How do occupancy sensors and daylight harvesting systems contribute to energy savings in a lighting system?

Occupancy sensors and daylight harvesting systems are strategies used to reduce energy consumption in lighting systems. Occupancy sensors detect the presence or absence of people in a space and automatically turn lights on when the space is occupied and off when it is unoccupied. This prevents lights from being left on in empty rooms, corridors, or offices, saving energy. Occupancy sensors use various technologies, such as passive infrared (PIR) sensors, which detect changes in heat caused by human movement, ultrasonic sensors, which detect movement using sound waves, and microwave sensors, which detect movement using microwave radiation. Daylight harvesting systems use photosensors to measure the amount of natural light entering a space and automatically dim or turn off electric lights when sufficient daylight is available. This reduces the need for electric lighting during the day, saving energy. Daylight harvesting systems typically use closed-loop control, where the photosensor directly controls the dimming or switching of the lights, or open-loop control, where the photosensor provides information to a control system that manages the lights. A daylight harvesting system dims or switches off the electric lights to maintain a constant light level in the space, supplementing the available daylight. Both occupancy sensors and daylight harvesting systems can be used independently or in combination to maximize energy savings in lighting systems. These systems are most effective in spaces with intermittent occupancy patterns or significant access to natural light.