Possibilities for Energy Efficiency Improvement

SERBIAN JOURNAL OF ELECTRICAL ENGINEERING Vol. 18, No. 1, February 2021, 95-114 UDC: 620.92:727(497.11Kragujevac) DOI: https://doi.org/10.2298/SJEE2101095R

Energy Benchmarking in Educational Buildings in the City of Kragujevac – Possibilities for Energy Efficiency Improvement

Ana Radojević1, Danijela Nikolić1, Jasna Radulović1, Jasmina Skerlić2

Abstract: The implementation of energy efficiency measures and use of renewable energy sources in educational buildings can significantly contribute to reducing energy consumption, but also to CO2 emissions in the entire public sector. The paper shows the comparison of energy consumption indicators for 61 elementary school buildings which have previously been divided in 12 groups, according to the period of construction and size, based on the national typology called TABULA, as the first step of further study on how to use the renewable energy sources. The aim of this paper is to use the energy benchmarking process to select representative facilities which are suitable for applying renewable energy sources, for their further energy efficiency improvement.

Keywords: Energy benchmarking, Educational buildings, Electrical energy consumption, CO2 emission.

1 Introduction The role of local governments is not only to manage energy consumption in public buildings, but also to promote energy efficiency and renewable energy sources. That is why it is important to encourage the use of renewable energy sources in public buildings, as a good example for all citizens. Using solar energy by installing photovoltaic panels on school buildings, for example, can be a good way to raise citizens’ awareness of the importance of using renewable energy sources.

1Faculty of Engineering, University of Kragujevac, Sestre Janjić 6, Kragujevac, Serbia; E-mails: [email protected]; [email protected]; [email protected] 2Faculty of Technical Sciences, Kosovska Mitrovica, Serbia; E-mail: [email protected] 95 A. Radojević, D. Nikolić, J. Radulović, J. Skerlić

On the other hand, school buildings are not only significant consumers of energy for the public sector, but also for all buildings. When examining electricity consumption in the United States, school buildings were ranked third and accounted for 10.8% of the total building electricity consumption, behind office buildings (20.4%) and retail and department stores (20.4%) [1]. In China, school buildings rank fourth in the total area of all buildings, after office facilities, retail business space and hospitals. That is why, a series of construction standards for public and residential buildings in various climate zones have been adopted, in which the thermal features of envelopes and the design of HVAC are mandatory for energy efficiency. Here are some of the examples of these Chinese standards and regulations, among others GB 50189- 2005: Design Standard for Energy Efficiency of Public Buildings [2]. Since 1989, China has designed and applied over 40 energy efficiency (EE) standards and over 20 mandatory energy labels for a number of domestic, commercial and selected industrial equipment [3]. Similar to other countries, energy efficiency standards have key role in reducing the energy consumption of room air conditioners (RACs). Chinese RACs standards have been redefined according to the American and Japanese standards [4]. It is believed that building energy efficiency standards (BEES) are one of the most effective policies to reduce energy consumption, especially when the rapid urbanization is taking place, as in China [5]. The electric power consumption of Finland schools has increased by 49% in the last 40 years. The electric power consumption was higher in newer school facilities than in older ones, but this was not the case with the daycare centers. This is because newer schools are equipped with more of electrical equipment compared to older schools, whereas the amount of electrical equipment has relatively stayed the same in the daycare centers regardless of the construction year. This issue would require more detailed research, but if it would prove to be the case, then it would be more beneficial to install PV panels to newer schools than in older ones [6]. The aim of this paper is to select representative school facilities on which to further analyze the possibility of using the renewable energy sources.

