Date of Award

Fall 2023

Project Type

Thesis

Program or Major

Mechanical Engineering

Degree Name

Master of Science

First Advisor

Martin Wosnik

Second Advisor

Nathan Laxague

Third Advisor

David Fredriksson

Abstract

A rising demand for macroalgae (or seaweed) has led researchers to seek out methods of increasing macroalgae aquaculture yields. Macroalgae is a food product, and may be used in biofuel, animal feed, and fertilizer. Applying upwelling technology to macroalgae aquaculture has been shown to increase biomass yield. A wave-powered upwelling device (or water pump) generates cold, nutrient-rich water flow to the surface of an aquaculture operation. A wave pump device developed at University of New Hampshire was refurbished and outfitted with instrumentation to determine its performance. Testing in the laboratory on both the device and instrumentation was conducted to prepare for field testing. An ocean field deployment of the device was conducted in March 2023. Five days of high-quality data were produced, revealing a maximum average flow rate of 16.5 gallons per minute, in corresponding average sea state conditions of 2.2 feet significant wave height and 5.9 second period. The maximum efficiency of the device over the course of deployment was estimated at 0.5%, which is an indicator that the current design is undersized for the tested wave conditions. A WEC-Sim numerical model of the wave pump was created and validated using the field data. Comparing the average WEC-Sim model data to the field data resulted in a percent difference of approximately 19% for flow rates, 22% for stroke heights, and 16% for stroke periods, which is considered a successful model validation. A conceptual design for a modified, improved wave pump was generated, where increased flow rate and drawn depth were the motivating specifications. The modified design was modeled using WEC-Sim, which produced an average flow rate of 119.6 gallons per minute, and an efficiency of 4.8%. Determining and improving the efficacy of wave pump devices to benefit macroalgae production is a developing effort.

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