I had assembled all these interesting VAWT designs - but which was best for my purposes?
If I had sufficient resources, just hooking prototypes of each design up to some sort of electrical generator and measuring output power at various wind speeds would give me the answers I sought.
I settled for the cheap alternative: build small scale models and measure the rpm of each for those various wind speeds.
I said "cheap" but I didnt say "quick" - in fact this lead me off into a LOT of sub-projects, all measured in weeks rather than minutes: build a basic cup-type anemometer wind vane; work out how to measure and record its rpm (and that of the candidate wind turbine model under test) via an electronic circuit coupled to my computer's parallel port; Write software to monitor the parallel port for those signals and record them at regular intervals.
caveat; my electronics knowledge is sketchy at best, and any prototyping of circuits is always accompanied by puffs of smoke at regular intervals marking the demise of yet another semiconductor.
At first I tried to use a combination of leds and opto transistors, with a light-beam chopper to detect rpm, but I had so much trouble with extraneous light affecting the sensor that i gave it away in favour of magnets and hall effect sensors.
I used the Honeywell SS443R sensor because - well they were the only ones I could find , and a guy called Hadley Rich, who runs a small company called Nicegear that deals in stuff that crazed inventors like me like to tinker with, got them to me without hassle.
I had already got the opto sensor hooked into the parallel port (pins 12&13 for the 2 separate sensors, from memory, + pin 25=common GND ) via a LM339 comparator so left that in place and just swapped the hall effect sensor in place of the opto sensor on the input side of the LM339. It may be possible just to hook the sensor output (active low) straight into the par.port input pins. I'll put up a drawing of the circuit real soon. (postscript: done this , see later blog)
Then it was a case of a bit of C code to interrogate the parallel port and detect any change of either input pin (remembering that there are a couple of standard addresses for parallel ports, ox378 and 0x3bc, both commonly used)
I even sent the data to the web server of my router, where another program (php this time, arent I versatile! ;-) ) recorded and graphed it for me.
For a more useful analysis I sorted a coupla hours worth of readings by base (my cup anemometer) wind speed and plotted the average speed for each test model against that anemometer.
Next post: the results! exciting stuff, eh???