Part vortex shedding sensors, ultrasonic flow sensors
Sensors forenergy monitoring “If you cannot measure it, you cannot manage it”(Narris, 2017). Therefore, to monitor and manage a building, there is a need forequipment such as sensors and meters (Narris, 2017). “Sensor is a device thatresponds to a physical stimulus (such as heat, light, sound, pressure,magnetism, or a particular motion) and transmits a resulting impulse (as formeasurement or operating a control)” (Merriam-Webster, 2017).
Wilson (2005)stated that different physical properties such as light intensity, temperature,pressure, force, flow, etc., can be measured using various sensors. Therefore,sensors are classified according to the measured parameters (Engineersgarage,2017). This part of the final essay reviews several common types of sensor suchas temperature, flow, electrical power and occupancy sensors which are applied toenergy monitoring in buildings. Temperature is an important measurement in buildings(Narris, 2017). Thermocouples, resistance temperature devices, thermistors, etc.,are temperature sensors (Juliantrubin, 2017). Thermocouples are used often dueto their low cost, the wide range of temperatures they can monitor (200 to 2600oC),robustness and simplicity (Axmad et al.
, 2016). However, this type oftemperature sensor also has certain disadvantages such as being prone tocorrosion and being difficult to calibrate (Sciencing, 2017). Being difficultto calibrate of thermocouples is likely due to their large range of temperaturethat they can measure.Compared to thermocouples, resistance temperaturedevices (RTD) have high accuracy and stability (Axmad et al.
, 2016).Additionally, they are easy to replace and install. However, RTDs are expensive(Polytechnic Hub, 2017). Axmad et al.
, (2016) stated that “thermistors are the most accurate andsensitive type of sensors for temperature reading”. This means they have theability to determine insignificant changes in temperature very quickly; theycan ensure fast responses in seconds (Get Revising, 2014). Their response timesare shorter than those of RTDs, but this is the same with thermocouples (Axmad et al., 2016). However,this type of temperature sensor work on batteries (Get Revising, 2014). Clearlythis is a disadvantage because batteries need to be changed periodically.
Air and liquid flows are measured via flow sensors(Wilson, 2005). Flow sensors have various measurement equipment such asmagnetic flow sensors, positive displacement flow sensors, vortex sheddingsensors, ultrasonic flow sensors and turbine-based flow sensors. Among them,ultrasonic flow meters demonstrate excellent results in terms ofnon-intrusiveness and accuracy (Axmad et al.
, 2016). However, this type of flowsensor demands a significant investment for its installation (Flowmetrics Inc,2017). Occupancysensors are used to determine the presence of occupants via their movements;the light will switch on when a sensor determines that there are people in theroom and will switch off when the room is unoccupied (Axmad et al., 2016). Also, Axmad et al.
, (2016) stated that “although many studies have demonstrated the importanceof occupancy information for whole building climate control, occupancy sensorsin buildings are currently mainly used for lighting control purposes”. Indeed, “use of occupancy sensors can save up to 30% electrical energy used forlighting” (Garg and Bansal, 2000). A motion detector is one of the main kindsof occupancy sensors, which use infrared detectors,ultrasonic detectors, etc.
(Sustaining Our World, 2015). Infrared detectors are not able to determine differences in objects ifthose objects have similar temperatures. Therefore, data received from infrareddetectors can be inaccurate in many case (Online Science, 2017). This is one ofthe main disadvantages of infrared detectors. Ultrasound sensors need to be calibrated carefully to avoid incorrect orfalse commands.
For example, small movements of the ventilation system cancontribute to enabling switches (Sustaining Our World, 2015). These sensors can be used with two communication technologies such aswired and wireless. Wireless technology is cheap and has low cost of operationand installation (Axmad et al., 2016). This type of communication technology is used often due to itssimplicity and flexibility (Abubakar et al.
, 2017). In turn, the wiredtechnology is reliable (Axmad et al., 2016).