scholarly journals MISALIGNMENT AND LAG TIME OF WIND AND WAVE OCCURRENCE BASED ON 10 YEARS MEASUREMENTS IN THE NORTH SEA NEAR THE GERMAN COAST

2018 ◽  
pp. 13
Author(s):  
Arndt Hildebrandt ◽  
Remo Cossu
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
North Sea ◽  
Offshore Wind ◽  
Wave Loads ◽  
Wind Speeds ◽  
The North ◽  
The North Sea ◽  
The Impact ◽  
The Waves

There are several intentions to analyze the correlation of wind and wave data, especially in the North Sea. Fatigue damage is intensified by wind and wave loads acting from different directions, due to the misaligned aerodynamic damping of the rotor regarding the wave loads from lateral directions. Furthermore, construction time and costs are mainly driven by the operational times of the working vessels, which strongly depend on the wind and wave occurrence and correlation. Turbulent wind can rapidly change its direction and intensity, while the inert water waves react slowly in relation to the wind profile. Tuerk (2008) investigates the impact of wind and turbulence on offshore wind turbines by analyzing data of four years. The study shows that the wave height is increasing with higher wind speeds but when the wind speed drops the reaction of the waves is postponed. The dependence of the wave height on the wind speed is varying because of the atmospheric stability and different wind directions. Fischer et al. (2011) estimated absolute values of misalignment between wind and waves located in the Dutch North Sea. The study presents decreasing misalignment for increasing wind speeds, ranging up to 90 degrees for wind speeds below 12 m/s and up to 30 degrees for wind speeds above 20 m/s. Bredmose et al. (2013) present a method of offshore wind and wave simulation by using metocean data. The study describes characteristics of the wind and wave climate for the North and Baltic Sea as well as the directional distribution of wind and waves. Güner et al. (2013) cover the development of a statistical wave model for the Karaburun coastal zone located at the southwest coast of the Black Sea with the help of wind and wave measurements and showed that the height of the waves is directly correlating with the duration of the wind for the last four hours.

Relative Motion During Single Blade Installation: Measurements From the North Sea

2020 ◽  
Author(s):  
Aljoscha Sander ◽  
Andreas F. Haselsteiner ◽  
Kader Barat ◽  
Michael Janssen ◽  
Stephan Oelker ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
North Sea ◽  
Relative Motion ◽  
Significant Wave Height ◽  
Offshore Wind ◽  
Wave Excitation ◽  
Significant Wave ◽  
The North ◽  
The North Sea

Abstract During single blade installation in offshore wind farms, relative motion between nacelle and blade root due to wind and wave excitation pose a significant challenge. Wave excitation can be modelled considerably well by employing state-of-the-art simulation tools and can, therefore, be included in installation planning. Other phenomena, such as flow-induced vibrations are hard to capture and hence challenging to account for when defining installation procedures and limitations. Here, we present measurements conducted during the installation of an offshore wind farm consisting of multi-megawatt turbines installed on monopile foundations in the North Sea. A custom-built sensor capturing linear & angular acceleration and GPS-data was deployed atop the nacelle. Both partially and fully assembled turbines displayed complex oscillation orbits, swiftly changing amplitude and direction. Mean nacelle deflection correlated strongly with significant wave height as well as mean wind speed. As wind speed and significant wave height showed a strong correlation as well, it is difficult to discern which load drives the observed relative motions. While wind loads are significantly smaller than wave loads on partially assembled turbines under installation conditions, additional momentum induced by vortex shedding may prove sufficient to cause the observed effects.

