Hitachi starts mega-turbine designs

Hitachi has started the first conceptual sketches for 10MW and 20MW models of its downwind offshore wind turbines.

The Japanese company will model the supersize machines on its HTW 5.0-126, which is to see its maiden installation next year off Kamisu in Ibaraki prefecture, before being rolled out commercially in 2015.

"We see the 10MW as very much an extension of the 5MW, upscaled," states Kyushu University professor Shigeo Yoshida, who led the design team at Hitachi that hatched the smaller model and now consults for the company.

Like the 5MW concept, the Hitachi 10MW and 20MW turbines will  be downwind designs whose conical rotor faces away from the prevailing wind-stream.

The monsters' flexible all-GRP blades – the length of which has not been finalised – will turn two-stage geared drive-trains powering a permanent magnet generator.

Downwind offshore designs are growing in number, with Germany's Aerodyn planning to erect a 6MW two-blade model for Ming Yang off China in the spring, and US outfit Nautica working on a floating spar-based concept.

Hitachi's 10MW and 20MW designs are set to be unveiled by mid-2015, with expectations that the smaller of the two will be three-bladed and the larger being "investigated" to fly a two-bladed rotor.

"I have long been interested in two-bladed designs but there are many problems to solve before committing," says Yoshida.

The Hitachi project is part-funded by Japan's New Energy and Industrial Technology Development Organisation (Nedo).

The company has a pair of its 2MW downwind turbines – which are powered by conventional three-stage gearboxes and double-fed induction generators – installed on the ground-breaking Goto Islands and Fukushima Forward floating wind demonstrator projects off Japan.