ENERGY PRODUCTION


and maintenance of non- renewable energy equipment. These include the use of laser cladding (adding metal to the surface to improve its properties) in repairing gas turbines. In contrast to conventional arc welding, laser cladding delivers less heat to the components thereby reducing the chances of distorting them. Beams from fibre lasers delivered to the end of a robotic arm can also reach awkwardly sited components that would otherwise be beyond repair. As well as manufacturing


new equipment for energy generation, lasers can also be used in the decommissioning of power plants at their end of life. For example, the cutting up of contaminated components is playing an important role in the dismantling of shut-down nuclear power stations, reducing health and safety risks as well as increasing efficiency.


Wind turbine blades The manufacturing of wind turbine blades is a complicated process, with one of the most involved stages requiring the precise positioning of the fibreglass mat, carbon fibre prepreg, and decals that they are made from inside curved moulds. This is carried out by hand to maximise homogeneity. But using laser projection systems to project alignment lines rather than measuring and positioning via mechanical templates can significantly increase productivity. This is because the laser


projection, which is guided by CAD data, improves accuracy and therefore end-product quality as well as minimising the chances of human errors being made. Laser projection also ensures reproducibility, and reduces cost. It is faster, because the layers can be positioned more easily and rapidly, and it is possible to use several laser projectors simultaneously with overlapping regions that facilitate different teams working concurrently on multiple areas of the blades. Having a uniform composition for the blade material is vital for optimising the


energy efficiency of the blades since irregularities in their shape reduces their aerodynamic efficiency, which results in poorer performance. Shape optimisation is also important so that uneven loading can be avoided – this can otherwise result in vibration as the blades turn. Vibration increases wear, and results in the need for more maintenance of the turbine and ultimately reduces the length of its service life.


Laser cladding In the energy sector, laser cladding can be used in the repairing of steam and gas turbines, shafts and gear components, as well as for cladding water walls and tubes in boilers. In this technique, which is alternatively known as laser metal deposition, metal is deposited onto a surface by being fed in powdered or wire form into a laser beam that is scanning across a component and locally melting its surface as it does so. Laser cladding improves the properties of the surfaces it treats, enabling it to effect repairs on parts that have become damaged, or are worn with age. Compared with conventional


arc processes, laser cladding is faster, more efficient, automatable, and less likely to distort the component since it heats it up less. Because the deposition is more efficient in laser cladding, it also requires less material to produce the same result. There are many variants of


laser cladding. Two or more powders can be mixed together for instance, and the flow rate of each controlled to allow for a graded material to be produced. Various different types of laser


“Laser cladding is more efficient, automated, and less likely to distort the component because it heats it up less”


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Laser projection can increase productivity in manufacturing turbine blades


are used for cladding, depending on the type of material being clad and the component geometry. For example, near-infrared high-power direct diode lasers (HPDDLs) are a good choice for cladding over large surface areas, because this wavelength is absorbed well by most types of metal and the diode output can be shaped into a long line, perfect for scanning across components rapidly.


Micro turbines For micro gas turbine components, the cleaning of surfaces prior to welding as well as cleaning to remove contaminants, corrosion and debris is another application that benefits from the use of lasers. Fibre laser cleaning, in which the dirt and contamination is vaporised, has the advantage over chemical cleaning that the process produces less hazardous waste chemicals. It is also a simple process to automate, and can remove multiple different types of contamination in one step. Holes can also be drilled into


micro turbine blades by fibre lasers. While nanometre pulse lasers are a good choice for removal of the ceramic coating (that protects the turbine blades


from the extremely high working temperatures), quasi continuous wave (QCW) fibre lasers are ideal for drilling precise holes at very high speed.


Solar energy During the manufacturing of solar cells, after the diffusion of the impurity atoms that the semiconductor material has been doped with, an etching process needs to be carried out around the edges of the cell. This is to stop current flowing between the electrical contacts at the front and back of the solar cell. By using a laser to ablate a groove around the cell’s perimeter, the required electrical isolation can be produced as the path for the current has been broken. Laser processing for this step avoids the potential for damage to the rest of the solar cell from the splashing of acids in the wet chemical etching process, or the risk of too much damage occurring to the cell edges if plasma etching is used to create the required electrical isolation. Laser fired contacts are also


showing promise for improving the efficiencies of solar cells, and are used in the cutting and marking of semiconductor wafers. In addition, lasers can be


g THE 2023 GUIDE TO LASER SYSTEMS LASER SYSTEMS EUROPE 23


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