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Comment by prewett | Hacker News Reader

The article says "in addition to reducing carbon emissions" in regard to the Tesla. I can't see how electric cars actually reduce pollution/emissions of any kind.

Typical coal -> electricity is 33% efficient, but can be up to 50% [1], electricty to battery is 75% [2], and electric motors are about 92% [3]. The typical efficiency will be .33 * .75 * .92 = 23%, with a maximum of 35%. Gasoline engine efficiency is 25 - 30% [4], so we aren't really improving pollution much with electric cars, until wind/solar makes up a substantial part of our grid.

Now it will certainly _move_ the pollution from the cars in the cities to the power plants elsewhere (which is a good thing), but it really isn't preventing pollution.

[1] http://en.wikipedia.org/wiki/Fossil-fuel_power_station#Basic...

[2] http://www.futurepundit.com/archives/006554.html

[3] http://www.engineeringtoolbox.com/electrical-motor-efficienc...

[4] http://en.wikipedia.org/wiki/Engine_efficiency

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You're counting all the deficiencies of electricity through the life cycle of how it gets into your car, but not for how oil gets turned into gas and then into your tank.

Less than half of electricity in the US is from coal. Also, because of how power plants / grids work, there is excess capacity available that electric cars can use (overnight charging) without increasing power generation.

> Less than half of electricity in the US is from coal.

And the rest is from Canada :)

You are forgetting a few things:

1-Coal is not the only power source there is 2-Batteries are not the only energy storage device there is 3-It is difficult to upgrade a whole fleet, as we can see by the difficulty of changing it to be a electric-only fleet. Power plants are much easier to upgrade by comparison - all cars are then instantly more efficient. 4-Electric engines do not have to be kept running while the car is stopped (heavy traffic, or traffic lights). This benefits them greatly in heavily populated urban centers. 5-You can have regenerative breaking and recover some of the lost energy. However small, this is something gas engines cannot do. 6-Several components are not needed. Electric engines do not have the same lubrication requirements of internal combustion engines. So no oil, no heat sinks and water pumps (except in some implementations, to cool batteries while charging), electric generator (unless hybrid), exhaust pipes, fuel catalysts, spark plugs (and no high-voltage coils), fuel pumps.. the list goes on and on. In some implementations you could even get rid of the differential transmission and drive the wheels independently. Some do not even need to shift gears, as electric motors can reach very high RPMs (and have a large power to weight ratio). 7-Less sound pollution

Points 4, 6, and 7 are a pretty compelling argument for electric cars, at least in cities (plus the shifting of exhaust outside the city).

I just find it difficult to believe that converting three times (electricity source -> electricty -> storage -> mechanical energy) is going to be more efficient than converting once (gasoline -> mechanical).

It might not be, but still, we have only so much oil around, and many more electricity sources, so in the long run electric is a better option.

Several Reasons why

- As you said, pollution from power plants have less effect on humans, because of distance and filters - You are comparing vehicle best case efficiency with Electrical worst case - Electrical power can be produced from clean sources, gasoline can't be used without creating pollution - Electric can potentially be smaller and lighter because of a very simple mechanism compared to the gasoline engine and all the components around it. (But batteries efficiency must be improved to really reduce weight)

Don't most large power plants in the Western world have 'scrubbers' and other measures that limit the amount of carbon/other pollutants that they actually release into the air?

If not now, is that a technology that's moving forward fast enough to be a partial solution in the future?

Efficiency isn't the same carbon/NO2/whatever emissions. A lot of inefficiency comes from waste heat and mechanical losses (that's true both in electrical generation AND gas/diesel engines of course) and even then fossil fuels only make up 75% of US power.

Now that said the overall win is still probably smaller than marketing would be willing to admit.

It is enabling an improvement in "total" efficiency which in the end is the only thing that matters.

The sum of the different parts being greater than the individual components...

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