I bought a PMA (permanent magnet alternator) on E-bay for $130. It's based on a Delco car alternator but like many companies do, this unit was modified for being outdoors, the windings removed from the rotor and replaced with permanent neodynium (the strongest available anywhere) magnets. This eliminates the need for such high rotational speeds to generate usable power. Normally, a car alternator needs to spin at least 1000 RPM to be useful. Mine spins at 150 RPM and already puts out 12 volts, perfect for charging the bank of batteries that will power the camp.
The blades are 24 inch Turbo Torques from http://www.windynation.com/ and ran $96. Three blade designs are best in good wind as there is less drag and turbulence. For low wind, I've opted for a five blade design which makes up in torque what it loses in speed.
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| My dad in our makeshift "workshop" |
I wanted to obey the rule of thumb that the turbine reach fresh undisturbed air some 30ft above any objects. Unfortunately, I'm a one man operation. Maybe a two man show when dad's at camp. Hoisting a large mast would mean using a winch and gin-pole or hinge. I opted for a telescoping antenna mast that can easily be extended in height. Mine is 34ft extended. The mast ran around $130 and $60 for shipping. The 40 or 50ft models come in longer sections and cost a whopping $130 more to ship! Most of this project was done on a shoe-string budget to make sure it worked before getting in too deeply.
The upper end of the mast is 1-1/4" in diameter and most frames and mounts for this stuff is set up for 1-1/2". To get around this, I opted to mount the alternator, blades and tail on a frame that sits atop a 4 ft section of PVC. The PVC pipe then simply slides down over the mast. The weight and length of PVC section mean it's not going anywhere even in stiff winds. It's free to spin around the mast and face the wind. The PVC connects to a 1-1/4" slip fit connector that's threaded on the top. That in turn screws into a 1-1/4" galvanized floor flange.
I used an aluminum channel for the tail instead of the PVC because in the cold of winter, PVC may break, while deteriorating in the sun. So finally we set up the telescoping mast, only partly telescoped, and mounted to the shed instead of guyed with wires. Now it was time to test this venture for real.
The first video shows open voltage in a good breeze, the second, how much current it puts out when charging a battery. Next stop, the ridge above lot 8 with a set of 12V batteries and a charge controller. Note: We're not in the mountains here. We're in our "testing grounds", on Long Island's Peconic Bay where my father and mother make their home.
It's been frustrating at times, thinking out designs only to have better ideas or downright failures. It's also been a terrific learning experience. After all, "Many returns to Home Depot? Frustrating. Many moments working with my brother, IslandGirl, my son and dad? Priceless!"
