FLYING CARS WERE A LOSER IN ITALY, TOO

Photo: Amilcare Porro

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 [right], the driver, or, more accurately, the pilot, seems to be paying a fine.

Giampiero Porro

IEEE Member

Como, Italy

CLOSE READING

You might be pleased 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 estimating annual worldwide oil consumption [January]. My figure for 2005 is 1.09 cubic miles, but that is close 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 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.

The authors reply: The phrasing proposed by Haynes is excellent; we wish we had thought of it ourselves. As for the definition of a cubic mile of oil, or CMO, and the conversions, our main source, Ripudaman Malhotra, at SRI International, elaborates as follows: “If one does a straight conversion of 153 quadrillion Btus into kilowatthours, as Jacovides did (1 Btu = 0.293 watt hour), the answer is 44.8 trillion kWh. But that straight conversion does not apply to thermal plants converting fuels to electricity. For such a situation, a factor of 10 000 Btus = 1 kWh is typical. So, when comparing electrical output, we used 1 CMO = 15.3 trillion kWh. This 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 Ink-equipped devices was given as “160 to 170 pixels per square inch.” The correct measure is “160 to 170 pixels per inch.”

In “Electric Power Steals the Show” [Spectrum Online, February], the phrase “320 nanometers of peak torque” should have been “320 newton meters of peak torque.”

—Ed.