| Summary: | In British Columbia the Floating Vertical Raceway (FVR) system has only recently been introduced as a technique to produce low cost salmonid smolts. A FVR is constructed of synthetic rubber sheeting and may be assembled at, and/or within, an existing off-shore marine net pen. The FVR is filled with freshwater or varying proportions of freshwater/saltwater and thereby floats on the denser saltwater. Mixed results have shown that inconsistent and unreliable designs can prevent successful application of the FVR systems. The design problems are generally associated with stability and turgidity of the raceway.
In this study a computer generated spreadsheet simulation (CGSS) was developed to predict the technical and economic feasibility of 3 FVR scenarios through several production cycles. The program provides a tool to assist producers, investors and banks to assess the technical and economic feasibility of a FVR system.
An analysis of the CGSS behaviour provides valuable insights for prospective operators and farmers. Results indicate that for a FVR with a volume of 100 m3 influent water flow rates of 150, 300 and 600 1/min will incur oxygen deficiencies at 160, 180 and 210 days into a production cycle, respectively. Flow rates higher than 2000 1/min raise the fresh water head order of magnitudes above the observed heights of 0.01-0.3 m. The added force of this water could cause the investigated liner and outlet screen to fail. A FVR shaped as either a frustrum, hemisphere, paraboloid, or cuboid, adheres to stability criteria. Turgor is maintained for these four shapes as long as the current velocity is not greater than 1.1, 1.6, 1.2 and 1.15 m/s, respectively.
After criteria for technical feasibility were determined, economic feasibility was investigated. To obtain a ten year cash flow, it was assumed that the initial selling price of an Atlantic salmon smolt was $3.50. For one of the three hypothetical farm cases examined, net cash flow remained positive throughout all cycles and a surplus was accumulated. One hypothetical farm failed due to the low number of stocked smolts. The final hypothetical farm maintained a positive cash flow through most cycles but accumulated a deficit due to the large capital costs of PVC piping (45.32%). The lowest production cost of a smolt was $1.37.
Conclusions from test simulations on the CGSS indicate that the FVR system is technically and economically feasible. The spreadsheet developed during this investigation is concluded to be an effective tool to investigate alternative strategies, designs and economies for smolt production within a FVR. === Applied Science, Faculty of === Chemical and Biological Engineering, Department of === Graduate
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