I created three goals in my “One Goal Accomplished…” blog. I have created two lessons out of my externship. They are posted in the “Lessons on the Loose.” What I have left to do this summer is to make a windmill and remake ten calculus videos. The windmill is something that may extend beyond the summer. I am having trouble just starting. If you are not interested in making a windmill, read no further.
To start, I want to clarify the scale of my project for those that may have come across this blog in an attempt to do research on a DIY wind project. For now, I just want to be able to connect my turbine to the grid to counter some of the electric components we are running in the house. My husband and I would eventually like to live “off the grid”, but for now we are just exploring the possibilities and working to learn the process of moving that direction in an affordable way… “teacher- salary affordable” and “a high potential I buy these parts and mess this up affordable”. So, I am aiming for it to be pretty free. My ignorance is also far above my knowledge, so know that I am not at all a credible source. I have, however, included the very helpful links I used. Believe me, I know this research results in a web of questions.
I began this project by researching fin design. I thought that was a good place to start because I was sure that there was a perfect mathematical design that would maximize the efficiency of my turbine. My husband actually accused me a trying to math this project to death. My mind was being boggled as I battled with aerodynamics. Then I found http://sc4geography.net/windmill/description.html - another great account of someone’s experience with a DIY wind turbine. I used this as a big reference. I think the best thing was finding the following quote at the link I mentioned above:
“This process can be very educational and you can get carried away with this if you are not careful. If you are looking for the perfect design, stop right now. After 3000 years of windmill technology, there is still no perfect design. There are advantages and disadvantages to every design (in my opinion).”
It was at this site I had to change the game plan because I found in this and several other readings that selecting a motor was in fact the place to start.
Motors will produce a certain amount of voltage given the rotations per minute. I was working backwards. Given that motors are already built with specified Volt-to-RPM Ratios, knowing the motor you have, you can design your blades to ensure they are capable of the desired RPM.
Here are some things I learned in my motor research:
1.) I preferred to find a brushless motor- some motors, expecially treadmill motors have brushes on them. Brushless motors are more weatherproof than those with brushes (http://sc4geography.net/windmill/description.html)
2.) I wanted a direct current (DC) motor. You could use an AC motor, but you would need to have extra hook-ups to convert the energy correctly- I will not even pretend to understand why. I originally had the idea of using a fan motor, but that is AC you see. (http://www.instructables.com/answers/AC-Motor-to-Wind-turbine/). Good DC motors would be treadmill motors, washing machine motors, moped motors,… car motors, but they would require a lot of torque to get going.
3.) I was looking for a motor in the ball field of 3 amps given the average windspeed of 13 mph around here, and a ratio of .035 Volts-to RPM as specified at http://www.windynation.com/articles/wind/making-wind-power-how-choose-right-motor . There are excellent explanations at this website.
4.) I wanted free or at most a $30 motor.
I did many calculations and had idealizations of the perfect type of treadmill motor I could find. Looking though ebay, the prices of not free were a bit too high because I am a cheapo, so I resorted to searching for free treadmills on Craig’s List. The travel time and the fact that I could not know the volts, amps, and volt’s-to-rpm ratio without disassembling it first made me go back to ebay.
And so I am waiting- waiting for a treadmill to magically appear on the curb, or waiting for one of my low bids to win on ebay.
So, I have accepted this will be an ongoing project for potentially the year. I will take pictures and po
I will let you know what I end up with. In the mean time, I will be working on creating ten new calculus videos. I will post them here!