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 (Appendix A).
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.
It was observed that the air-conditioning in SIT@Dover was primarily relying on chiller units. These chiller units function by supplying cool water throughout the building, with fans to blow the air, cooled by the water, out into the classrooms. This system is operated via SIT@Dover’s main controls. For this reason, the team has decided, after much deliberation, to focus on lights only, since the lights are controlled manually in individual 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 utilities 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 utilities 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 (see Appendix B). Although there are areas in the 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 observed 34 classrooms (see Appendix C) in SIT@Dover from 6pm to 10pm throughout the period from 23 October 2017 to 27 October 2017. The number of classrooms whose lights were turned on until 10pm was half the total number observed. Additionally, it was observed that security guards accessed these classrooms and turned the lights off at 10pm. With these observations, the team determined the current implementations for energy conservation were as such, which were counter-effective.
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 simple – only a re-routing of electrical wiring is needed. This will connect the sensor to the main electrical circuit that leads to the lightings. With that, 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 in a vacant classroom.
5.2 Types of Motion Sensors
Research has identified three types of motion sensors, with each utilizing different forms 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. This processed signal can then be used to control classroom lights. The sensor detects a wavelength range of 8 to 12 micrometers, which corresponds to 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 penetrate glass doors, windows and concrete walls.
||2) Cannot detect differences between humans and animals with similar temperature range.
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
These dual sensors are activated when both microwave and infrared detect motion. For instance, a dual sensor will start out on the passive infrared setting, consuming less energy. When the passive infrared sensor is tripped, the microwave sensor will turn on,.
Figure 3. Combined types of Motion Sensors
Table 3. Pros and Cons of dual sensor
|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 its benefits in classrooms.
5.3.1 Choosing the Type of Sensor
After looking into the different types of sensors from the 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 utilities bills, allowing the institute to be more productive in other avenues where required.
5.4 Evaluation of Proposed Solution
Evaluation involves the installation of the PIR motion sensor in classrooms only. For that, the team has come up with a few projected challenges that SIT@Dover and its students would face.
5.4.1 Cost of Rewiring the Main Electric Circuit
Although PIR sensors are very cheap, the cost of hiring professional electricians to perform the rewiring works is expensive, considering a large number of classrooms. However, the costs can be earned back from the savings incurred over the years of saving electricity by cutting unnecessary wastages.
5.4.2 Disruption of Classes
Electrical works may disrupt certain classes from having their lessons in the particular classrooms where the works may be done. In order to mitigate this, the electrical works may be done either on weekends or after office hours, where there are very few, if not zero, classes going on. Another possible solution is to liaise with the administrative division on the schedule of classes.
5.4.3 Unexpected and Unwanted Switch Off
As supported by the team’s survey, students have opined that the lighting units may switch off in the midst of classes, where there is minimal movement. This may be true only when there are very few students in a classroom. When a classroom is packed with more students, there is a larger tendency for movement to occur within a span of 15 minutes, triggering the motion sensor to keep the lights turned on.
5.4.4 Classrooms Used as Sleeping Areas During Camps
During student orientation camps, classrooms are used as sleeping areas for campers and also act as important rooms (i.e. operations room, logistics room) for the camp committee members. For this reason, lights should remain turned off even if there is movement in the room to prevent campers from waking up due to sudden light exposure. In order for this to happen, a master switch can be fitted into the main electrical circuit as well for each individual classrooms, as shown in Figure 4. This will help deactivate the motion sensor and control the lighting units in accordance with what the user wants. This feature should only be used in such special circumstances, but not on ordinary days.
Figure 4. Circuit diagram of a master switch with PIR sensor (adapted from: CircuitDigest.com)
This report follows wholly on the information and research gathered using the following methods:
6.1 Obtaining Photographic Evidence in SIT@Dover
Our team, on random days, stayed in school up to 9pm to investigate the different areas of the school, mainly the University Services Centre and Academic Plaza. We then took pictures of the classrooms where lighting units were left turned on. These classrooms would be the places where the PIR motion sensors are installed.
6.2 Identification of Students’ Opinions
A survey was conducted by our team on students’ habits (if they turn off the lights), and their feedback on having motion sensors in classrooms to control the lights was taken into account. The results were then analyzed and used to support the notion that motion sensors in classrooms would help the institute to cut utilities costs.
6.3 Product Selection Through Online Research
In order to recommend solutions for the institute, the team performed online researches on the most suitable product. Each product was carefully evaluated through a number of considerations and conditions identified by the team, and chosen as the ideal product for the proposed solution.