demand simulation / energy demand

Owned by Iris Reichenbach
Last updated: Dez. 10, 2020 by Artur Sartison
4 min read

Here, the building's energy requirements for heating, hot water, electricity and cooling over the entire year are determined and displayed. This can be done in two different ways. Either the demand is simulated hourly from the building data (geometry, layered structure of the walls, g-value of the windows etc.) and the climate data, or the energy demand is imported. For a fine tuning, the value determined in this way can then still be scaled.

Simulation of the demand

Before the calculation can be started, the following basic requirements must be met:

  • Climate reference location is selected
  • There is a building that has floors and rooms
  • Rooms have components (e.g. walls, windows) and the components have a structure (e.g. layers, g-values for windows) with reference to the component catalog
  • All required dimensions and orientations are entered
  • The building is zoned, each room is assigned to a zone. The zones or usage profiles also determine the usage behavior

If it is determined at the start of the calculation that the requirements are not met, no calculation is performed. If the prerequisites are fulfilled, the following values can be calculated:
The primary calculation results represent the required heating and cooling capacity, which must be provided by a heating or cooling system to ensure the desired temperature behavior. The heating or cooling capacity is also referred to as "heating load" or "cooling load" in this context.
The calculation always takes place for the whole year. The program use/generates automatically the external conditions (solar radiation and outside air temperature). These are average values which are calculated from the climate data of the last years. The source of the climate data can be selected in the Climate Data view. This means that the program does not ensure that the desired temperature behaviour is maintained even in "extreme" years (e.g. particularly warm summers or cold winters).
If the interior components (wall, ceiling, floor) belong to only one room, there is no thermal balance with the adjacent rooms. Rooms with such a structure are self-contained with regard to the interior components, i.e. the heat exchange takes place only via the outer wall/outer walls. Such a thermal behaviour is not close to reality, therefore the adjacent room should be specified for each interior component. This is done in tabular form in the building input under "Components (rooms)" in the column "Also belongs to room". For buildings from HotCAD the assignment is done automatically.

Import of the demand

The "Import" button can be used to import data from a file in .csv or .txt format for the energy demand.

The captured profiles of the project are not taken into account if data has been imported. Select the file in the following dialog box. In the "CSV Import" window, specify the data format for the import:

  • Number of header lines
  • Separator
  • Decimal separator

In the selection boxes above the table you can assign the contents of the respective columns to the profiles.

Not all values must be set necessarily.

You can choose here:

       


In the table, when a file has been imported, the check marks in the "Imported" column are set at the corresponding positions. If you want to calculate the values from the entered building data and profiles after the import, you must first uncheck the "Imported" column.

Scaling of the simulated or imported demand

After the simulation or import, the demand can also be scaled, i.e. the given line is adjusted while maintaining the course of the year in such a way that the annual energy demand or the maximum load corresponds to an entered value. This is done in the table by checking the box for manual input. For the heating the demand can be determined here in different ways, namely from the heating load, the annual energy demand or by estimation from the consumption.

Display of results

The determined loads are graphically displayed in a yearly duration line. This means that the loads are plotted over the total hours of the year. From this it can be seen for how many hours per year a certain load exists. The graphic representation of the annual duration curve contains data on:

       

The individual graphs can be shown or hidden using checkboxes. If you click on the diagram, the resolution of the graphic display can be changed with the mouse wheel.

Example of an annual duration line. In this case, there is a heating load (red line) of at least 7 kW for almost 500 hours per year and a load between 5.3 and 7 kW for another 500 hours.