Results of the icing atlas are presented in the Finnish Wind atlas map interface. The results are shown in 2,5 km x 2,5 km grid for three levels (50 m, 100 m, 200 m) above the surface. In map format we represent hours of active icing [>10 g/m/h per month/year], passive icing [>10 g/m per month/year] and estimation of power production loss due to icing [%]. These values are also given in table form for each grid point. From the tables one can also find additional information about the intensity of active icing. As a difference compared to wind data the icing results are calculated only for three height levels without the division to different wind direction sectors.
Active icing is the time period when ice is actually accumulating. Final products present the hours when active icing exceed a thershold value 10 g/m/h.
Passive icing is the duration of ice cover on the target surface. Passive icing period lasts until the ice melts or falls down due to mechanical stress. Melting/falling was assumed in the the calculation, if the temperature of two consequetive time steps were above +0.5°C. Final products present the hours when passive icing exceed a thershold value 10 g/m. This has been estimated to be the amount of ice, which starts to affect on wind power production.
Estimation of production loss
The ice load on the turbine blade is considered to weaken the power production. The estimation of the power loss due to icing is achieved by using weakened power curves. In addition, during the most intence ice accumulation period, wind turbine is assumed to be stopped. Production losses have been reported as a percentage [%] of the annual / monthly total power production as presented in Finnish Wind Atlas.
In addition to map based products, 6 new products can be requested from individual grid poits or sub-areas in a table form (see table below). Four of the values represent the average lenght of the acitve icing periods in 4 different strength classes. 5th column represents the average length of the passive icing periods. The final column represents the power loss estimate given in percentage of the average production estimate. The values are given on three heght level: 50, 100 and 200m above the surface.
|>10 g/m/h (active)
||>10-50 g/m/h (active)
||>50-100 g/m/h (active)
||>100 g/m/h (active)
||>10 g/m (passive)