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27 Nat. Resources & Env't 37 (2012-2013)
Extreme Weather Impacts on Offshore Wind Turbines: Lessons Learned

handle is hein.journals/nre27 and id is 105 raw text is: Extreme Weather Impacts on Offshore Wind Turbines: Lessons Learned Kimberly E. Diamond 'r1,ue to more intense weather conditions than originally anticipated, hundreds of offshore wind turbines in Europe are undergoing extensive repair. Many of these ' repairs are attributable to the turbines' designs, which were not engineered to withstand the force and duration of cer- tain metocean (meteorological and oceanographic) conditions and extreme weather to which they unexpectedly have been exposed. Miscalculations relating to violent, extended storms of greater intensity and stronger winds than predicted have caused more extensive damage than envisioned as a result of these storms' impacts on wave height, wave force, and an active shift- ing seabed in the form of scour and migrating sandwaves. As a result, costly repairs to rectify turbine foundation issues and undersea transmission cable exposure are underway. Also, these weather events and the navigational risk mitigation measures implemented to address them have caused vessels navigating around wind farms to encounter breach of contract risks. As the United States endeavors to launch its offshore wind industry, consideration should be accorded to these and other extreme weather-related potential risks to future domestic off- shore turbines in the short and long terms. To protect against these risks, it is important to understand wind, wave, and tidal conditions, as well as shifts in air and sea temperature pro- jected to occur over and beyond the next two decades-during an offshore turbine's approximately twenty-year operational life cycle. Addressing these risks at an early stage will help inform policy and enable stakeholders to take adequate pre- cautions to mitigate these risks where possible. This article ,will examine (1) issues impacting offshore wind turbines in the North Sea; (2) how these issues and other extreme weather conditions, including hurricanes, could impact turbines placed in the Gulf of Mexico or in Wind Energy Areas along the East Coast in the future; and (3) what, if any, risk mitigation measures can be taken from a policy and legal perspective to address these risks going forward. The North Sea experience illustrates how weather con- ditions factor heavily into timing for offshore wind farm construction and general operations and maintenance pro- cedures. Seas need to be as calm as possible for turbine foundation installations. Mean wind speeds vary seasonally. Generally, the spring and summer months are the only months during which the North Sea is relatively calm, turbines may be installed, and vessels can perform ordinary course turbine oper- ations and maintenance procedures. However, during fierce storms, severe sea states arise, thereby increasing the health and safety risk that workers will slip on or fall off turbine plat- forms or the slick decks of installation or maintenance vessels, Ms. Diamond is Counsel at Lowenstein Sandler PC, in the firm's New York City office. She may be reached at kdiamond@lowenstein.com. causing worker injuries or fatalities. Weather-related worker accidents and injuries must be minimized. Also, severe sea state waves may hold adverse consequences for turbines them- selves. Whereas wind force impacts turbine blades, wave force impacts turbines' lower to bottom areas, such as their plat- forms, foundations, and cables transmitting the wind energy generated to the transformer station. From a property risk per- spective, wave heights surpassing 15 meters can significantly damage an offshore wind turbine's platform. Although weather conditions are closely monitored so wind farm construction planners can prepare timing of operations and arrange back-up plans, incorrect estimates for extreme weather's arrival time, intensity, and duration can result in unanticipated breaks dur- ing turbine installation and maintenance. Currently, it is unclear how North Sea offshore turbines will withstand repeated exposure to extreme winds. Onshore tur- bines in the UK, for instance, generally are not designed to withstand sudden onslaughts of extreme winds. In December 2011, 150 mph winds hit Scotland and northern England, caus- ing one onshore turbine to burst into flames. Extreme winds cause large vibrations and loads, creating significant fatigue on turbine blades even when they are not spinning and have auto- matically shut off when wind speeds (or other factors) reach certain maximum threshold levels, which will vary depend- ing on the location of the turbine. This fatigue has resulted in smaller onshore turbines experiencing blade throws-having their blades torn off and hurled toward surrounding objects. In an offshore turbine context, where turbine blades are gener- ally longer and heavier than onshore turbine blades, a falling blade can seriously damage or sink a vessel and injure or kill crew members. While RenewableUK, the trade and professional body for the UK's wind and marine renewable industry, charac- terized extreme onshore winds as freak weather, with changes in global weather patterns, it is difficult to predict whether similar extreme wind anomalies will occur more frequently in the future, either onshore or offshore. Extreme winds, there- fore, carry with them increased risk of turbine damage and the accompanying cost of turbine repair and replacement. While it is obvious that bouts of increased extreme winds, wave heights, and wave force can result in increased finan- cial risk associated with damaged turbines, what is less obvious are the other related risks these occurrences bring to vessels navigating around wind farms. During a severe sea state, bru- tal storms and their high mean wind speeds are correlated with significant wave heights. These factors can increase naviga- tional risks. High waves can be dangerous to smaller vessels, causing them to become disoriented, lose stability, or cap- size due to cargo shift. Vessel damage can contribute to vessel control loss, loss of emergency power, damaged or lost cargo, loss of shipping gear, increased collision risk with other ves- sels or turbines, and loss of investment (financial loss). Drift is NR&E Fall 2012 37

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