Posted: 6/2/2011 6:46:31 PM EDT
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I've heard of people who tie a solar array, windmill or hydrogenerator into their house and the electrical meter runs backwards during times when they are producing more electricity and feeding it into the grid than what the house is consuming. Well today was a windy day and I had a box fan plugged in and facing the window. The fan was turned off, but the breeze was blowing and making the fan rotate. Would this make my meter go backwards? Would it matter what direction the fan was blowing (clockwise vs. counterclockwise?) Should I buy a bunch more box fans and plug them into a power strip, and put them into the backyard so I can have my own wind farm? |
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Quoted:   Not sure if serious... Of course I am serious. Electrical motors and generators are designed very similarly. In fact, if you take the motor out of say, a model race car, and hook the two power leads up to a volt meter, you will get a reading if you spin the motor by hand. The whole alternating current thing though confuses me. I am not sure if it would still work that way. Waiting for an answer and explanation... |
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I am not an electrical expert, but in order for it to be a generator you have to have it hooked up to something. On the most basic level, your fan with the switch turned off is not connected to the grid so it cannot produce power to the grid. Your fan only turns so easily because there is no load to stop it from turning. Its only slowed down by friction and air resistance. If you hooked up your fan blades to a generator, that generator would have to be small to be able to generate any power at all. Think about it, what would happen if you replaced your fan motor with a car alternator and a battery and sat it in your window? You guessed it, nothing.  |
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Quoted: I am not an electrical expert, but in order for it to be a generator you have to have it hooked up to something. On the most basic level, your fan with the switch turned off is not connected to the grid so it cannot produce power to the grid. Your fan only turns so easily because there is no load to stop it from turning. Its only slowed down by friction and air resistance. If you hooked up your fan blades to a generator, that generator would have to be small to be able to generate any power at all. Think about it, what would happen if you replaced your fan motor with a car alternator and a battery and sat it in your window? You guessed it, nothing. Awwww sheeit. I hope there's still time to cancel my Amazon order for 3 dozen box fans! |
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Power derived from wind has an actual mathematical formula created about 100 years ago. I forget what it is exactly, but there's three important figures in it:
The diameter of your turbine, windspeed, and your actual efficiency. In a steady 12 mph wind, even a decent 15 ft diameter home made jobber is only going to convert around 120 or so watts of wind power to electricity. I won't swear to these figures as it's been awhile since I did the math, but I think they're in the ballpark. But more importantly, some rules of thumb. Double diameter, multiply power by 4. Double windspeed, multiply power by 8. This is all a gross oversimplification. Alot depends on how the alternators on them are wound. Some produce alot of power in higher windspeeds but none at all in lower windspeeds. Some are less efficient overall, but are wound to produce power even in low windspeeds. But take your box fan idea. What's the diameter on that? 2 feet? So roughly 1/64 that ballpark figure I gave assuming the same windspeed. Each one would make you less than 2 watts of power. That windspeed estimate is generous, too btw. It assumes you're able to put them all on a bunch of 15 or 20 foot towers. Wind turbines need to be a good 15 or 20 feet above nearby obstructions to get less turbulent/higher speed air. |
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