Potential of Solar Energy in Residential Rooftop Surface Area in Semarang City, Indonesia

Abstract

This study examines the potential of solar energy in the urban environment with a case study in Semarang, Indonesia by analyzing the intensity of solar radiation and the residential rooftop area. The study aims to obtain a quantitative description of the potential for electricity production from rooftop solar photovoltaic systems in residential areas and estimate the mitigation potential of CO2. The estimation method has adopted the hierarchies assessment: estimation of physical, geographic, and technical potential. This study shows the residential roof area spread over 16 districts in the city of Semarang is 412,987.50 m2 to 2,083,387 m2 has the average potential to of solar energy every year of 44,051 - 222,222 MWh/year. Total the low-carbon electricity is equivalent to 40.87% of the total electricity consumption in 2018 at Semarang City and reduce 1,394 tonCO2 in a year. Potential electricity production is proposed to set rules for the future empowerment of solar energy and analyze the potential at different time levels, such as monthly, weekly and daily.

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Potential of Solar Energy in Residential Rooftop Surface Area in Semarang City, Indonesia
Djoko Adi Widodo1*, Purwanto Purwanto1,2, Hermawan Hermawan1,2
1Doctorate Program of Environmental Science, School of Postgraduate Studies, Universitas Diponegoro, Semarang, 50241, Indonesia
2Department of Chemical Engineering, Faculty of Engineering, Universitas Diponegoro, Semarang, 50275, Indonesia
A R T I C L E I N F O
A B S T R A C T
Article history:
Received: 02 June, 2020
Accepted: 16 July, 2020
Online: 28 July, 2020
This study examines the potential of solar energy in the urban environment with a case
study in Semarang, Indonesia by analyzing the intensity of solar radiation and the
residential rooftop area. The study aims to obtain a quantitative description of the potential
for electricity production from rooftop solar photovoltaic systems in residential areas and
estimate the mitigation potential of CO2. The estimation method has adopted the
hierarchies assessment: estimation of physical, geographic, and technical potential. This
study shows the residential roof area spread over 16 districts in the city of Semarang is
412,987.50 m2 to 2,083,387 m2 has the average potential to of solar energy every year of
44,051 - 222,222 MWh/year. Total the low-carbon electricity is equivalent to 40.87% of the
total electricity consumption in 2018 at Semarang City and reduce 1,394 tonCO2 in a year.
Potential electricity production is proposed to set rules for the future empowerment of solar
energy and analyze the potential at different time levels, such as monthly, weekly and daily.
Keywords:
Geographic Information System
Residential Rooftop
Solar Energy Potential
1. Introduction
Increasing concerns on the use of carbon-based or fossil fuel-
based energy are apparent around the world. Approximately 70%
of the global electricity supply is currently generated from fossil
fuels [1]. It is estimated that if global energy demand grows from
2010 to 2030 at 1.5% per year, it could lead to an increase 22% in
oil consumption, 42% in natural gas and 53% in coal during a 20-
year time frame [2]. The use of fossil fuels for electricity
generation releases greenhouse gases into the atmosphere, which
causes climate change. The problems are considered not good
from an environmental perspective, especially the utilization of
electrical energy from unsustainable resources such as increases
carbon dioxide concentration in atmospheric from greenhouse gas
emission, environmental safety from energy production
techniques, unstable prices of energy, and depletion of fuel
reserves from carbon sources [3, 4]. Due to extensive
exploitation, fossil fuels have gradually become depleted and the
problem of global warming increases. Therefore, all the countries
should develop alternative energy sources in order to reduce the
potential risk of depletion of available fossil fuel energy supplies
and to overcome degradation of environmental [5]. Nowadays,
many nations are facing increasing challenges in order to diversify
energy sources. Most countries that tend to the development of
low carbon sustainability pathways have made climate change
mitigation a major concern and increased the research about
analyzing various mitigation policies of climate change in the
national context [6]. Renewable energy sources are very
imperative in their potential to play a dual role in mitigating of
global warming and assure long-term energy security. Renewable
energy is a vital element for every sustainable solution [7, 8].
