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Wind
resource assessment is the practice of collecting data to
evaluate the wind at a candidate wind
generation site. Although
the term may be used for other wind generation-related data collection
activities, this is the most common meaning.
Wind energy success is all about location, and selecting the right site is critical to cost-effective wind generation. Several factors are required for a utility-scale wind project to be sited, but the most important of these is a good wind resource. Site selection typically begins with wind
prospecting, the search for a good general location for a wind energy facility.
Wind data in this early stage may come from maps and publicly available databases of historical climate
data. Wind maps provide a rough estimate of the average annual wind at a proposed site.
Besides wind resource assessment, the candidate sites will be evaluated for:
- Land compatibility -- wind speeds are affected by the surrounding terrain
and by potential obstacles, including nearby trees, vegetation and buildings.
- Government zoning and permitting regulations -- governmental permits
and environmental impact studies may be required in certain communities.
- Proximity to transmission lines -- large farms require access to a transmission
line with the capacity to handle the power output of the farm.
- Land owner and community support -- if the wind farm is to be built on
someone else's land, approval and compensation will be required. Also,
political and community leaders and area neighbors may need to be educated
about the proposed site to alleviate any potential concerns.
As the focus becomes narrower, wind energy
developers use wind measurement on or near the candidate site, and computer modeling to use data from nearby sites such as airports, data collected at the site, and historical weather information to project wind at the site.
What wind speeds are required for cost-effective wind generation will vary depending on several factors:
- Land, equipment, and infrastructure costs
- Price that is paid for wind power
- Cost of money to construct the wind farm
When considering wind generation, one important thing to consider is that the power in the wind increases dramatically as the wind speed increases (power is proportional to the cube of the wind speed). Thus, a 10 percent increase in the wind speed, from, say 7 to 7.7 meters per second, translates to 33 percent in energy potential.
Although computer models of wind flow over terrain have improved dramatically in the last several years, there is still no substitute for data recorded at the site. Until recently, the most widely accepted method of measuring the wind at a site is to use wind
sensors mounted on a met tower, recorded by a wind data
logger. For best results, the tower should be at least as tall as the hub of a likely wind
turbine. This can create a challenge as wind turbines can be 80 meters or above at hub height, while the most popular style of meteorological
towers used for prospecting, tilt-up temporary masts, are 50 or 60 meters in height.
Remote sensing technologies such as Second Wind's Triton® Sonic Wind Profiler measure wind at higher heights.
In addition to complete wind resource assessment, remote sensing systems can be used for wind prospecting. The advantage of remote sensing is the substitution of measured wind data for modelled wind data. Current industry practice is to use measured data from validated remote sensing technologies in combination wtih met tower measurements in financing a wind farm. For more information see The Experts Say...
Useful links to learn about wind measurement for wind energy potential (wind resource assessment):
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