Indicators of annual specific electricity consumption and CO2 emissions per unit area [kWh/m2] and per user [kWh/user] were calculated. After that, from two groups (in which the highest electricity consumption and CO2 emissions are 68.37% and 74.53% of the total consumption/ emissions), one representative facility was selected. Only electric energy consumption was analyzed, because the goal of the study was to select facilities which would be the best for using renewable energy sources. CO2 emissions are also included in the study, because in the public sector of the city of Kragujevac, one half of the total CO2 emissions from all public 96 Energy Benchmarking in Educational Buildings in the City of Kragujevac… buildings come from educational institutions and out of all emissions from educational institutions, 73% come from elementary schools. Thus, energy rehabilitation of these facilities and the use of renewable energy sources on them become one of the tools in the fight against climate change. Comparing buildings by consumption can be a criterion for determining on which building we should first implement energy efficiency measures. After that decision, we can prioritize energy efficiency measures using the criteria of primary energy consumption and initial investment cost [7]. Data on energy consumption and school buildings have been analyzed for years and there are numerous data available in the literature. Data on global energy consumption in schools can be easily found in the literature. These are uncategorized data, e.g. energy type is not specified (primary or final energy), or data that does not specify the building type (primary school, secondary school, schools with/without pool or canteen, etc.). Although some authors have been showing that Display Energy Certificates (DEC) can be used ,s energy consumption, and therefore allow a fair benchmark׳to quantify school only a minority of the EU countries have this category of buildings fully addressed on their national Energy Performance Certification legislation [8]. Furthermore, as can be concluded from the survey, there exists great difference in per unit energy consumption between different types of universities classified by schools’ discipline, nature and level, which would be taken into account when the energy consumption evaluation indexes system is established [9]. Research conducted in Italy has shown that it is possible to analyze representatives of individual groups of schools and do extrapolation that will help decision makers. The results could be extrapolated to each corresponding cluster and this could help the Public Administration in decision-making and prioritizing the energy retrofit of the buildings’ stock with the lowest cost-efficiency ratio. Future developments will therefore analyze more in detail the two reference buildings in order to evaluate the persistence over time of the energy savings, the cost-effectiveness of further retrofit interventions, and the effect of management measures [10]. Research of the indicators in elementary and high schools in Taiwan has shown that, in 67 senior high schools, 62 junior high schools and 102 elementary schools, the values of their energy usage per person (kWh/person/year) were 1163, 469, and 465, respectively [11]. In order to investigate the characteristics of school building energy consumption, energy consumption of 17 schools in Tianjin have been counted and discussed. Based on the statistics, the results indicate that the average comprehensive energy consumption of school per unit area is 121.81 kWh/(m2a),

97 A. Radojević, D. Nikolić, J. Radulović, J. Skerlić the average energy consumption per person is 36 kWh/(pa) and the average electricity consumption is 36.07 kWh/(m2a) in 2007. It is found that the energy consumption per unit construction area is lower than the average energy consumption of public buildings, which is 257.61 kWh/(m2a) in 2015.The main reason is that the quality of the thermal environment is poor and the running time of school is short. However, the school’s total energy consumption is large and we should pay more attention to it. At the same time, we point out the problems of the school energy consumption in Tianjin based on the statistics and proposed energy-saving reforms [12]. The annual primary energy use in Cyprus schools is 116.22 kWh/m2 year [13]. In the Brussels Capital Region the certificate “is based on consumption data for electricity and fossil fuels used for all purposes, based on meters or invoices”, and “the EP indicator is calculated on the basis of the occupied floor area.” An index of CO2 emission is also foreseen. The mean value emissions and energy consumption anticipated for school and college buildings category is 40 2 2 kgCO2/m yr and 230 kWh/m yr, respectively [14]. The average power consumption per unit area of the surveyed public buildings is 47.96 kWh/(m2a). The average values of office, hospital and school building are 65.74 kWh/(m2a), 86.00 kWh/(m2a) and 24.31 kWh/(m2a), respectively [15]. Similar to Korea, there are two problems in Serbia as well – schools in rural areas, small in size, attended by a few students, which are not worth investing in. The second problem is that there is no precise national statistics which would enable comparison of school facilities in Kragujevac and other cities in the same climate zone. There are only general data [16]. The other problem is that, for most small and medium-sized buildings, there is usually no room for sub-metering by end-uses owing to expensive installation and management costs. The end-use data for small and medium-sized buildings are actually a national blind spot. The third problem is that even if each end-use was sub-metered, there is no national benchmark (e.g. statistical distribution) of similar buildings, so it is difficult to determine whether the amount of energy used is appropriate [17].

