IEEE Spectrum March, 2007 - 3

"Theplanewas
absolutelyflying!"
-GiampieroPorro
FLYING CARS WERE A
LOSER IN ITALY, TOO

Regarding the "Winners &
Losers" coverage [January], I
was attracted to the article
about Terrafugia's "roadable
aircraft," because it reminded
me of my childhood. The
attached picture [above] shows
a vehicle built a long time ago
in a project my uncle, Amilcare
Porro, worked on here in Italy.
My uncle spent his entire life
designing airplanes, first at
Caproni Aeronautica and then
at Aeritalia until he retired.
The year when this picture
was shot I can only estimate
as around 1960. As it shows,
the plane was absolutely flying! It was one of two photos
I found in a shoebox; in the
second picture, the driver,
or, more accurately, the pilot,
seems to be paying a fine. [To
see the second photo, go to
http://www.spectrum.ieee.
org/mar07/forum.]
Giampiero Porro
IEEE Member
Como, Italy

CLOSE READING

You m ig h t b e ple a s e d to
know that "It's a Wiki, Wiki
World" [Technically Speaking,
December] was recently read
and reread (very, very carefully) by approximately 4000
people in varying degrees of
despair. The article in question was used in this year's

exams for 312 positions for
English-language teachers in
state-run schools in Greece.
It was one of the two texts
given for reading and comprehension, and it was the basis
for the essay-writing question. Although the temptation
to hate the article was great,
I must admit I enjoyed it. It
was a pleasant and interesting
read in an otherwise unpleasant situation.
Pinelopi Tsagana
Greece

A VERY LARGE
AMOUNT OF OIL

The concept of a cubic mile
is a good one for estimati ng a n nua l worldw ide oi l
consumption [January]. My
figure for 2005 is 1.09 cubic
m i les , but t h at i s c lo s e
enough. Basically, the equivalent energy of a cubic mile
of oil is 163 quadrillion Btus
or 48 trillion kilowatthours.
You said this corresponds to
52 nuclear plants, but it seems
to me that you are off by a factor of two.
Things get more hairy with
the wind turbines. Assuming
50 percent of the maximum
output on average, it would
take about 6.6 million turbines or 132 000 each year
for 50 years-assuming they
last that long. I did not do
the calculation for solar panels, but it would take quite a

IEEE Spectrum | March 2007 | NA

spread to produce an average
of 2.1 kilowatts.
Linos J. Jacovides
IEEE Life Fellow
Grosse Pointe Farms, Mich.
I did some calculations and
concluded that what you were
trying to say was that if in
50 years, you built so and so
many plants and operated
them all full tilt for a year,
you could generate electrical
energy approximately equal to
what could be generated from
a cubic mile of oil. Why didn't
you just state it that way?
Harold E. Haynes
IEEE Member
Cherry Hill, N.J.

explains why Jacovides found
our estimates to be off by more
than a factor of two for nuclear
and wind turbines.
"As for the photovoltaics,
taking an availability factor of
0.2 into account-the amount
of time the PV unit can expect
to be actually generating electricity-the energy produced
by a 2.1-kW system on a typical
day would be 2.1 times 24 times
0.2, or about 10 kWh. At a solar
insolation level of 6 kWh per
day per square meter, the area
required would be 1.68 square
meters, or 18 square feet.
Given that commercial solar
panels have efficiencies of
about 15 percent, the resultant system would not require
more than 120 square feet.
Indeed, Sanyo offers modules
(roughly 3 feet by 4 feet) that
are rated at 195 watts. Ten of
these modules were the basis
of my original calculations for
a 2.1-kW PV system."

CORRECTIONS

In "E-Newspapers: Digital
Deliverance?" [News, February], the resolution of E Inkequipped devices was given
as "160 to 170 pixels per square
inch." The correct measure is
"160 to 170 pixels per inch."
The authors reply: The phrasing
In "Electric Power Steals
proposed by Haynes is excellent; the Show" [Spectrum Online,
we wish we had thought of it February], the phrase "320 nanoourselves. As for the definition
meters of peak torque" should
of a cubic mile of oil, or CMO, have been "320 newton meters
and the conversions, our main
of peak torque."
-Ed.
source, Ripudaman Malhotra, at
SRI International, elaborates as
follows: "If one does a straight readers are invited to comment in this
conversion of 153 quadrillion
department on material published in
Btus into kilowatthours, as
IEEE Spectrum, and on matters of
Jacovides did (1 Btu = 0.293 watt interest to engineering and technolhour), the answer is 44.8 trillion
ogy professionals. Letters do not
kWh. But that straight conver- represent the opinions of the IEEE.
sion does not apply to thermal
Letters may be edited for space and
plants converting fuels to elec- clarity. For more letters, see "...And
tricity. For such a situation, a
More Forum" at http://www.spectrum.
factor of 10 000 Btus = 1 kWh
ieee.org. Contact: Forum, IEEE
is typical. So, when compar- Spectrum, 3 Park Ave., 17th floor, New
ing electrical output, we used York, NY 10016, U.S.A.; fax, + 1 212 419
1 CMO = 15.3 trillion kWh. This 7570; e-mail, n.hantman@ieee.org.

www.spectrum.ieee.org

AMILCArE Porro

FORUM

http://www.spectrum.ieee http://www.spectrum http://www.ieee.org http://www.spectrum.ieee.org

Table of Contents for the Digital Edition of IEEE Spectrum March, 2007