A power generation technology of renewable energy is a
solution to the concerns of the use of fossil fuels [9]. Solar energy
is a potential renewable energy resource for the world to recovery
the environmental problems with clean energy [10, 11]. The solar
energy is widely regarded as a source of major renewable energy
expected to contribute to the security of energy supply and
environmental protection. Solar energy is readily available, the
most abundant,and clean of all renewable energy resources to
date, universal, noiseless and non-polluting [11, 12]. Solar energy
resources have a significant role in future energy resources [13,
14]. Solar power technology is one of the main solutions to fulfill
the increasing global energy demand [15]. There are two
technologies used to harness solar energy: solar thermal and solar
photovoltaic [16, 17].
Photovoltaic technology has become a promising renewable
energy supply from clean energy sources in all of scale
production [18, 19]. Its use can produce resources with zero
emissions, zero noise, and reliability [20]. In the last
ASTESJ
ISSN: 2415-6698
*Corresponding Author: Djoko Adi Widodo, Email: djoko.adiw@gmail.com
Advances in Science, Technology and Engineering Systems Journal Vol. 5, No. 4, 397-404 (2020)
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https://dx.doi.org/10.25046/aj050446

D.A. Widodo et al. / Advances in Science, Technology and Engineering Systems Journal Vol. 5, No. 4, 397-404 (2020)
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decades, photovoltaic technology has been growing more rapidly
than other renewable energy sources. Solar photovoltaic systems
in rooftop are increasingly becoming fundamental system in the
energy sector globally. It is reported that they contribute around
50% of the total installed solar energy capacity [21, 22].
Photovoltaic is seen as the main climate change mitigation
technology. Achieving this potential requires large-scale
photovoltaic installations, either on the roof of a house or as an
array mounted on the ground [23].
Local renewable energy generation through photovoltaic
systems mounted on a rooftop buildings in urban areas with great
potential for mitigating emissions of greenhouse gas [24]. The
potential of photovoltaic electricity generation on the rooftop
depends from several global, local, temporal, and spatial
variables [25]. The geographical potential of a rooftop solar
photovoltaic system of an area can be determined by estimating
the availability of the roof area in a certain percentage [26]. The
intensity of the solar radiation in Indonesia is around 4.8 kWh/m2
per day in all its regions. It means that every 1 m2 with the solar
module can produce 4.8 kWh of electricity every day [27]. The
solar photovoltaic potential of a rooftop can be determined
hierarchically through of different stages: (i) potential of physical:
the total amount of solar energy that reaches the surface target, it
can be called total solar radiation on the roof; (ii) potential of
geographical: spatial availability of roofs in buildings, where solar
energy can be obtained, it can be called to as the roof area
available for solar photovoltaic installations; (iii) technical
potential: the total amount of electricity that takes into technical
characteristics of solar photovoltaic systems: module efficiency,
it can be called electricity generation [28, 29].
Based on the literature review, the primary energy
combination for Indonesia's electricity generation is still largely
dominated by fossil energy sources such as coal and petroleum,
especially in big cities [30]. Clean energy from the energy source
of solar radiation should be utilized. Therefore, the investigation
of the potential of solar energy in urban areas is also required to
determine the contribution of solar energy as a clean energy supply
for domestic use and the reduction of CO2. Government policies
regarding the use of PV systems in roof buildings should be set to
support the National Energy Policy in 2025, which increases the
role of new and renewable energy, by 36% in 2050. This study
aims to obtain an estimation of the solar energy potential and
mitigation of CO2 potential based on photovoltaic roof systems in
Semarang City as one of big city in Indonesia. The rooftop solar
photovoltaic system in Semarang City is currently not widely
installed, even though geography and meteorology have great solar
energy potential. Until 2019, a rooftop solar photovoltaic system
has only installed 95 kWp capacity in 3 government buildings and
is connected to the national grid. Specifically, studies have not yet
been carried out on the potential of local area solar energy for
electricity production in the roof space of buildings in a
comprehensive manner. In this study, the evaluation of solar
energy potential focuses on the roofs of residential areas
considering that buildings are a potential area for solar panel
installation in urban areas. This paper is a preliminary study,
undertaking the work of estimating the potential roofs of buildings
and residential houses. From this study will have the knowledge
and description of the potential of roofs of buildings and houses
for the production of electrical energy from the sun.
