Superconducting coils are expected to reduce the weight of wind turbines
Wind turbines, each of which is nearly 60 meters long, rotates against the top of the tower, and the 250-ton engine room contains turbine generators and other things that need to be powered. If everything is doubled and magnified five times, the huge size and weight are the ultimate problems for builders of offshore wind farms.
In general, the greater the power of each turbine, the better, wind farm operators have been demanding higher power offshore turbines. If a 20 MW wind turbine is built with today's technology, the weight of the top of the machine is very large, and only the cabin will weigh nearly 1,100 tons. The three blades of the turbine itself weigh nearly 40 tons and span more than 250 meters. A pedestal weighing 1800 tons can support all of these structures, about 170 meters above sea level.
In order to reduce the weight of the generator, a lighter permanent magnet made of a superconducting coil is used instead of the directly driven permanent magnet. The electromagnet is relatively light, the superconductor can carry a large amount of current, they have a high current density, and the maximum cross-section of the copper conductor The cross section is several amps per square millimeter. In experimental superconducting turbine windings built for the ultra-power 10 MW turbine project, the current density jumped to an astonishing 58 A/mm~2. The design requires a 163 metric ton generator that can reduce weight by 26% compared to what is built using today's permanent magnet technology.
High temperature superconductors, such as ybco beryllium (ybco), have great potential because they become superconducting at temperatures below 90 Kelvin, and temperatures are sufficient to cool with inexpensive liquid nitrogen rather than expensive liquid helium. A few years ago, AMSC, a leading manufacturer of beryllium copper, produced a rough turbine design, but most of the recent European superconducting wind turbine projects have independently solved another superconductor, magnesium diboride.
The superconductivity of magnesium diboride was discovered in 2001. It lost its resistance below 40k, but its cost was much lower, so that it exceeded the cerium oxide in every cost analysis. Beryllium copper, 4 euros per meter ($4.63) of magnesium diboride, may not be the best performing material, but it is the best value for money.
The rotor coil is made of flat copper wire with a magnesium diboride wire embedded in it. The copper strengthens the relatively fragile magnesium diboride and removes heat from it. The superconductor magnesium diboride filament is wrapped in copper. And other elements in the strip support structure. The ribbon is then carefully rolled into a "track" shape to form a high power electromagnet of the turbine, the geometry of which is the most difficult part. The "track" coil is generally rectangular in shape, and the sharp corners create stress on the wire, causing the superconductor to rupture, and a special tool must be developed to entangle.
Reprinted from the network