Maryland wind energy area site characterization assessment using cluster analysis with bathymetry and chirp sub-bottom profiling data
Date
2020
Authors
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Publisher
University of Delaware
Abstract
There has been a significant rise in the construction and development of large-scale offshore wind farms as the global need for renewable energy increases. Each project includes a procedure of leasing, permitting, planning, and construction which can take several years to become operational. A vital step in this process is efficiently and accurately performing a site characterization of geological and geotechnical parameters in order to plan for the most suitable location and type of wind turbine foundations given the surficial and subsurface nature of the lease area. Foundations can account for approximately 25% of total project cost and their installation contributes to the majority of construction delays, making efficient and accurate site characterization invaluable. ☐ In this thesis, the Maryland Wind Energy Area (WEA) was used to demonstrate a site characterization method involving a K-Means Cluster Analysis of bathymetry data to apportion the WEA into clusters with distinct properties. Once the presence of anomalous paleochannel features were identified, selected Chirp data were analyzed from each of the clusters. Analysis of the Chirp data yielded first-order surficial and sub-bottom characteristics for each cluster. This method of characterization provided an efficient method to derive the overall surficial and subsurface nature of the WEA without expending the large amount of time required for processing, analyzing, and interpreting all available Chirp data. ☐ Results from the K-Means Cluster method indicated the Maryland WEA’s sub-bottom characteristics include three major units and in the western portion of the WEA a high-density area of paleochannels. From shallowest to deepest, the first unit consists of Holocene sands with thickness ranging from 0.5 to 6 meters (m). The second unit has subparallel reflectors corresponding to muds with finely interbedded sands and silts with a thickness ranging from 5 to 8 m. The third unit has a composition of quartzose, homogeneous, fine to very fine sand with scattered medium to coarse laminae and a thickness range of 3 to 24 m. ☐ After identifying and describing the major subsurface units, the merits and shortcomings of monopile, gravity, jacket, and suction caisson foundations were discussed with reference to the subsurface character of the Maryland WEA. A preliminary recommendation of the most appropriate foundation for the WEA is a combination jacket or tripod with suction caissons instead of piles. Jacket or tripod foundations use less steel and caissons are easily produced, installed, and decommissioned without the use of pile driving. This foundation type would be most successful in the eastern portion of the WEA due to the sediment type (i.e., sands, muds with interbedded sands, and quartzose homogeneous sand with scattered medium to coarse laminae) and water depths ranging from 22.5 to 42 m in that location.
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Keywords
Maryland Wind Energy Area, Offshore, Cluster analysis, Bathymetry, Chirp Sub-Bottom Profiling Data