Assessment of Low-Level Icing Conditions and Their Effect on Wind Power

Scientists from the Finnish Meteorological Institute (FMI) and Leading Edge Atmospheric (LEA, USA) have studied the near-surface icing processes. The outcome of the study is a real-time icing analysis-system LAPS-LOWICE, which is able to produce high-resolution grids of icing probability, icing rate, and ice load, as well as expected ‘‘clean'' (ice free) and ‘‘iced'' wind turbine power.

The wind power industry is highly sensitive to weather, and there is a clear impact on turbine efficiency associated with icing, which can cause significant power losses (even total shutdown of wind farms), faster wear of mechanical parts and safety threat (i.e. throwing/falling ice). This is becoming increasingly important as more wind power capacity is being built in cold climates, where there is a large threat of icing. Therefore, accurate analyses and forecasts of wind- and icing-related meteorological variables are of great importance.

The analysis and forecasting of icing is very difficult, especially close to ground. There is a great value in real-time observations if they are applied correctly and blended effectively with model fields. In particular, all data (observations and model fields) related to clouds and precipitation (satellite, METAR, SYNOP, T and RH-profiles, etc.) have proven to be of great interest and is important for the wind turbine icing and power production diagnoses and forecasts.

By blending 3D numerical model fields and observations in a manner that is consistent with the meteorology of icing, LAPS–LOWICE is able to produce high-resolution grids of icing probability, icing rate, and ice load, as well as expected ‘‘clean'' (ice free) and ‘‘iced'' wind turbine power. As a result, it became clear that power losses did not correlate well with measured icing loads but correlated reasonably well with the time history of icing rate in combination with ice loss due to melting, sublimation, and shedding. The LAPS–LOWICE system has potential to provide highly valuable analysis information to the wind power community.

The LAPS-LOWICE system has been validated against observations of power production and other fields (e.g., wind speed, temperature) for several wind farms across Sweden over five icing seasons: 2009–2014.

More information

Researcher Erik Gregow, FMI, puh. +358 29 539 4167, erik.gregow@fmi.fi

Full article in AMS JTECH journal: http://dx.doi.org/10.1175/JTECH-D-14-00151.1