2 Typology of Elementary School Buildings in Kragujevac The typology of elementary school buildings includes the classification of school buildings by size and construction periods, with the aim of defining possible levels of energy renewal, whose ultimate goal is reducing energy consumption in the public sector of the City of Kragujevac, but also contributing to energy savings and combating climate change throughout Republic of Serbia. Improving energy efficiency and reducing CO2 emissions would be achieved by implementing measures on the building envelope, on mechanical and electric power systems and by using renewable energy sources. 98 Energy Benchmarking in Educational Buildings in the City of Kragujevac…

The importance of typological classification of school buildings is reflected in wide applicability in making strategic decisions for the renovation of all school buildings in the city of Kragujevac. For defining the physical characteristics of the sample buildings, a research conducted in Serbia was used as part of the European project of creating typologies of buildings called TABULA. The national typology of school buildings [18] is a continuation of this research, within which 1,857 school buildings were processed. The national typology of school buildings implies their classification by size and periods of construction. The basic matrix of of school buildings typology is defined through four time periods: till 1945, 1946  1970, 1971  1990 and 1991, and three types by size 2 2 (gross floor area): smaller than 500 m , from 500 to 2000 m , and larger than 2000m2. Therefore, all schools in Kragujevac are divided into 12 groups, as shown in Table 1. Table 1 Matrix of the typology of elementary school buildings in Kragujevac (based on the national typology of school buildings in Serbia).

GROSS FLOOR AREA [m2] Year Smaller than 500 From 500 to 2000 Larger than 2000 Number of such schools Number of such schools Number of such schools Before 14 3 2 1945 Share in total area Share in total area Share in total area 3.79% 4.34% 7.27% Number of such schools Number of such schools Number of such schools 9 7 6 1946–1970 Share in total area Share in total area Share in total area 2.28% 3.9% 22.05% Number of such schools Number of such schools Number of such schools 2 4 7 1971–1990 Share in total area Share in total area Share in total area 5.56% 5.22% 42.23% Number of such schools Number of such schools 3 4 After 1991 Share in total area Share in total area 0.72% 5.22%

Number of such schools 2 NA Share in total area 0.37% 2 The largest number of users have large schools, over 2.000 m , built in the periods 1971  1990 and 1946  1970: 44.2% and 29.39%, respectively (Fig. 1). In

99 A. Radojević, D. Nikolić, J. Radulović, J. Skerlić some school buildings in rural areas, in addition to the fact that all school 2 buildings are smaller than 500 m , the number of users is often less than 10 (Fig. 2).

Big-sized schools constructed from 1971-1990 43.55

Big-sized schools constructed from 1946-1970 28.95

Big-sized schools constructed before 1945 5.23

Mid-sized schools constructed after 1991 7.4

Mid-sized schools constructed from 1971-1990 3.14

Mid-sized schools constructed from 1946-1970 1.3

Mid-sized schools constructed before 1945 6.27

Small schools, unknown year of construction 0.15

Small schools constructed after 1991 0.07

Small schools constructed from 1971-1990 2.07

Small schools constructed from 1946-1970 0.73

Small schools constructed before 1945 1.12

0 1020304050

Fig. 1  Distribution of no. of users [%].

Number of users

Big-sized schools constructed from 1971-1990 6204

Big-sized schools constructed from 1946-1970 4125

Big-sized schools constructed before 1945 746

Mid-sized schools constructed after 1991 1054

Mid-sized schools constructed from 1971-1990 447

Mid-sized schools constructed from 1946-1970 185

Mid-sized schools constructed before 1945 894

Small schools, unknown year of construction 21

Small schools constructed after 1991 10

Small schools constructed from 1971-1990 87

Small schools constructed from 1946-1970 104

Small schools constructed before 1945 159

0 1000 2000 3000 4000 5000 6000 7000

Fig. 2  Distribution of number of users.

