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Topic: Answer to the Fermi Problem
Replies: 0

 Richard Hake Posts: 1,251 From: Woodland Hills, CA 91367 Registered: 12/4/04
Posted: Feb 10, 2012 6:40 PM
 att1.html (4.1 K)

Some subscribers to MathEdCC might be interested in the answer to a
recently posed "Fermi Problem." It's in a recent post "Could the U.S.
Significantly Reduce Its Yearly Emission of CO2 By Covering Its
Rooftops With Photovoltaic Panels? #2" [Hake (2012b)]. The abstract

*************************************************
ABSTRACT: In a previous post "Concentration of Energy by Photovoltaic
Solar Panels" [Hake (2012a) I posed the following "Fermi Problem":

"What fraction 'f' of the yearly total U.S. fossil-fueled electrical
energy (and thus fraction of yearly tons of CO2 emission from U.S.
fossil-fueled electrical energy production) could be eliminated if
all rooftops in the U.S. were covered by photovoltaic solar panels?"

In this post I estimate f = 1.1 - considerably larger than the
estimate f = 0.08 of MathEdCC's Guy Brandenburg. Perhaps others would
like to consider this problem.

In Hake (2012a) I warned (paraphrasing): "Before recommending that
all U.S. rooftops be covered with PhotoVoltaic Solar Panels one
should consider the EMERGY associated with such a plan. Odum wrote:
"EMERGY measures both the work of nature and that of humans in
generating products and services. . . . The photovoltaic power grid
at Austin, Tex., evaluated by King & Schmandt (1991), is taking more
EMERGY out of society than it is generating."

So is the motto of Solar Forward <http://solarforward.com/>: "SAVING
THE PLANET, ONE SOLAR SYSTEM AT A TIME" a deception? I THINK NOT
because the evaluation of King & Schmandt (1991), failed to consider
the devastating decrease in EMERGY due to global warming if the
world's dependence on fossil fuels is not reduced.
*************************************************

To access the complete 18 kB post please click on <http://bit.ly/zT7dKj >.

Richard Hake, Emeritus Professor of Physics, Indiana University
Honorary Member, Curmudgeon Lodge of Deventer, The Netherlands
President, PEdants for Definitive Academic References which Recognize the
Invention of the Internet (PEDARRII)
<http://www.physics.indiana.edu/~hake>
<http://www.physics.indiana.edu/~sdi>
<http://HakesEdStuff.blogspot.com>

REFERENCES [URL's shortened by <http://bit.ly/> and accessed on 09 Feb 2012.]
Hake, R.R. 2012a. "Concentration of Energy by Photovoltaic Solar
Panels" online on the OPEN! AERA-L archives at
<http://bit.ly/wdkAoL>. Post of 6 Feb 2012 09:59:03-0800 to AERA-L
and Net-Gold. The abstract and link to the complete post are being
transmitted to several discussion lists and are also on my blog
"Hake'sEdStuff" at <http://bit.ly/Aimt1K> with a provision for

Hake, R.R. 2012b. "Could the U.S. Significantly Reduce Its Yearly
Emission of CO2 By Covering Its Rooftops With Photovoltaic Panels?
#2" online on the OPEN! AERA-L archives at <http://bit.ly/AsRbCR>.
Post of 10 Feb 2012 13:43:02 -0800 to AERA-L and Net-Gold. The
abstract and link to the complete post are being transmitted to
several discussion lists and are also on my blog "Hake'sEdStuff" at
<http://bit.ly/yPUZ6u> with a provision for comments.