Wind Farm Aspiravi Brugge is a wind farm located in Belgium completed in 2016. The project consists of five turbines with a hub height of 85 m and a rotor diameter of 71 m. The rated power per turbine is 2,3 MW and the rated total power is 11,5 MW. The turbines have been provided by Vestas. Further details are mentioned below.   Hub height: 85 m IEX: 2A Number of turbines: 5 Rated power per turbine: 2,3 MW Turbine supplier: Vestas Type: Onshore Turbine Tip height: 120,5 m Rotor diameter: 71 m Rated power total: 11,5 MW  

Wind Farm Aspiravi is a wind farm located in Belgium completed in 2016. The project consists of fifteen turbines with a hub height of 105 m and a rotor diameter of 90 m. The rated power per turbine is 2 MW and the rated total power is 30 MW. The turbines have been provided by Vestas. Further details are mentioned below.   Hub height: 105 m IEX: 3A Number of turbines: 15 Rated power per turbine: 2 MW Turbine supplier: Vestas Type: Onshore Turbine Tip height: 150 m Rotor diameter: 90 m Rated power total: 30 MW  

In February 2008 the Water and Electricity Company Aruba ("WEB") requested for proposals to "build, own and operate" wind farm Vader Piet and to supply all related electricity to WEB. The Vader Piet wind farm consists of 10 turbines of the Vestas V90 type with a hub height of 105 metres and a rotor diameter of 90 metres . The foundations consist of circular concrete bases with a diameter of 13 metres, which are anchored in the limestone rock. The 24 GEWI anchors have a steel diameter of 63 mm and are drilled into the rock to a depth of 10 metres (drill diameters of 200 mm). Several test anchors were installed to examine the behaviour and bearing capacity of this rock. Due to its high capacity, it was possible to strongly reduce the size of the foundation bases. The sub soil was also subjected to plate bearing tests. Based on the test results, an inspection programme was performed. In total, the Vader Piet wind farm produces 20% of Aruba’s total electricity needs.The rated power per turbine is 3 MW and the rated total power is 3 MW. The turbines have been provided by Vestas. Further details are mentioned below.Hub height: 105 mIEX: 2ANumber of turbines: 10Rated power per turbine: 3 MWTurbine supplier: VestasType: Onshore TurbineTip height: 150 mRotor diameter: 90 mRated power total: 30 MW

Wind Farm Playa Kanoa III and Tera Kora II on Curacao is a wind farm located in Curaçao completed in 2013. The project consists of ten turbines with a hub height of 80 m and a rotor diameter of 90 m. The rated power per turbine is 3 MW and the rated total power is 30 MW. The turbines have been provided by Vestas. Further details are mentioned below.Hub height: 80 mIEX: 1ANumber of turbines: 10Rated power per turbine: 3 MWTurbine supplier: VestasType: offschore TurbineTip height: 125 mRotor diameter: 90 mRated power total: 30 MW

Wind Farm Playa Canoa is a wind farm located in Curaçao completed in 1997. The project consists of nineteen turbines with a hub height of 46 m and a rotor diameter of 53 m. The rated power per turbine is 0,5 MW and the rated total power is 9,5 MW. Further details are mentioned below.Hub height: 46 mIEX: Number of turbines: 19Rated power per turbine: 0,5 MWTurbine supplier: Type: offshore turbineTip height: 72,5 MWRotor diameter: 53 mRated power total: 9,5 MW

Wind Farm Playa Kanoa II is a wind farm located in Curaçao completed in 2002. The project consists of eighteen turbines with a hub height of 60 m and a rotor diameter of 54 m. The rated power per turbine is 0,95 MW and the rated total power is 17,1 MW. Further details are mentioned below.Hub height: 60 mIEX:Number of turbines: 18Rated power per turbine: 0,95 MWTurbine supplier: Type: Offshore TurbineTip height: 87 mRotor diameter: 54 mRated power total: 17,1 MW

Two existing wind farms in Curacao at Tera Korá, 12 turbines installed in 1992, and Playa Kanoa, 18 turbines installed in 1999, were replaced by 10 turbines of the 3 MW class. On behalf of NuCapital, ABT was involved as engineers and for the foundation design. The new wind turbines have a hub height of 80 metres and a rotor diameter of 90 metres. The project was executed in a very short period between May 2010 and December 2010, almost 5 months shorter than usual.

