Laser applications in the energy industry
Laser projection can increase productivity in manufacturing turbine blades
Solar power is becoming a major player in various countries’ energy strategies, and is the fastest growing clean energy technology in the EU. During 2020, solar provided 5.2% of the EU’s electricity, for example, and has become the most competitive electricity source in many EU regions thanks to its cost decreasing by 82% over the last 10 years.
According to data from energy think tank Ember, wind power and solar energy combined generated 22% of the EU’s electricity in 2022, meaning that these two renewables overtook fossil gas (20%) and coal power (16%) for electricity generation for the first time. Meanwhile, in the UK, National Grid figures show that in 2022 26.8% of the UK’s total electricity generation came from wind turbines, and in 2020 the UK reached a point where 43% of its generated power came from renewable energy sources, specifically wind, solar, bioenergy and hydroelectric. The continuing growth of renewable energy is presenting increasing opportunities for laser processing techniques.
For example, laser processing is used in the manufacturing of the electronic parts of solar cells, simplifying and reducing the cost of production. Meanwhile the materials used to make wind turbine blades can be lined up within their moulds with the help of laser projectors, which enables time and cost savings as well as prolonging the service life of the blades due to increased accuracy. Various laser machining processes are also used in the manufacturing 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.
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.
Laser cladding is now being used in the repair of gas turbines (Image: Shutterstock/industryviews)
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 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.
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.
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.
Lasers are used to process silicon in the manufacture of solar cells (Image: Shutterstock/Diyana Dimitrova)
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 used to separate the electrical circuits of the individual cells of large solar panels. The laser ablates the layers of photovoltaic material down to the glass base layer in a scribing process. Lasers with wavelengths of either 532nm (green) or 1,064nm (IR) are typically used, and deliver a precise and consistent result.
In the UK alone, more than 20 nuclear facilities will be decommissioned by 2030. This process will include the cutting up of vast quantities of metal structures such as pipes and cylinders – some of which are contaminated with radiation. Flame cutting techniques are traditionally used, but laser cutting is an attractive prospect because it is faster and reduces the need for humans to work in contaminated environments. Fibre delivery can also allow laser cutting to reach areas that are otherwise extremely difficult to access.
While some parts can be simply cut up and then disposed of, others require decontamination either before long term storage or if they are going to be reused. It makes economic sense to recycle stainless steel, for example, but all of the layers of radioactive oxides that have built up on some nuclear power plant components must be removed before these materials can be reused.
Laser cutting and cleaning are both playing an increasing role in the decommissioning of nuclear power plants (Image: Shutterstock/Ugis Riba)
Nanosecond pulse (10-9s) high-powered lasers with energies in the tens of kilowatt range and wavelengths in the near-infrared region can be used to clean the radioactive residues off concrete in a process known as ‘concrete scabbling’, and to remove deposits from the inside of stainless-steel tubes, by oxidising the surface that needs cleaning. This laser ablation process is carried out layer by layer, with the ejected material vacuumed away via a suction pump.
One of the advantages of using a fibre-delivered laser for this task is that it can reach surfaces in tricky to access locations. Also, unlike using water jets or mechanical means, laser cleaning avoids the creation of secondary waste, which can end up redeposited on the surface of the component, and at the very least requires careful handling and disposal.
In the future, there is potential for pulsed femtosecond (10-15s) lasers to be used to create a new generation of solar panels made from etched metal surfaces. Researchers have shown that etching a nanoscale pattern into tungsten via a femtosecond laser allows the metal to selectively absorb light at solar wavelengths while reducing the heat dissipation at other wavelengths of light.
Another area in which lasers could play an important role is in the production of batteries for storing power, generated by renewable sources such as wind and solar, in residential settings. The types of batteries being proposed for this use would require their component materials to be accurately cut, and contain strong welds of dissimilar metals.
There are also studies aiming to demonstrate whether laser welding could provide a better alternative to conventional welding techniques for joining components in energy generation or related equipment. This includes the components of chemical tanks and pressure vessels used in the oil and gas sector, and those within technologies such as heat exchangers, and the support structures for wind turbines. These components may be subject to a variety of extreme conditions such as high temperatures and pressures, and corrosive substances. As a consequence, any welds used must comply with stringent safety standards.
Laser welding in these scenarios offers the promise of considerable efficiency improvements and cost savings, so not surprisingly, feasibility studies are ongoing.
Lead Image: Shutterstock/MimadeoWZ