Laser on Scottish floating turbine catches unusual wind shifts that can cut power by up to 18%
Off the northeast coast of Scotland, five turbines rise nearly 100 meters above the North Sea — the world’s first commercial floating offshore wind farm. A laser-mounted sensor just caught wind behaving badly in real time, and the findings challenge core assumptions behind how floating turbines are built and evaluated.
Offshore wind is not as simple as it looks
The common picture of offshore wind is reassuring: open water, low friction, steady airflow. Compared to onshore sites — where trees, hills, and buildings churn the wind into something turbulent and unpredictable — the sea looks like a clean slate. That assumption has guided turbine design and performance testing for years.
But modern offshore turbines are enormous. At Hywind Scotland, each rotor sweeps from roughly 20 meters above sea level up to about 175 meters. Across that vertical range, the wind doesn’t always behave as expected. Low-level jets can create a band of fast-moving air at a specific altitude, with slower wind both above and below it. Negative wind shear — where speed decreases with height rather than increasing — can flip the standard profile entirely.
When the wind profile shows negative shear, turbine power production drops by up to 18% relative to the reference power curve of an equivalent fixed-bottom turbine.
A laser on a floating turbine reveals the hidden wind
To get direct observation, researchers installed a nacelle-mounted Doppler lidar on one of the five turbines at Hywind Scotland, designated HS4. The instrument scanned along four separate lines of sight, collecting radial wind speed measurements at 10 distances from the turbine — ranging from about 0.3 to 2.6 rotor diameters upstream.
The turbine floats and pitches with the waves, tilting up to 7 degrees depending on wind speed, so the lidar’s measurement geometry shifts constantly. Correcting for that motion required a motion reference unit mounted on the nacelle to track pitch and roll in real time. Data collection ran through summer and autumn, producing nearly 6,700 usable ten-minute observation periods — enough to draw statistically meaningful conclusions about what the wind was actually doing.
One in three cases showed abnormal wind profiles
The results were striking. In 33% of examined cases, the wind profile within the rotor-swept area deviated from the standard logarithmic shape that models typically assume over open water.
Negative wind shear appeared in 22% of cases, concentrated in summer months from June through September and spread across the full range of observed wind sectors. Wind speed inversions — the defining signature of a low-level jet — were detected in an additional 11% of cases. Together, those two categories account for roughly one in three observations. That’s not a rare edge case. It’s a regular feature of the wind environment that floating turbines in the North Sea are operating in.
The power cost of getting the wind profile wrong
Abnormal wind profiles don’t just complicate measurement — they cut power output. When the wind profile shows negative shear, turbine power production drops by up to 18% relative to the reference power curve of an equivalent fixed-bottom turbine.
In the below-rated wind speed range, the mean power difference between negative-shear and positive-shear cases ranges from 5% to 10%, depending on how wind speed is estimated. Under negative shear, the standard deviation of produced power is nearly twice as large as under positive shear conditions. A case study from June 26, 2020, shows how extreme these episodes can get: during a 12-hour period dominated by low-level jet conditions, normalized power deviations reached up to 50% compared to the reference power curve.
Why standard power testing methods fall short for floating turbines
Current international standards for wind turbine power verification — defined in IEC 61400-12-1 — were designed for fixed, land-based turbines. They don’t account for turbine motion, and they don’t account for wind profiles that deviate from the logarithmic model.
The standard approach uses hub-height wind speed as the single reference point. This study shows that doing so introduces biases of up to 20% when the profile is non-standard — a significant error for any commercial performance assessment. One proposed improvement is rotor-equivalent wind speed (REWS), which averages wind speed across the full rotor disk. REWS works reasonably well when shear is positive, but under negative shear it can’t be calculated reliably without measurements in the lower rotor half, a gap the nacelle-mounted lidar couldn’t fully bridge.
What this means for the future of floating wind
Floating offshore wind is expanding into deeper waters where fixed-bottom turbines can’t be installed but wind resources are often stronger. Getting performance assessment right matters more as the stakes grow larger.
This study points to nacelle-mounted lidars as a practical path forward. They move with the turbine, stay aligned with the wind, and measure across multiple heights at once. Future campaigns will need configurations reaching from blade tip to blade tip to fully characterize speed inversions and enable accurate REWS calculations under all conditions — something current setups can’t yet deliver.
Energy yield predictions for floating wind farms may be systematically optimistic if they don’t account for how often the wind profile departs from the standard model. Refining those predictions — with better data, better instruments, and updated standards — is the work now ahead of the industry.
All the information is available here: Angelou, N. and Dubreuil-Boisclair, C.: Offshore wind profile characteristics and their impact on floating wind turbine power production, Wind Energ. Sci., 11, 3745–3762, https://doi.org/10.5194/wes-11-3745-2026, 2026.
Daniel García is an Editor-in-Chief with strong expertise in structural work and engineering principles. He combines this technical foundation with deep knowledge of energy, spatial design, and emerging technologies, bringing a forward-thinking and analytical approach to editorial leadership.
