Session: 09-05-01 Wave Energy: Hydrodynamics

Submission Number: 156178

Inflate, Deflate, Generate Part I: Capturing Wave Energy Through a Submerged Deformable Volume 

Wave energy is a significant and largely untapped renewable resource for electricity production. While many developers seek to build large wave energy converters (WECs) capable of producing power on the order of megawatts per unit, survivability remains a key challenge due to the overwhelming forces during storm conditions. To increase resilience and decrease costs, research into submerged WECs, constructed from flexible materials, has gained interest. While submerged devices have access to smaller wave energy resources than their surfacing-piercing counterparts, the weaker forces they face lessen the risk of their destruction. In remote locations that require limited but consistent power from a low-maintenance source, such as offshore sensors or charging remote components, they offer significant promise.

This paper serves as a report of ongoing research, describing the exploratory experiments, design, modeling, and planned testing of a compact, deformable, submerged WEC prototype. The objective is to develop a minimally sized, submerged device, capable of producing 10 watts of consistent power. The chosen strategy consists of a deformable bladder filled with incompressible fluid, connected to a hydraulic circuit. As waves pass over the device, an oscillating dynamic pressure field is created in the exterior environment, forcing the bladder to compress and decompress due to the pressure differential. The resulting flow driven in and out of the volume travels through a hydraulic circuit in which a turbine converts a portion of the kinetic energy into rotational energy. The combination of the back pressure stored in an accumulator and the negative dynamic pressure under wave troughs reinflate the bladder each cycle.

Sensitivity analysis was conducted through exploratory flume experiments to determine the relative influence of bladder characteristics, including volume, surface area, inflation percentage, membrane elasticity, and shape, on generated flow, informing prototype design. WEC-SIM modeling was then used to predict the prototype’s performance and power production (results pending). Intermediate-scale (1 meter deep) flume experiments are planned to validate the model results. The ultimate goals of this research are to 1) optimize the design for real-world applications, 2) identify sea states and depths that would merit deployment, and 3) determine what size a full-scale device would have to be to produce 10 Watts in a given deployment location.

Presenting Author: Matthew Gschwend Oregon State University

Presenting Author Biography: Matthew Gschwend is a graduate student studying wave energy and pursing an MS degree in Ocean Engineering at Oregon State University. Prior to grad school, Matthew got his bachelor's in Environmental Engineering at Harvard University before accepting a position NRGTree, where he was a project manager and solar system designer for 7 years. As a huge fan of waves, he decided to pivot from solar to wave energy to learn how to harness the power of the ocean. Matthew hopes to promote and accelerate the development and adoption of renewable energy throughout his career, and also to live on the beach.