Windplanblauw is located on the north-east side of Flevoland in the area of Swifterbant and Dronten. This is where Vattenfall, in cooperation with SwifterwinT and Molenrak B.V. is realizing Windplanblauw. The plan involves the replacement of 74 old wind turbines for 61 new ones, which are larger and more powerful. The project consists of two parts, namely the onshore part consisting of 37 wind turbines supplied by Vestas type EnVentus 5.6MW, and 24 wind turbines located in the IJsselmeer (Nearshore) supplied by GE, type Cypress 5.5MW. Operationally, the entire wind farm will have a capacity of about 340MW, enough yield the electricity consumption of 450,000 households (about 1.0mln people).WindplanBlauw consist out of 5 contracts namely:1. Contract WTG supplier Onshore2. BOP Onshore3. WTG Supplier Nearshore4. BOP Nearshore5. SubstationWindBase was involved in all the contracts, which included:1. Contract WTG supplier Onshore, Qa/Qc of the coatings, Welding of the tower, and the stairs but also problems which occurred during the lifting process..2. BOP Onshore, Active assessment of the design, risk controlled design review but also on the work method plans, maintenance plans and inspection plans3. WTG Supplier Nearshore, visiting tower fabrication process, QA/Qc steel towers and coating inspections4. BOP Nearshore, Engineering Bases of design, Active assessment of the design and risk controlled design review en inspections during construction.5. Substation Active assessment of the design, risk controlled design review but also on the work method plans, maintenance plans and inspection plans

Wind Farm Streepland is an onshore wind farm located in near the A16 in Drimmelen North Brabant and is executed in 2022. The project consists of 3 wind turbines with a hub height of 135 m and a rotor diameter of 149 m. The rated power per turbine is 5.2 MW and the rated total power is 15.6 MW. The turbines have been provided by Nordex. Consultancy Windbase engineering of the foundation, Crane Hard Stands and Quality Control on site. Further details are mentioned below.

Wind Farm Klaverspoor is an onshore wind farm located in the Netherlands and is executed in 2022. The project consists of 6 wind turbines with a hub height of 135 m and a rotor diameter of 149 m. The rated power per turbine is 5.7 MW and the rated total power is 34.2 MW. The turbines have been provided by Nordex. Consultancy Windbase engineering of the foundation and Quality Control on site. Further details are mentioned below.

Wind Farm Sainte Ode is an onshore wind farm located in Belgium and completed in 2023. The project consists of 5 wind turbines with a hub height of 114m and a rotor diameter of 131m. The rated power of the turbine is 3.6 MW and the rated total power is 18MW. The turbines have been provided by Nordex. Consultancy Windbase engineering of the foundation and Quality Control on site.Further details are mentioned below.

Wind Farm Denderleeuw is an onshore wind farm located in Belgium and completed in 2023. The project consists of 1 wind turbine with a hub height of 134m and a rotor diameter of 131m. The rated power of the turbine is 3.6 MW. The turbine have been provided by Nordex. Consultancy Windbase engineering of the foundation and Quality Control on site.Further details are mentioned below.

Wind Farm Ninove is an onshore wind farm located in Belgium and completed in 2023. The project consists of 1 wind turbine with a hub height of 120m and a rotor diameter of 117 m. The rated power of the turbine is 3.6 MW. The turbine have been provided by Nordex. Consultancy Windbase engineering of the foundation and Quality Control on site.Further details are mentioned below.

Wind Farm Aalst is an onshore wind farm located in Belgium and completed in 2023. The project consists of 1 wind turbine with a hub height of 120m and a rotor diameter of 117 m. The rated power of the turbine is 3.6 MW. The turbine have been provided by Nordex. Consultancy Windbase engineering of the foundation and Quality Control on site.Further details are mentioned below.

