How to accumulate torque of multiple independent gears?

I did not find any answers to this simple problem across the web, maybe seeking help in this forum helps:

As an example, let's assume we have multiple windmills, each of them producing torque, but each of them produces different amounts of torque, because they are not equally exposed to wind.

Now, how could one mechanically build some DIY gears and hacks to accumulate the energies/torques of the windmill-outputs together, without having back-effects to the windmills?

I want ONE output gear, which has the summed-up energy of all input-gears (windmills), and when input-gear-1 would turn the output gear faster than the input-gear-2, input-gear-2 should also be able to add its torque to the output-gear (instead of acting rather as a brake for the output gear).

I can't imagine that such a simple idea/problem has no solution yet in 2019, but I have to add that I am a complete noob in mechanics.

Important: I forgot to mention that I want to build this WITHOUT electricity or the use of any motors. Think in terms of plastic-garden windmills. Little, wooden or plastic gears. Is it possible to achieve this with plain mechanics? (No electricity or magnetism involved?)

• I'm voting to close this question as off-topic because windmills are not motor vehicle maintenance or repair. Aug 10, 2019 at 12:45
• I think the question could be rephrased to be on-topic. Toyota hybrids have the same problem: how to accumulate the energies/torques of electrical motor-generators and internal combustion engine. But, the rephrasing needs a lot of work and I'm not sure if the question would be the same anymore after that. Aug 10, 2019 at 12:51
• @juhist this querstion would be much better off in the Engineering Stack... Aug 10, 2019 at 12:53
• Yes, agreed. Perhaps we should propose it to be moved? Aug 10, 2019 at 12:53
• yeah, I'm sorry, as I am such a noob, I scrolled through the various available stack sites and read "mechanics" as a keyword of this forum, so I took a guess and asked here instead of anywhere else, but thanks for the hint!
– ElectRocnic
Aug 10, 2019 at 16:01

There is a solution for this and it's called planetary gearset.

All Toyota hybrids (at least the traditional not-PHEV ones) have a planetary gearset that sums together the power produced by motor-generators and the internal combustion engine. With two motor-generators, it also allows infinitely finely adjustable CVT that is electrically adjusted. So, it replaces the traditional automatic transmission and doesn't need a torque converter anymore like traditional CVTs do.

Actually, technology very similar to this is used in differentials to distribute power from one engine to multiple wheels, but the technology to do the opposite, to combine power from multiple shafts would be basically the same.

In wind turbines, the problem is that the rotation speed of the wind turbine varies, whereas electrical grid is constant at 50 Hz or 60 Hz. So, an entirely different problem than what you claim.

This problem is solved in doubly-fed electric machines where the magnetic field is produced by electricity and is made to rotate at a rate that is the difference between the turbine rotation speed and the electric grid "rotation frequency" (50 Hz or 60 Hz). Then the generator produces constant 50 Hz or 60 Hz even though the turbine may rotate at any speed. Also, you need an inverter only for the magnetic field, not for the entire electrical power produced by the machine. Much cheaper that way with wind turbines when compared to e.g. solar cells that produce DC and require an inverter for basically all of the power they produce.

• Thanks for your well-explained answer, however, as I updated the question, would it be possible to do this without electricity or magnetism involved? Just with "hard" materials like wood and plastics (or metal gears if you want?) The question actually comes from a planetary gear-set I 3D-printed. But how can I use that for this purpose (which is not clear from your answer)?
– ElectRocnic
Aug 10, 2019 at 16:07

We have a solution that is far more efficient in terms of material and space : each wind turbine produces electricity that can then be used in just about any amount necessary.

It's hard to tell what kind of answer is in scope because it isn't clear why you don't want one windmill to be a brake on another. It's not like you're losing the power - the "braking" windmill is turning faster. Any load you put on a windmill is going to cause such a braking effect.

But I have read that windmills work best under light torque - there's less wear on the gearing for one thing. So maybe that's a reason. Also, if you end up driving one windmill faster than the wind, that wouldn't be good.

The planetary gearset mentioned in another answer are one solution. A planetary gearset sums the rotation of two rotating inputs (weighted according to gear ratios) into one rotating output. The power load of the output is divided between the inputs according to the gear ratios and the characteristics of each input driver determines how that power allocation is divided between rotation speed and torque of that driver.

A torque converter such as is used on an automobile automatic transmission is another possibility. Just as it allows an engine to run faster than the input shaft of the transmission, it would allow one windmill to run faster than another connected one, while giving the latter windmill's output a boost. A simple fluid coupling might also do the job.

You don't want to convert to electric energy, but how about liquid or gas? Have each windmill pump water into a pipe and run that water through a turbine.