An Assessment of Energy Use in Semi-Closed Land Based Marine Aquaculture

Wasantha Jayatissa - 2000

The aim of this project was to investigate and improve the energy use in the controlled temperature land based aquaculture industry. The selected facility, Abalone South Ltd., is situated in Warrington, Dunedin. This thesis discusses the methods of calibrating a data acquisition system and presents an analysis of the energy use in the facility and the factors which influence energy use. The thesis also describes the method of creating an energy model for the heat pump. The model can be used to explain the variation of monthly energy requirement for the animal grow-out tank and identify the major energy streams and losses associated with the tank. The energy model was also used to analyse the effect of covering the tank and the effect of changing the makeup water temperature and flow rate.

Abalone South has a semi-closed water circulation system. The waste heat recovery from the tank water outlet has been identified as an opportunity both for energy saving and for minimising plant capacity. The amounts of saving in winter and summer seasons were estimated from model. Placing a counter flow heat exchanger between makeup and wastewater flows was suggested and implemented for capture the waste energy.

The model was employed to assess the energy demand for the heat pump due to the alterations in makeup water flow. This application shows the capacity of the heat pump was insufficient to cope with winter time energy demand when the makeup rate was increased. Proposals to overcome this problem were made and the model was used to determine the expected winter time reduction in tank temperature. The conditions suggested here were experienced in winter season.

The feasibility of employing model to assess suitable farming areas and possibility of employing other systems was discussed.