DAYSIM Header File Keyword: Advanced Dynamic Shading

Dynamic Shading Model (advanced)                        go back to 'shading' keyword

If a user wants to explicitly model one or several dynamic shading systems such blinds that cover only parts of a facade, then the shading device has to be defined in at least two states (fully opened and closed). In order to model the dynamics of a shading system in more detail, additional states can be modeled. An example are venetian blinds that are modeled (a) fully retracted, (b) fully lowered with the slats horizontal and (c) fully lowered with the slat closed at 45 degrees. The user may of course model other shading systems in any state imaginable up to a total of ten states per shading group. The one requirement is that the users specifies different shading states in the order of 'most opened' to 'most closed'. The reason for this is that in order to avoid glare DAYSIM will always start with the most opened state and than successively close the shading group until glare can be avoided. If the user thus defined a partially closed shading group state after the fully closed state DAYSIM will never select that intermediate state during an annual calculation.

For each shading state considered DAYSIM requires a RADIANCE file with the material properties and geometry of the shading system in a particular state. (The RADIANCE file may be empty for example when the blinds are fully retracted.) DAYSIM will calculate daylight coefficient and annual illuminance files for a base case plus each additional shading device state. The base case corresponds to the base scene file (geometry and material files) plus the RADIANCE file for each shading group in opened state. For example, in case of a single shading device group with three states, blinds up, slats horizontal and closed DAYSIM will calculate three sets of daylight coefficient and illuminance files for the blinds in all three states. In case there are two shading groups with two sets of blinds in three states each, DAYSIM will calculate five sets of DC and ILL files:

  1. blind groups 1 and 2 fully opened (base case)
  2. blind group 2 fully opened and blind group 1 in the first closed state
  3. blind group 2 fully opened and blind group 1 in the second closed state
  4. blind group 1 fully opened and blind group 2 in the first closed state
  5. blind group 1 fully opened and blind group 2 in the second closed state

In case the blind 1 is partly closed and blind 2 is fully closed DAYSIM is generating the additional DC file on the fly without a further ray-tracing run by consecutively subtracting the effect of blind 1 and 2 compared to the base case. This will yield accurate results in case the two shading systems behave 'additive', i.e.e they either do not overlap. It is worthwhile noting that using the advanced Dynamic Shading Module can be quite time consuming due to the number of ray-tracing runs required.

Below the syntax for the advanced shading model is shown. Apart from specifying the different shading device states the user also needs to provide information how the system is controlled. Go to Shading Control Modes>>

Syntax

shading -n [followed by n shading group definitions]

<base_file_name.dc> <base_file_name_no_blinds.ill>

      <shading_group_1_name>

      m control_keyword <shading_group_opened.rad> [followed by m lines]

      <shading_group_1_state1.rad> <shading_group_1_state1.dc> <shading_group_1_state1.ill>  

     

with n = 1 or 2 = number of shading groups

     m = number of states in shading group

     control_keyword = <string described under Shading Control Modes>

Examples

This systems consists of a single shading group made of manually controlled venetian blinds that are modeled in three states, full opened, partially closed and full closed.

  shading -1
    BaseGeometryShadingUp.dc BaseGeometryShadingUp.ill
shading_group_1
    2
    ManualControl BlindsOpened.rad
    BlindsPartiallyClosed.rad BlindsPartiallyClosed.dc BlindsPartiallyClosed.ill
    BlindsFullyClosed.rad BlindsFullyClosed.dc BlindsFullyClosed.ill

Note
In case there are several shading groups in the same façade, Daysim assumes that for an automated system the signal at the control illuminance sensor for one group is not influenced by the setting of the independent control group. For example, if a venetian blind is combined with an electrochromic blind system and the EC glazing is automatically control via an internal illuminance sensor, Daysim assumes that the venetian blinds do not block the view of the illuminance sensor when lowered. If they do, this would in reality lower the signal at the EC control point and switch the EC glazing into a clear state. Daysim will not reproduce this because the illuminances for different shading groups are assessed independently form each other.

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