Metsähallitus is about to launch wind measurements in Maalahti, Finland. These measurements are part of the plans to build an offshore wind farm 15 km off the west coast in Korsnäs. The first step is putting up the wind measurement mast in November.
Metsähallitus is building a measurement mast to study wind conditions in Bergö, Maalahti. Both a crane and a helicopter will be needed to install the mast, which will reach up to a height of around 170 metres.
The purpose of the measurements is to study wind conditions in the area, including the average wind speed, turbulence and variation in wind speeds at different heights.
The wind conditions will be measured as close as possible to the planned hub height of the wind turbines. Preliminary assessments indicate that the area has favourable wind conditions.
After some two years of measurements, the mast will be taken down.
Wind is measured by several methods
In addition to the several wind measurement sensors installed on the mast, the wind is also measured with a SODAR unit, which measures sound waves as they travel through the air, will also be used for wind measurements. The SODAR unit transmits acoustic pulses from the ground level up to 300 meters and calculates wind strength from their return signals. A SODAR unit looks like an everyday trailer equipped with a measuring device.
The measurements will also be complemented with LIDAR, laser technique in which low-power laser beams are transmitted into the atmosphere. This device, which is the size of a washing machine, calculates wind speeds up to a height of 300 m based on the back-scattered light.
The measurements will take around two years
Wind conditions are usually measured for one to two years before the decision to invest in a wind power plant is made. A long measurement period is needed because of every year is not the same, and measurements must be taken round the year.
Wind power plants have a life span of 25 to 30 years, which is why long-term wind data is needed to underpin the investment. Studies have shown that after two years, the accuracy of the measurement results will no longer improve significantly.
Stronger winds higher up
Wind conditions are measured at different heights. The higher you go, the windier it gets. There are also fewer completely windless moments higher up. Even if the day were flat calm at ground level, there is always some wind at the height of 200 metres.
Favourable wind conditions are important for the profitability of the power plant, whereas for safety reasons, it is essential to turn the plant off on stormy days. The wind power plant lives and moves along with the wind. A wind of approx. 10 metres per second already bends the blade tips of the turbine by several metres.
The same basic structure with 50 times higher capacity
Wind turbine technology continues to develop rapidly. Wind turbines are getting taller, and so far all old predictions of stagnating development have proven unfounded.
The basic structure of the wind turbine has endured, however, even if the modern plant’s capacity is 50 times higher. The optimal structure from the technical and economic viewpoint consists of a tower and a nacelle with three blades attached. As lately as in the 1980s and 1990s, wind turbines had competing structures which were peculiar-looking compared to today’s models. Their typical capacity was 0.3 MW or less. The capacity of the plants planned in Korsnäs is estimated at 12 to 20 MW.
Further information for the media
Ville Kokkonen, Wind Power Specialist, Metsähallitus, tel. +358 (0)20 639 4190, e-mail: ville.kokkonen@metsa.fi
Metsähallitus’ wind power communications:
Hanna Kaurala, tel. +358 40 350 4947, e-mail: hanna.kaurala@metsa.fi