WAT 4.2

WAT supports revised IEC 61400-1 and IEC 61400-12-1 standards

Monday 13 Feb 17

The Windfarm Assessment Tool (WAT) supports new site assessments in coming editions of IEC 61400-1 and IEC 61400-12-1. Other new features include de-trend correction to turbulence observations and simpler wind condition estimates for far-offshore projects.

Wind-energy siting engineers need to prepare for coming editions of some of the IEC standards. Edition 4 of IEC 61400-1 on turbine safety will involve a revised turbine classification system and new assessments of flow inclination, wind shear and terrain complexity. Edition 2 of IEC 61400-12-1 on power-curve measurements will include an extra zone for the terrain assessments and obstacle significance is evaluated differently. With WAT 4.2 you can already now see how these changes affect your wind energy projects.

Turbulence observations for wind energy projects are usually based on 10-min block statistics, where variance of the wind speed signal includes a contribution of the changing mean wind speed. The IEC standard recommends removal of linear trends in the time series before calculating variance. This correction will reduce turbulence estimates, but complete analysis is complicated by the lack of high-resolution time series. WAT 4.2 does, however, implement an approximate de-trend correction based on 10-min time series only. 

Site assessment in WAT is normally based on wind conditions calculated by WAsP Engineering, but this input is almost uniform over the area of a far-offshore wind farm. With WAT 4.2 you can replace WAsP Engineering results with estimates by models in the IEC 61400-3 offshore wind turbine standard.

WAT takes input in the Excel file format. This was previously done by Windows automation of a local Excel installation. WAT 4.2 applies a native Excel import filter independent of local Excel installations.

The user interface is improved by graphical elements and rearranged result tables. New table for inter-turbine distance and maximum turbulence intensity are added. The guide to appropriate project options is adapted to the chosen edition of the IEC standards.

New features in WAT version 4.2 (February 2017)

  • Support for IEC 61400-1 Ed.4 (draft)
  • Support for IEC 61400-12-1 Ed.2 (draft)
  • Approximate de-trend correction for observed turbulence intensity
  • Input for far-offshore sites independent of WAsP Engineering
  • Load Excel files on computers without Excel installation
  • Graphical improvements of result tables
  • New tables for wind-farm overview of effective TI and maximum TI
  • New table of inter-turbine distance
  • Better guide for project options

New features in WAT version 4.0 (October 2015)

  • A simplified user interface
  • AEP uncertainty estimates
  • AEP corrections for turbine availability and transmission power loss
  • Import of WAsP projects for AEP calculations
  • Power curve correction for local air density
  • Turbulence statistics by observed time series
  • Improved export and import of turbulence statistics
  • Improved indication of neighbouring turbines in the sector management dialogue
  • Transparent display of IEC 61400-12-1 performance measurement zones
  • Improved accuracy when reading IEC 61400-12-1 measurement sectors from a WAT project file
  • Support for IEC 61400-12-2 terrain and obstacle assessments
  • IEC 61400-12-x assessment with no WAsP or WEng input
  • Editor for obstacle geometry

You can download WAT 4.2 at our website.

23 FEBRUARY 2017