|Authors: ||O. Körner, E. Gutzmann, P.R. Kledal|
|Keywords: ||crop growth model, DSS, greenhouse climate, model, perch, simulation, software, tilapia|
A dynamic simulation model for a closed-loop aquaponic system was designed based on biological and physical sub-models of both the greenhouse cultivation system and the aquaculture system.
The complete model exists mainly of two components: (1) a complete greenhouse climate simulator including the cropping system and (2) the aquaculture system including recirculation system, PVC-containers and others for fish production.
The fish cultivation system was calibrated for two systems of 600 and 1000 m2 greenhouse system with 700 or 3000 kg peak biomass of tilapia fish (Oreochromis niloticus) production.
For validation and test, the model system was built in small scale at the site of Copenhagen University, Denmark, i.e. a greenhouse compartment of 100 m2 with three fish ponds dimensioned to the size needed for crop irrigation using a combination of leafy vegetables and herbs, and two varieties of fish, i.e. pike perch (Sander lucioperca) and tilapia.
The modelled combined system was implemented in a greenhouse simulator environment (The Virtual Greenhouse). Simulation studies where performed with the full model using tomato crop and a variation of fish cultures; i.e. the aquaculture ponds were set to a range of constant water temperatures for separate scenario studies, increasing with 2°C from 14 to 34°C. A standard Venlo type shelter of 1000 m2 was used for that.
The aquaculture system was dimensioned to the crops need of nutrients such that it produces 9 Mt tilapia fish yearly of which a peak system biomass content of 3t fish system-1 was calculated.
The fish feed was given to the optimum and the minimum intake capacity of fresh water at 12°C was calculated from transpiration and evaporation losses, as other water was recycled in the closed system.
Simulation results indicate that greenhouse climate is influenced through the aquaculture system with increased humidity levels and decreased use of energy for heating and CO2 supply.
The amount of energy saving for greenhouse heating increases with fish pond water temperature, while due to the metabolic activity inside the aquaculture system energy consumption for heating the water increased only little in that range.
Total energy saving (energy for greenhouse heating and the aquaponics system) increases almost linear with increased pond temperature with 41 MJ m-2 K-1 year-1. The developed model is useful for planning aquaponic systems and can be used as input model for predictive climate control in greenhouses with combined aquaculture production.
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