Week 7: Motion Sensors

Commercial buildings consume a vast amount of energy, and one way to reduce that is through the use of motion sensors.  In the simplest of explanations: motion sensors help buildings reduce their energy consumption by altering systems of occupancy, signaling them to turn on or off.  Occupancy information can be used to control various systems within a building: lighting, HVAC, computers, etc.  Passive infrared (PIR or PID) is the most common type of motion sensor found in buildings today.  PIR sensors work by detecting changes in infrared radiation and maps it against a predefined gradient.  This type of sensor has a low resolution: it has the ability to detect a change, but not specifics about the occupant.  This keeps costs low for both the physical sensor and the installation/maintenance costs.

Due to the inability for motion sensors to reliably communicate with other sensors, limited accuracy, and a lack of data collection capabilities, motion sensors are typically only used to control the lighting system.  The electrical consumption due to lighting can be upwards of 60% of the building’s total electrical use.  Occupancy sensors need to be able to sense movement in the room, so accurate calibration and placement within the room are a key aspect of them functioning properly. 

I think the accuracy and interaction between motion sensors will increase very rapidly due to the fact that sensors are becoming more powerful and cheaper – allowing more to be used and the data gathered and studied for further improvements.  The ability for systems to turn on and off automatically will greatly reduce the energy consumption of buildings.

Sources:

Melfi, Ryan; Rosenblum, Ben; Nordamn, Bruce; and Christensen, Ken, “Measuring Building Occupancy Using Existing Network Infrastructure.” IEEE, 2011.

Garg, Vishal and Bansal, N.K., “Smart occupancy sensors to reduce energy consumption,” Energy and Buildings, vol. 32, 2000, pp. 81-97.

Leephakpreeda, Thananchai, “Adaptive Occupancy-based Lighting Control via Grey Prediction.”  Energy and Buildings, vol. 40, 2005, pp. 881-886.

Comments on Other Blogs:

Audrey Ryan: Your post was extremely enlightening.  I like that you went through the different types of temperature sensors.  I am interested to see which type of sensor is used in different applications.

Ryan Taylor: I found it interesting how you thought about movement sensors: I was very narrow in my scope limiting my view on motion sensors to lighting control in rooms.  This is a great way to showcase how many different ways one type of sensor can be used.


Dave Barbalace: Do these seniors have the ability to interact with the HVAC unit to control the moisture or are they more used for alerting someone of the moisture level?  I think it is amazing that it is so small!