Innovative Energy & Research
Open Access

Energy plays an important role in every sector of life. Every day the needs for energy continue to increase in line with the increase in population. While the national energy reserves are mostly composed of fossil fuels and dwindling, so it is feared scarcity.

In 2000 and 2015, the electricity demand in Indonesia has increased 150% in line with the increase of the Gross Domestic Product. In 2017, Indonesia's Energy Efficiency Report states that Indonesia consumes up to 36% of total energy needs in Southeast Asia [1]. The energy consumption is spread in several sectors, such as households that consume up to 378.05 million BOE, transportation sector consumes energy up to 303.31 million BOE, the industrial sector amounted to 255.81 million BOE, and other sectors up to 112.13 million BOE [2].

The government was aware of this and tried to find a way to prevent such scarcity from happening. One is through energy conservation policy as stipulated in Government Regulation number 70 of 2009. Energy conservation or energy savings is an activity to improve efficiency in energy use. One of the policies is that users of energy sources must use energy economically and efficiently [3].

In Indonesia, the building sector contributes up to 70% of overall electricity consumption [4]. The energy consumption is dominated by the air conditioning system in the first rank and the lighting system in the second rank [5].

College as a place to gain knowledge is expected to have knowledge and awareness about the importance of energy savings and can apply them in daily learning activities. The savings are most easily done on the lighting system. The trick is to maximize daylighting, due to the use of daylighting is expected to reduce the use of artificial lighting [6]. The issue is not just turning off lights when not in use, but also looking at how these savings do not reduce the comfort of the occupants [7].

The background of this research is the results of the audit conducted by Rudiyanto, Adrya W & Ronaldo [8] in Building A of the Postgraduate Program at Diponegoro University. The Energy Use Intensity (EUI) score was 3.41 kWh/m²/month [9] (Figure 1). Where the EUI value is still very efficient by Ministry of Energy and Mineral Resources Regulation (PERMEN) Number 13 of 2012 [10]. Another finding is that lamps are the second largest major energy user after air conditioning, which around to 6.10% of total electricity consumption, while the air conditioning was 76.86%. According to this background, it is necessary to re-observe the savings opportunities in the lighting system. The lighting system was chosen because savings can be made with minimal costs, but still pay attention to the applicable standards.

Figure 1: Details of energy consumption from various types of buildings.

Postgraduate building A is facing south. Building A consists of 6 floors with an area of 4,802 m². This building is used for lectures, administration rooms, and offices for lecturers and employees. Office activities began on Monday-Friday from 8 a.m. to 4 p.m., while the lectures held from Monday to Saturday starting from 8 a.m. to 04:00 p.m. 1st floor area is 825 m², 2^nd floor is 797 m², 3^rd floor is 865 m², 4^th floor is 710 m², 5^th floor is 721 m², and 6^th floor is 884 m². Building A Diponegoro University Postgraduate is between the Old Building on the west side, BNI Building and Building B on the east side. Here is the documentation of the room to be observed (Figure 2).

Figure 2: Six room samples located in 2^nd to 5^th floor in building.

All the 6 room samples are located in 2^nd to 5^th floor in Building A. All the 6 room have a window that faces south, east, and west. Room 301, room 401 and room 501 has the same type of room. This study uses quantitative methods to analyze primary and secondary data on the 6 samples of a lecture hall in Building A.

Primary data is obtained by measuring the illuminance using lux meter. SNI 16-7062-2004 is used as a standard in determining the measuring point [11]. Based on these standards, measurement points are at the intersection of the horizontal line length and width of the room at any given distance with a height of 1 m from the floor. The determination of the measuring point based area of the room in which (Figure 3):

Figure 3: Example of determination of measurement points.

• If the room area is <10 m², then the measuring point is every 1 m.

• If the room area between 10-100 m², then the measuring point every 3 m.

• If the room area is >10 m², then the measuring point is every 6 m.

After luminance measurement results obtained and compared with recommendations on SNI 03-6197-2000 where exposure levels in a classroom at a minimum of 250 lux [8]. As for the secondary data obtained from literature sources.

Based on previous audits, researchers tried to look back on energy consumption in the room in Building A. Observations conducted on 6 room samples and the results are shown in the table (Table 1).

Table 1: Energy consumption of lighting systems in existing conditions.

Energy consumption is the result of multiplication of the lamp power and time usage of the lamp [12]. The Table 1 shows that under existing conditions assuming the entire room operates at 8 a.m.-6 p.m. on Monday-Saturday, all the 6 room samples in Building A consume up to 2.38 MWh/year of energy or pay electricity bills up to IDR 2,146,176,000 [13].

Before finding savings opportunities, it is necessary to measure the illuminance to determine the condition of the lighting system in each room. Illuminance measurements were done with a guide of SNI 16-7062-2004. Based on observations in the field and luminance measurements obtained the following data.

The table (Table 2) shows that the room with a south facing window receives more daylight than the room whose window orientation faces east and west, this is because the room has a bigger window than the one facing west and east. Besides that, from the west and east sides of the incoming sunlight is blocked by other building.

Table 2: Daylighting measurement results.

Based on observations in the field, it can be seen the characteristics of the 6 room samples as follows (Table 3). Based on the Table 3, the opportunity for savings can be done by adjusting the number of lights used, adjusting the time of the lights, and how long the lights are used as follows (Table 4).

Table 3: Characteristics of the room.

Table 4: Time lamps settings.

Based on the Table 4, the results show that total energy consumption after the adjustment is 1.7 MWh/year, which means that the adjustment was able to save 632,448 Wh/year only for the lighting system in the 6 rooms sample.

After knowing the amount of electrical energy consumption in the lighting system and billing costs for one year in the 6 rooms, it can be compared to energy consumption between the existing conditions and after being an adjustment.

From the Table 5 it can be seen that after adjustments were made, savings of up to 26.52% were obtained or if expressed in rupiah the savings were IDR 569.203.200 each year for 6 rooms sample. The savings value will be even more if applied to another room.

Table 5: Comparison of total consumption of electricity.

Based on the observations and measurements in the field, it was concluded that the improvement in energy consumption in the lighting system by adjusting the number of lights used, adjusting the time of the light, and how long the lamp is used resulting in savings of up to 26.52% from existing conditions. The biggest savings are obtained from room 501 with south and west oriented windows, this room gets good daylighting. Besides that, rooms with south-oriented windows tend to have a large intensity of daylighting because the incoming sunlight is not blocked by other buildings when compared to rooms that have west or east windows facing orientation.