Wind Farm Groen is an onshore wind farm located in the Netherlands and is executed in 2022. The project consists of total 15 wind turbines. Divided into 7 WTG with a hub height of 138 m and a rotor diameter of 153 m and 8 WTG with a hub height of 159 m and a rotor diameter of 163 m. The total rated power 93 MW. The turbines have been provided by Nordex. Consultancy Windbase engineering of the foundation and Quality Control on site.Further details are mentioned below.

Land foundation for wind turbines in the IJsselmeer? This requires a fundamentally different design approach. How did we at ABT and WINDBASE, in collaboration with SwifterwinT, TU Delft, Vattenfall, Aratis, GEvernova and Ballast Nedam, arrive at this solution? Read the English version of the article by colleagues Paul Schraven, Thomas Lankreijer, and Casper Meijer that was published in the latest edition of Land+Water. Land foundation for wind turbines in the IJsselmeer   For the design of the 24 foundations of wind turbines in the IJsselmeer near Lelystad, a different approach instead of a traditional monopile was made. After extensive research, a Cofferdam construction was chosen. The stiffness requirements from the turbine supplier and the collision load were among the design determinants.  Along the dike between Lelystad and Swifterbant, the view has changed remarkably in recent years: the iconic Irene Vorrink wind farm has been replaced by 24 imposing wind turbines on the IJsselmeer. These nearshore foundations are part of the larger project Windplanblauw, which involves replacing 74 old wind turbines: 37 onshore and 24 nearshore. When operational, the entire wind park will have a capacity of approximately 340 MW, providing enough electricity for the consumption of 450,000 households (about 1 million Dutch residents).  Dolphin or Cofferdam  Given the size of the turbine and the relatively shallow IJsselmeer, placing a land-based turbine in the IJsselmeer proved to be the best solution. Two promising foundation solutions were considered: the Dolphin construction and the Cofferdam constructions. The Dolphin construction consists of a system of vertical steel foundation piles with a concrete pedestal placed on top. The turbine can then be tensioned using prestressed anchors, similar to the practice with onshore turbines. The Cofferdam is a circular combined wall construction made of steel foundation piles with double Z-sheetpiles in between. The foundation is filled with sand to provide additional stiffness and strength, allowing it to better withstand various loading scenarios. On top of the foundation piles, a concrete pedestal is placed to support the turbine.  Basis of Design  In order to apply a land foundation in a near shore environment, it is necessary to adopt a fundamentally different design approach. A variety of factors that are typically applicable in either on-shore or marine environments must be integrated. These factors include the need to address ice loads, collision loads, scour, hydraulic conditions, and to translate typical land turbine-related requirements, such as "no-gapping" and "dynamic stiffness," to nearshore conditions. In order to translate these effects into design constraints, a Basis of Design (BoD) was established, outlining the practical design conditions. Some of the most significant conditions within this Basis of Design (BoD) pertain to the practical handling of ice and collision loads. In order to determine the requisite ice loads, recent measurements and an extrapolation of ice thicknesses from the IJsselmeer were employed by Deltares. Furthermore, in cooperation with TU Delft, a straightforward calculation model was devised to ascertain the maximum ice load on a range of structural components, including continuous walls and slender steel foundation piles. Although an ice load scenario is highly improbable, it could potentially affect the entire wind park. Consequently, special load cases – ULS & SLS ice (ultimate limit state & serviceability limit state) – were considered, ensuring that the turbine park remains fully operational even after such an event.   Deformed mesh of the turbine foundation after a collision load   Maritime research  A maritime study was conducted by Marin to assess the collision probabilities of different turbines with shipping vessels, given that the new turbines are positioned on both sides of the fairway. While the individual collision probabilities at each turbine location are relatively small, the cumulative chance of a random collision with a CEMT Class Va inland vessel (a large Rhine ship) was significant when considering all turbines. This cumulative risk was taken into account during the Basis of Design (BoD) phase.  