2. Methodology
2.1. The Study Area
The case study in this paper is Semarang City, Indonesia,
located between the 6°50’ – 7°10’ South and 109°35’ – 110°50’
East (Figure 1). The area of Semarang City is 373.70 km2, it has a
tropical climate condition and the type of climate according to the
Koppen classification is Tropical Monsoonal. The annual average
temperature is 26.7°C. The population is made by 1,815,729
people and the population density is 4,253 per km2 with a
population growth of 1.6% per year [31]. Administratively, the
City of Semarang is divided into 16 sub-districts [32]. Data from
the Central Statistics Agency of Semarang City (2018) shows that
electricity consumption in 2017 is 4,704,416 MWh/year or around
23% of the total electricity consumption in Central Java Province
with an area of 32,801 km2. On a national scale, the number of
customers has increased by 5.6% from the previous year, while
electricity consumption has increased by 1.6% [33].
Figure 1: The Map of Semarang City, Indonesia
Topographically, the city of Semarang consists of hilly areas
[34] lowland and coastal areas [35, 36]. Therefore, it has an area
referred to as a downtown area or lowlands and a high hills area
[37]. The downtown area of the city is the center of government,
trade, industry, and education activities. In contrast, the hilly areas
or upper areas of the city are mostly used for residential
areas [38]. In general, land use in the Semarang City area is used
for roads, residential areas or housing, buildings, courtyards,
industrial estates, the brackish water pond and field
[39]. Geographically, the coastal area of the city of Semarang is
strongly influenced by the sea wind from the north and the valley
wind of Mount Ungaran from the south.
2.2. Evaluation of Solar Radiation
Solar radiation is a solar energy that reaches the earth's surface.
The radiation consists from three components: direct beam,
diffuse, and ground-reflected radiation [40]. Direct radiation is
the direct emission of solar energy and intercepted by a surface
without interaction with many particle in the atmosphere
[41]. Diffuse radiation is scattered and intercepted in the
atmosphere by aerosols and gases [42]. The radiation reflected is
the one reflected from the field and surrounding
surfaces [43]. The three radiations, which are direct, diffuse and
reflected make up for the global radiation or total radiation
reaching the earth's surface. The amount of solar radiation that
reaches the earth's surface depends on its location, its atmospheric
influence, and its topography. Solar radiation is affected by the

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rotation of the earth's geometry and revolutions of the sun [44]. At
ground level, topographic influences such as slope, elevation, and
orientation affect the radiation to reach surface [45].
The Meteorology, Climatology, and Geophysics Agency
(BMKG) in Semarang Climatology Station conducts periodic
observations of solar radiation intensity. In order to estimate the
physical potential, this study uses solar radiation measured by
BMKG Climatology Station in Semarang City, Indonesia. The
potential of solar radiation is estimated for electricity generation
by photovoltaic on the roofs of residential areas in 16 sub-districts
of Semarang City by using the data from 2014 to 2018.
2.3. Evaluation of Building Roof Surface
Currently, along with the development of the population of the
city of Semarang also develops residential buildings in various
regions and correlates to increase the amount of electricity
consumed. Some studios show that the roof of residential buildings
has the potential to generate electricity from solar energy. Potential
use of roofs to generate electricity using photovoltaic media
conversion panels. Electric production from the roof of the
building can be intended to supply electrical energy needs so it
needs attention.
The availability of the building roof area for the installation of
a photovoltaic system can be determined by
evaluating the geographic potential of the Semarang city. In
the study, the area of the roof that has the potential to capture the
energy the solar radiation is estimated through the remote sensing
and Geographic Information System (GIS).
