Upgrade to 140 meter rotor diameter on a two-bladed downwind turbine

◀ Back to projects overview P201204-001-2BE

2-B Energy is developing a dedicated offshore wind turbine with a lower Cost of Energy (CoE) based on: a full jacket support structure concept with integrated design of support structure and foundation; suitable for large distance from the coast with helicopter access; sophisticated control system to reduce dynamic and extreme loads; and optimized for high availability by efficient service & maintenance & repair. The turbine is categorized as a 6MW, 2 blade horizontal axis wind turbine. The turbine is referred to as 2B6.

This project was initiated after FLOW Project P201101-002-2BE, Controller Optimization for 6MW 2 Bladed Offshore Wind Turbine, as the results of that FLOW Project showed significant reductions in loads. These reductions provided margin in the design to enlarge the rotor diameter. This project focusing on the upgrade the design towards a rotor diameter of 140 meter rotor diameter and another FLOW project focusing on advanced controller optimization control system. Both projects are interlinked due to this common goal: “Improving the 2B6 design”.

Main objective of the project
The result of FLOW Project P201101-002-2BE “controller optimization”, optimizing of the control strategy, presented significant load reductions. These reductions inspired the definition of this FLOW project with focus on rotor diameter and design of the turbine.

The main objective of this project is reducing Cost of Energy by increasing the rotor diameter from 130m towards 140 m.

The sub-objective is improving the 2B6-alpha design towards the 2B6-Beta design. Table 1-1 describes the main design requirements changes for the two designs.

The second sub-objective is having a documented design for the 2B6-Beta turbine which can be submitted to the certifying body for certification.

Main design requirements changes for the two designs

The problem statement can be defined as: Significant improvement of the design by applying Individual Pitch Control (IPC) and extended blade length at similar component dimensions resulting in at least a 5% decrease in the Cost of Energy compared to the original design.

The extended blade length at similar component dimensions is part of this FLOW project. All activities regarding the (IPC) control are performed in FLOW Project P201103-001-2BE “Advanced controller optimization for 6MW 2 bladed offshore wind turbine”.

The integrated design approach of wind turbine, support structure and control system enabled 2-B Energy to increase the rotor diameter of the turbine and achieve an increase of the annual energy production without large increase the CAPEX of the turbine. An integrated design approach is necessary as during the design phase of the wind turbine 2B6-Beta the interaction between the support structure and the Rotor-Nacelle Assembly (RNA) has been of major concern. It was observed that the support structure has a significant influence on the load level of the RNA. For offshore conditions, the water depth and soil conditions influence the design of the support structure significantly. Also the performance of the turbine depends upon the understanding of the system as a whole. This interdependency necessitates an iterative design approach, where in each step the system as a whole is assessed, and subsequently the influence, limiting factors and potential contribution to improvement of each component is identified. This integrated design approach leads to improvements resulting in a reduction of Cost of Energy.

Contribution of the project results to cost and risk reduction for Far-offshore wind energy
The estimated reduction in CAPEX and the increase in AEP for this project are quantified as:

CAPEX An increase in blade mass of 4% due to extended blade length

AEP Yield increase of 6.1% due to larger rotor diameter

The Cost of Energy reduction was quantified by using the FLOW Cost Model which results in a reduction of CoE of 5.44%. Although the comparison made here is between two 2-B Energy concepts/designs, the results achieved could also be applicable in a broader sense since the increase in rotor diameter can be applied to other turbine designs to improve the annual energy production.

This project focuses on the cost of energy reduction. The objective of this project to decrease the Cost of Energy with at least 5% is achieved. Significant improvements are realized by extending the blade length and design optimizations.

The documented design for the 2B6-Beta turbine was assessed and approved by DEWI-OCC in a D-Design Assessment (D-DA).