Re: [Phys-l] Nuclear Reactors

["Rick Tarara" <rtarara@saintmarys.edu>]

----- Original Message ----- 
From: "Hugh Haskell" <hhaskell@mindspring.com>
> The point here, of course, is that if we keep thinking up reasons why
> something won't work, we will never solve the climate problem.
> Creative, but level-headed thinking and planning is needed, here and
> abroad. My sense right now is that much of the rest of the world is
> well ahead of us in both.
> --

It is not a case of thinking up reasons 'why it won't work', but rather 
trying to be realistic about what it is going to take TO make it work.

OK--'cleaner' coal, if you wish, but with one of the world's largest 
supplies, coal (as clean as we can make it) is very likely to be part of our 
near future (next century) energy supplies.  With the inevitable phasing out 
of oil and natural gas, the net environmental problems of coal can be 
minimized.  Together with some nuclear, coal can provide the high-density 
power source that will be needed in _some_ locations.  It too can be phased 
out, but to do so that big IF about shipping power across country (say North 
Dakota to New York) has to be solved, a national (international if you wish) 
grid has to be designed and implemented--(that cost is almost never included 
in 'renewables' estimates)--or we really would need to develop something 
like Fusion power.

There are several things to include in discussing using wind and solar for 
the major fraction of energy needs:

1)  As you phase out fossil fuels, you then move many energy demands from 
'chemical' to electrical.  Heating and transportation energy must now come 
from the renewables.  Biomass could only handle a fraction of the 
transportation fuel needs--we just calculated (for our project) that 3% of 
the energy needs in 2100 in the form of biodiessel (from soybeans) and 
ethanol (from switchgrass) would require 150,000 square miles of land use. 
If we can back off of oil soon enough, then perhaps some specialized 
needs--big rig trucks and aviation might still draw from remaining petroleum 
reserves.   The big point here is that the electrical demand could triple 
without oil and natural gas, and then if you want to eliminate coal, the 
numbers become daunting.

2)  The population (U.S.) is going to continue to increase.  Can we hold the 
population down to say 450 million by 2100?  That will take some aggressive 
work in immigration policy.  If the country keeps adding a million or more 
immigrants a year, immigrants with traditionally higher fertility rates than 
the 'native' population, and generally more religious attitudes against 
birth control, 450 million would be a very low estimate.  So lets assume at 
least a 50% increase in population.

3)  Efficiency and conservation can certainly lower energy needs.  25% 
proves difficult (for my classes) to fully quantify, but that should be 
possible and maybe a bit better.  However, with the population growth it 
means the overall energy demand will increase and with the reduction or 
elimination of most 'chemical' energy sources, the demand for electricity 
rises sharply.

4)  So what's a 'reasonable' estimate of yearly energy demand in 2100?  We 
work with 20,000 TWh or a power demand of 2.3 TW.
What do such huge numbers really mean?  IF--you wanted to run the country on 
wind (assuming you had a grid and had generators spread so that you could 
guarantee the 25% availability at all times (according the Hugh), then using 
1.5MW generators (pretty much the standard although bigger ones are 
available) you need over 6 MILLION wind generators.  In a more realistic 
system, without any fossil fuel, you might split up the demand, but you 
can't get much more than 3% from Hydro (and the environmentalists want to 
dynamite all the dams anyway), maybe 3% from geothermal, might push 10-12% 
from biomass, but then you have to split the rest--over 80% between wind and 
solar.  Without coal and nuclear--this is huge.

5)  Effective use of solar (and to a lesser extent wind) will most likely 
require storage techniques--maybe electrolysis to hydrogen--to assure an 
'energy on demand' network.  Whatever the storage and distribution system, 
it will cost some big bucks.  We've estimated about $5 trillion for a 
hydrogen capable pipeline distribution system.

6)  Cost estimates have to account for the likely shorter lifetimes of wind 
generators and some forms of solar (PV panels) compared to fossil/nuclear 
plants (about 75 years) and dams (100 years or more).  We don't have enough 
experience to know the replacement rate for large wind generators, but it is 
likely to be at least twice that of current plants--this increases the cost 
above those normally estimated for the switch to renewables.  Again, such 
estimates are just to be somewhat realistic about the task--not to dismiss 
it.

**********************
To repeat what we do in my energy class--a MODEL of energy distribution for 
100 years in the future (one that still uses coal and nuclear but is heavy 
on wind and solar) costs out at $30-50 trillion--capital costs-- and uses 
about half a million square miles (much for biomass) of land.  What these 
numbers say, to me, is that this is not a 10 year, 20 year, or barely a 50 
year project.  To be affordable, the transition must be stretched over a 
century time frame.  However, clearly we need to start now (we are starting 
now) and will have to ramp up the transitions, but thinking we can eliminate 
the fossil fuels in a couple decades is, IMO, delusional.

Rick