The GIS software used in this study is ArcGIS 10.5. The
remote sensing data used in the form of aerial photos from the
high-resolution satellite imagery with a resolution of 5m x 5m. The
high-resolution satellite imagery of Semarang taken in the year
2017 was obtained from the results of the partnership with
geospatial information agency. The estimation of the roof area of
the settlements was conducted by the interpretation of the visual
object of building manually using the Geospatial Information
System (Figure 2). By using the geographic information
system, the area of the roof in the whole city of Semarang
spread in 16 sub-districts can be determined.
Figure 2: Visualization of Remote Sensing Approaches and Geospatial Information Systems
In this study for the purposes of calculating the potential of a
building roof carried out several stages as follows. The roof area for all high-rise buildings and houses is identified as a flat roof
through satellite imagery analysis. Roof identification is done by

D.A. Widodo et al. / Advances in Science, Technology and Engineering Systems Journal Vol. 5, No. 4, 397-404 (2020)
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each district so that the estimated roof area is more representative
of the character of the building in each district. Roof characteristics
for buildings with flat and sloped roofs are given with the roof
coefficient in equation (1) to determine the total roof in each
district:


 ()
where AR is a total rooftop area available per district in m2, n is
the number of polygons per district, Ai = area of each roof polygon
in m2 and RC is the available roof coefficient. The coefficient
value considers utilities placed on the roof such as water tanks, air
conditioners system, communication towers, etc. Besides, it also
considers the general construction conditions and strength of
building roofs. As a general rule of thumb, type of crystalline
photovoltaic module weighted 15-20 kilograms per square meter
(kgs/m2) of dead load on the roof [46]. RC coefficient is
determined around 12.5% - 15%. Roof coefficient (RC) considers
the regulation of roofing used for PV systems has not been
regulated by the Ministry of Energy and Mineral Resources of the
Republic of Indonesia.
Residential area in Semarang City consist of house and high-
rise buildings. The roof area according to the percentage of
concrete roofs 3.95%, roof tiles 72.66%, zinc 21.12% and
asbestos 2.18% [32]. Concrete-roofed buildings around 111
buildings with a minimum height of 7 floors. Residential house
building refers to the number of families around 424,628 houses
with roof tiles, zinc and asbestos.
2.4. Evaluation of Technical Potential
Solar energy received from sunray hits the earth and is
commonly called as solar radiation. Solar radiation can be utilized
and converted as electricity energy with photovoltaic
technology. Photovoltaic cells produce the electricity energy with
absorbing photons and release electrons which can be captured in
the form of electric current [47]. The cells can be grouped into
modules and arrays to produce a greater amount of power or used
individually to turn on small electronics. The potential for
photovoltaic electricity generation on residential roofs depends on
several conditions such as temporal, global, local, or
spatial variables [25]. The factors that influence electricity
generation are the total of solar radiation penetrating the earth's
surface. The available solar radiation and the roof area are
components in estimating the rooftop solar photovoltaic system
potential. The technical potential of a rooftop solar photovoltaic
system in Semarang City was be estimated by calculating
potential capacity of the solar PV rooftop system, CR in kilowatt-
peak (kWp) using the following equation (2) [46]:
  

 ()
With AR is the amount roof area available for installation the
solar modules in m2, CM is the individual module rated with
capacity in Wp (rated at 200 peak Watts), AM is the area of one
module in m2 (sized 1,487 meters by 0,992 meter), RCR is the
roof cover ratio, which is the part of roof area that the modules
will cover and value of RCR is 0.85. Energy yield (E) in kilowatt-
hour (kWh) calculated using this equation (3):
  (3)
GSR is the average global solar radiation over 5 years period in
kWh/m2/month. D is the derate factor value, that is converting
direct current (DC) to alternating current (AC). The derate factor
value ranges between 0.6 and 0.8 [46]. And typical derate factor
of 0.75 used in this paper.
