AMSC (American Superconductor and Texas-based TECO-Westinghouse Motor Co have been working an estimated $6.8 million project to design components for a 10-MW HTS generator. Another HTS device manufacturer, Germany’s Zenergy Power Group, is working with Converteam Ltd in the UK to commercialize an 8-MW HTS wind-turbine generator. Because of the practical limitations to erecting large turbines, a generator’s size and weight do matter, says Larry Masur, a Zenergy vice president. Several groups expect to have generator prototypes ready for testing within two years but commercialization will take 10-15 years to get competitive costs. Kite generated wind and other alternatives to turbines seem like the better approach.
Superconducting Wire Manufacturing Volume Needs to Increase and Wire Costs Need to be 3-6 Times Cheaper
Half of the Superwind project is making the wires cheaper,” says Abrahamsen, whose colleagues are working on a more efficient process to deposit the layers of YBCO (YBa2Cu3O7) superconducting cuprates that form coated conductors. “The cost of offshore wind power is about €1 million [$1.3 million] for 1 MW, and depending on the design, a 10-MW generator will require several hundred kilometers of HTS wire.” To compete with the cost of copper wire, which is around $50/kA·m, Zenergy’s Masur says that HTS wire manufacturing needs to ramp up, and the price of HTS wire needs to fall to $15–$30/kA·m—from values estimated by other sources to be as high as $100/kA·m at low-production volumes. That does not include the cost to maintain and operate the cryogenic equipment needed to cool the wire below its critical temperature.
The HTS generator project teams are also testing designs that eliminate the gearbox, which converts the low angular speed of a turbine’s blades to a higher rotor speed to match the electrical grid’s AC frequency. Gearboxes often break down, especially in the humid offshore environment, and that adds to the cost of maintenance. AMSC’s Gamble says that his team has already yielded a gearless design that increases the torque on the rotor, which makes it easier to control the speed of the blades and maintain constant power flow to the grid.
The promise of HTS wind-turbine generators has the support of sectors from environmental groups to governments. Musial says it may take 10–15 years for commercial 10-MW or greater HTS generators to take off. “This is not science fiction,” he adds, “but it is not a garage project either.”