Good evening, everybody, I'm new here so if I made any mistake, I apologize in advance. I've been thinking in a project from a while now and I want to share it with you seeking for your help and wisdom. Basically, I want to build a small wind turbine in order to charge a smartphone or a tablet and so far I have the following: 1. I found a rather big computer fan and these are its specifications: Name: Yate Loon D14BH-12 More: 2-pin, 12V, 0.7A @ 2800RPM, 140CFM, 48.5dBA Here is a photo: So my question is: - If this fan needs 12V in order to work and it's RPM is 2800, could I use it the other way around? I mean, Use the wind in order to create energy. Note: I made a small test connecting a small LED and I made the fan spin and it turned on a little bit for a little while (about 2-3 seconds) and it's obviously because of the poor spin I created. I live in a pretty windy city and I wanted to know what would happen if I'm able to reproduce those 2800 RPM? Would that create 12 volts? - If so, how can I know the amperage? Because the smartphone needs ~2.1 amps and 5 Volts DC to charge. - So, If I get those 12 volts, would it be necessary to reduce them to 5 volts? or can I send 5 volts to the smartphone and 7 volts to a secondary battery that I could use later on in order to charge the smartphone when there is no wind? Note: I could use a smaller fan in order to get those 5 volts. - Another question is: The wind is not going to be constant, a moment it can have a high velocity and a few seconds later it may not be windy at all so the fan will produce different voltage, Am I right? If so, How can I regulate the output of voltage and amperage in order to not blow my smartphone? This is by far the main questions I have. I apologize for my English. Hope you can help me, guys. Thanks in advance.