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November 2017

Making sense, and saving cents, with motion sensors

Lighting fixtures are like cars. They are at their most fuel and energy efficient when they are switched off… implicit but indisputable!

The automobile industry uses a relatively recent technology that enables hybrid vehicles to “sense” when they are stationary, and consequently switches off the engine. No more idling in traffic or at stop signs, saving a precious few seconds of fuel consumption and profound implications to energy saving, expenses and environmental concerns.

The lighting industry also understands this phenomenon, using motion sensors to detect when there is movement in an indoor space and more importantly when there is none.

Making sense…

There are two types of motion sensors, namely Occupancy and Vacancy.

  • Occupancy sensors (auto on/auto off) turn on lights within a space when the sensor is triggered by motion. After a time delay (which is user-designated) when the sensor no longer detects any motion, the lights are automatically shut off. No manual operation is required, making this a highly efficient and effective solution.
  • Vacancy sensors (manual on/auto off) require the user to turn the lights on when entering the space, and subsequently after a time delay if the sensor no longer detects motion, the lights automatically shut off.

Which motion sensors, where?

  • Occupancy-driven lighting controls, whether wired or wireless, are cost effective in locations that are used intermittently, like stairwells, break-rooms, conference rooms, and restrooms. Other good locations are classrooms, laboratories, warehouses, parking garages and parking lots. They are less likely to be cost effective in open office areas or busy lobby areas that have occupant traffic throughout the day. These spaces that have steady occupancy during the day and are unoccupied at night are better served by timer-based lighting controls.
  • Vacancy sensors could potentially yield greater energy savings than occupancy sensors because they give the occupant a choice of whether or not to turn on the lights. Ideal for offices and conference rooms, if there is enough ambient light, for example from daylight entering through windows, the occupant may choose not to turn on the lights at all. They can work well in other rooms with light switches near each entry. Vacancy sensors are not recommended for areas where there are many entries that do not have light switches like stairwells, corridors, or warehouses. In addition, they do not work well for areas where some level of lighting is needed immediately, like stairwells and mechanical rooms, unless the controls are set to dim but not turn off the lights during hours of expected use.

Saving cents…

Lighting use constitutes about 20% of the total energy consumption in commercial buildings. Adding lighting controls is a simple retrofit option than can save on energy costs while helping to meet environmental, corporate and government energy guidelines and mandates.

Studies have shown that adding lighting controls can reduce lighting energy use 10% to 90% or more depending on the type of space in which the motion sensors are installed. One study conducted on a university campus found that installing wired occupancy sensors to control lighting in more than 200 rooms in 10 buildings provided an annual cost savings of about $14,000 with a simple payback of 4.2 years.
University of Illinois. 2007. Occupancy Sensor Installation Report

How much you can expect to save when you install occupancy sensor lighting:

Break-room: 29%

Classroom: 40-46%

Conference Room: 45%

Corridor: 30-80%

Office, Private: 13-50%

Office, Open: 10%

Restroom: 30-90%

Storage Area: 45-80%

Warehouse: 35-54%

Lighting Research Center. 2012. Barriers and opportunities for lighting controls:

How do they work?

An occupancy sensor detects the presence of movement within its given range and transmits the signal to the control unit. If no movement is detected after a period of time set by the user, the controller determines the space is unoccupied and switches off the light. The control unit processes signals from the sensor to increase or decrease power to the light fixture. In a wireless occupancy sensor, the sensor sends a wireless signal to the controller, and the controller increases or decreases the power to the luminaire.

  • PIR Passive Infrared sensors have a thin film sensing material that generates electricity when exposed to heat. When an object passes in front of a background like a wall or the ground, the sensor detects the change in signal and converts that change into a pulse that sends a signal to a controller for a light. PIR sensors are passive; they don’t actively send out signals. Because they are passive, they require very little power, which makes PIR sensors an ideal sensor technology for wireless sensors. Ideal for smaller, enclosed spaces, spaces where the sensor has a view of the activity and warehouse aisles
  • Ultrasonic sensors detect occupancy by constantly emitting high-frequency sound energy signals (the Doppler effect) that can move throughout a room and around objects in a room. Because ultrasonic sensors are actively sending out a signal, they require more power and are hard-wired. Ideal for spaces requiring a higher level of sensitivity and/or where a clear line of sight is not possible because of partitions, tall furniture (e.g., bookcases), odd-shaped rooms, bath­room stalls, etc.
  • High-frequency sensors emit pulses of specific high-frequencies (~5 GHz), then measures reflection off objects (like walls) when those waves return to the sensor. In this manner, the whole area of detection is filled, and the reflections change when there is a moving object (like a person) in the area. The reflection mechanism means that the line-of-sight problems of PIR sensors are reduced, and the high frequencies emitted can penetrate most building materials.
  • Dual-technology sensors use PIR sensors together with another sensor technology, ultrasonic or microwave. Dual-technology sensors activate lights only when both technologies detect the presence of occupants. They can give a higher likelihood of “false off” conditions. Although one ultrasonic sensor can detect movement across large spaces, around partitions, or throughout odd-shaped rooms, a single wireless sensor could not, but several wireless PIR sensors, strategically located throughout the room, might achieve comparable coverage.

New opportunities and customers with lighting audits

Lighting audits are a great way to determine the cost-effectiveness of installing occupancy sensors. From the gathered data, our lighting engineers can determine the feasibility of installing occupancy sensors alone and/or how their installation could help reduce energy if included as part of a larger lighting project. This offers great opportunities for new revenue streams from existing customers and new markets.

Stanpro Lighting Systems is dedicated to offering you, our Canadian customers, the best in class when it comes to lighting solutions and control systems with our comprehensive range of occupancy and vacancy motion sensors to best suit your needs and applications, whether it be PIR, Ultrasonic, High-Frequency or Dual Tech.