As turbines grow taller and are installed in more remote and exposed locations, the risk of lightning strikes increases.
Calculations by Polytech show that minimum one out of five global wind farm locations have a significant risk of operations being severely influenced by lightning and are exposed to costly damage and repair if the blade design and/or lightning protection system (LPS) are insufficient.
To minimize downtime and mitigate repairs and minor cracks developing into major damages, asset owners should focus on efficient lightning monitoring and LPS integrity measurements. This will also support lightning-related claims between developers, OEMs and insurance companies.
There are two types of risk associated with damaged wind turbines concerning lightning which are turbine-specific risks as well as site-specific risks.
Turbine-specific risks are related to the LPS design of the turbine and the blade, the maintenance intervals and the related mechanical fatigue of the component during the lifetime. These risks are manufacturer and component-specific and can be impacted by design, manufacturing capabilities, quality assurance, or testing requirements.
Site-specific risks are directly related to the location and the environment of the wind turbine. Here an independent assessment can be made, and different sites can be compared with each other. The assessment of the lightning risk for a turbine is a combination of several aspects and Polytech has developed a method for structured assessment of lightning risk that includes the following parameters:
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Flash density: The most critical parameter for the lightning risk to a tall structure is the flash density. Wind turbines built in areas with higher lightning activities have a higher risk of intercepting downward lightning flashes or starting upward lightning events triggered by other nearby lightning activities.
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Risk of wind turbines being near the charged thundercloud: Another critical assessment criterion is the risk of the wind turbine being in proximity to the charged particles in the thundercloud. Typically, the charged thundercloud is kilometers above the wind turbine, and leaders approach the turbine from the sky, forming dedicated lightning channels which concentrate the electric field. This makes it easier for answering lightning leaders to form at the intended attachment locations and propagate towards the incoming lightning leaders. In case the charged thundercloud is nearby, the overall size of the electric field on the blade is higher, leading to a higher risk of lightning leaders starting in unintended places. Additionally, more upward lightning activities are expected, which can bring extra wear to the external LPS components, such as the tip and side receptors.
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Undetected Lightning: Depending on the lightning source, the reported flash density may not be correct. Particularly, upward lightning is often difficult to detect with Lightning Location Systems.
Polytech has digested more than 6.500 existing and upcoming onshore and offshore wind sites (>10MW total installed capacity) on the listed sites risks and categorized them into a risk index. 20% of the wind farms are in lightning dense areas where the risk high, very high or extreme number is (minimum 4 out of 9). Most exposed areas are the US, Southern Europe around the Mediterranean Sea and South East Asia (China, Japan, Taiwan, South Korea and Vietnam).
The result is the Global Site-Specific Risk Map below.
If you want to calculate the exact site-specific risk number for your site, feel free to use the free Polytech Online Site Assessment tool. All parameters mentioned above will be analyzed specifically for your site and a report will be made to document the results.
Data:
- The lightning data originates from the publication “WWLLN Global Lightning Climatology and timeseries (WGLC)”.
- The meteorological data comes from the Copernicus Climate Change Service (C3S).
- The elevation data is sourced from the Generic Mapping Tools (GMT) platform.
- The analysis includes 6567 wind farms globally with coordinates, each with a minimum of 10 MW installed capacity, sourced from Windpower.net.