CAREER: Experimental Modeling of Tidal Current Turbine Foundations: An Integrated Research and Education Plan

Iowa State University, Ames IA

Investigators

Abstract

This Faculty Early Career Development (CAREER) Program grant will advance the understanding of the unique behavior of tidal current foundations and improve science and engineering education at the elementary and high school levels, while promoting increased diversity in the field of geotechnical engineering. The research will investigate efficient and reliable foundation systems for undersea tidal current turbines. The foundations must be designed to resist high lateral loads as well as vertical and horizontal cyclic loading from the oscillating turbine blades, allowing the turbines to effectively absorb and harness the tidal energy while attached to the seafloor. Decreasing the cost of the foundation system can be an important part of making tidal power a viable and economical source of electricity. The research tasks will be used to produce educational products such as learning modules, demonstrations, animations and videos that will be implemented in the courses taught by the researcher and in K-12 outreach programs. A renewable energy lesson will be created for the 4th grade students at Booker T. Washington STEM Academy and the Girls Adventures in Mathematics, Engineering, and Science (G.A.M.E.S) camp for high school girls. The research objective of this project is to evaluate suction caisson foundation systems for tidal current turbines by examining the foundation performance using both 1g bench-scale (in transparent soil and Kaolin) and centrifuge testing under combined cyclic loading. This research focuses on the cyclic nature of the vertical, horizontal and moment loading due to waves, the rotation of the tidal current turbine blades and the change in direction of the horizontal loading due to ebb and flow tides. Although there have been many studies on the use of suction caissons as anchors with diameters less than 10m (Length/Diameter = 3-5), few researchers have investigated using suction caissons as foundation elements in soft clays with intermediate aspect ratios of L/D = 1-3. In addition, the unique vertical cycling and semidiurnal or diurnal (12 or 24 hr) tidal cycling of the horizontal load has not been accounted for in previous designs of suction caisson foundations. The focus of the experimental testing is to investigate the foundation performance, failure modes, load-displacement response, yielding behavior, and cumulative displacements under cyclic loading. The research effort will result in: (i) high quality laboratory data; (ii) load-displacement curves, and (iii) failure envelopes/interactions diagrams, that will allow for the continued study of the utilization of tidal current turbines as a renewable energy source.