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the
Rick, the context of my list of proposals was the question of
how we can "significantly" reduce CO2 emissions. The earlier
claim (since retracted) was that the "only" way to do this is
to make the electrical industry nuclear. At present, total
energy use by electrical utilities is about 36 quadrillion BTU's,
or about 37% of total U.S. energy use. Of that, about 70% comes
from fossil fuels (the rest is mostly nuclear and hydro).
Converting all these fossil fuel plants to nuclear therefore
reduces fossil fuel consumption by about 25 quadrillion BTU's,
that is, about 26% of current U.S. energy consumption. It's
true that no one item on my list of 11 could accomplish
this much, but you wouldn't need all 11 either. Any one of the
three big categories--transportation, space heating, and
renewable electricity--would be quite significant, and all
three combined could do a lot better than that 26%. Of course,
we can argue forever about what's "significant".
Agreed, but do the numbers. Move the average mileage up to 40 or even 50
mpg and see what percentage of the TOTAL energy use you save. It's on
doorder of 5% and now you've played your trump card. Everything else you
gains considerably less.
While your numbers are approximately right, I think you've rounded
them in your favor. Current energy use by cars and light trucks is
approximately 60% of the transportation sector, or about 16% of total
U.S. energy use. A 50% increase in efficiency therefore reduces total
energy consumption by 8%, not 5%. But I'm going to do better. There's
no law of physics that prohibits cars from getting 300 miles per gallon,
and even light trucks can do better than 100. I'll be conservative and
assume an average of 100 mpg for all cars and light trucks. Hybrid-
electric drive, lighter materials, and better aerodynamics are all
that's necessary, but throw in fuel cells if you like. That's
a five-fold increase over current efficiency, so it cuts current total
energy use by 4/5 of 16%, or nearly 13%. Carpooling and mass transit
might give a further 1/3 reduction, but that's now only another 1%.
The next place to look in the transportation sector is heavy trucks
used for freight. Even here, I suspect that hybrid-electric engines
and fuel cells might help a lot. Perhaps something can be done
about aerodynamics. Or we could move more freight by train. One
way or another, a 50% efficiency gain here should be possible.
That's 50% of only 4% of current total energy use, or 2%.
While we're on transportation, let's bring back passenger trains
(when the price of jet fuel becomes a significant chunk of a plane
ticket). The shift to trains from planes (and cars) could cut another
1% of total energy use, I think.
As a bonus, this huge decrease in petroleum use will reduce the amount
of energy that goes into refining petroleum (11.5% of the industrial
sector, 4.5% of total energy use), so I save another 2%, perhaps,
on total energy use. Let's see, I'm now up to 19% total savings.
You're right to point out that cars are the trump card, but that's
only because they use such a large fraction of energy currently.
No other specific end use is this large. But the next biggest is
still space heating, which could probably be cut in half with better
insulation and windows. This would save on air conditioning as well.
From the data I have, I'd estimate that residential and commercialheating and air conditioning currently use about 12% of our energy,
so saving half gives a 6% reduction. For most of the other half of the
heating, I'm going to go solar, but perhaps this shouldn't be counted
as "efficiency" (even though it's not new technology). I'll also
go solar for water heating.
The rest of the residential/commercial sector is lights and
appliances. As far as I can tell, these account for about 20%
of total energy use, if you include the losses in generating and
distributing the electricity. The best way to save here, actually,
might be to use more efficient generators (combined-cycle gas-fired
plants?) or cogeneration in suitable locations. But if you want
to get back to end uses, I suppose the first thing we should do
is get rid of all those incandescent lights. Improvements in
most other lights and appliances (fluorescent ballasts, better
refrigerators, LCD screens, etc.) won't be so dramatic, but they'll
still add up. One way or another, I don't see why that 20% can't
be cut to 10%, another 10% savings in total energy.
What's left is the industrial sector, mostly manufacturing. The
best way to cut energy use here is to make things last longer so
they don't have to be replaced so often. It's hard to be real
specific because the details are so complex. Of course, more
efficient motors, etc., can also help, as can cogeneration.
But let's be conservative and suppose the industrial sector
energy use is cut only by a third. That's still 11% of total
energy use, not counting petroleum refining which I already
accounted for.
So what are we up to? 19% from transportation and petroleum
refining, 16% from residential and commercial (not counting solar
heating), and 11% from industrial, for a total of 46%. If you
count low-tech solar space and water heating, we're up to more
than 50%, twice the practical upper limit you claim.
One more point: Everything I've discussed here is based on current
or foreseeable technology. Unexpected new technology can only help.
Some of the changes are already cost effective, though others might
have to wait for fossil fuels to get more expensive. In any case,
there's no need to wait until the year 2100.
Dan