Energy conservation in Singapore has been on the rise in recent years. As an open economy with no natural resources, Singapore is vulnerable to rising energy costs that can affect our economic competitiveness. It is crucial that we take steps towards becoming more energy efficient.
In the Dover campus of Singapore Institute of Technology (SIT@Dover), there is a tendency for students to leave the classrooms without switching off the lights. Students have indicated that there might be another class going on later, requiring no necessity to switch them off. In a rush for the next class, students might forget to switch the lights off. Moreover, there are some students who do not even bother about energy conservation.
With students developing such energy-wasting behavior, security guards have to switch off the lights in every classroom after office hours. As a result, unnecessary costs on manpower and finances are incurred. Hence, there is a need for motion sensing device that could automatically switch off the lights in classrooms.
2 Problem Statement
Too frequently at SIT@Dover, students do not turn off the lights in classrooms after using them, which results in energy wastage and an increase in utility expenses. Unless motion sensor devices are installed in these classrooms, the institute will continue to bear unnecessary costs that could be directed to more productive avenues.
3 Purpose Statement
The aim of this report is to recommend the estates division of SIT@Dover to install an automated control system in classrooms. By implementing this system, the university will be able to reduce energy consumption and utility bills expenses.
4 Current Implementation
Based on the team’s observations, there is currently no automated system in place to switch off lights in vacant classrooms. Although there are areas in school that are fitted with motion sensors, classrooms are not included. Only standard light switches are installed in these classrooms, requiring users to manually turn off the lights.
The team has also done data sampling of 48 classrooms in SIT@Dover after office hours throughout the period from 23 October 2017 to 27 October 2017. The results have shown an alarming number of classrooms, where lights were left switched on when the team patrolled the school compound (Appendix C). The team then compiled the sampling data and determined the average number of classrooms with the lights switched on (Appendix B).
5 Proposed Solution
With the existing implementation in SIT@Dover, the team proposes the use of motion sensors to automatically control the lights in classrooms.
5.1 Using Motion Sensors in Classrooms
The proposed solution would be to install motion sensors, fitted with a timer device, in classrooms so as to regulate the use of lights. The process for installing the sensors is rather simple as only a re-routing of electrical wiring is needed. This will connect the sensor to the main electrical circuit that leads to the lightings. From there, the sensor will automatically turn the lights on whenever someone walks into a classroom. Subsequently, the timer device will countdown for 15 minutes before turning the lights off whenever a classroom are vacant.
5.2 Types of Motion Sensors
Three types of motion sensors were identified, with each utilizing different types of radiation. The advantages and disadvantages of each sensor are listed down.
5.2.1 Passive Infrared (PIR) sensor
The PIR motion sensor uses a pyroelectric sensor to detect infrared (IR) radiation emitted by the human body. The IR radiation received by the sensor excites the electrons in the sensor’s substrate, creating an electric signal which is then amplified into a larger signal for processing. It detects a wavelength range of 8 to 12 micrometers to detect the IR radiation emitted by the human skin (33 to 38°C). It scans for rapid changes of IR energy in an environment, thus only detecting motion.
Figure 1. Passive Infrared Sensor
Table 1. Pros and cons of PIR sensors
|1) Economical and long-lasting
||1) Unwanted shutoff
||2) Cannot detect differences between humans and objects with similar temperature range.
|3) Cannot penetrate glass and concrete.
5.2.2 Microwave sensor
The microwave sensor generates microwave pulses into an area and detects any phase shifts in the receiving signal as the waves bounce off objects. It is an active sensor (constantly generating microwaves into its environment).
Figure 2. Microwave sensor
Table 2. Pros and Cons of Microwave sensor
|1) Very sensitive
|2) Works in harsh environment
||2) Requires external power source
||3) Able to penetrate through walls
5.2.3 Combined types of motion sensors
Dual sensors are only activated when both types sense motion. For instance, a dual microwave or PIR sensor will start out on the passive infrared sensor setting, as it consumes less energy. When the passive infrared sensor is tripped, the microwave sensor will turn on.
Figure 3. Combined types of Motion Sensors
|1) Extremely sensitive
||1) More expensive compared to other types of sensors.
|2) Resistant to outdoor exposures and other interferences
5.3 Benefits of Proposed Solution
The benefits have been projected by first, choosing the type of sensor, and then assessing how it will be beneficial in classrooms.
5.3.1 Choosing the Type of Sensor
After looking into the different types of sensors from our team’s research, the PIR sensor is the most suitable sensor for classrooms. The three main reasons are as follows:
- The PIR sensor is the cheapest type of motion sensors. Since SIT@Dover will be used for the next 3 to 5 years before moving to Punggol, it is best to use the cheapest type to fulfill basic motion sensing capabilities.
- The PIR sensor does not require any additional power source to function. It basically ‘waits’ for IR radiation to be absorbed by its pyroelectric sensor.
- The PIR sensor cannot detect through glass doors, windows or concrete walls. Hence it will only detect if someone walks into a classroom and not walking past a classroom.
5.3.2 PIR Motion Sensor in Classrooms
Having a PIR motion sensor installed in the classrooms of SIT@Dover allows for better regulation of lights. Whenever the classroom is vacant for 15 minutes, the lighting units will be switched off. This will help in saving electricity and reduction of utility bills, allowing the institute to be more productive in other avenues where required.