After consultation with the wind park operator, an AL (Accidental Limit State) approach was selected in the event of a head-on collision. This approach allows for the structure to be written off, after which the turbine must be dismantled in a safe manner. The BoD involved a pushover analysis of the foundation. An energy balance was established, converting the ship’s kinetic energy during a collision into crumpling of the ship’s hull and plastic deformations of the foundation structure. The crumpling of the ship’s hull was calculated according to both the ROK (Guidelines for Structural Design) and the DNV standard (Det Norske Veritas).  Proof of concept & design  Following the completion of the BoD and prior to the tendering process and drafting the contract based on UAV-gc (Uniform Administrative Conditions for Integrated Contracts), the two promising foundation variants (Dolphin and Cofferdam) were investigated and developed up to preliminary design (PD) level. This step demonstrated the feasibility of the design principles.  Key dimensions, such as the concrete diameter and indicative lengths/dimensions of the foundation piles, were determined. These dimensions remained relatively unchanged in the subsequent Detailed Design (DD) phase carried out by the contractor. For the design, advanced PLAXIS 3D analyses were conducted to calculate stresses in the foundation piles. The sheet piles and foundation piles were modeled as shell elements, with Z-profiles accurately connected to the steel foundation piles using predefined degrees of freedom to correctly represent the system’s stiffness.  Innovative construction principles  The analyses confirmed the feasibility of both design principles. A trade-off led to the selection of the Cofferdam as the optimal solution, which was then further developed in the DO phase. Ballast Nedam worked on the DO, including reinforcement design, with Windbase serving as an advisor to Windplan Blauw in the reviewing role within the SCB contract (System-Oriented Contract Management).  The contractor subsequently refined innovative construction principles, such as the installing frame for the steel foundation piles, the prefabricated lost formwork and reinforcement elements. Optimization was also carried out regarding the collision load to be considered. An interesting yet crucial detail was the cable routing to the turbine. The contractor opted for J-tubes attached to the sheet pile walls.  Execution  The use of prefabricated elements simplified the construction of the foundations and allowed for multiple operations. Construction began with the placement of four auxiliary piles with an H-frame. From this H-frame, the 22 steel foundation piles were accurately driven in a circular pattern to the required depth. After installing the steel foundation piles, sheet pile, the ring beams and the J-tubes were added. The foundations were then filled with moderately compacted sand. Prefabricated L-walls formed a large formwork into which the concrete base was poured. The exterior of the L-walls features an aesthetically which serves as a visual signal for future navigation in the waterway. Once the formwork was in place, the anchor cage as the core reinforcement was installed followed by the lifting of seven large reinforcement cages. The final step involved manual tying of the rebar to close the reinforcement cage. Using a floating concrete pouring plant, approximately 900 m³ of concrete was poured for each foundation. This base ring serves as the starting point for the tower and acts as the interface between the foundation work and the turbine structure. Once the grout had been applied and allowed to set, the 152 anchors securing the tower base ring to the foundation were pre-tensioned and safety features such as fencing, stairs and a davit crane were installed.  The pouring of the concrete in the foundation   Once the foundation contractor had completed the work, the various turbine components were lifted into place. For this purpose, a 1350-tonne crane was mounted on a special barge (a small ship) equipped with spud piles (which extend through the ship to the bottom of the lake). Mammoet designed this installation. To ensure the stability of the barge, third parties conducted dynamic interaction calculations based on standard soil profiles, wind directions and wave heights occurring in the IJsselmeer. At each turbine location, at least three spud pile positions were defined based on cable positions and in the subsoils, to allow for safe lifting operations.  Conclusion  The installation of the final wind turbine was completed on 20 March. We can reflect on a period of learning, during which complex calculations were carried out using Plaxis 3D and DIANA. These demonstrated that a land-based turbine on a nearshore foundation in the IJsselmeer meets the specified requirements and can be certified and installed.  Authors:  Paul Schraven: Design Lead Thomas Lankreijer: Geotechnical Advisor Casper Meijer: Senior Quality Inspector (all working at ABT and its subsidiary, WINDBASE)