Ice build up on blades is a huge problem for wind turbine downtime during winter months in some regions where more than 6 weeks of turbine standstill is common. This lost generation can run up into the GWh very quickly when the price of power is potentially at its highest in the winter months

Why is icing a problem?
Safety
Icing can be thrown large distances from the blade surface to cause harm to human life or property. The wind turbine’s safety protocol also requires physical inspection after an icing shutdown to confirm that the blade is free of ice prior to a local restart. This can be a slow process if there are no technicians available or site access is limited due to snow.
High loads
Blade icing can also add huge weight to the blades >800kg which puts more strain on the drive-train and structural components. This fatigue reduces the life of major components and reduces economic viability for life extension.
Lost revenue
GWh are lost every year due to icing shutdowns. Some of the shutdowns are justified but 50-70% of the this downtime could be avoided at certain sites. This could easily total over 100k EUR/season making a strong business case for an IDS retrofit.
What ice detection methods are available?
Common wind turbine ice detection systems (IDS) use:
Accelerometers – detecting mass imbalance
Power curve – detecting a difference in the power produced against the wind speed as the blades turn more slowly when laden
This allows them to build alarms into the wind turbine controller to shut down the turbine in the event of heavy ice build up. This prevents catastrophic damage to the turbine but relies on the turbine being in operation during measurements which means that ice throw is still possible and potentially you could have a turbine stuck in an alarm loop.
Secondary anemometers – delta between US sensor and impeded cup and ball sensor
The secondary anemometer ceases when freezing reducing the recorded wind speed measurement compared to the primary ultrasonic measurement. This nacelle based measurement is sub-optimal and often experiences different conditions than the blades.
These all have their shortcomings and typically rely on turbine operation and manual intervention to restore operation. We offer a system which is able to determine icing on the blade based off sensory data coming off the blade surface. Through taking impedance and temperature measurements at the point of ice build-up you can establish control feedback loops with the blade surface itself to determine when to stop the turbine and when you can safely restart it. Once a safe operating limit of ice build up (mm) is established, this alarm limit can be set and the amount and position of the sensors on the blade surface can allow for a remote picture of what is happening. This system is certified to DNV-GL standards allowing controller integration to enable automatic shutdown and restart. This means that a technician does not have to be found and deployed in the snow to inspect the turbine ahead of a local restart. Should a sensor fail then there is sufficient redundancy in the system to allow continued operation until a replacement can be made in better weather.


Comparing Ice Detection Methods
Nacelle based ice detection system
On Blade System
Accelerometers/power curve
Sensor position
Nacelle
Blade surface
Inside the rotor blade
Temperature measurement
X
✔
X
Preventative heating
X
✔
X
Wind speed for ice detection
0m/s
0m/s
2-3m/s
No SCADA integration required
✔
✔
X
No calibration required
✔
✔
X
Automatic Restart possible
X
✔
Yes with wind speed >2-3m/s
Sensor installation
Screwed onto nacelle
Rope Access
Installed in the blade
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