Analysis of the application of technology in reducing carbon dioxide (CO2) emissions at two high schools in West Jakarta

State Senior High School (SMAN) 96 is the first high school in Jakarta to be officially designated as a net-zero school with a Greenship Certificate by the Green Building Council Indonesia. In contrast, State Vocational High School (SMKN) 73 is not a net-zero school. The two schools are 100 m apart, located in Cengkareng District, West Jakarta. The purpose of this study is to analyze the application of CO2 emission reduction technology in the two schools. This study used a quantitative method. Because the school setting is in the urban area, it is not easy to find so-called indigenous technology. This study will look at the best available low carbon technologies implemented in both schools. The results show that SMAN 96 has electricity consumption and CO2 emissions lower than SMKN 73 because SMAN 96 already using the energy-efficient devices/appliances and minimizing the usage of AC and refrigerator which can increase the CO2 emissions. To reducing CO2 emissions, the two schools already implementing the use of solar panels. Furthermore, by using the solar panels it can save the electricity consumption and also solar panels produces emissions smaller than total electricity usage.


Introduction
CO2 emissions from human activities have relatively higher concentrations so it causing disruptions in the atmospheric balance system and ultimately harming the ecosystem and human wellbeing.Activities that cause CO2 emissions come from nature and humans (anthropogenic) such as CO2 emissions from transportation, waste, and household electricity consumption [1].Everyone in their daily activities that uses energy will produce CO 2 emissions, the more human activities, the more energy used so the greater the CO 2 emissions produced [2].
To reduce CO2 emissions, there are two approaches that can be taken to decide policies related to climate change, namely mitigation and adaptation.Mitigation is an effort to reduce sources or increase the absorption of greenhouse gases especially CO 2 , and adaptation is an effort to adjust human responses to climate change and its impact.There are four aspects of the difference between mitigation and adaptation, first is the scale of activity; second is the actors involved which in mitigation are the energy and transportation sectors and in adaption, the actors involved are the environmental sectors; third is the activity benchmarks; and the last is the time that needed to show result [3].
One of the first contributions for an institution to mitigate the global warming is to assess the greenhouse gas emissions resulting form its own activities both direct and indirect emissions [2].Low carbon education is an activity that has goal of creating a low carbon society through an education system that starts with schools [4].Net zero carbon schools or low emission schools are schools with buildings that have a low emission concept, are inexpensive in operation and most of their energy needs come from renewable energy, and are also initiatives to promote sustainable activities for students by minimizing carbon emissions in the school environment [5].
In 2022, the Governor of Jakarta has inaugurated four schools to become net zero carbon schools, and one of them is State Senior High School (SMAN) 96 Jakarta.The SMAN 96 has been certified Greenship by Green Building Council Indonesia and the first public school that have this certificate.The SMAN 96 has also met the basic requirements to be categorized as a net zero carbon school, namely by utilizing natural ventilation, minimizing the use of air conditioners and maximizing natural lighting.On the other hand, there is a State Vocational High School, namely SMKN 73 Jakarta which is not a net zero carbon school where this school still uses a large number of air conditioners, does not utilize natural ventilation, and does not maximize natural lighting.The purpose of this study is to analyze the technology that has been implemented in the two schools by taking an inventory of the use of electronic devices that use energy related to CO2 emissions.

Methods
Parameter used in this study are carbon dioxide emissions which calculated based on the consumption of electronic devices at SMAN 96 and SMKN 73.The reason to choose SMAN 96 and SMKN 73 as the research location are to analyze CO2 emissions from net zero school and non-net zero carbon school.The method used in this study is a quantitative method.The data used is primary data from the inventory of the electronic devices in schools.These data will be calculated the energy usage from the consumption of electricity in one day based on the power of electronic devices or appliances used in units of watts, which are converted into units of kilowatt hours (kWh), then multiplied by the duration of use and the number of devices.The results of calculating electricity consumption in one day are used to calculate consumption electricity in one month by multiplying one day's electricity consumption by the number of active working days [6].Then the electricity consumption data for one month will be multiplied by the CO2 emission factor of 0.87 Kg/kWh which has been stipulated in the Decree of the Minister of Energy and Mineral Resources 2021.This calculation is used to determine the value of CO2 emissions resulting from the use of electronic devices.

Profiles of the two schools
SMAN 96 (Figure 1) has an area of 6,080 m 2 with a total of 21 classrooms with a total of 600 students.This school has 2 majors namely Natural Sciences and Social Sciences.While SMKN 73 (Figure 2) has an area of 4,000 m 2 with a total of 400 students.This school only has 11 classrooms including a practice room.This school has three majors, namely Hospitality, Catering, and Travel Business.The two schools are 100 m apart, located in Cengkareng District, West Jakarta.School activities start from 6.30 AM to 2.30 PM every Monday to Friday, and Saturday half day for extracurricular activities.

