July 22, 2023

Energy efficiency: gasoline, electric, and hydrogen car

Imagine that you bought three pounds of vegetables, and immediately threw out two before starting to cook with the remaining pound.

Crazy, right?

But something like that is exactly what you do every time you put gas into your car's tank: about 70% of the energy in the gasoline gets wasted as heat, and only 30% is put out by the engine to move things.

Where the energy goes in a car, froman interactive graphic at fueleconomy.gov

But it gets worse than that: There are mechanical losses at every step of the drivetrain from things like friction and inefficiencies. So in the end, only 16 - 25 % of the energy you poured into the gas tank goes into moving the wheels, and your car, forward. In the end, it's more like buying five to six pounds of vegetables to end up cooking only one pound.

Sounds like a rip-off to me.

For electric cars or EVs, a large range of efficiencies are quoted, but fuelefficiency.gov says EVs convert over 65 - 69 % of the electrical energy from the grid to power at the wheels, and if you include regenerative braking, where the energy from forward motion gets put back into the battery, that efficiency goes up to 87 - 91 %.

That's more like it!

I get that 9-13% of my vegetables could be peels, stems and other inedible parts, and I can live with not putting those in my cooking.

Incidentally, hydrogen cars are almost as bad as fossil fueled cars, efficiency wise. The electricity to wheels efficiency is only around 34 - 37 %. That's a little better than that of a car with an internal combustion engine, but it really can't compete with the efficiency of a battery EV. And if the hydrogen comes from the cracking of methane (also called "natural" gas) powered by a coal plant, then the hydrogen car is worse than useless from a climate point of view. Did I mention that hydrogen is a corrosive gas that attacks metals and causes cracks? And that it's highly flammable? Hydrogen cars are only a thing in the minds of fossil fuel directors who are hoping to keep selling their fossil gas.

That's why my next car will be an EV.

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