A heavyweight discussion

One of the key challenges in building the large generators that wind turbines without gearboxes require (main story) is to provide sufficient structural support for a large diameter disc without incurring heavy mass and the large cost that accompanies it. The lessons provided by the bicycle wheel with tensioned spokes to provide a strong lightweight wheel design may come into their own in solving this problem. The concept was developed by Ed Spooner, formerly a professor of electrical engineering at Durham University in Britain, and adopted in a design known as NewGen.

For a 4 MW generator, the claim is that the NewGen permanent magnet generator (PMG) design weighs in at around 37 tonnes. That is an astonishing estimated 70% lighter than the equivalent conventional slow speed generator.

The efficiency of the NewGen PMG peaks at 96% at 50% load. The part load peak for maximum energy gain is a significant advantage for wind turbine operation compared with the induction generator, which reaches its peak efficiency at full load. The nature of the wind resource means that wind turbines mainly operate at part load.

Wind turbine technology has never looked like settling in any well defined rut, and the new divergence into PMGs is no exception to that rule. The potential for significant developments in direct drive design would seem to be far from exhausted.

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