Environmental Engineering Reference
In-Depth Information
The same division cannot be made as easily for offshore wind energy
systems for several reasons:
•
The blades and nacelle assembly are critical components in maximizing
the return to the U.S. government.
•
A design, manufacturing, or installation flaw in any of the elements of
an offshore wind facility will likely affect a significant percentage of a
wind farm, not merely the one facility.
•
The control elements including gearing, software and hardware systems,
sensors, and power supply may be critical in the ability of a blade, nacelle,
and support system to maintain integrity in severe weather conditions.
•
The dynamics and relative stiffness of the supporting structural and
foundation components, commonly envisaged as a monotower in shal-
low water (but which could be a vertical axis system, a floating system,
etc.), have an interrelationship with the stiffness and rotation frequency
and loads of the blades that must be carefully addressed in the design
for long-term performance.
Hence, it may be desirable to make the scope of the wind energy
CVA program much more comprehensive. Figure 5-1 identifies the key
components of a wind energy system. For comparison purposes, Item G,
the electric support platform, can be viewed as analogous to an oil and gas
platform. Table 5-1 compares the scope that may be necessary to ensure
coverage for a wind energy facility with that of an oil and gas facility.
Table 5-1 also has a column headed “type certification.” That column
represents the elements that would be satisfied under a comprehensive
CVA approach. As can be seen, only two elements, those of a design CVA
scope, would be covered for a turbine-nacelle-blade-tower assembly that
was type-certified to the International Electrotechnical Commission
(IEC) process (see Chapter 3).
“Type certification” addresses the design of a blade-nacelle-tower
subsystem in meeting a set of criteria. Physical proof testing of one man-
ufactured blade demonstrates the product's capacity and performance
(strength, deflection, etc.) in terms of the design definition. Type certi-
fication does not provide confidence that products as produced meet
the design conditions. In other words, the ability to manufacture one
device does not ensure that all devices will be manufactured to the same
performance characteristics. Type certification is not sufficient in terms
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