In article ,
Ignoramus25088 wrote:

On 2012-06-26, wrote:
On Mon, 25 Jun 2012 20:52:01 -0700, a friend
wrote:

On 6/25/2012 8:26 PM, wrote:
On Mon, 25 Jun 2012 22:08:16 -0500, Ignoramus6950
wrote:

I was thinking about electric cars today.

An internal combustion car, burns fuel inside cylinders and produces
energy according to Carnot cycle. Say, it makes 28% of energy from the
total BTU of fuel that it burns.

Compare it with an electric car. A coal electric power station
operates at efficiency of 33% (Wikipedia).

Then 10% of this is lost in power distribution.

More lost in stepping down line voltage to 220 volts.

Further, more is lost in a battery charger.

Then more is lost in the car battery.

Then more heat is lost in motor windings and power semiconductors.

This is probably by far less efficient than internal combustion an
distribution of gasoline!

And how is it going to reduce CO2 emissions, if more CO2 needs to be
burned as coal than would come from gasoline?

i
The only way it really "saves" anything is with hydro power, solar,
wind, or atomic. Possibly Natural gas.



the analysis above is flawed. First, if you use gasoline, energy is
lost in transporting it to the gas stations, pumping it, refining it,
etc. Second, energy efficiency is only part of the problem, the other
problem is emissions. even the cleanest car emits more pollutants per
unit of energy produced than a fixed plant. So, if you worry about
breathing, there is a second part of the story to consider.
Actually, todays cars burn cleaner than MOST coal fired power
plants.

And HYDROcarbons burn less carbon that pure carbons, a.k.a. coal.

That's because hydrocarbons also burn hydrogen.

So, what emits less carbon, a coal fires power station transmitting
power, used to charge batteries, or a hydrocarbon burning carm is not
obvious.

In your analysis, you need to cover the full lifecycle cost, which
includes making the car in the first place. Cars only last on average
seven years, so making them is a major component of both cost and carbon
impact. Batteries in particular are expensive to make, don't have a
very large capacity compared to a gas tank, and don't last all that long.

As others have pointed out, gasoline engines in cars are maybe 20%
efficient, whereas coal fired power plants are more like 40%, coalpile
to bussbar, but transmission and battery inefficiency eat much of that
advantage up. Batteries are not all that efficient at storing energy.

The basic advantage of a hybrid is that the battery handles the pulse
loads, like accelerating into traffic, so the gas engine can be sized
for cruise, and so can be smaller (about one half) and operates nearer
to its optimum rpm and load.

Joe Gwinn