[SGVLUG] Off-topic - for Tom - plug-in car that can power yourhouse

[David Lawyer]

On Fri, Apr 13, 2007 at 09:46:00AM -0700, Jeremy Leader wrote:

> So for example, I commute 20 miles to work, and 20 miles back.  So I could 
> just about do my daily commute for only the cost to recharge the battery 
> each night; if my employer provided free outlets in the parking garage, it 
> could cost me even less.  If I also use the car for short errands on the 
> weekend, I could be saving roughly $2 to $3/day * 365 days/year or up to 
> $1000/year.  At that rate, it would take 10 years for the add-on to pay for 
> itself (ignoring interest).  I wonder if the batteries could be expected to 
> last >3600 charge/discharge cycles?

Note that the average heat rate in the US for generation of electricity
is the equivalent of 30% efficiency (of conversion of heat from fossil
fuels to electricity) at the electric outlet (10% loss in
transmission).  This 30% is identical to the efficiency of the internal
combustion engine (gasoline).  So is electric power for automobiles
more energy efficient?  For using electricity the 30% efficiency is
reduced by: the loss for battery charging-discharging, loss in the
electric motor, increase in rolling resistance and aerodynamic drag
due to the batteries.  The result is perhaps a 20% efficiency for the
electric auto (or hybrid).  But few people know how to drive a car to
get 30% efficiency so the typical efficiency is only 10%-15%.  Nor do
they coast to recover more of the kinetic energy than an electric
vehicle can recover by charging batteries.  Thus the electric auto wins
except that coal from power plants emits 34% more CO2 per BTU of fuel
burned than gasoline does.  Most of our electric power is generated by
coal and new loads are likely to be powered mostly by coal.  So
electric cars are not environmentally much better than the gasoline
auto.

Coal is a lot cheaper per BTU that gasoline so it's a lot cheaper to use
electricity and in effect mostly run your car on dirty coal.  Electric
railroads for hauling freight are more feasible but we don't have them.

			David Lawyer