3 Overview of the Annual Specific Energy Consumption 2 and CO2 Emission per Unit Area [kWh/m ] and Per User [kWh/user] Depending on the Period of Construction and Size of School Facilities 3.1 Annual specific electricity consumption per unit area [kWh/m2] and per user [kWh/user] In this paper, we used the data from the Energy Efficiency Program [19]. Average annual specific electricity consumption per unit area [kWh/m2] for small schools, up to 500 m2, amounts to 68.03 kWh/m2.

100 Energy Benchmarking in Educational Buildings in the City of Kragujevac…

Maximum and minimum annual specific electricity consumptions per unit area [kWh/m2] for small schools, up to 500 m2, amount to 356.65 kWh/m2 and 0.42 kWh/m2 respectively, as shown in Fig. 3. Average annual specific electricity consumption per user [kWh/user] for small schools, up to 500 m2, amounts to 726.3 kWh/user. Maximum and minimum annual specific electricity consumptions per user [kWh/user] for small schools, up to 500 m2, amount to 9249.33 kWh/user and 13.87 kWh/user respectively, as shown in Fig. 4. Average annual specific electricity consumption per unit area [kWh/m2] for mid-sized schools, from 500 to 2000 m2, amounts to 25.8 kWh/m2.

Fig. 3 - Annual specific electricity consumption per unit area [kWh/m2] for all small schools, up to 500m2.

Fig. 4  Annual specific electricity consumption per user [kWh/user] for all small schools, up to 500m2.

101 A. Radojević, D. Nikolić, J. Radulović, J. Skerlić

Maximum and minimum annual specific electricity consumptions per unit area [kWh/m2] for mid-sized schools, from 500 to 2000 m2, amount to 39.41 and 10.19 kWh/m2 respectively, as shown in Fig. 5. Average annual specific electricity consumption per user [kWh/user] for mid-sized schools, from 500 to 2000 m2, amounts to 289.9 kWh/user.

Annual specific electricity consumption per unit area [kWh/m2] for all mid- sized schools, 500-2000m2

Natalija Nana Nedeljković- Veliko Polje 36.66 Sreten Maledenović- Lužnice 11.79 Jovan Popović-Šumarice 43.56 Sreten Maledenović 16.49 19.oktobar 19.05 Dragiša Mihajlović- Male Pčelice 14.31 Dositej Obradović 32.08 Julijana Ćatić-Ramaća 15.94 Sreten Maledenović- Cerovac 1 Sreten Maledenović- Gornje Jarušice 13.38 Sreten Maledenović- Resnik 16.49 19.41 Name of the school the of Name Svetozar Marković- Velike Pčelice Svetozar Marković-Gornja Sabanta 13.61 Jovan Popović- Drača 26.57 Prota Stevan Popović 103.77 Natalija Nana Nedeljković- Grošnica 34.93 Miloje Simović 19.62

0 20406080100120 kWh/m2

Fig. 5  Annual specific electricity consumption per unit area [kWh/m2] for all mid- sized schools, 5002000m2.

Annual specific electricity consumption per user [kWh/user] for all mid- sized schools, 500-2000m2

Natalija Nana Nedeljković-Veliko Polje 85.65 Sreten Maledenović- Lužnice 164.42 Jovan Popović-Šumarice 283.94 Sreten Maledenović 137.14 19.oktobar 172.19 Dragiša Mihajlović-Male Pčelice 80.79 Dositej Obradović 125.12 Julijana Ćatić-Ramaća 265.67 Sreten Maledenović-Cerovac 31.96 Sreten Maledenović- Gornje Jarušice 169 Sreten Maledenović- Resnik 137.14 Svetozar Marković-Velike Pčelice 1829.04

Name of the school the of Name Svetozar Marković-Gornja Sabanta 210.41 Jovan Popović- Drača 272.02 Prota Stevan Popović 693.29 Natalija Nana Nedeljković-Grošnica 150.85 Miloje Simović 114.03

0 200 400 600 800 1000 1200 1400 1600 1800 2000 kWh/user Fig. 6  Annual specific electricity consumption per user [kWh/user] for all mid- sized schools, 5002000m2.

