Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] The West Wing



Thanks

The charts ARE a bit confusing however--and the main point of confusion is
the electrical percentage. It makes a big difference whether you are
looking at NET END-USE or gross energy input. Of course that also will
show up in the totals--about 21 TWh net or 29 TWh gross. Most of the
difference comes because they account the coal and nuclear in terms of
thermal efficiencies (probably the same for the natural gas used for
electricity) but oil and most other natural gas use is accounted without
such adjustments. Therefore, only a bit more than a third of the energy
resources put into electrical power production shows up as net electrical
power--there are also line losses and the fact that most electrical
utilities must produce more power than they will actually deliver to
customers. This is all important as we look towards more wind and solar
production of electricity because these need only supply the actual energy
demand---that is, we can work with the 21 TWh number rather than the 29 TWh
number when trying to figure out what would be needed to 'go green'.
However, you then face the fact that neither wind nor solar are 'energy on
demand' resources and therefore to use either to provide large percentages
of our power needs (again total energy needs, not just current electrical)
will require either building facilities for considerably more than 100% of
expected demand and/or having a storage system for wind and solar (hydrogen
for example). Either way, while we can do better than the 33% net
electrical output of coal or nuclear, it will not be a one for one game
either.

The real important thing here though is to not forget that to really go
renewable, you have to replace the current oil and natural gas usage as
well as coal. That makes for a much more difficult task--try it. Use the
21 TWh, increase it by at least 50% for population increase--so over 30
TWh--then maybe reduce that by 25% for efficiency and conservation (we've
had a long discussion on PhySoc about this--but 25% is possible, more iffy)
so let's say 23 TWh per year. Now try and come up with that much energy
using wind, solar, and biomass and see how much land is involved. [Solar
at 300kWh/m^2, Wind at an average output of 30% the rated power and needing
a 7x(rotor diameter) spacing, or biomass at very low NET energy/land
density.] It can be done if a country has enough money and enough land.
An India or even a Japan will run into big problems with any such scenario.
The numbers--money and land are truly staggering. See

www.saintmarys.edu/~rtarara/ENERGY_PROJECT/ENERGY2100.htm

for student projects on this topic.
****************
To save space let me comment here on John Denker's note.

The common usage of fossil fuels is that it is fossilized remains of past
organic material--hence coal, oil, and gas. Nuclear may be 'dug up' but is
not commonly considered a fossil fuel.

Yes, even using very expensive (to recover) nuclear fuel, it is only a
stop-gap measure, but one that might be important as we try to back off the
CO2 producing fossil fuels.

Assuming you don't totally dismiss human contributions to global warming
(something that is becoming ever more difficult to do, IMO), the real
danger may be that we actually DO HAVE a couple hundred more years of such
fuels (at 2-3 times today's prices) that could possibly be recovered. What
effects would result from using 2-3 times more fossil fuel for another 150
years are open to speculation, but few atmospheric scientists would see
such as anything but a disaster.

Rick

[Original Message]
From: Folkerts, Timothy J <FolkertsT@bartonccc.edu>
To: <rbtarara@sprynet.com>; Forum for Physics Educators
<phys-l@carnot.physics.buffalo.edu>
Date: 5/26/2006 4:13:40 PM
Subject: Re: [Phys-l] The West Wing


The US DOE puts out really handy charts of US energy use, with "sources"
on the left and "uses" on the right (and "useful" vs "lost" energy at the
far right). it is a visual way to see what sources are important for what
uses. If you haven't seen it, here is a link to the 2002 version (the most
recent that I found right off hand).

http://eed.llnl.gov/flow/03flow.php