# Project: Charging devices with Eolic (Wind) Energy

1. Oct 19, 2015

### Nexo

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.

2. Oct 19, 2015

### rootone

Yes you can run an electric motor in reverse and have it act as a generator.
It won't be particularly efficient since it isn't designed for the purpose but it should work.
In addition to the 'generator' (the fan), it will help to add a rechargeable battery which can store the output continuously (until it's fully charged).
Now you can charge the phone from the stored energy collected in the battery even when there is no wind!
A voltage regulator circuit could be added to improve efficiency further but that is not necessarily needed.

3. Oct 19, 2015

### rbelli1

That type of fan typically uses a brush-less DC motor. This type of motor is a multi-phase electrically commutated device. You will not get any power out of it unless you replace the circuit.

BoB

4. Oct 19, 2015

### davenn

agree with Bob on that one .... no it wont work with that type of motor

5. Oct 19, 2015

### rbelli1

I've never tried it but an n-phase bridge hooked up correctly would give you something. I just checked a broken one I have here. It has a rather weak vinyl magnet in it. I doubt much power would be created even if you modified it.

You also want lots more swept area to get any usable amount of power. If you want to use broken computers for power your best bet is to use the magnets out of several hard drives. You might be able to get a reasonable amount of magnet wire out of the power supply too.

BoB

6. Oct 19, 2015

### Nexo

Thank you very much for your response.
I've heard that before (the efficiency part). There is no way to buy the fan with the generator integrated? Just as the on I have but instead of being a motor, it would be a generator.

I don't quite understand the difference, the motor can create energy as well as the generator, right?

I'm thinking about adding that additional rechargeable battery and my question is: If this motor generates 12V of output, can I redirect 5V to the smartphone/tablet and the other 7V to the rechargeable battery? If not, I can use a smaller fan, right?

I was thinking about the voltage regulator for the following: 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 damage the smartphone/tablet?

Thanks again.

7. Oct 19, 2015

### Nexo

Thank you all for your responses.

So, is settle, the motor is not an option. Therefore, I ask the following question: There is no way to buy the fan with the generator integrated? Just as the on I have but instead of being a motor, it would be a generator.

8. Oct 19, 2015

### rbelli1

If you get a large fan with a standard induction motor you could use that but it is not as simple as cutting the cord off and plugging it into your cell phone.

The motor needs to be rewired and an excitation current is necessary to start it all up. That gets you ac power. Then you need to convert that into 5V DC to charge your phone.

None of this is particularly difficult. You would learn a lot doing it. It is similar to the alternator in a car.

BoB

9. Oct 19, 2015

### rootone

1. As the other guys said, some kind of motors can easily be made to work backwards as generators, others kinds are not worth the effort.
2. Yes of course you can purchase small scale wind power generators, but since the power requirement to charge a mobile device is so very little, I doubt it makes economic sense.

10. Oct 19, 2015

### Nexo

How can I differentiate between a DC motor and a generator?

11. Oct 19, 2015

### rbelli1

A permanent magnet mechanically commutated DC motor can be used as a generator without modification. Most other types need some added circuity to be used as a generator. There may be some types that will not work at all as a generator.

The application as a phone charger will need some voltage conversion no matter what. It is unlikely that you will get exactly 5V out of any kind of generator.

BoB

12. Oct 19, 2015

### Nexo

I've seen a video in Spanish in which the kid uses a similar fan to mine (although smaller) and it generates up to 13 V.

And in a second video (also in Spanish) the guy changes the motor of the computer's fan for a generator and this only generates 2 V.

This is so confusing

13. Oct 20, 2015

### rbelli1

Both of those videos use permanent magnet mechanically commutated DC motor for the generator. The PC fan is just used for the fan blades. The two motors likely have different numbers of windings on the armature and are spun at different speeds so they produce different voltages.

BoB