Tests show a manufacturing defect caused the failure of a turbine off the coast of Nantucket, a mishap that has energized opponents of renewable energy.
Actually, magnetic bearings experience wear as well.
So called “permanent” magnets gradually lose their charge over time through interactions with opposing magnetic fields, heat, and mechanical stresses. Neodymium, for example, loses about 0.1% of it’s field strength per year even when it isn’t being used for anything. This is why you can’t use magnets to make perpetual motion machines:
Magnets are basically batteries that store energy in the form of a magnetic field, eventually they run out of charge and need to be re-magnetized.
This makes passive magnetic bearings really tricky to design, so most of those in use are active types that also employ sensors and electromagnets to ensure stability. These electronics also degrade over time, so usually a mechanical bearing is a better choice unless the use-case requires a frictionless axle.
Actually, magnetic bearings experience wear as well.
So called “permanent” magnets gradually lose their charge over time through interactions with opposing magnetic fields, heat, and mechanical stresses. Neodymium, for example, loses about 0.1% of it’s field strength per year even when it isn’t being used for anything. This is why you can’t use magnets to make perpetual motion machines:
Magnets are basically batteries that store energy in the form of a magnetic field, eventually they run out of charge and need to be re-magnetized.
This makes passive magnetic bearings really tricky to design, so most of those in use are active types that also employ sensors and electromagnets to ensure stability. These electronics also degrade over time, so usually a mechanical bearing is a better choice unless the use-case requires a frictionless axle.