3. Result and Discussion
3.1. Physical Potential
The estimation energy potential requires of solar photovoltaic
an evaluation of physical potential (using solar radiation),
geographic potential (roof surface availability), and technical
potential (system efficiency of photovoltaic). Table 1 shows
variations of average monthly global solar radiation in the
Semarang City area in 12 months each year. In this study, the
intensity of solar radiation was measured and recorded by BMKG,
Semarang Climatology Station for 5 years. The intensity of daily
global solar radiation is measured for several hours and tabulated
in daily average with units of Cal/m2/day. For analysis in this
study, the unit data of global solar radiation was converted to
kWh/m2/month.
Solar radiation that reaches the surface of the earth per unit area
and time is known as insolation (derived from insolation =
incoming solar radiation), or sometimes referred to as global
radiation. Insulation plays an important role in maintaining the
continuity of life on this earth and is very dependent on place and
time. Places represent the differences in latitude and the
atmosphere, especially clouds. Insolation is usually expressed in
units of Watt/m2 -sec which has the meaning of intensity or
strength. In another form, insolation is also measured in units of
hours/day, for example, the length of the sun shining on the earth
in one day. One day is also referred to as the length of the day, the
length of the sun on the horizon. The change in day length is not
too significant in tropical regions such as in Semarang City,
Indonesia, which is close to the equator. The farther away the
equator is, the greater the fluctuations in the irradiation. Based on
the definition issued by the World Meteorological Organization,
solar radiation is defined as the insolation power that exceeds 120
W/m2 [48].
3.2. Geographical Potential
The process of land use classification is a method of roof cover
detection. This method detects the roof of a building surface. The
utilization of satellite image data is very useful in this case. The
density of the settlement area in Semarang is
very beneficial in the estimation of the area by using GIS. It
enables the large – scale estimation with high
accuracy. Figure 5 is the result of the analysis of the
distribution rooftops area in the city of Semarang. Most
researchers use GIS to estimate the cross-sectional area with a
Table 1: Global Solar Radiation in Semarang City, Indonesia

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www.astesj.com 401
Month
2014
2015
2016
2017
2018
kWh/m2 per month
Jan
92.37
61.94
109.47
83.91
83.91
Feb
86.41
91.97
113.53
74.79
93.75
Mar
110.37
107.67
121.36
110.70
103.39
Apr
87.37
100.64
93.05
90.64
81.58
May
90.28
102.63
119.92
101.91
86.86
Jun
80.40
87.82
109.43
75.97
79.11
Jul
93.45
93.27
121.72
96.69
78.29
Aug
120.85
101.77
134.68
108.03
116.32
Sep
120.61
111.17
139.75
108.03
119.88
Oct
129.96
143.68
144.40
97.59
106.66
Nov
109.53
131.03
142.88
85.03
117.09
Dec
88.51
94.35
83.19
88.59
88.69
Table 2: Analysis setlements rooftop area per district in Semarang City, Indonesia
District
Total Area / Ai
(m2 )
Roof available / AR
(m2 )
Zone
Gunung Pati
8,719,100
1,264,269.5
High hills area
Mijen
6,580,800
954,216.0
High hills area
Tembalang
11,377,900
1,649,795.5
High hills area
Banyumanik
13,695,300
1,985,818.5
High hills area
East Semarang
3,958,200
494,775.0
Lowlands area
Candisari
5,140,700
642,587.5
Lowlands area
Genuk
13599.200
1,699,900.0
Lowlands area
Tugu
3,303,900
412,987.5
Lowlands area
Ngaliyan
16,667,100
2,083,387.5
Lowlands area
Central Semarang
4,422,500
552,812.5
Lowlands area
North Semarang
5,648,600
706,075.0
