XL Blade | Offshore wind turbine blade testing | ORE Catapult

Blade Stunners: Testing the Next Generation of Wind Turbine Blades

Published 22 May 2017

The experienced dockers at the Port of Blyth have seen it all over the years. But in early March, as the EEMS Duisburg carefully crawled its way up the river there, they were confronted with something new.

They were among the first people in the UK to witness the ship’s unique cargo: an 88-metre Adwen wind turbine blade, one of the world’s longest and most advanced. With its tip overhanging the 108-metre vessel’s stern, its colossal scale was clear: this was a supreme feat of engineering.

As impressive as it looks now, in years to come blades of this size will be the new normal. As part of the XL Blade project, ORE Catapult is collaborating with wind industry leaders Adwen and LM Wind Power to assist in designing, validating and deploying two of the world’s largest offshore wind turbine blades. This EU DemoWind-funded project isn’t just about length for length’s sake, though: the industry trend towards larger turbines with higher power outputs means that bigger blades are necessary if costs are to continue to fall.

The benefits of pushing the envelope can be seen in the Adwen blade’s contribution to reducing the levelised cost of energy (LCoE) through its lighter construction, and more predictable operational expenditure (OPEX) by means of its reliability-driven design.

The Duisburg was delivering the blade to our National Renewable Energy Centre in Blyth, where it will undergo a rigorous programme of testing in our 100m Blade Test facility. There, the project’s other 88m blade – manufactured by LM Wind Power – will undergo a pioneering programme of dual-axis testing.

“Testing bi-axially isn’t quite as simple as applying the single-axis test loads at the same time,” explains ORE Catapult’s Peter Greaves. “That would damage the blade more than in its service life, so we excite both axes at their resonant frequencies simultaneously. By doing this, the blade will experience load combinations that wouldn’t occur in practice, because the two frequencies are very unlikely to be the exact same. That drives the tip of the blade in what we call a Lissajous curve.

“We analyse the fatigue that the blade will encounter in its service life, then feed that into an optimisation routine so that the test matches the service life damage over as much of the blade as possible. Once we run the fatigue tests, we then repeat the static tests so that we know the blade will handle the loads even at the end of its lifetime.”

As well as reducing the time and costs of blade testing, this novel method – the brainchild of Peter, a Blades Structural Research Engineer at the Catapult – will subject the blade to loads and forces that are more representative of real-world operating conditions than the single-axis status quo.

Blyth and its state-of-the-art testing facilities are currently the centre of the Catapult’s blade R&D work. But in future, large-scale research projects could utilise the 7MW Levenmouth turbine to develop and validate promising new blade add-ons aimed at reducing offshore wind’s LCoE, and the operations and maintenance (O&M) costs around rotors.

O&M costs can represent between 16-23% of offshore wind LCoE, with rotor issues like structural integrity making up a significant chunk of that figure. Technologies that increase aerodynamic performance, reduce blade erosion, or strengthen the structure of the blade could all be retrofitted to the towering open-access turbine’s 83.5m blades. It’s estimated that combinations of these technologies could reduce LCoE by up to 4.7%.

Improving aerodynamic performance will have a positive impact on annual energy production (AEP), blade erosion protection has the potential to reduce O&M costs, and strengthening the structure of the blade could reduce blade failures by 50% while cutting maintenance costs.

“Our approach to industrial research and development, and the use of representative testing, brings benefits for equipment manufacturers, asset owners and investors,” says Peter. “By focusing on technology innovation to reduce unplanned maintenance, increase availability and output, and reduce the time and costs of bringing new technologies to market, we’re making big gains in the competitiveness of offshore renewables.”

Find out more about our world-leading wind turbine blade test facilities.