Page 12 RAIN July 1981 HOME BLOWN ENERGY A Look at Do-it-Yourself Wind by Micheal K. Nelson Small wind energy conversion systems are a backyard tinkerer's delight. Building one is quixotic, a dream of the earth and air shedding bountiful energy in a kinetic display of spinning blades. The rustle of leaves, a spring breeze, will arouse the gadgeteer in us to fantasies of home built pinwheels sprouting in the back yard. But our dreams can be quickly dashed by any well-read renewable energy expert. This type is quick to point out that home-built wind systems usually s_elf-destruct rather quickly when pressed into service. According to the average expert, it is wiser to spend our money on one of the many available commercial systems. He will usually go on to explain that there are few, if any, cost-effective locations for commercial systems where we live. The Bonneville Power Administration, for example, recently had two 1500-watt Enertechs installed near Goldendale, Washington. They estimate the per kilowatt hour cost of power from these systems to range from 17 cents to 38 cents. Costs such as this look pretty grim even when contrasted with thermal power. Bonneville's installation costs included a free-standing tower which could just as well be replaced by a guyed tower without compromising the system's integrity. They paid $8,000 for each system. A 1500-watt Enertech can be installed by the homeowner for about $5,500. Given the 40 percent tax credit, the bottom line is about $3,300 if the owner·does her/his own installation. Such an installation would produce power at between 7 and 15 cents/kwh at Bonneville's two sites. The 7 cent price tag at the first site is clearly cheaper than a new coal plant at 8 cents/kwh. There is an answer to all of this, of course. The owner-builder had it all the time. Go ahead and build it, or at least install it yourself. After all, even if it does fly apart in your backyard, at least you will be able to fix it yourself. Being able to maintain your wind system is almost a necessity for a cost-effective installation. A high reliability 1000 to 1500 watt wind system can be built by the owner-builder for under $1,500. Power from such a system would run as low as 3.2 cents at the Bonneville test site. Until mass production brings down the cost of commercial units, the only systems that are going to be cost-competitive in areas like the Northwest are the much maligned homebuilts. The generators that our renewable energy expert has in mind in his blanket condemnation are usually built out of old bicycle parts or junked automobiles. They are examples of attempts at appropriate technology using inappropriate parts. What our expert friend is overlooking is that the systems he has read about were failures primarily because they were first attempts. A second generation of commercial systems is appearing now. They are more durable and better built than the last. A second generation of homebuilts is also upon us. They too are the products of past experience. Backyard tinkerers have learned from their own and others' mistakes. A person doesn't watch six months' work self-destruct in a gale force wind without picking up a couple of insights. Before running out and carving a propeller or purchasing an Army surplus generator, do a careful literature search. Read everything you can find on wind systems, both commercial and homebuilt. Go through back issues of Windpower Digest and Alternative Sources of Energy magazine. Buy Jack Park's The Wind Power Book. Talk to people. Look at commercial wind systems. Understand how they work. Don't take anything as gospel. Remember that the test of a wind machine is survival. Look at systems that are working. Ask other people why theirs isn't. Get several sets of plans. Figure out what is wrong with every design that you look at. Above all else, learn to apply the dictum of St. Exupery, "A design is complete not when there is nothing left to add, but rather, when there is nothing left to take away." Simplify! Every addition to a wind system is another point of potential failure. Choose components that will stand up to weather, stress, fatigue, lightning. Build it to feel more like a product of the John Deere Tractor Company than an aerospace industry product. Quite a few sets of plans are appearing on the market, but it will be up to the home builder to separate the wheat from the chaff. Most of the plans that are available will require modification by the builder. The most frequent modification will be beefing up the hardware used. Also, most of the overspeed mechanism will have to be examined with a critical eye. Alternative Sources of Energy #24 contains a series of plans that are well worth examining. There are three sets of plans contained in this volume. Each is worth stealing an idea or two from, although all of them suffer from components which are too light to insure long-term durability. The first of these, the Noble wind generator, is an upwind horizontal axis machine that uses a pitch control governing system. The propeller is fabricated from urethane foam coated with glass and epoxy. Probably the weakest point in the design is the use of a chain sprocket in the first stage of the gearing mechanism. Mr. Noble acknowledges that this may have to be replaced. The machine is probably stout enough to run the 42 amp Delco alternator used, but if the system were sized up to a 1000 watt output, heavier parts might be required. The second system in this issue of ASE was designed to use the coning angle of the blades as an overspeed control mechanism. Unfortunately, a control system such as this has to fight the centrifu-
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