Operational Side Conditions
The Operational side conditions are constraints on the operation of a plant.
From the Component template library folder Operational Side Conditions, you can drag the components CO2_Restriction, Priority (switch-on sequence), Temperature Constraints Parallel Connections, and Temperature Constraints Series Connections to the scheme.
All other Operational side conditions can be optionally specified in the Input data of a component. The following constraints are available for selection:
An operational boundary condition becomes an active component part after it has been added by clicking the 
plus sign in the Input data form Operational side conditions or on the corresponding entry in the drop-down list of the split button 
Operating constraints in the component ribbon in the Forms group.
When adding the Operational side condition, an additional input form is displayed. Via the red menu button 
you open the menu where you can 
Remove the added item again. Each type of side condition can only occur once in a component.
If an Operational side condition from the Input data form is activated for a component, this is optionally indicated on the scheme by an Overlay symbol in the upper right corner of the component, as in the following figure.
added as a time series. Please note the advice on the consideration of operating constraints when using time series compression.
Maximum availability
Maximum availability (see following figure) means that the plant is not operated beyond a certain power.
The Maximum power can be specified absolutely or relatively, referred to the nominal capacity.
In order to specify the availability temporarily unlimited, its value is set to -1 at the corresponding times or to 1 or 100 % in case of relative specification.
Minimum Availability
The Minimum availability specifies the minimum power that the system must not fall below.
The Minimum availability can be specified as an absolute value or relative to the nominal capacity.
If the value is greater than 0, the plant must not be switched off (see following figure).
To temporarily remove the lower limit of availability, -1 is entered at the corresponding times for both absolute and relative minimum power.
Forced Operation/Standstill
With the operational side condition Forced operation/standstill a plant can be forced to operate or prevented from operating. The possible values are
Minimum Operating/Standstill Time
After each operating start, the plant must remain in operation for the Minimum operating time.
After each operating stop, the plant must remain switched off for the Minimum standstill time.
In order to avoid the reduction to a power close to zero and thus unnecessary operating hours without power output, a Minimum part load should additionally be specified in the Technical input data.
You can override the Minimum operating time and the Minimum standstill time with the value -1.
Maximum Operating/Standstill Time
The same rules apply as for the Minimum operating/standstill time. After the entered time, the system must stop or start.
Load Change Positive
The operational side condition Load change, positive (see following figure) sets an upper limit for the “speed” of the power change in positive direction. The power of the plant may not be increased by more than the specified value per unit of time. The default unit is kW/h.
The Big M (load change) value must be higher than any power otherwise occurring in the overall system. Big M is necessary for the solution of the mathematical optimization problem if it contains a load change ramp.
For an unlimited power change in positive direction -1 must be entered.
Load Change Negative
The same rules apply as for the Load change positive. The load change is limited in the negative direction.
Starts per Day
The operational side condition Starts per day limits the daily plant starts to the specified value. Just as for the Minimum operating and standstill time, a Minimum part load should be specified to avoid operation with minimum power output.
To override the limitation of starts per day enter -1.
Start Costs
The Start costs of a plant can influence its operation by changing the start/stop behavior. The value in EUR symbolizes the price for starting the plant from the idle state. It is included in the objective function of the optimization according to operating costs. A plant with sufficiently high startup costs will only perform a startup if it is profitable to operate.
Structural Optimization, Time Series Compression, Year-Round Coupling
Structural optimization without Time Series Compression and without year-round coupled constraint in the energy system considers the Operational side conditions directly in the main stage without the need for a preliminary stage.
Structural optimization without time series compression but with a year-round coupled constraint in the energy system considers the Operational side conditions directly in the pre-stage (Starts per day and Minimum and Maximum operating/standstill time only restricted). The subsequent operational optimization considers all operating constraints in the main stage.
Structural optimization with time series compression but withoutyear-round coupled constraint in the energy system is done in the simplified pre-stage. It considers only the Operating constraints Maximum/Minimum availability and Forced operation/standstill. The model message 8504 appears for the remaining, time-coupled, Operational side conditions, which are taken into account only during the subsequent operational optimization in the main stage:
Tip for Experts
See the chapter Modeling of Customized Components (for experts) for information on modeling operational constraints.
