Micro wind turbine - weather station

[Vladymir]

Hi everyone!
I'm building wireless weather station. The sensor will be located away from my house and because it consumpt a little bit of energy (few mA) it has to be powered by it's own energy supplier.
I've been thinking a lot, and the best option in this case seems to be micro wind turbine.
The avarage sensor power consumption is about 15mW up to 20mW, so the the turbine should deliver 20 up to 30mW in lowest wind (i wish 2m/s or less) and more in strongest wind.
This all will be storage in rechargeble batteries or in supercapacitor.
My question is: What type of electric motor will be appropriate? What about power electronic system?
regards!

 

[c_mitra]

If the duty cycle is around 50% (the wind turbine is producing 40mW power 50% of the time and very little rest of the time), most small motors can be used as generators. Perhaps you can also consider BLDC motors as possible generators and they will produce an AC power that can be rectified directly.

You need to consider various inefficiencies at several levels; if you need 15-20mW power for the sensor you should keep some reserve. You need regulators and stabilizers and the final power output at the generator may be 50-60mW. That can be easily met with a toy motor used as a generator. You need to experiment. Most critical part of the design will be the turbine.

 

[BradtheRad]

Spin a small cassette motor and it becomes a generator. Experiment with one to see if it provides sufficient voltage and mA. You may find you need to combine two or more.

 

[KlausST]

Hi,

Most probably the turbine wheel will not spin fast enough for the motor to produce enough voltage....
Then consider to use a gear box to increase motor RPM.

Klaus

 

[Vladymir]

1) I consider BLDC motor to be the best option, but I couldn't find a BLDC motor with low RPM value
What about AC motors?

2) What about electronic converter system between motor and batteries? Do you have any idea?

 

[c_mitra]

1) I consider BLDC motor to be the best option, but I couldn't find a BLDC motor with low RPM value

You need a 4 or 8 blade propeller to attach to the BLDC motor; you need one that will produce 5-7V output with 20-30 RPM. You need to experiment. The output must be regulated with some electronic converter. The propeller must be able to handle 5W of power (only part of the power will be converted into electricity).

Most AC motors will not work as a generator but brushed DC (universal motors) will work but the output will be strongly dependent on the RPM

 

[Vladymir]

My first idea was to use anemometer cups as a turbine. It's very simpe and the main reason - it's sensitivity for lower winds.
The anemometer cups can start rotate from about 2m/s and increase rotation with higher speed value.
But the problem is low rpm value.
What do you think about motor used in this project **broken link removed** ?

 

[BradtheRad]

What do you think about motor used in this project **broken link removed** ?

This project looks interesting. It requires extreme care to balance the motor on its pivots.
Do you have a supplier for the special cylindrical magnet?

Have you considered using a solar panel? Or rather, a string of small PV panels in series? You might even be able to fabricate your own, using experimental methods found on websites. A large homebrew panel is needed because their efficiency is low.

 

[Vladymir]

I've considered, but because of long nights in winnter months in my country, it wouldn't be the best solution.
And sun shines only in the day, wind blows constantly.

 

[c_mitra]

My first idea was to use anemometer cups as a turbine. It's very simpe and the main reason - it's sensitivity for lower winds.

This is an excellent idea and you can mount the motor vertically and many balancing problems will be gone.

Low RPM will produce low voltage but power output will depend on the size of the cups.