This article shows how to check regulations for street lighting in Speos. The content will focus on checking regulation for of sky light pollution.
Description of Regulations
The light pollution regulations were introduced to reduce energetic waste and to protect biodiversity. The main goal of regulation is to control and reduce the amount of light emitted toward the sky.
For that, two values are calculated:
Upward Light Ratio (ULR): It is the ratio of the light exiting upward (above horizontal line) by the total flux exiting the luminaire. The value is expressed in %. The nominal ULR is limited to 1% and on site to 4% (depending on installations)
CIE flux code 3: It the ratio of the flux exiting the luminaire directed in a cone of 75.5° (half-angle, in blue on below schematic) by the flux emitted downward (below horizontal line). The value is expressed in %. Depending on the installations, it should be greater 95%.
On the model used for the demonstration, the luminaire installation direction will be horizontal.
Model description
A model is supplied with this article. It consists of typical street light with 12 LEDs associated with collimators and pillow lenses to shape the beam. The LED source is already created, with a white LED spectrum with a color temperature of 2800K.
Materials are already applied on the model: polycarbonate for the lens and black paint on the housing.
Sensor creation and simulation
In this part, we will add the sensor to get the values required to check the regulation.
We will use an intensity sensor centered on the light and we will switch the orientation to Conoscopic.
The sensor is not oriented correctly, we first need to reverse the Y direction, to have the result centered on the ground.
We now need to change the size of the sensor to cover all directions around the light. For that, we will change the parameter Start in the Size area to 180°. We will also change the resolution to 1°, as on the picture below.
The sensor is now ready; we can create the simulation. We will create a direct simulation and select all the geometries, the LED source and the intensity sensor. We can change the number of rays to 2e+7 and run the simulation.
Result analysis and regulation creation
When the simulation is finished, we can open the result from the simulation tree. It looks like this:
This result is quite uncommon because we have chosen conoscopic as sensor type.
Theta will represent the elevation, 0° corresponding to the direction of the ground and 180° the zenith in the sky.
For the regulation, we need to compute:
Total flux emitted: it will be the area from Theta = 0° to 180° and Phi from 0° to 360°. It corresponds to all the map.
Upward flux: it will be the area from Theta = 90° to 180° and Phi from 0° to 360°
We can open the measure tool with this icon and we get this window:
We can first adjust the size of the area to the full map by clicking on this icon we can also click in the cell 'Area' to rename this area to 'FullSpace'.
We will now add a second area to measure the upward flux. For that, we can click on .
Attention, your selection needs to be on Area, Shape or Parameters before adding a measure, else it will create a new measure in the same area.
If the bar looks like below, it will create a new area:
Else, if it looks like below, it will create a new measure in the area selected:
When the area is created, we can rename it 'Sky' and change the size. We can first extend it to full area and then change Theta start value to 90°. We need also to click in the measure cell and choose Flux as measure.
We will now create rules to calculate the ratio. For that we will click on Add Global Rule icon and in Rule cell we will type a name, for example 'ULR_value'. In formula cell, we will type the formula with mathematical operator and variable names.
The variable name is made this way: 'AreaName.Measure'. For example, if we want to use the 'Flux' value of 'FullSpace', we will type 'FullSpace.Flux'.
So, for ULR_value, in Formula cell we will type 100*Sky.Flux/FullSpace.Flux and we will get the value in %.
We can also create another Rule, which we will call ULR, to check if the rule is fulfilled or not.
The Fomula will be 100*Sky.Flux/FullSpace.Flux<=1 or ULR_value <=1. If the value is below or equal to 1, the rule will be in green and status set to (passed) else it will be in red with status (failed).
The list of available operators and functions for global rules is available in the Speos Labs help: Operators and Functions for Global Rules.
We can now repeat the previous steps to create the cone of 75.5° area, downward area and the CIE Flux code 3 rule.
In our model, the CIE Flux Code 3 is fulfilled but not the ULR value. We will see later how to understand the ray paths leading to a high upward flux.
We can now save the result. The measure and rules are now visible in the simulation tree of Speos, like below:
Template export and reuse in sensor definition
To avoid repeating all these steps to each project, it is possible to export a template to reuse in another project.
For that, in the result we can click on File \ Export template, choose a name and save. The template has the .xml extension.
We can also import a template from File \ Import template and then choose the .xml file.
We can choose if we want to apply the displays options (scale, maximum value of scale,...) contained in the template and/or the measures (areas, rules,...). For this example, we need at least to have 'Apply measures' selected.
We can also use this template directly in the Sensor definition in Speos, the type of the sensor will be automatically changed to Conoscopic.
We can also choose if we want to have also dimensions of the sensor from the template, as on below picture. It will lock the size and sampling.
At the end of a simulation using a sensor with a template, we will have immediately the result in the simulation tree (value, rules, ...) and we open the result, the areas and rules are already created.
We can also open the html report and get the measures result.
Light expert
In this part, we will create a new simulation to analyze the lightpath of rays going to the sky.
For that we can copy/paste our previous simulation and set LightExpert to 'True' in the simulation definition. We will also increase the LPF max path to 1e+7. It corresponds to the number of light paths saved. We recommend avoiding very high value, as it will increase the file size.
We can also check in the Sensors tab of the simulation that the LXP cell is ticked for the desired sensor (Intensity.1).
We can now run the simulation (with CPU only).
At the end of the simulation, we have a new file in the Simulation tree, with extension .lpf. It is the file where light paths are stored.
We can double click on it; it will open the conoscopic result. Rays are displayed in the 3D view and new panels.
In the definition panel we can define the number of rays to display, the size and parameters of the animation.
With the icons in the 3D, we can select faces (required or excluded), create a section or launch ray animation.
Back to the conoscopic result, we can open the measure window and select the Sky area. The 3D is updated to display only rays reaching the Sky area.
We can see that the rays causing a too high value in the sky area are coming from a reflection on the bottom part of the light housing (highlighted in orange on below picture).
The material on this part is currently a glossy black painting. To reduce the reflection, we can try to change the material, for a matt black. There is one material file in the project called 'BlackMatt.simplescattering' (1% of pure lambertian reflection). We can apply it to the face. For that we will create a new material with and rename it BlackMatt.
We will change the Type in general to 'Face Properties', the Type in Surface Properties to Library and then select the file. With the Face selection tool, we will select the face in orange in the previous picture (where rays are reflected).
The Face properties replace the material only on selected faces. It means that in our examples, all the housing is in black glossy, except the selected face which is black matt.
We can now relaunch the simulation to check the regulations.
The ULR regulation is now passed.
To go further, another idea could also be to change the design and replace the full bottom face where light is reflected by bars crossing. This won't be covered in the presentation.
Additional resources
Additional documentation, examples and training material
Speos user guide
Article
Ansys Learning Hub trainings