Andres Garcia
I’m afraid I was seriously disappointed by your response to the letter, “Ethanol’s the Answer?” (Oct. 9). You said that “...researchers from Cornell University and UC Berkeley...” conclude that “....making ethanol from corn consumes more energy than the ethanol produced actually contains.....” But the facts are that the vast majority of studies on the energy balance of turning corn into ethanol show a positive energy balance of around 33%, and come from organizations at least the equal in prestige of Cornell and Berkeley. The two studies you quote are in a distinct minority, and, if I remember correctly from when I researched this issue in depth, the author from Berkeley was at one time a grad student of the author at Cornell. And even if the energy balance “is” negative, the vast majority of the energy behind ethanol is used making fertilizer, and that energy comes mostly from coal, not from imported oil. Next time, try using ALL the data, and not just the subset that happens to agree with your prejudices.
My own personal energy preference is to build lots of nukes, (both burner and breeder types), and resume nuke-fuel reprocessing, but I’m not going to fault ethanol using false premises.
Duane K. Wolcott
It should be said that David Pimentel, the Cornell researcher who did the original analysis, published his work in a peer-reviewed journal. Pimentel also chaired a Dept. of Energy panel that investigated ethanol production. The primary criticism of his work seems to come from a consultant hired by the National Corn Growers Assoc. As far as I can tell, this consultant’s criticism has not been peer reviewed. And NCGA obviously had a vested interest in the results.
Roots of the shortage
It is easy to see why there is a “shortage” of engineers: It is an unstable way to earn a living. Before the Great Depression, professional engineers made more money per year than doctors. After World War II, however, returning veterans flooded engineering schools, which kept expanding through the 1980s to handle the flood. The relative economics eroded. So, most engineers counsel their kith and kin to go into other fields. Then manufacturers cry about having to loosen import quotas to allow more foreign engineers to come in.
George H. Morgan
MW? What’s that?
Although I’m not a mechanical designer, I read your magazine to learn about the field and keep up with the latest innovations. But your recent article on the automation of solar-cell factories (“Solar production shifts into high gear,” Sept. 11) confused me a bit. You used the term MW to express the size of a photovoltaic plants. Do you mean megawatts? If that is a production measure, it seems like it should be MW per unit time, like MW per year. Or did you mean million wafers? That would still need a time period to be completely clear.
Bruce DeRienze
MW is the abbreviation for megawatts. In PV industry parlance, a 100- MW factory has the capability to put out 100 MW-worth of panels in a year.— Leland Teschler
Europeans and their diesels
I found your editorial on mileage quite interesting. (“MPG figures aren’t what they seem,” Sept. 11). The truck and heavy-equipment diesel folks have been dealing with NOx for several years, ever since emission regulations came into play. Basically, diesel engines emit NOx when combustion temperatures are high and emit particulates when those temperatures are low. So there’s a continuing interest in striking a balance between the two because both are regulated as part of air quality.
The Europeans are not concerned as much about NOx as they are about particulates. In recent years, there was strong political pressure to reduce particulates, so devices were quickly fitted to diesel-powered passenger cars to get this done. This let European car engineers continue their focus on increasing thermal efficiency and mileage.
For trucks and heavy equipment, Europeans are quite fond of using urea. It is injected into the cylinders after combustion where it transforms NOx into benign chemicals. There is a good infrastructure supporting urea in Europe, a network of suppliers and distributors that doesn’t exist in the U.S. Recently in the U.S., however, there has been a move toward using urea to meet the latest round of emission regulations on diesels. However, those moves come with several caveats, including assurances that diesel engines will work without urea and that there will be enough urea outlets to supply the fleets of trucks and heavy equipment.
John Fletcher
Ps and Qs: Another of life’s mysteries
In recent issue of MACHINE DESIGN (Backtalk, Oct. 9) it stated that “Mind your P’s and Q’s” comes from unruly English pub customers not minding their pints and quarts. Actually, back in the days of setting type for printing, manual typesetters were issued that warning because of the visual similarity between the lower case p’s and q’s. Looking at the backward type to verify the letters “p” and “q” could understandably be confusing.
Stanley J. Zielinski
This familiar phrase has many possible origins. If the reader’s version is to be considered — and it is a popular one — you’d have to explain why we aren’t minding our b’s and d’s, another pair of mirror-image letters. An alternative theory is that the p stands for pleases and the q for thank-yous, turning the phrase into an admonition to watch your manners, a meaning it still holds. One of my favorite explanations is that it stems from the British Navy and was a reminder to sailors not to get their pea-jackets (p’s) dirty with their tarred queues or pigtails( q’s). And there’s at least one other explanation, that it originally meant learning the alphabet. A poem written by Charles Churchill around 1763 says: “On all occasions next the chair / He stands for service of the Mayor, / And to instruct him how to use / His A’s and B’s, and P’s and Q’s.” — Editor
Ethanol — a corny idea?
Mileage and ethanol are still fresh on the minds of our readers, despite the fact gas prices have come down considerably, at least in the Midwest. Meanwhile, another engineer gives us the lowdown on urea, which could be coming to the U.S. soon.
