11.20 can be augmented with differential equations to a SDTD (Fig. If numerical accuracy is required, the process should be studied further with a system dynamic tool diagram (SDTD) and modelled in dynamic system simulation software. It is obvious that CLD and SFD are very useful for system understanding, when the model does not require numerical accuracy. Figure 11.19 shows an example of both types of loops. When connecting two nodes from both sides, one creates a closed cycle that can have two characteristics: (1) a reinforcing loop that describes a causal relationship, creating exponential growth or collapse within the loop or (2) a balancing loop in which the causal influences keep the system in an equilibrium. A negative causal link thus causes a change in opposite directions. When both variables change into the same direction, then one can speak of a positive causal link. This depends on the relation of the variables to one another. Figure 11.19 shows that such edges can be marked as either positive or negative. These nodes are connected by edges, which form a connection between two variables accordingly. When drawing a CLD, variables are pictured as nodes.
![stella architect causal relationship stella architect causal relationship](https://www.mdpi.com/sustainability/sustainability-11-03456/article_deploy/html/images/sustainability-11-03456-g003-550.jpg)
These diagrams can create a foundation for understanding complex systems by visualizing the interconnection of different variables within a system. temperature regulation in the house) 11.7.2 Causal Loop DiagramsĬausal loop diagrams (CLDs) are a tool to show the feedback structure of a system (Sterman 2000). The reinforcing loop (R) is one in which an action produces a result which influences more of the same action and consequently resulting in growth or decline, where as a balancing loop (B) attempts to bring things to a desired state and keep them there (e.g.
![stella architect causal relationship stella architect causal relationship](https://www.iseesystems.com/resources/help/v1-4/Content/Resources/images/interface-Example13.png)
11.19 Causal loop diagram (CLD) illustrating examples of a reinforcing and a balanced loop within aquaponic systems.
![stella architect causal relationship stella architect causal relationship](https://blog.iseesystems.com/wp-content/uploads/2017/12/image-2.png)
11.18 Example of a flow chart in aquaponics (only RAS and HP exchange)įig. In the flow chart, fish food and water are added to the fish tank, where the feed is taken by the fish for growth, the water is enriched with the fish waste and the nutrient-enriched water is added to the hydroponics system to produce plant biomass. Figure 11.18 shows a simple flow chart in aquaponics. This can help, for example, in finding missing components and unbalanced flows and mainly influencing determinants of the subprocesses. To get a systemic understanding of the aquaponics, flow charts with the most important components of the aquaponics are a good tool to show how material flows in the system. In the following, flow chart and CLDs will be described. In aquaponics, flow charts or stock and flow diagrams (SFD) and causal loop diagrams (CLDs) are commonly used to illustrate the functionality of the aquaponic system.