Maximum and minimum annual specific electricity consumptions per user [kWh/user] for mid-sized schools, from 500 to 2000 m2, amount to 1829.04 and 31.96 kWh/user respectively, as shown in Fig. 6. Average annual specific electricity consumption per unit area [kWh/m2] for big-sized schools, over 2000 m2, amounts to 21.78 kWh/m2.

102 Energy Benchmarking in Educational Buildings in the City of Kragujevac…

Maximum and minimum annual specific electricity consumptions per unit area [kWh/m2] for big-sized schools, over 2000 m2, amount to 39.41 and 10.19 kWh/m2 respectively, as shown in Fig. 7. Average annual specific electricity consumption per user [kWh/user] for big- sized schools, over 2000 m2, amounts to 143.6 kWh/user maximum and minimum annual specific electricity consumptions per user [kWh/user] for big-sized 2 schools, over 2000 m , amount to 300.07 and 57.82 kWh/user respectively, as shown in Fig. 8. Indicators per user are extremely high for small area schools, less than 500m2, for all periods of construction. These schools are located mainly in rural areas and the number of students is often ranging from one to several, usually with one teacher. So the total consumption of electricity and primary energy is divided by a small number. That is why it is impossible to compare the indicators in these schools with the indicators in the urban area schools that are attended by several hundred students. Annual specific electricity consumption per unit area [kWh/m2] for all big- sized schools, over 2000m2

Julijana Ćatić 10.19 Sveti Sava 23.11 Dragiša Mihajlović 16.87 Milutin i Draginja Todorović 24.55 Vuk Stefanović Karadžić 16.66 Mirko Jovanović 27.5 21. Oktobar 27.06 Stanislav Sremčević 18.91 Dragiša Luković Španac 31.5 Jovan Popović 39.41 Treći kragujevački bataljon 20.58

Name of the school of the Name Svetozar Marković 23.86 Moma Stanojlović 14.2 Radoje Domanović 23.02 Đura Jakšić 16.38 Živadinka Divac 14.65

0 1020304050 kWh/m2 Fig. 7  Annual specific electricity consumption per unit area [kWh/m2] for all big-sized schools, over 2000 m2.

Annual specific electricity consumption per user [kWh/user] for all big- sized schools, over 2000m2

Julijana Ćatić 300.07 Sveti Sava 109.4 Dragiša Mihajlović 171.23 Milutin i Draginja Todorović 133.29 Vuk Stefanović Karadžić 77.46 Mirko Jovanović 98.15 21. Oktobar 130.66 Stanislav Sremčević 109.14 Dragiša Luković Španac 220.65 Jovan Popović 213.91 Treći kragujevački bataljon 79.07 Svetozar Marković 206.15 Nameof the school Moma Stanojlović 57.82 Radoje Domanović 133.27 Đura Jakšić 163.36 Živadinka Divac 94.59

0 50 100 150 200 250 300 350 kWh/user Fig. 8  Annual specific electricity consumption per user [kWh/user] for all big-sized schools, over 2000 m2. 103 A. Radojević, D. Nikolić, J. Radulović, J. Skerlić

2 3.2 Annual specific CO2 emission per unit area [kWh/m ] and per user [kWh/user] 2 Average annual specific CO2 emission per unit area [kWh/m ] for small schools, up to 500 m2, amounts to 61.78 kWh/m2.

