The purpose of the Windfarm Assessment Tool (WAT) is to ease IEC 61400-1 wind-farm assessment. WAT is intended for WASP Engineering (WEng) users but will run on any PC without license. We may decide to build its functionality into WEng at a later stage.
Risø will in no event be liable for any damage or lost of profit arising from the use of WAT. Use at own risk and please check the results! Array management is not mentioned in IEC 61400-1 and should this strategy be allowed in the future it might rely on concepts different from herein.
WAsP Engineering provides the following wind conditions at individual turbine sites in a wind farm:
This is nearly everything needed for wind related aspects of the wind-farm assessment described in the IEC61400-1 standard. With WAT you can calculate of the effective turbulence intensity including wake effects by a modified version of the method of Appendix D of this standard. The modifications were introduced to enable modeling of the irregular turbine arrays typical for wind farms in complex terrain. The wind-farm assessment also needs mean-wind climates, and this is why we must include WAsP results in addition to those of WASP Engineering.
In-situ power performance measurements are done by combination of data from an operating turbine and an adjascent met-mast. IEC 61400-12-1 specifies rules on 1) wind directions to be exclude from the analysis due to wake effects, and 2) the need for initial 'site calibration' with an additional mast at the turbine site prior to turbine installation. These rules are based on wake geometry and terrain complexity around turbine and met mast. .
Some WEng users has asked for gust factors. The gust is the expected maximum of a, say 3-sec, runing-mean average of the turbulent wind speed and the gust factor is the exceedence from the mean wind normalized by the standard deviation. The typical gust factor is about 3 and, assuming Gaussian turbulence, it may be estimated from the spectrum. WEng calculates site-specific turbulence spectra and the gust factor is calculated in WAT.
| Ver 2.5 (Sep 2008) | Support for in-situ power performance measurements according to IEC 61400-12-1 Annexes A (obstacles) and B (terrain). Cartwright & Longuet-Higgins type gust factors by local spectra. Bug fixes: 1) selection error with IEC61400-1 Edition 2 turbine certificates. 2) site list sorting error for identical turbine names |
| Ver 2.4 (Dec 2007) | Improved support for turbines in WASP *.wtg format, which can have multiple performance tables |
| Ver 2.3 (Nov 2007) | Corrected a WAT-project reading error related to the Windows Regional and Language Options |
| Ver 2.2 (Oct 2007) | Corrected WEng-IEC turbulence matching and characteristic/representative TI calculus - the method is unchanged but WAT versions 2.0 and 2.1 had implementation errors. Preparation for integration with WEng 2.1 |
| Ver 2.1 (Aug 2007) | Corrected PDF plot according to wind class |
| Ver 2.0 (July 2007) | Support for IEC 61400-1 edition 2, turbine class S, windfarms with a mixtures of turbines, array management with effect on annual energy production, hierarchical site list, save/reload WAT projects, improved user interface, and help file |
| Ver 1.3 (Feb 2007) | IEC complex-terrain indicator. Cosmetic changes to user interface. |
| Ver 1.2 (May 2006) | Solved problem reading input data for two turbines only. Prepared for sector numbers different from 12. Allowed calculation when certain sectors has zero background turbulence intensity, however, with suitable warning since this indicates problems with the WEng calculations. |
| Ver 1.1 (Feb 2006) | More graphics and simplified user interface. |
| Ver 1.0 (Jan 2006) | A utility program originally used for internal work was updated and released at a WASP Engineering course. |