Optimization of solar water-heating combisystem deployed in an aquatic farm to mitigate hypothermia damage

In aquatic farms (AFs), renewable heating systems can aid in preventing hypothermia in aquatic creatures by maintaining an appropriate water temperature. However, heating and maintaining AFs at a certain water temperature during a cold stream event is difficult. As a technical and economical solution, a localized “survival zone,” with the appropriate water temperature, can be created in the water pool, where aquatic creatures can aggregate. Here, STAR-CCM+ was employed to simulate the three-dimensional temperature conditions of an AF in extreme weather and examine the survival zone volume. TRNSYS was used to simulate solar collectors (SCs) and a heat pump (HP) combisystem under the required heating capacity. The Taguchi method was used to optimize the geometry of the AF. In STAR-CCM+, eight parameters (distance between inlets 1 and 2, inlet heights, outlet positions, inlet velocity as fixed mass flow rate, barrier length, barrier position, barrier thickness, and barrier number) were compared. Of them, the two inlet heights, outlet positions, barrier length, and barrier position were selected according to their difference in percentage of the survival zone and set the orthogonal array for deployment in the Taguchi method. The survival zone of the AF's optimized geometry increased by 40%. In TRNSYS, three heating systems—namely boiler heating system, HP–boiler heating system, and SC-HP-boiler heating combisystem—were compared for their heating gain, contributions, payback period, and CO₂ emissions. Thus, solar combisystems effective in reducing CO₂ emissions are uneconomical and are not the most suitable heating system for cold streams. Nevertheless, boiler heating systems are potentially the most suitable for the optimized geometry of the AF during a cold current, particularly for instant heating.