Bench Degree·WIND POWERchapter

Appendix A: The Bench

The whole volume’s kit in one place. Every experiment in this book is on this list, so you should never have to stop mid-chapter and wait two days for a delivery. Each chapter names what it needs when it needs it and points back here; if you would rather order once and be done, order from this list.

This is the cheapest volume in the series, and it is not close. Chapter 1 costs about $15 if there is a box fan in the house, and it puts the central result of the book in your hands: two rotors of the same size in the same wind, one of which produces several times what the other does.

The starter set that carries you through Chapter 6, which is the whole of the aerodynamics, is about $65. Bought new from nothing, the entire volume comes to roughly $200, and a third of that is one optional instrument discussed in Section 4.

Nothing here is specified by brand or by part number. Every item is described by function, size or rating, so the list stays orderable from anyone, anywhere, for as long as the book exists. Suppliers change and a printed link dies permanently. A specification does not.

Section 1: The starter set, for Chapters 1 to 6

Starter set total: about $65, or about $90 if you need a fan and a kitchen scale.

Section 2: Added for Chapters 7 to 18

Second set total: about $135, and about half of that is the anemometer.

Section 3: Free, and worth more than most of what is above

Section 4: The one expensive thing, and whether you need it

A logging anemometer. A unit with a data output and a mast costs $60 to $150, and a proper met mast is a different order of expense entirely.

You do not need one, and Chapter 10 says so in the box itself. The alternative is a hand anemometer at about $30 and a stubborn habit: readings at the same times each day, written in a notebook, for a month. The distribution you draw from a stubborn month is good enough to make a real decision with, and the chapter is honest that a month of hand readings and a year of logged readings answer different questions.

Where the logger earns its money is if you are actually considering buying a machine. A small wind turbine is a four-figure purchase whose output depends on the cube of a wind speed you have not measured, so $150 spent on measurement before $4,000 spent on hardware is the best value in this entire volume. Chapter 15 exists to talk you out of a bad site, and it can only do that with numbers.

What to buy first if the budget is one item: the hand anemometer. It appears in five chapters, it makes Chapter 5’s Betz demonstration quantitative, and it is the difference between knowing your rotor is better and knowing by how much.

Section 5: What you already own more of than you think

A box fan is a wind tunnel. Not a metaphor and not a compromise. It gives a steady 2 to 4 m/s (6.6 to 13 ft/s), it has speed settings, and every aerodynamic result in this book is obtained in front of one. La Cour built his tunnel at Askov in 1896 and 1897 to answer exactly the question Chapter 3 asks you to answer with a fan.

Your phone is four laboratory instruments. Slow-motion video counts rotor revolutions to better than one percent. A free sound level application measures the fifth-power noise law in Chapter 6. The accelerometer finds an unbalanced blade in Chapter 17. The audio spectrum analyser finds a tower’s natural frequency in Chapter 12, which is the number that must avoid the blade passing frequency at every rotor speed the machine uses.

A kitchen scale is a force gauge. Chapter 5 measures rotor thrust with one and gets the eight-ninths result out of it, which is the second half of the Betz argument and the half nobody demonstrates.

A wine cork is a variable-pitch hub. Drill it radially and it holds a blade root by friction alone, which is what makes Chapter 14’s feathering experiment possible, and which is also why that box tells you to keep clear.

Your car has a three-phase generator with a rectifier in it, and Chapter 11 takes a scrap one apart to explain why a modern turbine uses a permanent-magnet machine and a full converter instead.

And a paper clip is a fatigue specimen. Chapter 17 bends twenty of them through different angles, counts the cycles to failure, plots it on log paper and recovers an exponent between 3 and 5. That is the number the entire structural design of a wind turbine turns on, and it costs nothing.

Section 6: The experiments, and where they are

Twenty-seven, and the whole list fits on the kit above.

The five in bold are the ones to do if you do only five. The first delivers the whole thesis of the book for fifteen dollars, because a rotor that looks like it should be better is worse by a factor you can measure. The second is la Cour’s 1897 experiment repeated with a box fan and worse instruments, and you will get his answer. The third shows you a stall, with smoke, and after that Chapter 14’s storm behaviour is obvious. The fourth measures the thrust and finds eight ninths, which is the half of the Betz argument almost nobody demonstrates. And the fifth is the only experiment in this series whose most useful outcome is a decision not to buy something.

Eleven of the twenty-seven cost nothing at all, and four of those need only a spreadsheet, a notebook or a published data sheet. This is the cheapest subject in the series to learn honestly, and the reason is that a rotor is a shape rather than a machine: card, corks, glue and a fan will show you almost everything that a 3 MW turbine does.

The safety gear, which is not optional

Wear this for the experiments the book says to wear it for. The reasons are on the Before You Start page at the front, and in the chapter that owns each experiment.

Section 7: Kits

A single collection covering the starter set, the anemometer and the blade materials, ordered once, is the obvious convenience and it is being worked on. When it exists it will be at benchdegree.com/kit/wind-power, and that address is deliberately the only place it will be published: suppliers and product listings change, and a link printed in a book cannot be corrected. The specifications above can be taken to any supplier and will still make sense in twenty years.

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