[ChuckMcM]

An internal combustion motor is, at best, about 20% efficient [1], whereas if you burn the same fossil fuel in an electric power plant using a combined cycle configuration you can reach 60% [2].

Now the electric company loses some of that by sending over wires to your house (or where ever the charger is) but its still a big win. What that means in mathematical terms is that if you took the same fossil fuel we burn today in cars and instead made electricity out of it and ran our cars on the generated electricity, we could either have nearly 3x the cars for the same fuel, or the same number of cars using 1/3 the fuel.

The win here is that if you have room to build a big heavy specialized machine to convert fossil fuel to electricity you can invest in all the things that make that really efficient. Whereas if you have to put an engine in every car, there is a financial and weight limit to how complex you can go (not that some of the extreme low sulfur diesels aren't wicked complex, they are).

Also you don't need rare earths. You only need them for permanent magnet motors. A fully electric car can by built with practically none, they are available locally if you need them[3].

[1] "Most steel engines have a thermodynamic limit of 37%. Even when aided with turbochargers and stock efficiency aids, most engines retain an average efficiency of about 18%-20%.[11][12] " - http://en.wikipedia.org/wiki/Internal_combustion_engine

[2] "In general in service Combined Cycle efficiencies are over 50 percent on an on a lower heating value and Gross Output basis. Most combined cycle units, especially the larger units, have peak, steady state efficiency efficiencies of 55 - 59%. " - http://en.wikipedia.org/wiki/Combined_cycle

[3] The US used to be the world supplier of rare earths, China just did a Wallmart on us and drove domestic suppliers out of business, the DoE has put them back into business - http://arstechnica.com/science/news/2010/12/us-rare-earth-mi...

[FrojoS]

I agree with your point, though I guess its probably more like 2x the cars. Also, in colder countries / states, the equation doesn't look as rosy. In winter, you use the heat generated by the combustion engine. Hence, efficiency goes way up.

Without knowing any numbers, I would assume, that at the moment, an additional, fossil fuel based, heating system would do the best job for an electric car. Webasto [1] for instance sells those.

[1] http://www.parkingheater.com/

[adrianN]

When calculating the efficiency of electric cars you must also take into account the losses from the battery. I'm pretty sure charging a battery is not 100% efficient.

[ChuckMcM]

Absolutely, the electricity -> chemical -> electricity cycle gets less power out than you put in.

The fuel cycle is still fossil fuel -> (stuffs) -> car moves.

There are many ways to change around the (stuffs) part of the equation. The claim is that converting fossil fuel to electricity in bulk is much more efficient than converting it into mechanical work locally through exothermic chemical reactions.

We could keep trying to detail efficiencies (or non-efficiencies) in the problem but as Glieck pointed out in his Chaos book, you can compute the length of the British coastline by drawing a line around the island and get one number, or you can zoom in and include the bays and harbors and protrusions and get another number, all the way to going around each grain of sand on the beach and getting yet another number. Clearly the closer you look at the coastline length the 'longer' it gets, but that extra length is misleading.

[artmageddon]

Good point-my understanding is that you do lose some capacity with each charge over time. The one thing that the parent should've noted - which would support his point - is that oil must also be transported across oceans / highways to refineries and then transported again to individual gas stations, which is in itself a drain on resources. Being able to send power over power lines, I imagine, beats those as well.

[acroyear]

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