Posters

Abstract

Floating LIDARs (FLiDARs) have become an established technology and are the measurement method of choice for offshore windfarm wind resource assessments. The Carbon Trust provided strong and consistent support for the maturation of the technology, with the IEA and now the IEC developing industry guidance. However, a major challenge to effectively using FLiDARs (and ultimately cost of finance) is the determination of a reasonable and representative measurement uncertainty. Historically, the wind industry has been cautious in utilising new wind measurement technologies, arguably rightly so, to maintain investor and lender confidence. This has been implemented in applying conservative uncertainties to the wind measurement data, resulting in apparently low confidence in the wind climate, even when an on-site FLiDAR wind measurement campaign has been undertaken. As an example, for a recent wind farm the authors are aware of, the consideration of a lowest associated uncertainty approach would have adopted a regional off-site met mast rather than the on-site FLiDAR measurements as the primary measurement. When considering the excellent alignment between FLIDARs and met masts, clearly this cannot be the correct approach. Windfarm reconciliation exercises are now commonly carried out by consultants, validated the estimated energy production against the operational performance, with the distribution of the deviations being compared with the stated uncertainty of the estimates. A similar approach can be undertaken comparing wind measurements within a region and investigate whether the deviations align with the stated uncertainties of those measurements. Due to the volume of datasets and availability of associated third party assessments, the Dutch sector of the North Sea is a prime opportunity to undertake this type of exercise. There are currently five completed FLiDAR campaigns, Borselle, HKZ, HKN, HKW and TNW, as well as four cup anemometers or LIDARs on fixed offshore structures: Europlatform, Lichteiland Goeree, OWEZ and IJmuiden. The methodology for the assessment is as follows: * Review wind resource assessment reports from each campaign * Apply spatial adjustment from a wind map * repeated for different wind maps to confirm robustness of the conclusions * the deviations represent the total uncertainty of the wind measurement campaign, constituting: 1. wind measurements 2. long-term correction 3. spatial adjustment (both horizontal and vertical) 4. methodology / analyst's prerogative If we calculate and subtract the uncertainties for the later three categories, the remaining uncertainty is due to the wind measurements. At the time of writing this abstract, the initial findings are: * uncertainty of FLIDAR measurements is much lower than current assumptions, * FLIDAR measurement uncertainties are lower than cup anemometry on met masts, * The FLIDAR uncertainty is anticipated to be less than 1% (overall measurement uncertainty). Prior to our presentation at the workshop in June, we plan to conduct additional analyses including: * independent review of the approach, by co-authors at ERM * assessment of confidence in these uncertainties, i.e. what is the likelihood that these findings are due to chance or specific to the region * repetition of this exercise in other regions where there is access to multiple measurement sources and types