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Risks for wind turbines

Risks for wind turbines

Victoria von Richthofen | 01/14/2022

TOPseven Risiken für Windkraftanlagen

Dangers for wind turbines and how to avoid them

There are currently more than 30,000 wind turbines in Germany. Last year, 420 new onshore wind turbines with a capacity of 1,431 (MW) megawatts were newly built in Germany. With 132 million megawatt hours in 2020, wind power was the strongest energy source in Germany. This is roughly equivalent to the electricity consumption of a city such as Berlin, with around 3.7 million inhabitants being able to be supplied with energy for ten years. Thus, wind turbines are one of the most future-oriented and important renewable energy sources. However, the construction of the turbines is not always easy because some are up to 200 meters high. This article describes the risks and dangers for wind turbines in detail.

The transport

Considering the size and weight of a wind turbine, the transport from the production site to the destination can pose problems. Moreover, the nacelle, tower and rotor blades are transported separately, each trip poses a new risk. The problem with transporting a nacelle, for example, is the weight: a nacelle of a 2.0 megawatt turbine can reach a weight of up to 70 tons. Due to this, a heavy-duty transporter must be used to bring the construction elements safely to their destination. Nevertheless, it can happen that not everything goes smoothly and property damage can occur. The situation is similar with the tower of a wind turbine; the difficulty here is primarily the size rather than the weight. The majority of the towers already assembled in Germany are made of tubular steel, which can be up to 30 meters long. If the tower reaches a length of 22 meters, the transport becomes a challenge for truck drivers. The diameter of the tower is also often underestimated, because it poses a danger when passing bridges. Typically, these have a height of 4.2 meters, which is the regular diameter of a 2 MW wind turbine, according to the German Wind Energy Association. If this is not considered when planning the trip, a critical situation can quickly arise. Last but not least, transporting the rotor blades is probably the biggest challenge. Since the blades are produced in one piece, they can be transported only in this way. The length of the blades is therefore a challenge, especially in wooded areas or on curves with tight radius. An Enercon E-70 turbine with a rated power of 2000 kW/ 2300 kW has a rotor diameter of 71 meters – with such a length it is sometimes impossible for the driver to keep everything in view. The blades can quickly get stuck or bumped, which can damage them. Detailed planning, testing and securing of the routes to be driven is therefore of great importance for a smooth operation.

The assembly

The assembly of onshore and offshore turbines can also pose hazards. After the turbine components have been safely transported, they have to be unloaded. With such a size and such a high weight, precision is required. Especially when using a crane, even small mistakes can cause major damage. Moving too quickly can cause the weight to shift and, in extreme cases, cause a system part to slip off. Loose brackets or crane ropes, which can break, also pose a hazard. But it is not only onshore wind turbines that pose risks during assembly. Offshore structure construction is largely comparable to shipbuilding. Concentration and special attention are therefore required for planning and execution. Especially during the assembly of offshore wind turbines, there is often a risk of falling due to the large, heavy components. These must therefore be placed slowly and accurately.

Defective components

Not only transport and assembly are associated with risks, neglected maintenance can also become a hazard. Due to their technical complexity, wind turbines require regular maintenance. Maintenance and inspections are performed at specific intervals to check all major mechanical and electrical components. This can ensure that the turbine is in perfect condition at all times. If not, regular inspections can indicate possible defects and damage at an early stage. If failures or malfunctions occur, they must be localized and remedied as soon as possible. If components such as the rotor, gearbox or nacelle are defective, costly repairs may be necessary, which can cause long downtimes. Therefore, regular maintenance is very important.

The natural hazards

Due to their height, lightning strikes in wind turbines are not uncommon. A defective lightning protection system can cause massive damage: buckled rotor blades, damage to electronic control systems and, in the worst case, the burning down of the entire turbine. Basically, a differentiation is made between a direct and an indirect lightning strike. A direct lightning strike usually hits the rotor blades, which can damage or even destroy the blade. An indirect lightning strike, on the other hand, strikes the power grid at a spatial distance from the wind turbine. The possible overvoltage from the grid to the wind turbine can damage the electronic components.

In addition to lightning strikes, icing of wind turbines at low temperatures is not uncommon. In northern Germany, wind turbines freeze for an average of 7 to 14 days per year, and even more than 30 days at high altitudes. Depending on their nature, this ice accumulation can have a negative impact on the aerodynamic properties of the system. Their weight imposes static and dynamic loads that can lead to malfunctions or mechanical overloads. If the rotor blades freeze unevenly, there is also a risk of oscillations and vibrations during operation, which can lead to an emergency shutdown.

Corrosion also poses a risk to wind turbines. The most severe corrosion occurs in offshore wind turbines because they are exposed to water with high salinity and extreme humidity. Steel corrodes and rusts when it comes into contact with oxygen and water. This weakens the components and their durability. The water leads to the decomposition of the metallic foreign bodies, while the salt improves their conductivity and makes them more reactive. This process can damage the offshore wind turbine and, in the worst case, endanger its stability.

 

Conclusion

Transporting wind turbines and assembling them involves many risks. To prevent these, some preventive measures can be taken. On the one hand, detailed planning of the transport is an important factor. Securing the transport route and precise planning of the route are the decisive factors here. Secondly, the appropriate insurances should be taken out. While these do not minimize risks, they do help if damage occurs.

Further links

BWE BundesverbandWindEnergie (German)
EnergieAgentur.NRW (German)

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