Proliferation of Sensors in Buildings
Why have lights on in the private office when no one’s there? Why cool (or heat) outside air to ventilate the conference room if no one’s in it? Why have design ventilation rates for the lecture hall when it’s only holding half the students it was designed for? And at night or during unoccupied periods, why let the copy machine, water cooler, or coffee pot amass phantom plug loads?
These instances and more are examples of where humidity, carbon monoxide, carbon dioxide, and infra- red occupancy/motion sensors could be prolific in design and retrofit applications. When you consider and address where your energy is being lost, racking up savings is theoretically easy.
However, when applying sensors for control applications, there are a few key things to keep in mind. Consider:
- Quality sensors are needed for accuracy
- How will the sensors be maintained, i.e. calibrated? This cost can impact the savings.
- How often will the sensor need to be replaced (avg. life is 4 years for CO2 sensors)
- How are the sensors integrated for control purposes?
- Can the sensor or sensor platform provide real time energy management and / or measurement and verification data?
Unfortunately, I see too many sensors that have been left in place because of the issues above. For example, CO2 sensors drift up over time according to DOE research. If not calibrated regularly (every 6 months per ASHRAE), the sensors will overstate occupancy and thus waste energy. This completely defeats the sensor’s purpose.
Smart sensor application for smart buildings requires consideration of the above factors for functionality and life cycle costs. With such affective use and attainable savings, I see the trend for smart sensor applications taking hold.