IES Irradiance Calculator

This program calculates the average irradiance at a specified height in a room based on an IES file of a light fixture placed centrally in such a room. This is used to sense check some calculations in my investigations on modelling far UVC in some rooms.

Setup

1. Create and activate the virtual environment:

   On macOS/Linux:

   # Make the setup script executable
   chmod +x setup_venv.sh
   
   # Run the setup script
   ./setup_venv.sh

   On Windows:

   # Create virtual environment
   python -m venv venv
   
   # Activate virtual environment
   .\venv\Scripts\activate
   
   # Install requirements
   pip install -r requirements.txt

2. To activate the virtual environment in future sessions:

   • On macOS/Linux: source venv/bin/activate
   • On Windows: .\venv\Scripts\activate

Usage

1. Make sure your virtual environment is activated (you should see (venv) in your terminal prompt)

2. Place your IES file in the same directory as the script or provide the full path to the IES file.

3. Modify the parameters in the main() function of ies_irradiance_calculator.py:

   • ies_file_path: Path to your IES file
   • room_width: Width of the room in meters
   • room_length: Length of the room in meters
   • mounting_height: Height at which the light fixture is mounted in meters
   • target_height: Height at which you want to calculate the average irradiance in meters

4. Run the script:

python ies_irradiance_calculator.py

Output

The program will output the average irradiance in micro W / cm^2 across a flat surface at a specified height.

How it Works

1. The program parses the IES file to extract the photometric data (W / sterradians at different values of theta, phi in the diagram above).
2. It creates an interpolator to estimate candela values at any angle.
3. For each point in a grid at the specified height, it:
   • Calculates the distance and angles to the light fixture
   • Determines the candela value at those angles
   • Applies the inverse square law to calculate irradiance
4. Finally, it averages the irradiance values across all points to get the average irradiance at that height.

Irradiance Calculation Geometry

Below is a diagram showing the geometry and formula used for irradiance calculation at a given point:

Notes

• The default grid size for calculations is 0.5 meters. You can adjust this in the calculate_average_irradiance method.
• The program assumes the light fixture is mounted at the center of the room.
• All measurements should be in meters.