A European wind turbine maker found itself with an emergency: their new clean-energy turbines were efficient, effective and state-of-the-art – but they were too noisy.
It turned out that ESA’s advanced Darwin planet-hunter study provided a smart answer: using the same approach that keeps multiple telescope mirrors precisely aligned to cancel out turbine vibration before it becomes noise.
“Certain countries set certain limits on the amount of noise a turbine can make,” explains Nicolas Loix, CEO of Micromega Dynamics, a Belgian company whose main business includes controlling the vibrations produced by everything from machine tools to paper-making.
Wind turbines produce two different kinds of noises. The first is the motorway-like drone from the blades. The other is ‘tonality’ – an irregular shriek from the gearbox.
Tonality is even more annoying than broadband whirring noises, so governments regulate these noises very strictly. Often, the only way to keep a shrieking wind turbine from disturbing the peace of an idyllic countryside is to operate the machine at less than full power. When customers face these kinds of problems, usually it’s late in the design phase and there’s very little time to solve the problem..
In the case of the shrieking wind turbine, the company MicroMega looked back to its work on the Darwin-planet hunter. Darwin’s telescopes look for Earth-like planets. However, for this to work, the mirrors of each small telescope must be in constant alignment. To move the mirrors, Micromega developed a high-precision mechanism using magnetic bearings. This mechanism would adjust the mirrors under the exacting circumstances of space, which required that the bearings work with high precision, zero friction and at very low temperatures.
Generating a counter-vibration – with the same size as the vibration producing the tonality, but in the opposite direction – proved to be the answer: “We kill the vibration before it reaches the surface where it becomes sound.”
Darwin was not selected to make it into space but the space simulations developed by MicroMega came in handy as they set about designing an actuator to quieten the wind turbines. However, the challenge did not end there: “Wind turbines are huge, and they have many parts. It’s like trying to seal a box full of water. If it has one hole, ok. But we have many, many holes, and we need to close them all.”
Within eight weeks, however, Micromega was able to develop a solution from scratch.