A definition of Wind Power Meteorology can be found in [1]. It can formally be described as applied geophysical fluid dynamics resting on a combination of meteorology and applied clima- tology. It concerns itself with three main areas:
micro-siting of wind turbines, estimation of regional wind energy resources, and short-term prediction of the wind power potential, hours and days ahead.
Micro-siting is defined as estimation of the mean power produced by a specific wind turbine at one or more specific locations. In addition, proper methods for calculating the turbulence conditions, the extreme wind conditions, and the effects of rotor wakes are needed.
Regional assessment of wind energy resources means estimating the potential output from a large number of turbines distributed over the region. Ideally, this results in detailed, high- resolution and accurate resource maps, showing the wind resource (yearly and seasonal), the wind resource uncertainty, and areas of enhanced turbulence.
Forecasting of the meteorological fields, hours and days ahead is one of the great challenges of meteorology. The tremendous increase in com- puter power and of the observational density – by satellites in particular – and quality have con- tributed to a marked increase in forecasting skills over the last couple of decades. This, in turn, has made it possible to construct a metho- dology by combining numerical weather prediction models with micro-siting models to predict the power output from specific wind farms up to 48 hours ahead.
The guiding star for almost all research and development in wind energy is “bring down costs (per kW hour) and bring down uncertain- ties (on wind energy projects). When, in the future, the wind turbines are more reliable than aircrafts and operation and maintenance costs
are negligible, the challenges in wind power meteorology still exist.
The guiding principle for improving wind power meteorology output is straight forward: the more relevant physics that can be implemented in the methods, the more general and realistic the models and the more accurate and reliable the results.
Today we see a rapid development in the three main areas of wind power meteorology. In micro-siting and regional assessment we are approaching the point where giving the coor- dinates at any spot an Earth, we can calculate the wind resource and the design wind climate – and with a reasonably well known uncertainty.
This is possible due to the model development where now linear micro-siting models are com- bined with adapted CFD models again com- bined with meso-scale meteorological models.
This together with the amount of accessible high resolution databases advances the development. Among the most useful data- bases are NCRP/NCAR/ECMWEF reanalysis data, SRTM30 elevation data, GLCC land cover data and Google Earth.
The greatest challenge is still to make reliable predictions in very complex terrain and/or very complex climatology. Other challenges are rela- ted to the prediction of the turbulence con- ditions and extreme winds (50 years return design wind) at specific sites. As an example:
the problems of determining the design wind in areas with occurrences of hurricanes. Another challenging problem in siting is that of wind farm wakes. We have a reasonable hold on calculating the wake effects from one wind turbine to another. But the wake climate inside a very large wind farm and the wake influence from one large wind farm to another is still a subject for intense research. Especially at off- shore, these effects can have large economical consequences if not handled right.
14
FVS•Workshop 2006 Erik Lundtang Petersen•State of the Art and Challenges in Wind Power Meteorologie
E. L. Petersen Risø National Labora- tory, Technical Univer- sity of Denmark, Wind Energy Department erik.lundtang@risoe.dk
State of the Art and Challenges
in Wind Power Meteorology
For the short term prediction much progress have been made after the researchers have combined several of the global weather predic- tion models and further have made use of the ensemble predictions. For example, for the Nordic system in has been shown that the use of the models reduces the cost of regulation by approximately 40% and further, that the ability to predict the uncertainty of the short term prediction gives another 40% reduction in regulation costs.
A very large challenge in wind power meteoro- logy is verification. Having predicted the wind resource and the turbulence conditions at a site, how do we know how realistic the predictions are? In situ measurements are the only – but costly solution. Up to today, it has been neces- sary to erect a mast that reaches at least hub height. But a laser anemometer that can measure up to 100 meters as reliable as a cup anemometer is now a fact and soon reliable turbulence measurements will be added.
Wind power meteorology is a scientific discipline that today embraces a fast growing number of scientists around the world. As argued above it is also a very important discipline for the global advancement of the utilization of wind energy.
The amount of papers in this field, that every year is submitted to The European Wind Energy Conference, is stunning and ever increasing.
Readers that want to learn more about wind power meteorology are recommended to look through a number of the conference proceed- ings and e. g. the journal Wiley Wind Energy.
Literature
[1] E. L. Petersen et al., Wind Power Meteoro- logy, by Wiley Wind Energy, Vol. I 1997.
15 FVS•Workshop 2006 Erik Lundtang Petersen•State of the Art and Challenges in Wind Power Meteorologie
