On Thu, 3 Feb 2000, Stirling Westrup wrote:
> > In response to Stirling's post, I wrote all about how much power
> > solar collectors could produce...
In reviewing those numbers, I found 3 errors in my calculations
(need more caffeine I guess), but since the errors compensated for
each other somewhat the conclusions come out almost the same.
If you could surround the equator with a 10 mi band of solar cells
you would roughly equal current annual power consumption. If allow
for the lack of "land" at the equator, you have to widen the solar cells
on the available land accordingly. Population growth can be
handled by increased efficiency in the cells (technological
progress). One of the real points that I think Stirling is trying to
make is the problem of increased per capita energy consumption in
developing countries. For that, I would agree we will need to increase
the efficiency of our energy utilization.
> > (b) ... re: per capita power consumption & growth rates
> Granted. Still, I have a feeling that that will be compensated for by
> the sheer number of third-world countries that enter the computer age
> in the next few decades.
The problem is that transportation is the big cost. The question is
whether entering the computer+communications age will require the
transporation costs we currently have in developed countries or whether
"virtual" tele-working and bulk package delivery (of e-ordered goods)
will significantly decrease those costs?
Most of the population growth & development is occuring in relatively
moderate climates, so the heating requirements are less significant
than say the U.S. or Europe. As the recent Transmeta announcements
show, you don't *need* a 200W computer (2x human power requirements)
to get something that does the job. A couple of watts will do just
fine for most things. You can counter argue that computer will need
more power to do more sophisticated stuff (e.g. speech recognition)
and I'll counter that all you are really doing is increasing the
effective "population" slightly. The question becomes whether the
added intelligence is effectively used to increase the overall
efficiciency (technology growth per W of power input from food
or electricity)). If we end up sucking up all of the power
into ever fancier VR games, then we might as well burn the planet
now and get it over with.
> > (c) ... re: improvements in technological efficiency...
> Yup. Oh, I think the *technology* will improve, but I'm not forcasting the
> arrival of *commercially viable* new technology. There just doesn't seem
> to be enough demand (sad to say) to cause the improvements in cost per
> unit that will be sufficient to convince people to switch to alternative
> methods. I'd love to be proved wrong on this point, BTW.
What you are saying is the problem is that there are no mechanisms
to bring future costs into the present to *shift* technology inertia
into more effective paths so we don't end up paying a huge bill later.
The problem is getting *full* cost allocation. The California
regulations effectively do that. Some might argue that it would
simply be better to implement Carbon taxes and make the consumer
pay. Being realistic however I think the regulators have an easier
path driving the manufacturers into producing better vehicles and
encouraging the goverment to help fund the R&D. It may not be the
most efficient from an economic perspective, but you step on fewer
toes and that probably is what makes it work.
> > (d) ... re: solar cell efficiencies
> Hmmm. I think that was most likely part of the assumption. Then again,
> what's the current per-capita cost of 10^9 km^2 of the expensive kind
> of solar cell...
Whatever it is now is going to be pretty irrelevant if you are going to
cover 10^9 km^2 with solar cells. That drives your infrastructure costs
down so low that the expensive kind aren't horribly more expensive than
the cheap kind.
> > (e) That we don't use other more efficient technologies such
> > as heliostats and heat pumps to harvest the solar power...
> These devices tend to be more expensive and require more maintenance, no?
No, currently they are cheaper. Some of them have moving mirrors or fluids
but presumably you could engineer these for long lifetimes and planned
maintenance. I suspect you can push efficiencies up to ~40% using these
> Are they really cheaper when the energy cost of their manufacture
> and maintenace are factored in? My guess is yes, but not by the
> margin you believe.
Well, thin shiney aluminium and steel supports aren't particularly
expensive now. But as I said before, Si is more abundant. If you built
the factories to produce this amount of solar cell or heliostat power
harvesting devices the costs would probably end up in the same ballpark.
> Granted. My point was just that there just isn't as much solar energy
> reaching the planet as some people seem to think. Putting a solar cell
> on top of every car won't suffice.
Granted, but if your car could get 500-600 W/m^2 in the U.S. and
convert it directly to human "consumable" energy at ~20-30%, your
car *would* harvest enough power to "operate" a human... Now operating
the car is a little different story...
> Neither will paving all our roads and rooftops with solar cells.
Well, the continental U.S. (sorry John...) is ~7.7x10^6 km^2 with
roughly a billion acres cultivated (~4x10^6 km^2 or 5.2%). Now
the "urban wisdom" numbers I've heard say something like 1-2% of
the U.S. is "paved over" (which seems high in comparison to the
farmland). So say we take 1% of the continental U.S. and use
the previous, fairly conservative conversion numbers. That gives
about 25 EJ of power annually. Which is of course less than
the ~80 EJ we currently consume. But technological progress on
the efficiency side of production and consumption should push
those numbers closer to each other. Doubling the automobile
gas milage alone probably knocks the 80EJ down to 65-70 EJ.
We all know there is room for improvement the problem is to
get the incentives in place to make the investments to go there.
> One of the things *I've* been hoping that nanotech would give
> us is a food production system efficient enough to let
> most of the grain belt be returned to its natural state.
I think relatively "good" bio(nano)tech will make significant progress
in this respect. You should have enough solar collecting area
on the roof of an average home to supply the power to feed yourself.
Even using our terrible ~80 EJ U.S. annual consumption, it still
works out that each individual only needs 15-20 m^2 of collection
area. For anyone except people dwelling in city apartments, they
probably have that much land or more. The people in cities have to
buy land in Arizona or Texas and pay the grid taxes.
This archive was generated by hypermail 2b29 : Thu Jul 27 2000 - 14:03:22 MDT