Basic Concept
The typical Objective functions of Structural optimization (Annualized overall cost and Net present value) contain a combination of investment and operating costs. As a rule, these costs are in inverse proportion to each other, i.e., higher investment costs lead to lower operating costs. In order to investigate this dependency more closely, a multi-criteria optimization can be performed in the environment of the net present value optimum.
To do this, fix the investment costs within a reasonable range and optimize the energy system according to the respective operating costs. The result is a Pareto front, which describes the dependency between investment and operating costs. The Paretofront shows which additional investment costs would result from the further reduction of operating costs and whether large leaps in operating costs are possible due to insignificantly higher investment costs (see the following figure).
In total, a number of structural optimizations is calculated here. This increases the calculation effort. Subsequently, the user can select a suitable dimensioning (solution) and carry out the operation optimization based on this.
Operation
Make the settings for structural optimization in the 
Simulation form under the tab Settings and the subtab Structural optimization (see follwing figure).
To perform multi-criteria optimization, select Multi-criteria in the Mode drop-down list. The form expands as a result (see the following figure).
In addition to the Interest rate, the number of Economic time periods in years, and the Period duration (predefined unit a), the Size of the search environment can also be set for multi-criteria optimization. This influences the maximum distance between the Results of optimum net present value calculated in the Pareto front.
Optionally, you can Use your own compressed time series. If you activate this function with a check mark, two additional input fields for the Length of typical period (hours) and the Time points per typical period are displayed (see following figure).
Start the simulation after making all settings.
After all structures (solutions) in the Pareto front have been calculated, the simulation process is interrupted and a message appears (see the following figure).
Confirm the message with OK. Minimize the Simulator window. Familiarize yourself with the calculated results in the Simulation form, under Settings → Structural optimization → Results. Select a Solution for which the operational optimization is to be performed from the Use results drop-down list (see the following figure).
Continue the simulation by clicking the play button 
in the Simulator window (see following figure).
The selected Solution structure is now fixed and an operational optimization is calculated on this basis.
The video shows the steps of multi-criteria structural optimization described above.