Lowlands area
West Semarang
11,071,300
1,383,912.5
Lowlands area
Gayamsari
3,694,700
461,837.5
Lowlands area
Pedurungan
16,660,300
2,082,537.5
Lowlands area
South Semarang
6,204,600
775,575.0
Lowlands area
Gajah Mungkur
7,017,500
877,187.5
Lowlands area
Total
137,761,700
18,027,675
Table 3: Technical potential of rooftop solar photovoltaic system in Semarang City, Indonesia
Distric
CR
(kWp)
Energy Potential (MWh/month)
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Gunung Pati
9,465
10,098
12,139
9,941
11,001
9,490
10,602
12,756
13,147
13,648
12,842
9,723
9,465
Mijen
7,144
7,622
9,162
7,503
8,303
7,163
8,002
9,628
9,922
10,301
9,693
7,338
7,144
Tembalang
12,352
13,177
15,840
12,973
14,355
12,384
13,835
16,646
17,155
17,810
16,758
12,688
12,352
Banyumanik
14,867
15,861
19,066
15,615
17,279
14,906
16,652
20,037
20,650
21,437
20,172
15,272
14,867
East Semarang
3,704
3,952
4,750
3,890
4,305
3,714
4,149
4,992
5,145
5,341
5,026
3,805
3,704
Candisari
4,811
5,133
6,170
5,053
5,591
4,824
5,389
6,484
6,682
6,937
6,527
4,942
4,811
Genuk
12,727
13,578
16,321
13,366
14,791
12,760
14,255
17,152
17,676
18,351
17,267
13,073
12,727
Tugu
3,092
3,299
3,965
3,247
3,593
3,100
3,463
4,167
4,294
4,458
4,195
3,176
3,092
Ngaliyan
15,598
16,641
20,003
16,382
18,128
15,639
17,471
21,021
21,664
22,490
21,163
16,022
15,598
Central Semarang
4,139
4,415
5,308
4,347
4,810
4,150
4,636
5,578
5,748
5,968
5,615
4,251
4,139
North Semarang
5,286
5,640
6,779
5,552
6,144
5,300
5,921
7,124
7,342
7,622
7,172
5,430
5,286
West Semarang
10,361
11,054
13,287
10,882
12,042
10,388
11,605
13,963
14,391
14,939
14,058
10,643
10,361
Gayamsari
3,458
3,689
4,434
3,631
4,019
3,467
3,873
4,660
4,802
4,986
4,691
3,552
3,458
Pedurungan
15,592
16,634
19,995
16,375
18,121
15,632
17,464
21,012
21,655
22,481
21,154
16,016
15,592
South Semarang
5,807
6,195
7,447
6,098
6,748
5,822
6,504
7,825
8,065
8,372
7,878
5,965
5,807
Gajah Mungkur
6,567
7,006
8,422
6,897
7,633
6,585
7,356
8,851
9,121
9,469
8,910
6,746
6,567
Jumlah
2,084,833
134,969
143,992
173,090
141,754
156,862
135,324
151,175
181,896
187,461
194,610
183,123
138,641
combination of Digital Elevation Model (DEM) data. In the development of engineering, the surface area of a extensive

D.A. Widodo et al. / Advances in Science, Technology and Engineering Systems Journal Vol. 5, No. 4, 397-404 (2020)
www.astesj.com 402
application of cities using other techniques such as LIDAR and
aerial photography is highly unlikely, because of the high
cost. Data are in the form of a vector. This study found the results
of the calculation of the available roof area calculated using
Equation 1 are shown in Table 2. The coefficient of the roof (RC)
for the high hills area is 0,145 and the lowlands area is 0,125. The
coefficient difference considers the general utility of a building
roof in Semarang City.
The most potential areas of rooftops in settlements Semarang
(more than 12%) are in the region of Ngaliyan and Pedurungan
sub-districtsts. Other regions that have a big proportion of the
rooftop area consist of Tembalang, Banyumanik, Genuk dan West
Semarang. Those sub-districts are dense regions that have the
potential of the roof distribution more than 8% of the area of the
roof of the whole. Because those regions are narrow and most
areas are developed with high rooftop potential. However, large
areas, such as Tembalang and Banyumanik, although located in
hilly areas have the potential roof area to reach 8-9% of the total
area. The developed area is influenced by the level of
development of the region itself. In contrast to other regions,
Gunung Pati and Mijen with their wider area are less developed
because these regions are the rein green belt of the city.
