# How to tie (2) AC output wind turbines together?

Registered Users Posts: 122 ✭✭
I have (2) istabreeze 12V 500watt wind turbines that produces AC current. And I have a 300watt mppt charge controller for wind turbine. The controller accepts only AC input from the wind turbine and then it does it operation by converting it to dc, etc.....

To connect one of the wind turbine is no problem but how would I tie the two wind turbines to the input of the controller so that both turbine output is seen by the controller so you get more wattage?
Is it possible to tie AC outputs? how you go about this without causing any issues?

• Solar Expert Posts: 3,009 ✭✭✭✭
Re: How to tie (2) AC output wind turbines together?

Welcome to the forum Fabian.
To answer your question, it will not be possible to connect your two AC turbines together and have them work properly - - - UNLESS you first rectify the AC output of each turbine, separate from the other, to DC power. Only then can you combine the two turbines to produce a single output, which will be DC.
Good luck.
• Registered Users Posts: 122 ✭✭
Re: How to tie (2) AC output wind turbines together?

The wind turbines produce 3 phase AC current and the mppt controller accepts 3 phase input. With this is mind I have an idea.

Suppose I connect a blocking diode on one of the AC phase or blocking diodes on each AC phase to prevent one turbine current from flowing to the next turbine would that make a difference and allow the output to be double without any back feed current? Should all phase have a blocking diode and what kind/type?
If it cannot work do you have any other suggestion that might work in this regard?
• Banned Posts: 17,615 ✭✭
Re: How to tie (2) AC output wind turbines together?

If you put diodes in you no longer have AC you have DC.

If the input of the controller is meant to take the 3 phase AC output of the turbine it will not work properly if DC is applied.

You can not parallel the outputs of two separate AC sources unless they are specifically designed to do so: the Voltage, frequency, and waveform will not be in sync between two turbines except by coincidence (i.e. almost never).

In short you can't use the two turbines on the one controller.
• Solar Expert Posts: 1,571 ✭✭
Re: How to tie (2) AC output wind turbines together?
Fabian wrote: »
I have (2) istabreeze 12V 500watt wind turbines that produces AC current. And I have a 300watt mppt charge controller for wind turbine.

So 1000W of potential power from the wind turbines and a 300W controller. Even if you could tie them together in the same controller, why would you? It seems you'd be running a risk of overcharging the batteries and/or burning out the controller since the turbines can produce much more than the controller can handle.
• Registered Users Posts: 1
Hi Everyone, I so hope this forum is still live.
We live in South Africa where our National Energy Provider is fast becoming obsolete. It seems that tfe service is next door to non existent and the prices just keep going up and up. Massive equipment failures take place daily due to poor maintenance of sub stations and constant load shedding.
So we NEED to get off tfe grid.
We have available 2 3kw VAWT's with 3phase 48volt alternators and also a rectifier with each unit
I did question if it would make sense to coupleboth turbines into one controller. Which i believe is also 48 volt . Thus sending rge 3bergy from both turbines into the 48volt capacitor.  From there it would all flow through an inverter to 220volt for domestic use.
Can this work?
• Super Moderators, Administrators Posts: 32,639 admin
Sorry to hear what is happening there...

I suggest you create your own thread/discussion so that we can focus on your needs. But I will give some initial suggestions here.

First, VAWT (vertical axis wind turbine) have not been worth the costs. I would highly suggest that you simply stay away from them. If you are still interested, make sure you get Monthly harvest data (Watt*Hours per month) over, at least, a 1 year period--Hopefully near you, or similar wind conditions.

HAWT (horizontal axis wind turbines) put on a high tower (minimum 10 meters high, no up wind buildings/trees/etc.) highly suggested.

HAWT turbines generally need a brake to shut down in high winds and for service. Placing a short circuit on the output of a HAWT is also used to control overspeed (short circuit places high torque requirements on alternator, which slows rotation and causes blades to "stall"). Good turbines include several (backup) systems to shut down (including furling--some method of pointing turbine sideways to wind--pivoting tail, head, etc.).

And wind turbines, at the very least require a tower and controller+wiring (typically 2x more money than the HAWT itself). You need equipment to place the tower (cement foundation and/or cable stays), equipment (or tilting tower) to get the turbine 10-30+ meters in "clean" air flow, and service once a year +/- .

My general suggest is to measure/understand your loads (suggest 3.3 kWH or 3,300 WH per day will run a small/energy efficient home with a refrigerator, LED lighting, washing machine, small well pump, laptop computer, cell phone / radio charger, etc.).

Design the battery bank to support those loads (2 days storage, 50% max discharge for longer battery life--Basically 4x your daily loads).

Then design the charging system to support your battery bank (10-13% rate of charge for solar) and your loads (based on your location/hours of sun per day by season, etc.).

Once you have a solar power system running, then look at wind power to supplement your solar system during bad weather/poor sun/winter if needed.

Just taking a guess. Worcester, fixed array, pointing north, no shade (trees/buildings/mountains/bottom of valley):

### WorcesterAverage Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 56° angle from vertical:
(For best year-round performance)

 Jan Feb Mar Apr May Jun 6.96 6.90 6.29 5.33 4.37 3.94 Jul Aug Sep Oct Nov Dec 4.12 4.60 5.42 6.08 6.58 6.70
It appears you have very good "hours of sun" per day throughout the year. So, unless you have other reasons/issues, I would highly suggest working out a solar charging system first, then fuel driving genset for backup. And lastly, a HAWT for bad weather.

And to not keep you guessing--I, personally, am not a big fan of small wind. Folks do use turbines, but typically in very windy locations. If the wind is not "annoying" in your area ("flagging trees", etc.), then turbines may not be a great resource.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 239 ✭✭✭

You can not parallel the outputs of two separate AC sources unless they are specifically designed to do so: the Voltage, frequency, and waveform will not be in sync between two turbines except by coincidence (i.e. almost never).

I think if the two wind generators were timed so the phases were in time, that you could probably combine the two together

but this poses problems in itself