Areva's new model: first it was a monster, now it's a 'killer'

Looking beyond the M5000-116, Areva is pressing ahead with final fine-tuning of a longer-bladed “killer turbine” dubbed the M5000-plus by company engineers.

Featuring flexible 66-metre, 23.5-tonne glass-reinforced plastic blades, the new 5MW offshore turbine — being marketed as the M5000-135 — will have a rotor diameter 19 metres wider than the current production model, with a swept area of 14,326 square metres. That is almost 4,000 square metres more than the 116.

The aim in developing the larger M5000, which will have a 365-tonne top-head, has been to “increase power production without jeopardising track record”, says Areva Wind research and development director René Balle.

“The 116 has, since 2004, been recognised as a monster platform both in terms of innovation and size,” he states. “But in 2011, it was felt that the turbine platform needed to be extended with an improved performance.

“As we are a one-product company — we only have the M5000, after all — it was also seen to be important that we not go off on some mad adventure in designing the next turbine. We wanted to build on the credibility that we earned over the past years.”

To this end, the power train, which has been “measured over and over again from every angle over the past eight years”, was “all but off limits” to the design team, with the longer blades meant mainly to provide a “buffer in the machine’s load envelope” in a broader range of wind speeds.

The 135’s blades, although based on “identical” aerofoil profiles to the 116, have less carbon and so are “softer”, in keeping with a design shift meant to cushion gust-driven loads.

“Though conventional wisdom has been that longer blades need more carbon for stiffness, we feel that simulation and control methodologies have developed a great deal in recent years,” notes Balle. “Our move to flexible blades is a move into a new world that we feel very confident about.”

Engineered for top tip speeds of 90 metres per second (m/s) in wind speeds of 9m/s, the blades have been fashioned to meet “several thousand” wind load profiles.

Germany’s Fraunhofer Windenergie & Energiesystemtechnik is in the frame to perform dual-axis load and extreme fatigue tests on the blades on the Areva test bench in Bremerhaven, starting early next year.

In the second quarter, blades will be mounted on a 135 prototype at a nearby onshore site with “offshore-like” wind conditions. Serial production is expected to start towards the end of 2013, when Areva “has clarity about first orders for the M5000-135”.

The new turbine, which will have gearing systems for its synchronous permanent-magnet generator, supplied by Finland’s Moventas, will feature 16 subsystems with full redundancy and 1,300 sensors feeding back data so that 80% of operation failures can be handled remotely from shore.

“That this is [the fullest realisation] of the M5000 is clear. And this is true, I think, of what you see in the wider industry,” says Balle. “You start with a very conservative load configuration for a rotor and power train, and when you have measured your machine and know exactly where you are, then you scale up to your maximum size and power output.

“Our testing programme — even on a turbine that is a product evolution — is the most extensive we have ever undertaken and has required quite a budget, but for an offshore machine there is really no room to underperform on reliability.

“Even with eight years’ development of the platform, we are still putting it through the fullest testing and verification programme.”