By James R. Stalker

Successful wind energy assessment efforts require adequately established long-term (> 20 years) wind behavior at potential wind project sites. Measurements, from such traditional instruments as anemometers or from more advanced measurement platforms such as sodars or lidars will not help overcome the issue related to the time requirement for long-term wind energy analysis. Additionally, measurement platforms, both traditional and advanced, will only provide data at limited locations and heights. This spatial coverage limitation may prove to be a significant issue for wind farm sites within complex terrain locations.

When clearly known wind farm energy performance variability is of utmost importance for wind project developers and financiers alike, limited wind measurements in space and time are proven to be inadequate, expensive, and time consuming.

Fortunately, there is a cost-effective and timely alternative.  An example of such an alternative is based on an Atmospheric Simulation Technology, developed by Dr. James Stalker. This simulation technology offers location specific, height specific, and time specific wind information, not only at a much lower cost but also within a fraction of the time. For example, the 100-m height wind information can be obtained for only a few 10′s of thousands of dollars compared to much more expensive measurement efforts.  Also, yearlong assessments can be completed within weeks.

As important as the above two advantages are for simulation based wind energy assessments, the greatest benefit is in their ability to provide comprehensive spatial information within weeks. In other words, project developers do not have to rely on measurements made at a single location or use just one year measured data to determine long-term wind energy variability. In other words, wind project developers and financiers need to ask themselves this question: “Would we not measure wind for twenty years at every possible location within a prospective site if we had all the money and time in the world?” The answer would be a resounding ‘yes.’ And yet, these folks are currently relying on short-term (often one year) measurements at a handful of locations.

Well, simulation based methods offer wind information for multiple years within a small fraction of the time and for a fraction of the cost. Why not use these alternatives then? Several explanations are often offered in the wind industry why limited measurements are relied upon instead of using some of these established simulation techniques. For example, one may hear that the industry is used to seeing and being content with only yearlong measurements followed by statistical long-term projections. Another explanation might be that the simulation techniques they have employed thus far have proven to be inadequate, etc.

It will understandably take some time for the wind industry and the simulation based wind information providers to overcome the above limitations. But, in the meantime, it will make a good financial sense to combine one year measurements with multiple simulation years to quantify wind energy resource variability so one can invest in wind projects with more confidence.

Wind simulation techniques offer physically realistic explanations on why the wind speed or direction is of a specific magnitude at a specific location. Should a wind project developer be just happy to see a measured annual average wind speed value of 8 m/s, without knowing the causes behind such wind speed regime? Do wind measurements offer this type of critical information? No. This is because wind measurements just measure wind speed (the end state) and not the causes (the atmospheric forces) that lead to the observed wind. There is a simple reason why measurement efforts do not include measurements of forces because such efforts will be prohibitively expensive. Instead, measurements involve just the end states of wind speed, leaving a huge void in our understanding of the wind regime.

Fortunately, again, wind simulation techniques offer valuable insights into these forces responsible for observed wind. From a cost standpoint, a time standpoint, and from the standpoint of the critical causal information, wind simulation techniques are imperative in future wind energy resource assessment efforts.

However, wind simulation techniques must be carefully chosen to meet one’s wind project development objectives. Attention must be paid to the following factors to reduce the errors that can potentially be introduced in such techniques.

• Use highest spatial resolution possible and quality input data sets to drive these models or expect unknown and potentially large errors

• Use thoroughly tested atmospheric models or expect unknown and potentially large errors

• Use well established computer platforms or expect unknown and potentially large errors

• Employ people with the expertise to run these models or expect unknown and potentially large errors

James Stalker is an atmospheric scientist with over nineteen (19) years of meso-mircorscale modeling experience and expertise as a researcher and as an entrepreneur.