Add costs to objective function

Q&A
1

Hallo everyone,

For my research, I set up an energy system model with multiple sectors. I am still quite new to OEMOF and need help for my problem.

After setting up my energysystem, I created additional model constraints by adding Pyomo blocks with the constraints and additional variable. This works fine for me.
Now I have the situation that one of these variables causes costs that must be summed to the total costs. In summary I have this model:

New variable with constraint and costs:
Var_new = Var_model1 + Var_model2

C_new = Var_new*c_new

New total costs:
minimize(C_total,new) = minimize(C_total + C_new).

Question:
How can I include these new costs in my model objective function?
Creating additional blocks could be a solution, but I was thinking of a simpler way by just adding costs to the objective function (also with the view that creating additional blocks might not work in all cases).

I hope my problem was understandable and that you could help me.

Best, Matthias

1 Like
2

Hi Matthias,

Sadly I do not have an answer, as I am new to OEMOF too. But I have the same question, so I want to share my interest in case you find a solution or if someone else can share it with us (if it exists).

Best wishes, Mauricio.

3

Dear Matthias,

the oemof.solph Model is an extende pyomo.Concrete Model. We store the objective function at: model.objective. The attribute objective is a pyomo Expression, which means you can simply add any such Expression to it.

expr = sum(model.you_variable[i,o,t] * your_costs[t] for i,o in model.YOUINDEX for t in model.TIMESTEPS)
model.objective += expr 
model.solve()

I can not be more specific, as I don’t now what the name of your variable and its index is. I assumed that you have a timeindex and something like the oemof flow logic (from, to)…
Hope this helps!

4

Thank you a lot. This is exactly what I needed.
I did not know that it can be done by simple pyomo expression addition.

Best, Matthias