Forecasting offshore wind speeds above the North Sea

Wind Energy ◽  
2004 ◽  
Vol 8 (1) ◽  
pp. 3-16 ◽  
Author(s):  
Jens Tambke ◽  
Matthias Lange ◽  
Ulrich Focken ◽  
J�rg-Olaf Wolff ◽  
John A. T. Bye
Keyword(s):  
North Sea ◽  
Offshore Wind ◽  
Wind Speeds ◽  
The North ◽  
The North Sea

Validation of ERS-2 SAR offshore wind-speed maps in the North Sea

2004 ◽  
Vol 25 (19) ◽  
pp. 3817-3841 ◽  
Author(s):  
C. B. Hasager ◽  
E. Dellwik ◽  
M. Nielsen ◽  
B. R. Furevik
Keyword(s):  
Wind Speed ◽  
North Sea ◽  
Offshore Wind ◽  
The North ◽  
The North Sea

scholarly journals On the effects of inter-farm interactions at the offshore wind farm Alpha Ventus

2021 ◽  
Vol 6 (6) ◽  
pp. 1455-1472
Author(s):  
Vasilis Pettas ◽  
Matthias Kretschmer ◽  
Andrew Clifton ◽  
Po Wen Cheng
Keyword(s):  
North Sea ◽  
Turbulence Intensity ◽  
Wind Farm ◽  
Wind Farms ◽  
Energy Transition ◽  
Offshore Wind ◽  
Wind Speeds ◽  
The North ◽  
The North Sea ◽  
Layer Flow

Abstract. The energy transition means that more and more wind farms are being built in favorable offshore sites like the North Sea. The wind farms affect each other as they interact with the boundary layer flow. This phenomenon is a topic of current research by the industry and academia as it can have significant technical and financial impacts. In the present study, we use data from the Alpha Ventus wind farm site to investigate the effects of inter-farm interactions. Alpha Ventus is the first offshore German wind farm located in the North Sea with a fully equipped measurement platform, FINO1, in the near vicinity. We look at the effects on the wind conditions measured at FINO1 before and after the beginning of operation of the neighboring farms. We show how measured quantities like turbulence intensity, wind speed distributions, and wind shear are evolving from the period when the park was operating alone in the area to the period when farms were built and operate in close proximity (1.4–15 km). Moreover, we show how the wind turbine's response in terms of loads and generator and pitch activity is affected using data from a turbine that is in the vicinity of the mast. The results show the wake effects in the directions influenced by the wind farms according to their distance with increased turbulence intensity, reduced wind speeds, and increased structural loading.

scholarly journals Storm Anatol over Europe in December 1999: impacts on societal and energy infrastructure

2021 ◽  
Vol 56 ◽  
pp. 141-153
Author(s):  
Anthony J. Kettle
Keyword(s):  
Wind Energy ◽  
Storm Surge ◽  
North Sea ◽  
Rogue Waves ◽  
Offshore Wind ◽  
Forest Damage ◽  
Offshore Wind Energy ◽  
The North ◽  
The North Sea ◽  
The Impact

Abstract. Storm Anatol impacted the North Sea and northern Europe on 3–4 December 1999. It brought hurricane force winds to Denmark and northern Germany, and high winds also in Sweden and countries around the Baltic Sea. For many meteorological stations in Denmark, the wind speeds were the highest on record and the storm was ranked as a century event. The storm impacts included extensive forest damage, fatalities, hundreds of injuries, power outages, transportation interruptions, as well as storm surge flooding on the west coast of Denmark. Strongly committed to wind energy, Denmark lost 13 onshore wind turbines destroyed during the storm. An important industry insurer noted that this was a remarkably low number, considering the storm intensity and the large number of turbines (>3500) installed in the country. In 1999, offshore wind energy was just getting started in Europe, and the storm provided an important test of environmental extreme conditions impacting offshore infrastructure. This contribution takes a closer look at the regional met-ocean conditions during the storm. A brief overview is made of the wind field and available wave measurements from the North Sea. An examination is made of water level measurements from around the North Sea to characterize the storm surge and identify possible meteo-tsunamis and infragravity waves. Offshore accidents are briefly discussed to assess if there had been unusual wave strikes on shipping or platforms. At the time of the storm in 1999, there was a growing awareness in the scientific community of possible changes in ambient sea state conditions and the increasing threat of rogue waves. The offshore wind energy community had become aware from the impact of rogue waves from damage at the research platform FINO1 in the southern North Sea during severe storms in 2006, 2007, 2009, and 2013. Storm Anatol may have been another rogue wave storm at an earlier stage of offshore wind energy development.

