Master of Engineering Science
Mechanical and Materials Engineering
DeGroot, Christopher T.
Raceways are used in the aquaculture industry to farm fish species that swim against an upstream current. Raceways often draw water from a large waterbody and hence, their temperature changes due to seasonal variation, which directly affect the production yield. This study investigates a novel approach to regulate the raceway water temperature in a sustainable way by utilizing geothermal energy exchange. Energy models were developed to simulate heat transfer in a geothermal borehole heat exchange system and in the raceway system. The two models were then coupled to simulate the thermal regulation of the raceway water via borehole heat exchangers. Results demonstrated that a raceway can be thermally regulated via a geothermal borehole system. The raceway temperatures, in some sites, were found to increase by up to 200% in winter months and decease by up to 17% in summer months, and consequently, increased the duration of optimal raceway temperature range by 100%-400% for some fish species.
Summary for Lay Audience
Aquaculture is a growing method of farming fish that can lessen the burden on natural habitats brought on by fish capture. Raceways are used in aquaculture to grow fish species that swim against a water current, such as trout or salmon. A raceway typically draws water from a large waterbody in close proximity. The seasonal variations change the temperature of the waterbody, which in turn vary the raceway temperature. This variation results in the raceway temperature often being outside the optimal growth range for most of the species, causing slow growth, disease, and often fish death. Therefore, controlling the water temperature is necessary for higher production yield and economic viability of the aquaculture industry. This thesis focuses on a novel application of using the ground heat to control the raceway temperature. As the ground temperature beneath a certain depth remains constant year-round, it provides heating to the raceway water during cold winter months and cooling during the warm summer months. This heat exchange with the ground is carried out via a U-shaped pipe that is placed in the ground (borehole heat exchanger). By passing the raceway water through this pipe, heat between the water and ground can be exchanged.
In this thesis work, two models were developed; one to simulate the heat exchange between the borehole system and the ground, and one to simulate the energy exchange of an aquaculture raceway system based on natural weather conditions and the inlet water conditions to predict the raceway temperature. Parametric studies were conducted to study the effect of key system parameters on the energy exchange. The two models were then coupled to simulate the thermal regulation process for raceways at five geographically different locations. Results demonstrate that the ground heat could effectively regulate the raceway water temperature. In comparison with the unregulated case, the results show that by thermal regulation, the raceway temperature, in some sites, could increase by up to 200% in winter months and decease by up to 17% in summer months and consequently, the duration of optimal raceway temperature range could increase by 100%-400% for some fish species.
Kuska, Mitchell H., "Energy Modelling to Evaluate the Thermal Regulation of Aquaculture Raceways using Geothermal Heat Exchange" (2019). Electronic Thesis and Dissertation Repository. 6724.