Hi, This is my first posting, so I'll just introduce myself. My name is Bryan and I've been working on vertical axis wind turbines for a few years. I am a Mechanical Engineer by training but now I'm a stay-at-home dad. I started Caleb Engineering a number of years ago to do contract machine design out of my home; thus the name Caleb on a lot of things. My hope is to develop a VAWT worthy of selling someday, but for the time being this is more of a hobby. In the past, I posted my work on the forum at vawts.net; however, that forum is no longer up and running. I'm hoping it would be okay to start posting here. This video is a short demonstration of my latest VAWT. Currently, I have been working on the control side of things. Lift style VAWTs have a rather narrow power band and I've made a "shield" for an Arduino that should allow me to program the current being drawn from the wind turbine up to 4 amps into a 12 volt battery; about 50 watts of controlled load through a buck type regulator. The initial tests of the board have been promising, but I have to get a battery and assemble another wind turbine to test it with. So it will be a little while before I can report on it.
Hi Bryan, welcome to the board and glad you landed here. Nice VAWT and it really works! We wish you success! Everybody always wants one. I have a Ginlong PMA down in the garage just waiting for something like that.
I've only been able to demonstrate 3 watts output in about a 5 m/s wind. I'm hoping for at least 20 watts out in an 11 m/s wind. The turbine is 0.35 m^2.
Here is a video of the control circuit. The idea is to control the load on a VAWT so that it stays near the optimum tip speed ration since lift type VAWTs may stall if overloaded and lose power. By using the current controller, I should be able to look at the input voltage, calculate a desired current, convert that to a PWM value, and output that signal and get the desired current. It won't be perfect. I'd be controlling current to the battery as opposed to current from the turbine. I was figuring on estimating turbine current based on the input voltage, output voltage and an assumed efficiency. I have to assemble another VAWT to actually try it out, but it looks like it will do the job. The transistor does get hot when running a couple amps through it. The next version would have a heat sink and the micro-controller will probably be mounted right on the board.
Here is that latest controller. There were four things I did not like about the previous controller: it did not have its own micro-controller, it only controlled output current so I had to guess what the input current was, there was no direct RPM sensing (it had to be estimated using input voltage), and one or more components was getting hot. So here is a controller that controls the current going into it (out of the turbine). An ATTiny85 sets the current to be proportional to the square of the RPM.
This is a copy of the previous VAWT and the latest version of the controller. Now for some wind to try them out together.
