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"ClusterDesign and EERA-DTOC are the two major research projects on offshore wind farm clusters because they are developing the design tools for the clusters of offshore wind farms of the future", says Rory Donnelly, the ClusterDesign coordinator of 3E. Throughout their active period ClusterDesign convenes three workshops.
The objective of the first and the second workshop is bilateral exchange with the target groups and other activities under the auspices of the European Commission. These are joint workshops with the sister project EERA-DTOC. One workshop is organised by the EERA-DTOC consortium and the other by the ClusterDesign consortium.
The third workshop aims at disseminating the ClusterDesign results, particularly at demonstrating the ToolBox and presenting the Best Practices to the industry.
 

The first workshop took place on 6 June 2013 in London. The target audience consisted of offshore wind farm developers, strategic planners, wind farm operators, and utilities. Project staff presented intermediary findings of EERA-DTOC and ClusterDesign, and revealed how the design tools for future offshore wind farms will look like.
 
The London workshop started with introductions to the projects.

Peter Hauge Madsen, the EERA-DTOC coordinator of DTU Wind Energy, explains: "EERA is the European Energy Research Alliance. And DTOC is the Design Tool for Offshore Clusters, which is the main deliverable of the project."
As its name suggests, the project EERA-DTOC is run in the framework of the EERA. It is co-funded by the EU under the FP7 programme from January 2012 to June 2015, bringing together 22 organisations.
"EERA-DTOC focuses on designing clusters of wind farms while taking into account wind farm wake losses and wind farm electrical cabling. DTOC is composed of interfaces to existing design tools as available among the consortium, and is due December 2014", Madsen says.
 
The project ClusterDesign receives EU/FP7 co-funding too, but runs from December 2011 until May 2016. The consortium consists of 6 organisations.
According to Donnelly, ClusterDesign focuses on modeling and validation, and creates a ToolBox as the main deliverable.
He continues: "The modeling addresses four aspects of wind clusters: wind resources and wakes, electrical topology, fatigue load, and intelligent control. The latter two aspects mark the difference with EERA-DTOC. Validation of model outcome takes place by using existing as well as newly measured data."
The ToolBox will consist of two modes: a design mode validated with data from existing farms, and an operational mode validated with real-life data. The design mode integrates flow modeling, calculation of fatigue loads for varying turbine modes, and calculation of topology costs and operating costs. The operational mode allows for the selection of the optimum turbine setting at any time given a fixed topology, current meteorological measurements, current turbine states and pre-computed simulation results.
Donnelly: "The ToolBox is due October 2015, but will be preceded by a pilot version in April 2014."
 
After the introductions came the presentations on EERA-DTOC.
 
Gregor Giebel (DTU Wind Energy) gave an overview of the EERA-DTOC software under development. "Based on user requirements and user stories we created a product vision and identified two types of main users and various types of associated users. Through open interfaces we will connect many IPR-protected design tools. The software will support manual optimisation processes through design scenarios employing Levelised Cost of Energy as the cost model," Giebel says.
 
Gerard Schepers (ECN) elaborated on these scenarios: "They are needed in order to demonstrate the EERA-DTOC capabilities. The definition of the scenarios is underway, and feedback from the users is invited."
 
Pierre-Elouan Réthoré (DTU Wind Energy) zoomed in on wake modeling on the farm and the cluster scales, and the coupling between the two. According to Réthoré the primary goal of the wake modeling is to identify, to benchmark, to provide guidelines for, and to couple the existing wake models which are able to operate over farm and cluster scales.
 
Mariano Faiella (Fraunhofer IWES) gave details of the electrical scenarios under construction. He explains: "The aim of these scenarios is to optimize the grid layout while taking into account clustering of wind farms, grid code compliance, power plant ancillary services, and impact of variability and predictability of the wind resource."
 
Elano Cantero (CENER) addressed energy yield prediction of wind farm clusters. "We translate either measured or virtual wind data into representative long-term wind data at hub height, and, by using a general power curve, determine gross values of the annual energy production and the percentiles of that production. In subsequent steps we determine net values of the production by taking into account the losses due to operation and maintenance, internal wakes, and electrical layout."
 
This completed the contributions from EERA-DTOC, and subsequently attention shifted towards ClusterDesign.
 
First, Dirk Steudel (Senvion) addressed mechanical load calculations in wind farm clusters. In order to improve the wake modeling, computational fluid dynamics is combined with turbine models. "Apart from the wind speed, we take into account horizontal and vertical wind shear, as well as turbulence," explains Steudel. The actual combination of models is found to have a large impact on the blade loads, but nearly none on other loads and the power. A fast estimation method for a whole wind farm is under development, and will be validated through measurements in a full-scale offshore wind farm.
 
Next, Aidan Marchand (RWE) outlined the objectives of wind cluster control. Marchand: "We aim at lowering the cost per megawatt generated by increasing the power output of a given wind cluster and reducing the turbine loads per megawatt generated. And we aim at enabling the cost effective provision of ancillary grid services by optimal generation of reactive power and using active power delivery options for frequency control." To this end a Wind Farm Management System and a Wind Cluster Controller are developed for a full-scale offshore wind farm.
 
Finally, Thanos Kyriazis (3E) presented details of the ClusterDesign ToolBox. This ToolBox is developed on the basis of product specifications and user needs from the consortium, and for that reason covers the interaction of wind farms within a cluster, the topology of the farms and the cluster, the connections to the grid, and the control of the wind farms. It will come in a design mode and an operations mode, both consisting of interfaces to existing models.
 
The workshop in London ended with a panel discussion on the opportunities and challenges of design tools for the smooth operation of clustered offshore wind farms.