Algorithm and system design of a geothermal temperature control system for aquaculture

摘要

A control system was designed to warm ponds by adding geothermalK warmed water, and then to maintain pond temperature for successful egg maturation and broodstock growth in channel catfish ictalurus punctatus. This system may also be enhanced to vary pond temperatures to study biological responses and to cool ponds by adding cool water. In designing a control system of this nature, consideration o f bio logical constraints is essential. Various fish species spawn and grow at different temperatures.In this study, the goal was warming of the pond from ambient (approximately 10 deg C) to a breeding temperature of 26-27 deg C. Constraints on the heating rate and temperature variability were desired to maintain fish health and facilitate growth. Sincecold fronts can move through during the early spring (Jan-March), the desired time to raise broodstock, it was essential to maintain appropriate temperatures via some method of control. Fotir ponds were controlled independently with feedback control. The system consisted of temperature measurement devices (type T thermocouples), a central electronic control unit, electronic switches and electrically actuated ball valves. In response to the temperature sensed by each thermocouple, the controller sent amessage to either close or open the valve. When the valve was opened, warm water was added to the pond to increase the average pond temperature. Hardware and algorithm design and initial system testing were the major components of this project. The finaldesign incorporated information on relevant biological parameters, and safety, features including peak pond temperature, independent aeration and water pressure control median isms. Initial results indicate this should provide successful control of thisbiological system, and ongoing studies suggest similar mechanisms may be used for additional control objectives.