From the outside, most wind turbines look similar – three blades at the top of tall tapered towers, painted light grey – but exciting developments are taking place hidden from sight, inside the nacelle. This is where the next wave of innovation in wind is happening.
Wind turbines face two notable engineering challenges: variable-speed operation and gearbox failure. In early wind turbines, the grid-connected generator required the blades to spin at a fixed speed, corresponding to the power line frequency. In high-wind conditions, the turbine would suffer high mechanical loads and perform inefficiently. Modern wind turbines have a variable-speed rotor that allows the turbine to capture a greater fraction of the wind energy, but require costly power electronics to perform the conversion process.
Gearbox failure is a problem encountered by both fixed- and variable-speed turbines. Often cited as the least reliable component of wind turbines, the gearbox converts the rotor’s 15-20 rpm speed to the 2000 rpm required by the generator. The industry expects today’s gearboxes to last 7-11 years, which means they may have to be replaced several times in the 20-year lifetime of a wind turbine. In 2009, gearboxes in all 30 turbines forming the Kentish Flats offshore …
