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5 Watts for $25
This is a project to make a wind turbine that has performance and price comparable to a 5 Watt solar panel. The idea is to make as much energy as a 5 Watt solar panel for a material cost of $25. Such a device would be used in a place such as Haiti where the infrastructure was destroyed by an earthquake to provide low wattage power for lighting. The idea is to compliment the solar panel in systems such as these: http://www.addyourlightproducts.com/
At this time I am shelving this project because I haven't been able to design a successful turbine that can meet the budget target. The biggest problem I ran into is the bearings. The bearings are only separated by 3/4" and any abnormal loading on the blades results in high bearing stresses and enlarging of the hole in the plate. I want to try a slightly different approach without the $25 limit.
Currently, the pole plates have been cut and formed. The bearings fit into the pole pieces and placed on a test stand. Spacers were added to relieve the bearings of loads caused by the magnets attracting eachother. Of course that adds cost, but it should help with performance. Holes were added to the tabs to facilitate the use of screws if necessary or, as in the photo below, zip-ties.
A Quick Test Run
I just put the turbine out in a very light breeze to see if it would turn. The blades are mounted at an 8 degree angle and are fashioned like a Lenz2 only the curved part only forms a quarter circle.
I've decided to wind this stator as a serpentine coil with 100 turns of 26 AWG wire for each leg. The first step was to wind the coils on a 9" diameter form. The wire was then bent and positioned using a fixture as below.
Fixture pdf file. If you print it, be sure you are printing at full scale. (Check dimensions)
Some photos of pouring the stator. The form is simply two sheets of wood with a 1/2" hole drilled through the middle to position the shaft. Between these two sheets is a 1/4" board with a 6-5/8" diameter hole cut in it. Everything was waxed throroughly before pouring. Masking tape was wound around the cable to seal the tube on the bottom and keep resin from leaking out. The wires were fed through holes near the upper end of the tube and these were soldered to the ends of stator coils. Fiberglass cloth was used to give the final product a little more strength.
Final assembly simply involves sliding on a couple washers to act as spacers, sliding on the rotors, installing a few spacers and topping it off with a CPVC cap. The blades will be added later after some electrical tests and blade performance checks.
The unrectified voltage output of the turbine was measured for various RPMs using an oscilliscope. The magnitude of the output was promising as can be seen in the figure below. The data lies along a line and the peak to peak voltage is quite high. Using all three phases, the generator should begin to conduct into a battery at around 90 RPM. (Assuming a factor of about 1.4 instead of 1.7 because the waveform is not quite sinusoidal.)
The bad news ...
As can be seen from the photo of the oscilliscope output, the phase angle of the generator is wrong. The two curves are 60 degrees apart and they should be 120 degrees apart. One of the coils must have been wired backward. So to get the full capability from the generator, another stator will have to be poured.
5 Watts for $25 v. 2.0
While I was quite happy with the performance of the previous turbine, it is becoming apparent that lift style blades will be a necessity to keep costs down. The higher speed will limit the amount of copper required. A second version is now in the works that will have a few improvements over the previous one and facilitate the use of lift type blades.
Please Note: Information displayed on this web site in text and/or video form is for documentation purposes only. Nothing presented here should be considered professional advice or instruction. The visitor should follow safe procedures in their own projects and check all information for accuracy. Caleb Engineering, LLC is not responsible for any losses that may result from errors, misprints or display of improper procedure.