Electricity consumption
The electricity source for SMAN 96 and SMKN 73 comes from the State Electricity Company (PLN), whose electricity generations are dominated by coal-fired power plant.Table 1 shows the monthly electricity consumption used in kWh by the two schools in the last three months (January -March 2023) based on their electricity bills.In January 2023, both SMAN 96 and SMKN 73 consume less electricity than in February and March.Actually, the January bill comes from electricity usage in the previous month, namely December.In mid-December the schools had Christmas and New Year holidays so there was no electricity consumption from school activities except for electronic devices that have to be plugged in all day such as a refrigerator and few lights.The average electricity consumption of SMAN 96 (net zero carbon school) is 5,490 kWh, unexpectedly higher than SMKN 73 (non-net zero carbon school), which is 3,899 kWh.Ideally, the analysis of electricity bills is based on one year of data, but unfortunately the data available is only three months.

Number of electronic devices
The inventory of electronic devices in both schools can be seen in Table 2.These devices are dominantly used every day.The total number of electronic devices at SMAN 96 (289 units) is more than SMKN 73 (257 units).The main difference is that there are ovens and refrigerators at SMKN 73 because it is a vocational school with has major in catering, these devices are used for culinary practices.While SMAN 96 does not use oven and refrigerator at all.The number of air conditioners (AC) in SMKN 73 is more than double that of SMAN 96 which has twice as many classrooms as SMKN73.This is because several rooms require AC, such as a hotel practice room which is designed as a hotel where there are reception rooms and guest rooms and each of these rooms uses air conditioning.

Electricity consumption by electronic devices
Table 3 and Table 4 show the electricity consumption from the electronic device usages on each floor at SMKN 73 and SMAN 96.At SMKN 73, the total electricity consumption of the dominant electronic devices used every day is 7,834.04kWh/month with the largest electricity consumption coming from the use of AC, namely 4,059.96kWh/month (Table 3).The AC capacity used varies, namely 1 PK, 1.5 PK, and 2 PK.The highest energy consumption from using AC is on the 1 st Floor, which is 1,294.48kWh/month because the number of AC units installed is the highest compared to other floors and also the AC capacity is relatively large.Furthermore, the highest electricity consumption also comes from the use of refrigerators (1,620 kWh/month) and ovens (432 kWh/month) for culinary practice at SMKN 73.The total electricity consumption at SMAN 96 is 5,104.84kWh/month, which is less than the SMKN 73, with the highest electricity consumption is also from AC, 2,353.60 kWh/month (Table 4).The location of the highest use of AC is on the 3 rd Floor where the chemistry, physics and computer laboratories are located.These laboratories use AC with a capacity of 2 PK.The second highest consumption of electricity comes from the use of one elevator (lift) because the power required by the elevator is greater than that of other electrical equipment, even though the elevator does not operate all the time.Although SMAN 96 is designed to make the most of natural light, the electricity consumption for lighting (lamps) is quite high (479.04kWh/month), higher than the electricity consumption for fans, computers and projectors.The location that consumes the most electricity is on the 3 rd Floor where the number of classrooms on the 3 rd Floor is more than the other floors.The comparison of the electricity consumption of the two schools can be seen in Figure 3. Without comparing the electricity consumption of ovens, refrigerators and elevators which have been described earlier, Figure 3 shows that the electricity consumption from the use of AC is the highest in the two schools.SMAN 96 uses central air conditioning which tends to be more energy efficient, while SMKN 73 has several rooms that use air conditioners which are not energy efficient.Also, SMAN 96 saves energy by replacing the air conditioners with fans.The energy needed by the fan is much smaller than the AC and the fan does not cause air pollution due to the use of freon in the AC.Even though the number of lamps used at SMKN 73 is less than at SMAN 96 and the power of the lamps is the same, the electricity consumption from using lamps at SMKN 73 is higher than at SMAN 96.This is because the use of lamps at SMKN 73 still uses fluorescent lamps while at SMAN 96 all lamps already use LEDs, energy saving lamps.

