22 May 2002
Conventional salmonid culture processes in northern fish farms sometimes require oil- or natural gas-based water heating systems to improve productivity, and this in the context of a continually increasing cost of fossil fuels and environmental constraints. This paper presents a thermodynamic/mechanical development project and a six-month field demonstration of a heat-reclaim system including an original, custom-made water-to-water heat pump and a passive heat exchanger installed in an existing fish-farming facility in Canada, in order to eliminate fossil fuels and thus improve the environmental performance of such systems. The purpose of the heat reclaim system was to heat fresh, cold water used in salmonid culture by using the energy recovered from the waste water. The system’s energy balance was achieved from several thermodynamic parameters measured and/or calculated during two consecutive, 3-month production cycles (temperature, pressure, enthalpy and flow rate for both water and refrigerant sides, electrical power and energy, etc.). A data acquisition program with a long-distance data transmission system and a complete data computing software were developed for this particular study. A simultaneous collection of breeding data also allowed to establish a precise production balance and to determine the alevin production cost. Significant savings in industrial production and energy operating costs in a cold climate ultimately resulted in a very short pay-back period of the initial capital investment.