Weather Conditions

Wind

According to the Central Institute for Meteorology and Geodynamics (CIMG): Value V10 (2 sec gust in 10 metres over a period of 10 years according to the Austrian Standard ÖNORM B 4014) = 56,94 m/s (205 km/h).

The German Wind Institute (DEWI) calculated the maximum 2 second gust at an air density of 1.1 kg/m³ and under standard dynamic pressure to amount to 54.77 m/s.

Using the measured maximum 1 second gust of 46.9 m/s from January 2000 (10 min. maximum 33.8 m/s) and the Weibull parameters a = 8.4 m/s and c = 1.62, DEWI determined the maximum 3 second gust (once in 50 years) according to Bergström to amount to 58 m/s.

It can be expected that maximum wind speeds for Oberzeiring will be below 60 m/s although at other exposed sites in Austria in the last 10 years maximum wind speeds of over 60 m/s have been measured. This is due to the fact that the wind park is situated below an altitude of 2000 m and located on the southern ridge of the Alps.

The wind turbines will be designed for 2 second maximum wind speed values of 60 m/s.

Icing

The Austrian Standard ÖNORM "Ice and Snow Accretion" has no information about ice accretion for sites at 1,900 metres. Therefore the CIMG was commissioned with the calculation of maximum ice accretion for the wind park site. The result was to expect a 5 cm layer of ice accretion on all sides.

In reality at measuring sites with heavy ice accretion, the build-up of ice can be enormous. The maximum values show a 45 cm ice layer on guy lines and a 1,050 mm (over 1 metre) on the mast.

Temperature

Measured minimum temperatures at Oberzeiring:

In the measuring period June 1999 to June 2000, only one day was measured at the site of the planned wind park with a temperature below -20°C.

The lowest measured temperature was on 25 January 2000 at 0:50 a.m. and amounted to -20.85°C.

The period with a measured temperature of under -20°C lasted for 5 hours.

Measured minimum temperatures for other measuring stations in the Alps:

In order to define the minimum temperature at the wind park site in 1,900 m, the CIMG examined data from the meteorological measurement station Villacher Alps (2,156 m) The temperature data from this station, which is also located on the southern ridge of the Alps, would be typical for the wind park site in Oberzeiring.

According to the data from a measuring period of 6 years (1994 - 2000), the following minimum temperatures were measured at the met station Villacher Alps:

-34.9° to -30.0 °C 4 hours
-29.9° to -25.0°C 4 hours
-24.9° to -20.0°C 109 hours

It was agreed that the wind turbines would be designed for a minimum operational temperature of -20°C.

Lightning stroke density at the site

A report about the expected average lightning stroke density at the site was made by the Austrian Lightning Detection & Information System (ALDIS).

The average lightning stroke density based on the lightning frequency from the years 1992 - 2000 was predicted to be 3.81 lightning strikes/km² and year.