I have seen a high wind turbine.it rotates by wind and produce electricity. How electricity is produced by such a slow movement of wings?the dynmo which produce electricity must be rotated at high speed, how it works to produce electricity? secondly,when there is no wind, wouldn’t it stop electricity production??
In: Engineering
> How electricity is produced by such a slow movement of wings?
Gears can be used to change the speed of the rotation, but it should be noted as well that electricity can be produced by slow rotation it just means a lower frequency.
> when there is no wind, wouldn’t it stop electricity production??
Yes. This is one of the major limitations of renewable energy sources, they tend to be unreliable. If the wind doesn’t blow there isn’t any wind power, if the sun isn’t shining there isn’t any solar power, etc. Power storage is a big challenge in making renewable energy viable.
Slow rotation is sped up with gears. A quick search for step-up gearing should easily demonstrate the concept. And yes, electricity stops being generated when the wind stops and the blades slow down. This is inconvenient, since it means that you have to be able to store the electricity for when it is needed, or use a different power system when the wind stops.
ELI5: Turbine is connected to a generator via a set of gears which form a gearbox and increase the rotational speed to a useful RPM for a generator
So this is probably more of an r/askengineers answer, but i’ll do my best.
Your question is correct, there is a big problem with wind turbines spinning way slower than the power grid. Generally the power grid ‘spins’ at 3000 or 3600 RPM (50/60Hz depending where you live) and wind turbines are so slow you can watch them.
Older style wind turbines used gearboxes to increase the rotation speed, but this is pretty inefficent and there is still another problem which is related to your question. If the wind speed drops, and the turbine slows down, how does it still generate electricity? Or worded another way, if the power grid speed is fixed and the turbine speed varies, how does this work?
A few core principals first:
In electric motors and generators, it is possible to double the number of magnets inside the motor, which halves the speed. So a standard motor has 1 magnet with 2 poles and spins at 3000 or 3600 RPM. Another motor might have 2 magnets with 4 poles and it will spin at 1500 or 1800 RPM. The same thing works with generators, more magnets means it can spin slower but still keep up with the power grid. This is a principal of syncronous machines, which is what most power generators are. Its possible to take this to the extreme and have say, 128 poles and a motor or generator that spins at 56 RPM, which is startiing to get close to wind turbine speeds.
There is another thing here, motors and generators do not need to be syncronous. Exactly how is a bit complicated, but the most common type of large electric motor, called an induction motor is not syncronous and will in fact run slightly slower than the power grid does. With an induction motor, if you spin it slightly faster than the power grid, it becomes an induction generator and starts to feed power back into the grid. This combined with lots of poles and/or gearboxes is also how some older wind turbines worked. These older wind turbines needed to spin fast enough to start pushing power into the grid, but they tended to stop when the wind speed was low, so they had limited usefulness.
As technology improves it usually gets more complicated, so stick with me here, and a bit more explination.
Inside a motor or generator there are two main parts, a spinny bit in the middle called the rotor, and the stationary bit on the outside called the stator. What we are worried about in a generator in terms of speed is the difference between the speed of the rotor and the stator. So with the stator stationary, the only speed there is is the rotor, but what happens if we start to spin the stator as well as the rotor?
You can see that if the stator spins at the same speed and in the same direction as the rotor then they are both spinning together, and there is no relative spinning, so the output speed is zero. But if we spin the stator backwards the difference in speed between the two gets larger. In fact we can vary the output speed of the generator by spinning the stator at different speeds, regardless of the input speed. To be clear, energy is still coming from the turbine, all we are doing is making it look like the generator is spinning faster than it actually is. I don’t think any wind turbines ever actually did this, but it turns out there are some clever tricks we can do with electronics to make the magnetic field in the generator behave as if the stator is spinning relative to the rotor, and that is how many modern wind turbines work.
Lastly, there is also one other way of doing this which involves way more electronics but less mechanical stuff. Grid power is alternating current and so is the power from the turbine, but with large power electronics we can convert alternating current into direct current, and then we can convert direct current back into alternating current. This seems like a lot of work, but as large power electronics gets cheeper, this is becoming the more common way of doing all this. By making DC current and then converting back to AC, we can make the output frequency anythign we want.
Anyho, i hope this was the answer you were looking for. Personally i find this kind of power enginering really interesting and your question is a really good one.
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