Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
John Madsen (1) F P Alia Ponte (1)
(1) University of Delaware, Newark, United States of America
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Presenter's biographyBiographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited
Dr. Madsen is an associate professor in the Department of Geological Sciences at the University of Delaware (UD). He is a governing scientist/member and the coordinator of educational programs for UD’s Center for Carbon-free Power Integration. His research is focused on the geological and geotechnical aspects of offshore wind project development. He graduated from Iowa State University with a Bachelor’s degree in Geology and the University of Rhode Island with a Ph.D. degree in Oceanography.
Role of geological models and geotechnical characteristics in reducing costs and uncertainties and assessing risks in the development of offshore wind projects
An underutilized data set in the decision making process for siting of large-scale offshore wind projects are a region’s geological setting and associated geotechnical characteristics. The geotechnical properties of bottom/sub-bottom sediments are fundamental to the selection and design of turbine foundations, emplacement of transmission cables, and scouring near bottom installations. Since foundations and cabling are significant costs, if project siting, and even the location of individual foundations within a project, can be selected based on preferred geological/geotechnical conditions that enable more economical solutions, there is an opportunity to significantly reduce costs associated with developing offshore wind projects.
This presentation focuses on the variable geological/geotechnical properties along the Mid-Atlantic continental shelf of the Eastern United States (US) and how knowledge of this variability can be utilized in reducing costs and uncertainties and placing constraints on risks associated with offshore wind projects in this region. The Mid-Atlantic is particularly important since it extends along the most heavily populated portion of the Eastern US and it is a key focus area for offshore wind energy development. The methodology employed models how this geological/geotechnical approach can be used in planning for offshore wind development in coastal areas around the globe.
Main body of abstract
Coastal regions have geologically evolved under conditions of sea level rise/fall resulting in three-dimensionally variable sedimentary deposits. These sediments are in turn characterized by differences in their geotechnical properties which fundamentally impact engineering solutions (e.g., foundation selection/design, transmission cable emplacement). As an example of variability, along the US Mid-Atlantic shelf networks of paleochannels, created by ancient river systems during periods of lower sea level, occur in the sea bed. During subsequent sea level rise, these paleochannels were in-filled by coarser- to finer-grained sediments. As a result, sub-bottom sediments are quite variable both in terms of their classification and their spatial (including vertical) distribution. Paleochannel locations, and their associated variable sediment types, can be mapped and their complexity in terms of variable geotechnical properties, can be taken into consideration when selecting, designing, and siting turbine foundations. Avoidance of these paleochannels, and their associated heterogeneous sediments, can result in simpler, more economical designs for foundations.
In addition to cost reduction considerations, extensive knowledge of the bottom and sub-bottom sediments can be utilized to reduce physical uncertainties associated with siting, construction, and monitoring (e.g., scouring) of offshore wind projects. Bottom sediments comprise the benthic habitat of a region and thus are a key component of the marine ecosystem. Geological/geotechnical information on bottom and sub-bottom sediments can be integrated within a marine spatial planning framework to serve as one of the data sources to be included in risk analyses that consider impacts of offshore wind projects on marine life.
The geological setting, and its implications for geotechnical characteristics, should be considered with other first-order factors including wind resources, water depths, wave and current conditions, access to onshore grid infrastructure, and ecological and human impacts, in determining optimal sites for offshore wind projects. The identification of preferential sites based on geotechnical properties requires integration of geological and geophysical data with soil/sediment characteristics. Utilizing these data can result in cost effective design solutions for foundations, cabling installation, and scour prevention. It also can reduce physical uncertainties, and, within a marine spatial mapping framework, be used in developing project risk assessment.
Upon completion participants will:
Appreciate more fully the role that geological models and geotechnical characteristics can play in reducing costs and uncertainties and assessing risks in offshore wind projects.
Understand that the types and geotechnical properties of sediments influence project costs because of their control on the selection of the type and design of turbine foundations and their impacts on the emplacement of transmission cables and the degree of scouring near cables and foundations.