Overview: Daylight harvesting (DH) systems in smart buildings use sensors and Building Automation Systems (BAS) to automatically dim or switch artificial lights based on available natural light, significantly cutting energy costs, reducing carbon footprints, and improving occupant comfort by maintaining consistent illumination. These systems integrate photocells (light sensors) with dimmable fixtures and controllers (BAS) to measure ambient light (lux levels) and adjust electric light output, using either open-loop (natural light only) or closed-loop (natural & electric) controls to optimize energy use in offices, schools, and retail spaces, enhancing sustainability and well-being.
How it Works
- Sensors Detect Light: Photocell sensors measure the intensity (lux) of natural daylight entering a space, often near windows or skylights.
- Data Sent to Controller: Sensor data is sent to a central lighting controller or the main Building Management System (BMS).
- BAS Adjusts Lights: The controller uses programmed algorithms to adjust dimmable LED fixtures, either dimming them down or switching them off if sufficient natural light is present.
- Maintains Constant Levels: As daylight fades, artificial lights gradually brighten to keep the overall light level consistent for occupants.
Key Components
- Light Sensors (Photocells): Measure ambient light.
- Dimmable Fixtures: LED lights that can change brightness.
- Lighting Controller/BAS: The brain that processes sensor data and controls fixtures.
Types of Control
- Open-Loop: Measures only natural light; good for hallways/garages.
- Closed-Loop: Measures both natural and artificial light; common in offices.
Benefits in Smart Buildings
Integration: Can work with automated window shades and Demand Response programs for even greater efficiency.
Energy Savings: Reduces electricity demand for lighting, a major energy consumer.
Cost Reduction: Lowers utility bills and maintenance costs.
Sustainability: Decreases a building’s carbon footprint.
Occupant Comfort: Provides consistent, natural-feeling light, boosting mood and productivity.