A homemade Wind Turbine

And a brief description of the construction thereof.

wind turbine

Electricity is expensive to buy, but as it turns out, not all that expensive to make. Provided of course you don't intend to compete with Drax, or supply the whole street. This ramble describes the process of making a wind turbine in a light hearted way, it is not detailed instructions on how to manufacture your own turbine, but it may be of assistance to anyone contemplating the hows, whys and mechanics involved in such an undertaking.

Too many words, skip to the end.


If you have a shed, it makes creating stuff a lot easier, I mean sure, you could build a helicopter on the kitchen table after tea, but then you have to put everything away before bedtime so that the table is free to eat breakfast off. The moving stuff around takes up far more time than the project you are trying to construct does. This is where the shed comes into it's own, you can lay stuff out and work on it, close the door and go do something else, and then return to the shed, open the door, and be right back making stuff again, no moving this and tidying that, it's just, well, better.

pole

The pole I acquired to put the wind turbine on.


The first thing that is needed when building a wind turbine is somewhere to put it. It is no good building the best wind turbine ever seen, if you have to keep it under the bed or behind the sideboard. I acquired a pole for this purpose. It is an ex-electric company pole, one of many that the electric companies remove and replace every year, so it is already treated with creosote or bitumen and used to being outdoors in the rain. I'm sure that not everyone can just erect a 25 foot pole in their backyard without attracting attention. Let's just assume for a moment that your neighbours are OK with the idea, you still have to be prepared for when the local council turn up with their hand outstretched. (Remember, there is nothing that money can't fix.) How you proceed is your problem, I'm just pointing out the possibilities.

You could attach a moderately sized wind turbine to your house, but bear in mind that it is a piece of moving machinery and will at times be under severe stress from gusts and gales, and any minor imbalance will cause vibrations which need to be taken into consideration, or it could literally shake your house to pieces. This is why a good pole is the best solution. A new pole will set you back £200 or so, a good second hand one, a good deal less. You still need it delivering and erecting, which will incur additional costs of course. Your pole should comply with BS EN 1990, or some jobsworth will find fault with it, which will only further increase your construction costs.



So having procured a pole, the next thing is to build the actual generator. The large wind turbines that you see on wind farms, make 'mains' or 'grid' electricity, 230 volts AC @ 50Hz. Which is fine if you have loads of money, a big enough pole and are prepared to deal with the complexities that this entails. But my wind turbine is not like them, it is similar in many respects, but much simpler, both to build and to operate. Back in the 19th century, scientists figured out what they called electromagnetism, just google it if you need more detail. What it means in practise, is that if you have a wire and a magnet close together, by moving either the wire or the magnet, a current will flow in the wire. This is the basic principle that the wind turbine is based on. So to make the generator, we require both wire and magnet, arranged in such a way that a rotating motion causes the wire and the magnet to move with respect to each other. The wire is where your freshly minted electricity is going to come from, so of course it requires extending to a place where you can actually use your home made electric. It therefore makes sense, that if something is going to have to move, it really should be the magnet, otherwise the wire gets all taffled up and eventually breaks.

coil

The wire, all coiled up prior to encapsulation and the generator clamped to the bench for testing.

With this mind, we can design the generator in such a way, that the wire stays still, and the magnet moves, the piece with the wire that stays still is called the stator, and the bit with the magnet that moves, is called the rotor. Wire, being flexible and wobbly, has a hard time staying still, especially when being accosted with a moving magnet, so the wire is coiled up into tight little bundles and encapsulated in polyester resin. This prevents the wire from moving and makes the whole thing easier to deal with. You need a lot of wire, otherwise you only make a little bit of electricity, and if you're going to the trouble of having an erection of this magnitude, you might as well make the best use of it and produce as much as you reasonably can. I used a total of nine coils of wire, three coils per phase, this allows me to make three phase electricity, which, as everyone knows, is the best kind of electricity to have, being of a higher quality than the normal kind. The wire costs in the region of £40 for enough to make all the coils. With all this wire, all coiled up and concentrated in one place, you need a really good magnet. The one you stick your shopping list to the fridge door with is really not up to the job. I say 'a' magnet, but in reality I used 24 magnets, arranged with alternating polarity, North, South, North, South. etc., attached to two steel discs, a foot or more in diameter, thus making two really big magnets from 24 little ones. When I say little, they were one inch by two inch by half an inch, not really that small. The magnets were grade N42, neodymium, so called, rare earth magnets, wickedly strong and could quite easily break your fingers or cause other severe injuries if not handled with extreme care. These magnets are around £3 each.

chassis and mount

The naked chassis and the mount for the top of the pole..

The steel discs with the magnets attached, are also encapsulated in polyester resin, it serves to protect the magnets from moisture which causes them to rot, and also helps to keep the individual magnets in the right place on the disc. The magnetic forces are incredibly powerful, and a blob of glue is no match for two magnets trying to attack one another. The discs are mounted on a stub axle, reclaimed from an old car in a scrapyard, I'm sure new ones are available but I'm a big believer in good second hand bits, it is invariably cheaper to begin with, and also good for the environment, reusing things that would otherwise be destroyed. The stub axle is mounted on a backplate and the magnet discs, (rotor) and the coils of wire, (stator) are assembled using stainless steel threaded rod. The use of stainless steel is not to prevent it going rusty, but because of the non-magnetic property of stainless. If normal, mild steel threaded rod is used, the rotor doesn't spin smoothly because the magnets are attracted to the mild steel and causes the rotation to feel lumpy. The high quality three phase electricity is fed to a bank of rectifiers, which cause the output to become DC, which is then connected to a bank of lorry batteries. This 24 volts is the end product of the generator. There is no phase matching required, it doesn't really matter how hard the wind blows, 24 volts DC is 24 volts DC, no compatibility problems at all.

chassis

The blades and the tail.

The chassis was constructed from some box section that just happened to be a good sliding fit over a scaffold tube. This allows the whole thing to rotate and follow the wind, and was cheap because it required no expensive parts to produce. I'm sure a more elegant solution could be found, using roller bearings and whatnot, but I doubt that a cheaper variant could be made. The tail was made from some scrap tubing and is around 8 feet long, the actual vane area of the tail which is responsible for keeping the wind turbine pointing into the wind was made from a reclaimed plywood crate and is somewhere around 4 square feet, which is enough surface area to control the rest of the wind turbine. The turbine blades, which are each 5 feet long, were carved by hand from old ¾" plywood shelving and then painted with a tin of the finest white gloss that I found in a skip. Balancing the blades was fiddly because it had to be done outdoors due to height limitations inside the shed, and it had to be done in that 15 minute period just after tea when the wind stops blowing, otherwise they just caught the slightest draught and set off spinning. The hardest part was getting the whole thing mounted on the top of the pole. It took me and a local farmer with a forklift, to get the turbine high enough to lower it onto the mount that I had previously attached to the top of the pole.

TL;DR - Conclusion.

I have since purchased some cheap solar panels off the eBay and have got these wired up to the same battery bank. The state of charge is monitored by a small computer which controls the whole system with relays. The 24 volts in the battery bank is used to power an inverter. The output of this inverter is used to power the central heating boiler and pumps, the fridge and the freezer and all my computers. In the event that the sun isn't shining and the wind isn't blowing, the computer switches the whole lot over onto the mains. If there is a power cut, it automatically uses the power stored in the batteries, to keep the heating on and the fridge cold. This is an on-going hobby/project and the configuration changes regularly as I play around and fiddle with various bits.



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