There are two possible choices of objective function for urbs problems, either the costs (default option) or the total CO2-emissions can be minimized.
If the total CO2-emissions are minimized the objective function takes the form:
w∑t ∈ Tm∑v ∈ V − CB(v, CO2, t)
In script model.py the global CO2 emissions are defined and calculated by the following code fragment:
/../urbs/model.py
In the default case the total system costs are minimized. These variable total system costs ζ are calculated by the cost function. The cost function is the objective function of the optimization model. Minimizing the value of the variable total system cost would give the most reasonable solution for the modelled energy system. The formula of the cost function expressed in mathematical notation is as following:
The calculation of the variable total system cost is given in model.py by the following code fragment.
/../urbs/model.py
The variable total system cost ζ is basically calculated by the summation of every type of total costs. As previously mentioned in section sec-cost-types, these cost types are : Investment, Fix, Variable, Fuel, Revenue, Purchase, Start-up and Environmental.
In script model.py the individual cost functions are calculated by the following code fragment:
/../urbs/model.py