Stator and rotor have to rotate in opposite directions

Why in opposite directions?

It sounds like it is wired wrong

The efficiency will depend on the quality and efficiency of any gearing that makes them go in the opposite direction

The relative motion is what counts. We use a similar set-up in our testing dynamometers. Is this set-up for testing purposes or for actual power generation? Is the field on the rotor? How can you control the level of the field magnetism? How are you removing the generated power from the "stator"?

oK fine

I am a mechanical engineer. I would like to do my PhD on vertical Axis windmill which must be directly beneficial to my village and around. So I have formed my own methodology in mechanical side. In that I have an idea to rotate a twin turbine in opposite directions where the stator and rotor of the generator are integral with the turbines, to get more generator speed( more things to be analysed) as well as a balanced power on load conditions( my imagination only). I think the relative motion would be more while compare with the conventional one. it would not be a problem to draw the power form the stator, we can connect it to a slip ring.

Diction alert:

A rotating stator is no longer a stator--no longer static. It would become one of two rotors.

Very poor idea. It would work, BUT:

* You would have two sets of slip rings, one for your rotor field excitation and the other for your power output (i.e., high current) from your rotating stator. This will make your generator considerably more unreliabile than a conventional setup.

* The mechanism that you use for this will be very complex adding much to the cost with zero benefit

* You can design your windmill to get the generator RPM that you need without counter spinning both the rotor and stator.

* You say that you are working on a PHD??? I would think that you would do some analysis first! If you are rotating twin turbines in opposite directions, mounted coaxially, you will get LESS output than if you have one turbine due to the interference of one to the other. If you have two seperate turbines not mounted coaxially, the mechanical clap-trap will be horrendous with much energy loss in the transmission. You are ALWAYS better off with one big wind turbine. Crack the text books and do some PHD calculations.

* A wind turbine always is most efficient when there is nothing around it to disturb the air flow. Laminar air flow hitting the turbine, and no additional turbulance behind it from any other source will give you the most power output. The ideal wind turbine is located a long way from any tree, structure, other turbine, etc, and is high up to minimize the effect of the ground (Note: a high tower is not a good idea from an economic standpoint because of increased capital costs. In a vertical axis windmill, having the bottom of the vertical windmill say 12 feet off the ground just above the generator is the way to go. It is always good to have things that move high enough off of the ground so that anyone standing under them can raise their arms without getting hit for safety.)

* It is very difficult to make a wind turbine that is economically competitive with conventional means of generation, so you must think simple, rugged and reliable. In this case, a simple design is also the more efficient design.

Slip rings are a big headache. They are un-reliable and will need regular maintenance.

Look up brushless generators. They are much more reliable. The only maintenance is when the bearings wear out.

Whoa, if both are rotating at the same speed and same direction you have zero power generated. One of the problems with wind mills is they are variable speed and use electronics to make DC to go into a storage battery or AC for the grid or both.

So counter-rotating turbines would be similar to the counter-rotating propellors used on some aircraft (fixed-wing and helo), a single center shaft for the outboard prop and the inner prop rides on bearings with one end bearing fixed to the center shaft and holding the generator rotor in place inside the rotor hub to minimize brushes, a planetary gearbox could also be mounted on the primary or center shaft to drivelock the counter-rotating propellor to fix the speed ratio.