For wind park investors, energy production is an indicator for profit. To estimate how much wind will be available for a planned wind park during its lifetime, wind specialists designed a process called the wind measurement campaign. To obtain the best possible understanding of available wind resources across the wind turbines rotor area and the project area, measurement devices are placed in carefully selected locations. The main goal of these devices is to obtain a sufficient amount of good-quality data to characterize the wind resource. Our wind specialist Romana Madic explains more about how these campaigns work and how she uses these in our wind project in Croatia: VE Lički Medvjed.

‘Green Trust as the initiator, developer and consultant in wind project VE Lički Medvjed, designed and carried out a wind measurement campaign for this project. The terrain in the area of the planned wind farm is characterized as complex. Of course, the forested mountains look beautiful and give an amazing view. But this forested mountains with up to 300 meters of elevation differences can also bring challenges for wind measurements,’ Romana explains.

Lidar systems compared to traditional meteorological masts
Romana explains which system is used for our project in Croatia: ‘Next to meteorological masts, for this measurement campaign, remote sensing devices -Lidar WindCube v2.0 are used. Within the field of wind measurement technology, the lidar system stands out as an innovative, flexible, and in cases of forest areas, a more nature-friendly solution, compared to traditional meteorological masts. Lidar devices, like the WindCube v2.0, use laser beams to measure wind speed and direction at various heights.’

‘While raw lidar measurements provide valuable data, they may not be entirely accurate in complex terrains due to the diverse and unpredictable flow patterns. The wind goes with the flow that has been disturbed by terrain, forestry, or structures and may result in a lidar perceiving and consequently measuring something different compared to a conventional cup anemometer. The cup anemometers measure only a single point, while the lidar assesses and averages the wind over a volume, assuming flow homogeneity across the volume of measurement. In complex terrain or locations with a lot of obstacles like industrial areas, this assumption is no longer valid, and measurements become inaccurate. When the flow is complicated there are likely variations in what is being measured and might be obvious when the two technologies are compared. To overcome these limitations on raw measurements, advanced correction techniques have been invented by lidar manufacturers and leading wind industry consultants–like vector averaging and corrections for complex flows using Computational Fluid Dynamics (CFD).’

How we measure at VE Lički Medvjed
‘At one measurement location, measurements were made simultaneously using a meteorological mast and a lidar,’ Romana tells. ‘Available data from both devices overlapped (concurrent measurement) over a period of seven months. This made it possible to compare the corrected lidar measurement according to the aforementioned recommendations, with the measurements obtained from the meteorological mast. The reference height for the analysis was 75m. By analysing the data in the windPRO software (MCP module), an exceptionally good correlation (0,996) between the two measurements was obtained. At the same time, other indicators of the quality of prediction using corrected lidar measurements were very good.

Based on the analysis results, we can state with certainty that the corrected lidar measurements are very reliable for use for the wind resource assessment. I think the Lidar wind measurement corrections in complex terrain are important because of its terrain-adaptive accuracy and it’s reduced uncertainty. In general, this contributes to the optimization of wind energy projects, which play a central role in the global transition to clean and renewable energy sources,’ Romana says with a proud look on her face. ‘Isn’t it beautiful helping this transition in this way’?

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