NEESR-CR: Capacity and Performance of Foundations for Offshore Wind Towers

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This award is an outcome of the NSF 09-524 program solicitation "George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)" competition and includes Texas A&M University (lead institution), the University of Connecticut and Prairie View A&M University (subawards). This project will utilize the NEES equipment site at Rensselaer Polytechnic Institute.In the last few years, interest has been increasingly focused on alternative and renewable sources of energy. Wind energy as an alternative to fossil fuels is receiving close attention while the number megawatts produced has been rapidly increasing. In many locations in the United States and internationally, construction of onshore wind farms has raised environmental and aesthetic concerns. In addition, the terrestrial wind cycle and the daily energy use cycle are not well matched, with peak winds occurring when the energy demand is at its lowest, requiring the development of energy storage strategies and devices. On the other hand, offshore wind farm development can avoid most of the aesthetic issues, with the added benefit of stronger and sustained winds at lower heights and more aligned wind and usage cycles. The goal of this proposal is to evaluate the most effective foundation system for offshore wind towers by examining the performance of different systems when the structure is subjected to both wind and wave loading. Intellectual meritThe project will carry out centrifuge testing in the NEES@Rensselaer facility. The testing program will focus on monopiles and suction caissons. Preliminary testing will be conducted using testbeds at Texas A&M University to evaluate the design of the tools and the models, as well as the sensors. The testing will be used to characterize the response of the foundations systems under a comprehensive range of loading conditions similar to those an offshore wind tower would be subjected to. Numerical analysis will be used to simulate the response of the tower-foundation-soil system with realistic soil models. The numerical and soil models will be validated against the testing. Broader impact The foundations currently used for offshore wind towers may not be the most effective solution for this application, especially in weaker soils. Foundation designs which evolved in the offshore oil and gas industry are not readily applicable to wind tower foundations offshore and design codes are not providing sufficient guidance for designers. Since foundations account for a significant part of the cost of offshore wind towers, choosing the most effective and most economical system will improve the viability of offshore wind energy generation.Undergraduate students from Prairie View A&M University, a Historically Black University, will work with the researchers at their campus, TAMU and UConn throughout the project. Additional undergraduate involvement will be promoted through summer REU experiences. Outreach efforts will be directed towards K-12 students, through demonstrations and teacher involvement in the research activities. The educational and outreach plan addresses diversity by promoting hand-on activities, increased interaction and integration of research and education, which have been effective in improving the retention of underrepresented groups in engineering. Data from this project will be archived and made available to the public through the NEES data repository. This award is part of the National Earthquake Hazards Reduction Program (NEHRP).