Ice throw reloaded – studies at Guetsch and St. Brais

Ice throw studies

Gütsch and St. Brais February 8, 2012

René Cattin

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Icing in wind energy

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Icing in Switzerland

Wind map of Switzerland

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Icing in Switzerland

Icing map of Switzerland

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Gütsch

2‘300 m asl

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Gütsch

Enercon E-40

Enercon E-44

Enercon E-44

Does ice throw occur? - How often? - How far? - How heavy? - Where?

Ca. 7 days/year meteorological icing Ca. 30 days/year instrumental icing Ca. 150 days/year temperature below 0°C Wind turbines equipped with blade heating

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Alpine Test Site Gütsch COST Action 727: Atmospheric Icing on Structures 2005 to 2009

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Method

After each icing event, the area around the wind turbine is inspected for ice throw. All found ice fragments are recorded -  Distance -  Angle -  Size -  Weight -  Type of ice (rime, glaze, wet snow) -  Photo of ice fragment

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Method

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Method

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Methodik

•  Not all events could be captured

•  Inspection partly delayed

•  Exact time of ice throw unknown

•  No distinction between ice throw and ice fall

Inspections during 4 winters (2005 bis 2009) à 32 icing events recorded à 228 ice fragments documented à Also during summer

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Ice throw study Gütsch

Maximum distance: 92m (2.25 rotor diameter) Maximum weight: 1.8 kg

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Ice throw study Gütsch

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Ice throw study Gütsch

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Ice throw study Gütsch

Föhn

à Risky areas seem to be dependant on wind statistics under icing consitions

Icing

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Ice throw study Gütsch

Types of ice

Rime Glaze Wet snow

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Ice throw study Gütsch

Distance to wind turbine

50%

Rotor blade

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Ice throw study Gütsch

Angle relative to wind turbine

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Ice throw study Gütsch

Resultate

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Conclusions

•  Ice throw occurs

•  Wind conditions during icing event define risk areas

•  Ice throw when blade is moving downwards?

•  50% of ice fragments found under rotor blade

•  Heavy ice fragments (> 600 g) under rotor blade

•  Ice throw also during summer time

à Übertragbarkeit der Resultate auf grössere WEA??

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Counter measures

•  Routing of winter walkway was changes

•  Warning signs were installed

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Conclusions

Further study during winter 2011/12

2 Enercon E-82 Hub height 78 m Enercon blade heating

St. Brais 1‘100 m asl

No real icing events so far

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Ice throw model SWIM

•  Simple Wind turbine Icethrow Model

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Ice throw model SWIM

•  Simple Wind turbine Icethrow Model

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Ice throw model SWIM

•  Simple Wind turbine Icethrow Model

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Thank you…

METEOTEST Fabrikstrasse 14 CH-3012 Bern www.meteotest.ch

…for your attention