Technical Report Draft 1

1  Introduction

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 therefore crucial that we take steps towards becoming more energy efficient.

In the Dover campus of Singapore Institute of Technology (hereby known as SIT@Dover), there is a tendency for students to leave the classrooms without switching off the lights. Students of SIT@Dover have indicated that there might be another class going on later and requires no necessity to switch them off. Moreover, students, in a rush for the next class, might forget to switch the lights off. Coincidentally, there are students who do not even bother about energy conservation.

With students developing such energy-wasting behaviour, the probability of students not switching off the lights is rather high. As such, security guards have to switch off the lights in every classrooms around the school after office hours. As a result, the institute bears unnecessary costs on manpower and finances which could be directed to more productive avenues.

2  Problem Statement

Too frequently at SIT@Dover, students do not turn off the lights of classrooms after using them, which results in energy wastage and increase of 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, SIT@Dover will be able to reduce energy consumption and these savings could be directed to more avenues to improve the institution’s facilities.

5  Proposed Solution

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 on lights 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

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

Pros	Cons
1) Economical and long-lasting	1) Unwanted shutoff due to zero movement of any human in the sensor’s range.
2) Generates electricity for self-powering through the absorption of infrared light. Does not need external power source.	2) Cannot detect differences between humans with objects that have a very 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

Pros	Cons
1) Very sensitive	1) Expensive
2) Able be used in a harsh environment where the heat cycles are not regular.	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

5.3  Benefits of Proposed Solution

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:

1. 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 fulfil basic motion sensing capabilities.
2. 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.
3. 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 the 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 administration 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 are 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 X. This will help deactivate the motion sensor and control the lighting units in accordance to what the user wants. This feature should only be used in such special circumstances, but not on ordinary days.

insert figure here (electric circuit with master switch and sensor)