Input Parameters for Simulation and Optimization
In addition to the model on the TOP-Energy scheme, there are input parameters that affect simulation and optimization modes. Specify these in the Simulation ribbon, in the form of the Simulation node, and in the Options menu for Simulation. The settings of the individual Simulation nodes may differ from each other. They are saved in the project for each Simulation node (except the solver).
Objective Function of the Operational Optimization
In the Simulation ribbon, select the objective function (target function) of the Operational optimization via the split button in the group Operational optimization (see following figure).
There is a choice of:
Operating costs,
Primary energy,
CO2 emissions, and
The objective function for optimization determines which size is minimized with optimal control. The objective function Operating costs is the standard selection.
Operating Costs
Operating costs include all running costs of the modeled energy system. This includes, for example, the fuel and electricity costs from the tariff components and other cost items that can be set in the individual components, such as personnel and maintenance costs.
Primary Energy
Primary energy is set in the source components of the system, i.e., mainly in the electricity, fuel, heating, and cooling suppliers. The Primary energy factor (PEF), which represents the primary energy input per kWh of energy consumed, is stored in the respective Technical input data form. Because it varies depending on the location or district heating mix, you should adapt it to the specific conditions.
The feeding of electricity into the electricity supplier results in a negative primary energy input or a negative share in the overall balance.
CO2 Emission
CO2 Emission is calculated in the same way as primary energy consumption. The supplier components have stored the CO2 emission factors, which are balanced according to energy consumption.
User-Defined
User-defined costs include all user-defined costs that cannot be allocated to the above categories. These can be modeled individually, they do not occur in the standard TOP-Energy components.
Optimizing Operation With Look-Ahead
In the Simulation ribbon, the Gap and the time of Termination of the search for a solution are set separately for the Mainstage and the Pre-stage.
Settings of Look-ahead (time frame for calculation) and Result time frame are done in the Simulation ribbon in the group Operational optimization (see following figure). The functionality of Look-ahead is described in the linked article.
Solver
External solvers are used to solve the MILP problem. Unlike the other simulation settings, this setting is not specific to the individual simulation node, but affects the entire project. The selected solver is not saved in the project.
Structural Optimization
Settings for Structural optimization are made in the Simulation ribbon in the group Structural optimization and in the Simulation form under the tabs Settings → Structural optimization.
Reference Condition
In the Simulation form, the Reference condition tab is located next to the Simulation tab under the Settings tab (see the following figure).
The information in it can be taken from the Project Master Data.
The reference state for the enthalpy calculation (Reference temperature, Reference pressure) can be entered under the heading Pressure and temperature in the reference state. This has no influence on the simulation result regarding mode of operation, energy conversion of the components, and resulting costs because the performance of the components is calculated from enthalpy differences. In thermodynamics, the reference state is only required for calculating enthalpy.
In the illustration of the enthalpy values deviating numbers can be observed. If, for example, you look at the specific enthalpy \(h\) of a steam state in the component State Determination, this variable assumes a different value depending on the reference point. When comparing steam tables from different sources, it is important to ensure that they refer to the same reference temperature (usually 25 °C).
In TOP-Energy all reference values above 0 °C at 1 atm can be selected. Errors may occur below or at 0 °C because the phase of the medium changes in the reference state.
Ambient Condition
In the form Ambient condition, the ambient conditions for the exergy calculations (Ambient temperature, Ambient pressure) and, if necessary, time series can be stored under the heading Pressure and temperature in the ambient condition (reference for the calculation of exergy).
These input data are only relevant in certain cases: in combination with the components Dry Cooling Tower, Wet Cooling Tower, Hybrid Cooling Tower, Fresh_Air, Heat Demand Building, if exergy analyses are involved or certain exhaust gas temperatures are of interest.
