Euros eyes 90-metre rotor blade

German rotor blade maker Euros is sketching out a design for an ultra-long "90-metre-plus" model with an eye on the emerging market for supersized offshore wind turbines.

The concept, based on the 81.6-metre-long blade fashioned for the Mitsubishi Heavy Industries' (MHI) 7MW SeaAngel prototype about to begin trials in the UK and Japan, would fit 8MW-class machines such as the recently announced giant from Areva.

"It is at the preliminary design phase," Euros head of materials Alexander Krimmer tells Recharge. "As a company we feel there is a robust need for such a blade and there is a gap currently and so you have to have the technology ready [on paper]."

“The blades [for the SeaAngel] are proof that our design was not too bad so we will not change too much I would guess. We look forward to further proving our 81.8-metre concept once these turbines are operational.”

The Euros M-EU167 blade — three of which are waiting to be bolted on the SeaAngel being prototype tested at Scotland’s coastal Hunterston testing centre and another set destined for MHI’s Fukushima Forward floating units off Japan – is  a low-weight 32.5-tonne design built around ultra-stiff carbon-fibre reinforced-plastic spar caps for high load-bearing and durability.

Final fatigue tests of the 81.6-metre model, which Krimmer notes have been “very successful to this point", are under way on a Fraunhofer Institute for Wind Energy System rig in Bremerhaven, Germany.

The geometry and aerofoil of the 90-metre blade would mirror the 81.6-metre model “scaled up proportionately and fine-tuned”.

Krimmer says the cost constraints remain the “central challenge” to developing ultra-long offshore blades for the 8-10MW turbines now coming to market.

"We are under a great deal of pressure in terms of cost, which is interfering with the speed of our plans. This is the main issue, not the engineering of such a huge blade that performs at high reliability,” he stresses.

"Still it is hard to guarantee it will have a 25-year lifetime given how many uncertainties, particularly in the area of materials fatigue and so on, that there are. No one yet knows how [in financial terms] how to value reliability."

Euros plans to build a new fabrication hall in Sassnitz, northern Germany, for construction and testing of the new, longer blade once a first order is inked. A prototype would take “around a year” to manufacture.