Hello
This is my first time to use Vensim, it is a good experience so far but I can't simulate my model because I get the Simultaneous Equations involving error (attached screen shot), also attached screenshot of my model.
I tried to add initial values to different variables on the loop but first I didn't get any different results, second I actually don't know how to choose he right variable to add initial value to
The first problem is "waste generation"
The equation is
waste generation = waste generation+in inventory waste
This can never be calculated as you need to know "waste generation" before you can calculate it. So what is the correct equation here? Should "waste generation" really depend on itself?
"in inventory waste". I'm not sure what you are trying to do here,
IF THEN ELSE ( untreated waste < system capacity * 12
, in inventory waste=untreated waste
, in inventory waste=system capacity * 12 )
1. What is the "12"?
2. The equation I think you are trying to implement is
IF THEN ELSE ( untreated waste < system capacity * 12
, untreated waste
, system capacity * 12 )
The final problem, "system capacity". I'd expect to see some delay in the increase/decrease of capacity. Make "system capacity" a level, and increase/decrease over time. This will break this simultaneous loop.
Thank you !
I changed the waste generation equation, modified "inventory waste" equation as you said and made system capacity a level
Now when I run the model I get the attached error (floating time error) also I have problem with System capacity units, after integration it mismatch with production units
I think you need to go back a step and have a think about the system. "number of production lines" should be a level instead of capacity. Then "System capacity" = CAPACITY OF PRODUCTION LINE*"no.production lines"
Don't use ACTIVE INITIAL at all, I don't think you need it for this model.
