We live on a forested hillside with mountains on three sides, where the winds that we experience are highly variable with abrupt changes in direction. After visiting Hugh Piggott's Web site and reading his book, "Windpower Workshop," I realized that we live in an area that is not well suited to wind power. However, we needed something to supplement our solar panels on the dark, cloudy days of the rainy season, so I was not willing to give up on the idea of wind power, especially since we often have winds night and day during the cloudy season.
On the Web I looked at some designs of vertical axis wind turbines and decided that I might adapt one of these for our site. It would have the advantage of standing up to our gusty winds with often violent changes in direction, it would be quiet, and it would be bird friendly. Acknowledging its inefficiency, I will refrain from calling it a wind turbine and instead call it a garden ornament that generates a little electricity.
I started by bending some ribs out of 1/8-inch x 3-foot welding filler rod.
I inserted the ribs through holes drilled at 30-degree angles to one another in a spiral around a 1/2-inch galvanized electrical conduit and glued everything in place with epoxy cement.
I then glued panels of heavy poster paper to the ribs.
My idea was to make a double helix symbolic of DNA.
I painted the poster paper with a couple of coats of polyester resin and smoothed out the ridges and bumps with autobody filler. After sanding everything smooth, I put a layer of fiberglass mat on each side and applied another couple of coats of polyester resin.
Not wanting the thing to be translucent and show all my messy filling and patchwork, I applied a final coat of polyester resin to which I had added finely ground charcoal. This photo shows one of the problems that I ran into because of my lack of experience with polyester resin. The resin shrank as it cured, creating dimples in the underlying paper.
All black just didn't look right, so I painted one side to give it some color and to make it look interesting as it turned in the wind. And turn it did! Hanging by a rope from a rafter in the carport as I painted it, it clearly wanted to "fly."
For the alternator, I adapted one of the designs in Hugh Piggott's book, "Wind Turbine Recipe Book." But before I could start making the alternator, I had to make a little coil winder. Every turn of the crank tripped a counter so that I could be sure that each coil had the same number of turns of wire.
This is the setup for winding the coils. Each coil had 320 turns of 21 AWG magnet wire. You can see a couple of finished coils on the table in the background.
I placed the 12 coils on a pattern that I had drawn on paper to get them properly aligned and then glued them together with patches of fiberglass cloth.
I then made a mold out of plywood, with the placement of the coils clearly marked on the bottom.
I used a wooden "spider" tied on with string to lift the ring of coils as a unit and place it in the mold. I connected and soldered the coils in 3 sets, each with 4 coils connected in series and with the 3 phases wired in a star.
With the help of a mechanic in Yuscarán with connections to junked parts dealers and a machine shop, I bought a pair of front hubs from a junked car and had 2 disks made from 1/4-inch steel plate.
Because I couldn't do any cutting, grinding, or drilling once the magnets were in place, I assembled everything without the magnets to test it. I'm glad that I did because I had to do some minor adjustments that required some drilling and grinding.
I then removed the top disk and checked the placement of the stator. The stacks of nuts and the washers fix the space between the two disks, since I would not be able to use a wrench once the magnets were in place.
This is the mold for the cowling. To make the dome, I made a "wedding cake" from a stack of polystyrene disks, "frosted" it with autobody filler, and filed it to shape with a bastard file. The skirting is a strip of aluminum flashing.
I made the cowling in two halves to facilitate mounting it. I painted the mold with polyvinyl alcohol (release agent) and then applied two layers of fiberglass matting with polyester resin.
This is the completed cowling being tested for fit before installation.
To place the magnets precisely, I used a cardboard template.
I glued the magnets in place with super glue, alternating the north and south poles facing upward. The marked magnet is to be sure that the magnets of the facing disks line up with the correct polarity.
I placed the disk with the attached magnets into a waxed mold.
I poured polyester resin into the mold, and after it was set, I painted on more polyester resin, placed a piece of fiberglass matting cut to shape on the wet resin, and painted more resin on top.
This is the cast rotor disk after removal from the mold.
I cast both rotor disks in the same manner. I then sanded and painted everything to protect it from moisture. By adjusting the screws, I lined up the stator between the rotor disks with a 1 mm space between them. Mounted on the bracket below them, you can see the bridge rectifier on the right and the box for the "kill" switch on the left.
This is how the whole thing looks after setting it up. After I fixed a squeaky bearing, it is silent, and in a good wind, our "garden ornament" will generate 500 watts.
No comments:
Post a Comment