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FEATURE WIND TURBINE MANUFACTURE


are not the only type of customers we serve.’ Huge constructions such as wind turbines have the sort of thick-walled structures that Højerslev is looking to use his powerful laser on. ‘By a thick wall we mean 40mm to 150mm, but we cannot penetrate 150mm. It is to be used on parts of the hull,’ explains Højerslev. LWT does not only use a laser for its welding; it combines it with a consumable in a process known as hybrid welding. ‘When you weld such large thick specimens, you add filler material and can have problems with shrinkage and cooling rate so you need something extra. So, in addition to the laser source in the weld pool we’ll apply an arc welding system,’ explains Højerslev.


An outline contour of each material layer that goes into a turbine blade is projected onto the mould to aid manufacturing





pattern bond and pattern number so all the information for the lay-up process is projected into the mould.’


Where metal is needed for renewable energy systems that have to brave the elements of the coast and seas, lasers do the cutting


Lasers showing their mettle Where metal is needed for renewable energy systems that have to brave the elements of the coast and seas, lasers do the cutting. One user of laser systems for the marine and offshore technology industries is Denmark’s Lindoe Welding Technology (LWT). Its chief executive officer is Christian Højerslev. ‘We are in a former ship yard, so we think of large industrial components,’ he says. LWT assists Danish industry in developing production technologies based on high-power lasers. The company’s initial focus is welding and in particular, using the most powerful commercially available high- power laser in the world for that process. ‘We have a powerful laser capable of 32kW


of power. That puts us on the map. We want to use this power on different applications, somewhere we can use all the power. So we have interest in the offshore wind turbine industry,’ says Højerslev. ‘They represent a customer-base we are very devoted to, but they


18 PHOTONICS FOR RENEWABLE ENERGY 2013


Aesthetic challenges The competitive challenge for LWT is to be able to compete with existing technologies, the typical welding systems and surpass the standards expected by those processes. ‘The trick is, with classical techniques you will have a lot of distortion due to the large thermal effects that are happening during welding,’ explains Højerslev. ‘But what we do with laser welding is melt a more confined volume and that gives you two benefits: you do not need to use so much time or money, and your visual appearance will be much nicer; more neat.’ With hybrid welding the weld bead is smaller and can be as small as 2mm across or as much as 10mm. For Højerslev’s customers this has an aesthetic value. As well as welding large structures, LWT


also offers services in cladding. ‘It is surface engineering by welding. You could design a surface that copes with a particular situation,’ says Højerslev. ‘You’re welding something on to the surface. Cladding uses the laser and you can add powders to select the chemistry of your surface layer as you want. It’s a very delicate process to build up a nice surface.’ He explains that, with pistons and bearings for maritime applications, you need to do something because of the very harsh environment. However, Højerslev still describes cladding as a last resort. ‘You spend some money on the surface, which is your last resort; sometimes it can fix the problem but there are no golden bullets. As Højerslev points out, even the cladding will eventually erode. As renewable energy provides more and


more of humanity’s power needs, the wind turbine farm will occupy more and more of our fields and seas for decades to come and lasers will make these huge structures stronger and more lightweight to enable them to deliver the higher efficiencies needed. l


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