Comparison of Umbilical Installation Analysis Using Two Irregular Wave Spectra

2010 ◽  
Author(s):  
Airindy Felisita ◽  
Ove Tobias Gudmestad ◽  
Lars Olav Martinsen
Keyword(s):  
Wave Height ◽  
North Sea ◽  
Physical Environment ◽  
Wave Spectra ◽  
Irregular Wave ◽  
The North ◽  
Bending Radius ◽  
The North Sea ◽  
The Impact ◽  
Jonswap Spectrum

Umbilicals are widely used to provide monitoring and control functions for distant satellite wellheads in subsea developments. Detailed analysis is required to predict the behavior of the umbilical during the installation process. Finite Element Analysis is performed to determine the limiting operational sea-state for the installation operations. This paper presents work carried out with Acergy Norway AS, comparing two irregular wave spectra that are commonly used for installation analysis in the North Sea. The purpose of the study is to select the most suitable method for the installation analysis with respect to different types of installation operations. Selection is carried out based on several limiting criteria, including top tension, compression, minimum bending radius and the tension at the touchdown point. The JONSWAP spectrum and Torsethaugen spectrum are used to model the physical environment of the North Sea. Both of these spectra are especially designed for North Sea environment. The JONSWAP spectrum represents the fetch-limited (or coastal) wind generated seas, meanwhile the Torsethaugen spectrum represents the wave conditions in open ocean areas where the waves are dominated not only by local wind seas but are also exposed to swells (Torsethaugen and Haver, 2004). Two types of installation operations are selected for this work, which are the “buoyancy overboarding” for dynamic umbilical installation analysis and “normal lay” for static umbilical installation analysis. The analysis shows that the Torsethaugen spectrum generates higher tension forces compared to the JONSWAP spectrum. On the other hand, the JONSWAP spectrum generates higher compression and lower bending radius. However, the differences between the results using these two spectra are not large. This is due to the limited wave height and period applicable for installation operations. This work only covers wave height of Hs = 2.5–4.0 m and wave period of Tp = 6–14 s. The selection of these low conditions is based on typical sea states for installation operation (without consideration of survival conditions). Since there is only small variation on the results from the two spectra, both JONSWAP and Torstehaugen spectra are considered suitable for analysis of installation operations. It is further noted that although the Torstehaugen spectra will often provide a more realistic representation of the physical environment, forecast or measured weather data is rarely presented in this form, therefore the JONSWAP or other single peak spectra must be used for decision making offshore. This study has validated that for the range of condition studied, this is an acceptable approach. The conclusion from this study is only applicable for low sea-states and without considering effects from different direction of wind seas and swells components in the Torsethaugen spectrum. Therefore further work is required to fully asses the impact of directionality between the wave components and the impact of higher sea states which are applicable to survival conditions.

scholarly journals The 3 km Norwegian reanalysis (NORA3) – a validation of offshore wind resources in the North Sea and the Norwegian Sea

2021 ◽  
Vol 6 (6) ◽  
pp. 1501-1519
Author(s):  
Ida Marie Solbrekke ◽  
Asgeir Sorteberg ◽  
Hilde Haakenstad
Keyword(s):  
Wind Speed ◽  
Wind Power ◽  
Offshore Wind ◽  
Data Set ◽  
Norwegian Sea ◽  
Offshore Wind Power ◽  
Wind Speeds ◽  
The North ◽  
The North Sea ◽  
Simulated Wind

