Ken Chaddock wrote:

Morgans wrote:

"Robert M. Gary" wrote

Electric cars use power that may be produced using oil. The idea is
a large, centeral engine is more efficient (less oil, less
expensive, etc) than millions of individual CO dumping engines.
Whether that central engine burns oil or butter makes no difference,
as long as its more efficient than the individual engines.

The only problem with that point of view, is that every energy
transformation and use carries a penalty of a percentage of the
energy being lost.

This is "theoretically" true but not "practically" true. A central
power station that is burning petroleum products to generate
electricity would likely be using large gas turbines with efficiencies
pushing 60%. Transmission losses to the end used might account for 2%
and the electric motors of the cars would be running about 95%. So
overall "system" efficiency would be running over 55%...which is
*much* higher than your typical Otto cycle internal combustion engine
at around 25%...

That description is more theory than reality. The current installed base
of thermal power plants in the US, mainly coal-fired is about 35 percent
efficient. Yes, there are new turbine designs that approach 60 percent,
fired by natural gas, but there aren't many of them around, nor are many
being planned. More typical for new natural gas, simple cycle plants is
an efficiency of about 45 percent.

Distribution losses in just the last 1/4 mile from the local substation
to your home are probably 2 or 3 percent. Overall losses of the entire
grid are in the order of 15 percent.

Finally, you have left out the charge/discharge losses of batteries on
the electric cars, which are perhaps 70 percent efficient with current
technologies.

Multiplying all of that out, yields an overall efficiency of about 20 or
25 percent.