Bench Degree·WIND POWERchapter

On the Cover

How the cover of every Bench Degree volume is chosen. One question, and it is not who got there first or who is famous. If we could bring anyone back to teach you this subject, who would you actually want at the bench? That is the whole test. It picks people who did the work with their hands, who checked things themselves, and who would be worth standing next to. Every one of them actually lived, which is why a cover portrait in this series is either a real document or openly a drawing, and never a photograph of something that did not happen.

Poul la Cour, 1846 to 1908, engraved from an undated portrait.

He is not here for being first, because he was not, quite. Charles Brush lit his own house in Cleveland from a wind machine in 1888, three years before the Danish government funded a schoolteacher in Jutland to look into wind electricity. Brush built the largest wind machine in the world. It was also the wrong shape, and Chapter 3 shows why.

He is here because of what he did instead of building something bigger. In 1896 and 1897 he built a wind tunnel at Askov Folk High School and tested sail shapes in it, small ones, one against another, keeping the numbers. Four slender cambered sails beat a rotor almost solid with blades, which every turbine on the horizon still obeys.

Then he solved storage, in 1900, in a way that reads as this morning’s press release. Batteries were expensive and short-lived, so he electrolysed water, stored the hydrogen and burned it in gas lamps to light the school. It worked for years, and several windows were reportedly blown out along the way. Chapter 3 has you repeat the first half in millilitres.

And then the thing that decided this cover. From 1903 he ran courses at Askov that trained rural mechanics as wind electricians, and from 1904 he published a journal for them. By the end of the First World War something like a hundred and twenty Danish rural utilities were running wind turbines. He measured, and then he taught the answer to people with no education in it so they could build the machines themselves. That is what this series is for, and he was doing it in 1897.

Albert Betz gets Chapter 5 to himself. His 59.3 percent governs every chapter here and an earlier plan put him on this cover. A book that asks you to test things belongs to the man who built the tunnel and then the school.

About the portrait. The source is an undated photographic portrait of la Cour, in the public domain by age, and it is small and soft: a few hundred pixels across, nothing like enough to print. That is exactly why this is an engraving. The lines can be drawn at any size, and the photograph only has to say how thick each one should be, which a program decides by reading the local tone. No generative model touched it, nothing was sharpened into existence, and no part of his face has been altered.

The rule for this series is that a cover portrait is a document or it is openly a drawing, and it is never a photograph of something that did not happen.

The full account of how this book was made, including which parts were written with the help of a language model, is on the copyright page and on the back cover, itemised using the five credits published at bookcredits.org.

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