Abstract. We validate a new high-resolution (3 km) numerical mesoscale weather simulation for offshore wind power purposes for the time period 2004–2016 for the North Sea and the Norwegian Sea. The 3 km Norwegian reanalysis (NORA3) is a dynamically downscaled data set, forced with state-of-the-art atmospheric reanalysis as boundary conditions. We conduct an in-depth validation of the simulated wind climatology towards the observed wind climatology to determine whether NORA3 can serve as a wind resource data set in the planning phase of future offshore wind power installations. We place special emphasis on evaluating offshore wind-power-related metrics and the impact of simulated wind speed deviations on the estimated wind power and the related variability. We conclude that the NORA3 data are well suited for wind power estimates but give slightly conservative estimates of the offshore wind metrics. In other words, wind speeds in NORA3 are typically 5 % (0.5 m s−1) lower than observed wind speeds, giving an underestimation of offshore wind power of 10 %–20 % (equivalent to an underestimation of 3 percentage points in the capacity factor) for a selected turbine type and hub height. The model is biased towards lower wind power estimates due to overestimation of the wind speed events below typical wind speed limits of rated wind power (u<11–13 m s−1) and underestimation of high-wind-speed events (u>11–13 m s−1). The hourly wind speed and wind power variability are slightly underestimated in NORA3. However, the number of hours with zero power production caused by the wind conditions (around 12 % of the time) is well captured, while the duration of each of these events is slightly overestimated, leading to 25-year return values for zero-power duration being too high for the majority of the sites. The model performs well in capturing spatial co-variability in hourly wind power production, with only small deviations in the spatial correlation coefficients among the sites. We estimate the observation-based decorrelation length to be 425.3 km, whereas the model-based length is 19 % longer.

scholarly journals Evolution of marine storminess in the Belgian part of the North Sea

2012 ◽  
Vol 12 (2) ◽  
pp. 305-312 ◽  
Author(s):  
D. Van den Eynde ◽  
R. De Sutter ◽  
P. Haerens
Keyword(s):  
Wave Height ◽  
North Sea ◽  
Scientific Evidence ◽  
Clear Trend ◽  
Wind Speeds ◽  
The North ◽  
Mitigation And Adaptation ◽  
Extreme Wind ◽  
The North Sea ◽  
Extreme Wind Speeds

Abstract. Severe storms have affected European coast lines in the past but knowledge on changes in storminess for the last decades is still sparse. Climate change is assumed to be a main driving factor with the potential to induce changes on the intensity, duration and frequency of powerful marine storms, including a long-term influence on peak wind speeds, surges and waves. It is, therefore, important to investigate whether in the last decades changes in the magnitude of storms, their duration and frequency could be observed. Understanding trends in storminess in the last decades will help to better prepare coastal managers for future events, taking into account potential changes on storm occurrence and magnitude to improve planning of mitigation and adaptation strategies. The purpose of this study was to focus on the evolution of extreme wind conditions, wave height and storm surge levels in the North Sea Region, especially in the Belgian part of the North Sea (BPNS). Based on the analysis performed it is concluded that no clear trend can be observed for the occurrence of significant increasing extreme wind speeds over the BPNS. Furthermore, one can conclude that not enough scientific evidence is available to support scenarios with increased wave height or storminess.

scholarly journals On the effects of inter-farm interactions at the offshore wind farm Alpha Ventus

2021 ◽  
Author(s):  
Vasilis Pettas ◽  
Matthias Kretschmer ◽  
Andrew Clifton ◽  
Po Wen Cheng
Keyword(s):  
North Sea ◽  
Turbulence Intensity ◽  
Wind Farm ◽  
Wind Farms ◽  
Energy Transition ◽  
Offshore Wind ◽  
Wind Speeds ◽  
The North ◽  
The North Sea ◽  
Layer Flow

Abstract. The energy transition means that more and more wind farms are being built in favorable offshore sites like the North Sea. The wind farms affect each other as they interact with the boundary layer flow. This phenomenon is a topic of current research by the industry and academia as it can have significant technical and financial impacts. In this study we use data from the Alpha Ventus wind farm site to investigate the effects of inter-farm interactions. Alpha Ventus is the first offshore German wind farm located at the North Sea with a fully equipped measurement platform FINO1 in the near vicinity. We look at the effects on the wind conditions measured at FINO1 before and after the beginning of operation of the neighboring farms. We show how measured quantities like turbulence intensity, wind speed distributions, and wind shear are evolving from the period where the park was operating alone in the area to the period where farms were built and operate in close proximity (1.4–15 km). Moreover, we show how the wind turbine performance is affected using data from a turbine that is in the vicinity of the mast. The results show the wake effects in the directions influenced by the wind farms according to their distance with increased turbulence intensity, reduced wind speeds, and increased structural loading.

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