Re: Worrying about the long term (was Global Warming (NUCLEAR))

[Daniel Schroeder <DSCHROEDER@CC.WEBER.EDU>]

> Dream on!  Car and truck fleet average at 100 mpg?  Not likely in anything
> like 'real' time.  Very long term...maybe.  {A big problem here is that
> these high mileage vehicles will not 'satisfy' many current drivers.  You
> therefore have to change the 'culture' to get them accepted.  That takes
> time.  [You've also included just about everything that is NOT a big truck
> in your 60% and it will be even harder to get some of the non-auto vehicles
> into your high-efficiency camp].}  Most construction since the early 70's is
> already fairly efficient (yes we could go 'super' efficient but what are the
> pay-back times).  Using heat pumps could help, but it depends how you make
> the electricity.  Gas fired furnaces are, I believe, pretty efficient.
> Really suspect your savings here are quite high.   I'll stay with my
> estimate of 25% for a realistic efficiency/conservation target over the next
> 25-50 years, but will be pleasantly surprised if it goes higher (well I
> won't be around in 50 to know).

Rick, you keep changing the rules.  A few days ago you said 25% efficiency
is the best we can do in 100 years.  Now it's 25-50.  Well, I'm glad
you've moved in my direction.

I should clarify that my efficiency proposals were not intended as
predictions.  To actually make it happen will take some combination
of decreased manufacturing costs for efficient technology and
increasing energy costs.  Both will probably occur, but I'm not
an economist or an engineer.

However, I am *not* proposing any radical cultural changes.  To take
cars as an example, I'm assuming the same utility and mix of capacities
as currently.  When I talk about 60% of transportation sector energy
being used by cars and light trucks, I'm including all pickups,
passenger vans/minivans, and SUV's.

You really think 100 mpg fleet average is a dream?  Do the physics.
When you drive a car, where does the energy go?  The answer is
thermal losses in the engine, braking, rolling resistance,
and air resistance.  Most braking energy can be recovered by
regenerative braking.  Rolling resistance can be reduced by
using lighter materials and better tires.  Air resistance can
be reduced by better aerodynamics (especially on the bottom of
the car) and somewhat smaller frontal area.  As for engines,
the future is in hybrid-electrics, in vehicles of all sizes;
then the size of the internal combustion engine is determined
by the average load rather than the peak load, so it can be
much more efficient and it can even shut off part of the time.
Eventually, the ICE may be replaced by fuel cells.

Look up the formula for the drag force in Halliday and Resnick.
Plug in a drag coefficient of 0.2, a frontal area of 2 m^2, and
any velocity you like.  Convert to miles per gallon and you'll
be amazed (if you've never done the calculation before).  Double
the fuel use to allow for rolling resistance and braking energy
not recovered, then double it again to allow for a 50% efficient
engine (perhaps available in a decade).  For reasonable average
speeds you'll still get a fuel economy well over 100 mpg.  For
a larger vehicle the frontal area goes up, but the drag coefficient
doesn't and of course you still use the efficient engine and
regenerative braking, so you can still get to 100 mpg although
it isn't as easy.  Some cars will have even lower drag
coefficients and frontal areas.  I honestly think that if fuel
prices were to quadruple right now, we'd see cars getting 100 mpg
within five years and the fleet average, including light trucks,
would be there in 25 years.  The only reason it will actually
take longer is because there's no incentive to do it now.

In any case, I hope you're around when it happens!

dan