LPD/UWLR Areas - Concepts
This command displays the Lighting Power Density and/or Upward Waste Light Ratio based on the luminaires within a user defined area.
Lighting Power Density (LPD)
Lighting Power Density is defined as watts per area where the area is dictated by the current display units in AGi32 (feet or meters). For example, if the current display unit is Feet, LPD is defined as watts/ft2. Initially, the watts are extracted from the photometric file when the luminaire definition is created. We recommend that you verify that the watts displayed in the Luminaire Definition are accurate, because the values in the photometric file may be nominal values, not accurate representations. The watts in the luminaire definition should be Luminaire Input Watts, not just Lamp wattage. Note: If a dimming factor is applied to a luminaire, the watts are not adjusted accordingly.
Upward Waste Light Ratio (UWLR)
Upward waste light ratio (UWLR)is defined as the proportion of the luminous flux emitted by the luminaire above the horizontal, in the installed position. The metric was developed by the Joint Standards Australia/Standards New Zealand Committee LG/2, Road Lighting, and is published in documents AS/NZS 1158.0:1997 and 1158.1:1997,Road Lighting, and 1158.2:1997, Lighting for Roads and Public Spaces (Part 2: Computer Procedures).
UWLR =FA / FB
where
FA= the flux emitted by the luminaire above the horizontal
FB= the total flux emitted by the luminaire
UWLR considers the total lumen and total upward lumen output for each luminaire. In order to calculate these values, the program creates a temporary internal photometric file for each luminaire label, tilt, roll and spin combination. This can be very calculation intensive if the application contains several luminaires at varying aiming angles.
Suggested Maximum UWLR Values
The Institution of Lighting Engineers (ILE, United Kingdom) has produced a document titled "Guidance Notes For The Reduction Of Obtrusive Light" describing the maximum value of UWLR for varying environmental zones.
|
Environmental Zone |
Category |
ULWR (max %) |
|---|---|---|
|
E1 |
Intrinsically dark areas, e.g., “National Parks”, “Areas of Outstanding Natural Beauty” or other “dark landscapes” |
0 |
|
E2 |
Low district brightness areas, e.g. Rural or small village locations |
2.5 |
|
E3 |
Medium district brightness areas, Small town centres or urban locations |
5 |
|
E4 |
High district brightness areas, e.g., Town/city centres with high levels of night-time activity |
15 |
Technical Details
A Luminaire's Insertion Point must be within or on the LPD/UWLR polygon to be included in the LPD/UWLR Area. The Luminaire Symbol and/or Aiming Vector are not used to determine inclusion in the LPD/UWLR Area.
LPD/UWLR Areas are dynamic entities that are updated automatically if the luminaires within or on the boundary change. This capability allows you to place LPD/UWLR Areas at any time, even before you add a luminaire to your job file. Light Power Density (LPD) and/or Upward Waste Light Ratio (UWLR) are dynamically updated (calculated) whenever the luminaire layout changes or whenever the job file is saved. Calculating UWLR may take several seconds to calculate in some situations. Therefore, it may be best to define LPD and/or UWLR Area(s) AFTER the luminaire layout is complete, if the luminaire quantity is large.
The LPD/UWLR Area boundary may be created in either a clockwise or counterclockwise direction. You may undo line segments one at a time while you are creating the boundary by using the Undo button or pressing Ctrl+Z on your keyboard. Once the boundary is created, there is no Undo functionality for recreation. You must delete the LPD/UWLR Area and recreate it if you make a boundary specification error.
If the option Create LPD/UWLR area from existing Drawing Entities, Room or Object is selected and there is more than one item in the location selected, the search order is: Room, Drawing Entity, Object.