26 = 0.79). That is, 80% of the electricity from your wall socket goes into the battery, the other 20% becomes heat. I can't find any numbers for discharge efficiency, so let's call it 100% for now. And electric motor efficiency is about 90%-95%.
Tally it up and you get:
ICE: 30% * 92.5% = 27.8% efficient
EV: 50% * 98% * 80% * (100%) * 92.5% = 36.3% efficient.
So really not that big a difference. If battery discharge efficiency is also 80%, then the EV is basically identical to an ICE in overall energy efficiency. Yes if solar and wind come down in price to match or beat coal, then you can drop the 50% at the front. But wind is still about 1.5x-2x the price of coal, and solar about 5x-7x the price.
Now look at the fuel price side.
Coal costs about $50/ton, and contains about 24 GJ/ton. That's $2.08 per GJ.
Gasoline costs about $2/gallon and contains about 120 MJ/gallon. That's $16.67 per GJ. Almost an order of magnitude more.
So there you have it. EVs are only 1.1x-1.3x more energy efficient than ICE cars. But their fuel source is 8x cheaper. That's why EVs are cheaper to operate than ICE vehicles.
Incidentally, if you're wondering why we're burning gasoline in our cars instead of cheap coal, the two obvious reasons are emissions and a liquid fuel being easier to manage than a solid fuel. But the biggest reason is energy density. At 24 GJ/ton, coal has 24 MJ/kg. Gasoline is 44 MJ/kg. So you only need to carry around half as much fuel (by weight) if you use gasoline instead of coal.