Introduction to Occupancy Sensors
All lighting systems are operated with lighting controls, devices that switch lights on and off or devices that dim light output. The most common and basic lighting control is a simple on-off switch, which, when flipped, opens and closes the circuit, feeding or cutting off the electric current necessarily to operate the lamps.
While the basic switch is economical in terms of initial cost, they can actually become quite expensive over time in terms of total ownership cost. If you look at most large city skylines at night, we see an almost majestic view of skyscrapers dotted with thousands of lights, each of them a window offering a view of an office or space that is lighted but unoccupied. Lighting system operation costs money, and yet organizations lose profits every day by paying to operate lighting systems when nobody’s there to work. It’s like paying workers to sit and do nothing.
A solution is the adoption of automatic lighting controls that switch the lights or dim them based on occupancy, time of day and availability of daylight. In this article, we will focus on occupancy sensors.
Occupancy sensors are automatic switching devices that sense human occupancy and control the lighting system accordingly, either by turning on/off the lighting system or, in tandem with other controls, increasing/decreasing light output.
Energy, a basic product for which the electric utility charges, is the result of a lighting system used over time: Power (watts) x Time (hours) = Energy (kilowatt-hours). If we reduce the hours of operation for a lighting system, then we can significantly reduce energy use and associated costs.
By turning off the lights when occupants are not present using occupancy sensors, we reduce energy waste that can result in a reduction in lighting energy consumption. According to the California Energy Commission, “Energy saving potential is highly dependent on baseline assumptions and operation, but values of 35% to 45% are typical.”
Occupancy sensors also can reduce the building’s peak demand, reducing demand charges, which are significant costs that may be imposed by the local utility.