OFFSHORE RESOURCE ASSESSMENT - Wind Resource Assessment: A Practical Guide to Developing a Wind Project - page 205

outside the project area. From this vantage point, the unit could produce a three-
dimensional grid of wind velocities up to and above the turbine hub height throughout
the area. The current maximum range of commercially available side-scanning lidar
units, which varies from 4 to 15 km, is promising. The use of side-scanning lidars
for wind resource assessment remains a relatively new application of this technology,
however. Consequently, additional validation will likely be necessary before it is fully
accepted for resource assessment.

Sodar. Sodar systems have been deployed offshore on fixed platforms both for
wind resource assessment and wind energy research (Figure 14-9). Sodar offers some
attractive attributes for offshore operation, such as moderate power requirements,
good reliability, and relatively low cost. However, sodar can be susceptible to acous-
tic interference. Data quality can be affected by the sound of wind whistling through
structural components, audible navigation aids, and noise generated by waves and
wildlife. Consequently, commercial floating versions of sodar have not been devel-
oped to the extent as lidar. While sodar may be a viable choice for some offshore
measurement campaigns, lidar's dominance is expected to continue to grow.

14.2.3 Using Existing Offshore Structures
In some instances, it may be possible to take advantage of existing structures to support
offshore wind monitoring towers and remote sensing systems. Provided wind condi-
tions at the site are reasonably representative of conditions in the proposed project
area, and provided the structure can support the desired monitoring system without
interfering in its operation, the use of existing offshore facilities can add value to a
resource assessment campaign at a much lower cost than a purpose-built platform.
Lighthouses on exposed points, C-MAN (Coastal-Marine Automated Network) sta-
tions in the United States and similar stations elsewhere, oil-drilling platforms, and
even small, low lying islands can be considered for this application.

(a) (b)

Figure 14-9. (a) Scintec sodar unit mounted on the Ambrose Light Coastal-Marine Automated
Network (C-MAN) station off the coast of New York, USA. Source: AWS Truepower. (b) A
Second Wind sodar unit being lifted onto a U.S. Coast Guard platform off the coast of South
Carolina, USA. Source: Second Wind.