CO 2 emissions from electricity usage
The calculation of CO2 emissions from electricity consumption using electronic devices can be seen in Table 5.The total electricity consumption at SMKN 73 is 7,834.04kWh equivalent to 6,815.61KgCO2 emission per month.At SMAN 96, the total electricity consumption per month is 5,104.84kWh which produces 4,441.20 KgCO2 emissions.The CO2 emissions from the use of electronic devices at SMKN 73 greater than SMAN 96.This can be influenced by the length of time the electronic devices are used and the number of units used.The amount of carbon emissions produced depends on how much electricity is consumed when using electrical equipment [7].Moreover, the use of electronic devices that are not energy efficient (or energy star label) can also increase CO2 emissions [8].The calculations of electricity consumption based on electronic devices of both schools are different from the monthly bills in Table 1, however the calculation for SMAN 96 seems to be more in line with the average monthly bills.

Technology in reducing CO 2 emissions
The two schools are located in the middle of a large and densely populated city, applying renewable energy is not easy to do, but these two schools have implemented one of the renewable energy technologies, namely the use of solar panels.One way to reduce carbon emissions is by utilizing renewable energy where one of them is from the sun [9], solar panels can reduce electricity consumption used and save electricity costs.By installing the solar panels, the energy consumption of coal-fired power can also be decreased and greatly assisting in the reducing of carbon emissions [10] The solar panels used in these two schools are on-grid systems where sunlight absorbed by the solar panels will be converted into energy which will then be connected to the school's electrical connection, then used to supply energy to all of the school's electronic devices.This on-grid system is still connected to the PLN network [10].The energy savings made by solar panels are limited because these solar panels are affected by sunlight and weather at the school location.
These solar panel are also able to save the energy load on both schools and can be used as backup energy when there is a blackout by the PLN.Furthermore, solar panels are considered to have an inoperated emission value or emissions during operation of 0 or it means that they do not produce carbon emissions at all [11].The carbon emissions produced by solar panels only come from their manufacturing and recycling process.However, the emission value produced in the solar panel process is much smaller than the total emissions from the use of fossil energy for electricity generation [12] and also using the solar panels can reduce the CO2 emissions in amount of 651 ton for 25 years [13].The use of solar panels at SMAN 96 is on school's rooftop as shown in Figure 4.There are 20 solar panels with 72 cells and capacity of 12,800 watt per day.Although SMKN 73 is not a net zero carbon school, it also uses solar panels which are installed on the side of the roof as shown in Figure 5.There are 40 solar panels with 32 cells and capacity of 8,800 watt per day.

Conclusion
The finding from the inventory of electronic appliances in this study is that the number of electronic appliances/devices used by SMAN 96 (net zero carbon school) is more than SMKN 73 (non-net zero carbon school), according to the size of the school and the student body at SMAN 96 which is greater.
Based on the calculation of electricity usage from electronic devices in one month, SMKN 73 consumes more electricity (7,834.04kWh/month), in line with the electricity bill in March where the kWh usage at SMKN 73 is higher than SMAN 96.Disregarding the use of electricity for ovens and refrigerators at SMKN 73 and elevator at SMAN 96, electricity usage for air conditioning is the highest in both schools compared to electricity consumption for fans, lights, computers and projectors.Indeed, the monthly electricity consumption for AC at SMKN 73 (4,059.96kWh) is almost double that of SMAN 96 (2,352.6 kWh) due to the number of units used at SMKN 73 is more than SMAN 96, on the other hand the number of classrooms at SMAN 96 are twice that of SMKN 73.It is related to SMAN 96 design that make the most of natural light and natural ventilation.
The CO2 emissions at SMKN 73 (6,815.61KgCO2) is greater than at SMAN 96 (4,441.20 KgCO2.), which can be affected by the duration of appliances usage and the number of appliances used.The low carbon technology that has been implement in the two schools is solar panel installation on the side ang on the rooftop of the school.The solar panel can be used as a backup power source and also save electricity consumption.The net zero carbon school program should be continued as a part of Indonesia's commitment to reduce carbon (CO2) towards global climate change.The program can be part of curriculum at the school itself.

Figure 3 .
Figure 3.Comparison of electricity consumption in the two schools.

Table 1 .
Electricity consumption in two schools in 2023.

Table 2 .
Recap of the number of electronic devices in two schools.Moreover, the number of computers at SMAN 96 is more than at SMKN 73, this is because the number of students at SMAN 96 (600 students) is more than at SMK 73 (400 students), for example, the computer laboratory at SMAN 96 uses 45 computers, while at SMKN 73 only uses 30 computers.The number of projectors at SMAN 96 is also more than that at SMKN 73, this is because the number of classrooms at SMAN 96 (21 classes) is more than that at SMKN 73 (11 classes).In addition, SMAN 96 also has an elevator (lift) because it has to meet the standard for students with disabilities, besides that this elevator can only be used by teachers.

Table 5 .
CO2 emissions from electricity consumption in both schools per month