3.3. Technical Potential
Potential techniques of the photovoltaic system in rooftop can
be referred to as the energy electrical generation analyzed for
settlements that are distributed on the 16 sub-districts
in Semarang city, Indonesia. According to the variation of GSR
per month in Semarang City and using a typical for derate factor,
energy potential is found and shown in Table 3.
The technical potential is indicated by the value of potential
energy proportional to the area of an available rooftop. The more
area of rooftop used for photovoltaic exposure leads to more
intensity of solar radiation the roof of the photovoltaic. It leads to
more potential energy. Table 3 shows the variation of the
potential energy per month which is produced from the roof of
settlements in each sub-district. Figure 6 presents Tugu sub-
district, which has the least roof area gained potential energy to
44,051 MWh/year. In contrast to Ngaliyan sub-district which has
the potential of generating energy electricity 222,222 MWh/year,
because the area surface of the roof provided for exposure of the
photovoltaic is also most extensive than the area of the roof
surface on the other sub-district.
3.4. Potential of CO2 Mitigation
The production of electrical energy from the rooftop solar
photovoltaic system model has the potential to reduce CO2
emissions. The reduction in CO2 emissions is proportional to the
potential energy produced from the roof PV system. The CO2
mitigation coefficient is used to predict CO2 migration in the city
of Semarang [49]. Figure 3 shows potential energy of solar
photovoltaic, and prediction of CO2 mitigation in Semarang City,
Indonesia. Installation of solar photovoltaic rooftop in Semarang
City can reduce 1,394 tonCO2 in a year.
4. Conclusion
An overview of the potential for solar energy based on the
photovoltaic roof system the potential of CO2 mitigation in
Semarang City has been obtained. The estimation of solar energy
potential has been focused on residential areas and refers to the
analysis of the use of residential roof surfaces for solar panel
installation. The technique of estimating solar
energy potential using GIS area analysis is very beneficial in a
wide area. This technique is very useful in estimating the area
precisely, with a low error rate. The land use analysis
technique with GIS that uses high-resolution satellite imagery
(CSRT) is more beneficial in terms of cost and time. The
estimation of the rooftop area is very dependent on the type of
image used. The higher accuracy of a satellite image leads to the
higher precision of the area to. In addition to the use of the data
with high accuracy, all the geographic data calculations are
based on geographic reference data.
Figure 3: Potential of solar photovoltaic rooftop and prediction of mitigation CO2 on the settlements in Semarang City, Indonesia
0
20
40
60
80
100
120
140
160
180
0
500
1,000
1,500
2,000
2,500
Tugu
Gayamsari
East Semarang
Central Semarang
Candisari
North Semarang
South Semarang
Gajah Mungkur
Mijen
Gunung Pati
West Semarang
Tembalang
Genuk
Banyumanik
Pedurungan
Ngaliyan
Rooftop Available (km2) Energy Potential (GWH/year) Mitigasi CO2 pertahun (tonCO2/year)

D.A. Widodo et al. / Advances in Science, Technology and Engineering Systems Journal Vol. 5, No. 4, 397-404 (2020)
www.astesj.com 403
This paper shows the potential of a rooftop photovoltaic system
of solar energy in the 16 districts of Semarang City is 44,051 –
222,222 MWh/year. The average monthly solar radiation
intensity in the 16 district of Semarang City ranges from 61.94 -
144.40 kWh/m2 per month, while the roof potential of each district
varies from 412,987.50 m2 to 2,083,387 m2. Based on the results
of the potential for solar energy, available roof area, and daily
solar radiation intensity has been described in each district, total
of solar energy potential from 16 district is expected to contribute
approximately 40.87% as clean or low-carbon energy to electrical
energy consumption needs of Semarang City with
reference electricity consumption in 2018. The value can reduce
1,394 tonCO2 per year in Semarang City, Indonesia.
Conflict of Interest
The authors declare no conflict of interest.
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