The use of daylight harvesting technologies needs to address both energy management and occupant comfort issues according to Dynalite .
Daylight harvesting involves the strategic substitution of artificial fluorescent light with natural light, slowly dimming lights to balance daylight entry, and this can achieve considerable energy savings.
Window treatments, such as curtains, blinds and glass-transmission factors become an important factor in daylight harvesting as they have a direct impact on how much natural light enters an office environment.
The correct selection of blinds and sensors becomes critical to both energy efficiency and occupant comfort and sensor positioning can be as essential as sensor selection. For example, positioning a photoelectric (PE) sensor within a direct pathway of reflected light from shading louvers can lead to incorrect lux levels being applied by the PE sensor.
Such demands on sensor functionality have led to the rise of multifunction sensor devices that incorporate PE detection for changing light levels, and passive infra-red (PIR) and ultrasonic for motion detection.
While commonly used in a single mode, these sensors can also have the intelligence to be used in ‘multi-mode’ to provide logic control. For example, if the sensor detects that lux levels have fallen below a specified value, then artificial lighting levels can be increased, but only when motion is detected. In this way lighting levels will be maintained for occupied areas only.
Motion detection functionality can be further configured to perform different routines according to the time of day. For instance, during the standard working day a sensor may be tasked to dim lights over a workstation by 25 per cent when all occupants have been gone for 10 minutes. After hours, the same sensor might action a gradual fade out before eventually switching off.