Maximum and minimum annual specific CO2 emissions per unit area [kWh/m2] for small schools, up to 500 m2, amount to 143.64 and 0.17 kWh/m2 respectively, as shown in Fig. 9.

Average annual specific CO2 emission per user [kWh/user] for small schools, up to 500 m2, amounts to 2327.028 kWh/user.

Maximum and minimum annual specific CO2 emissions per user [kWh/user] for small schools, up to 500 m2, amount to 25315.45 and 48.27 kWh/user respectively, as shown in Fig. 10.

Annual specific CO2 emissions per unit area [kWh/m2] for all small schools, up to 500m2

Vuk Stefanović Karadžić- Bukurovac 39.31 Vuk Stefanović Karadžić-Trmbas 143.64 Sreten Maledenović- Novi Milanovac 91.59 Dragiša Luković Španac-Baljkovac 104.01 Dragiša Luković Španac-Donja Sabanta 100.06 Prota Stevan Popović- Veliki Šenj 38.37 Mirko Jovanović-Petrovac 51.31 Milutin i Draginja Todorović- Ilićevo 43.43 Natalija Nana Nedeljković-Vinjište 34.88 Miloje Simović- Goločelo 69.53 Julija na Ća tić- Uglja reva c 29.27 19.oktobar-Donje Komarice 86.37 19.oktobar-Cvetojevac 78.17 Sreten Maledenović-Pajazitovo 101.22 Julijana Ćatić-Ramaća 79.25 Sreten Maledenović- Opornica 106.01 Svetozar Marković-Velika Sugubina 0.17 Svetozar Marković-Jovanovac 72.23 Miloje Simović- Drenovac 76.11 Julija na Ća tić- Ma sloševo 22.94 Julija na Ća tić- Vla kča 40.85 Julijana Ćatić-Ljubičevac 0.84 19.oktobar-Korman 69.06 Name of the the ofschool Name 19.oktobar-Botunje 63.8 Đura Jakšić- Gornje Koma rice 22.91 Svetozar Marković-Dulene 1 Sveti Sava-Poskurice 54.95 Sveti Sava- Donje Grbice 92.04 21. Oktobar-Dobrača 132.52 21. Oktobar-Kamenica 25.74 21. Oktobar-Rogojevac 62.02 Jovan Popović-Divostin 43.48 0 20 40 60 80 100 120 140 160 kWh/m2

Fig. 9  Annual specific CO2 emissions per unit area [kWh/m2] for all small schools, up to 500 m2.

Annual specific CO2 emissions per user [kWh/user] for all small schools, up to 500m2

Vuk Stefanović Karadžić- Bukurovac 943.43 Vuk Stefanović Karadžić- Trmbas 1539.01 Sreten Maledenović- Novi Milanovac 1831.89 Dragiša Luković Španac- Baljkovac 669.11 Dragiša Luković Španac- Donja Sabanta 25315.45 Prota Stevan Popović- Veliki Šenj 619.03 Mirko Jovanović-Petrovac 6657.58 Milutin i Draginja Todorović- Ilićevo 279.51 Natalija Nana Nedeljković- Vinjište 1144.08 Miloje Simović- Goločelo 1346.28 Julijana Ćatić- Ugljarevac 473.27 19.oktobar- Donje Komarice 1197.61 19.oktobar- Cvetojevac 631.15 Sreten Maledenović- Pajazitovo 3947.47 Julijana Ćatić- Ramaća 1320.78 Sreten Maledenović- Opornica 4240.27 Svetozar Marković- Velika Sugubina 48.27 Svetozar Marković- Jovanovac 973.48 Miloje Simović- Drenovac 1793.97 Name of the school the of Name Julijana Ćatić- Vlakča 474.34 19.oktobar- Korman 1567.65 19.oktobar- Botunje 940.98 Đura Jakšić- Gornje Komarice 1718.2 Sveti Sava- Poskurice 2057.67 Sveti Sava- Donje Grbice 1369.84 21. Oktobar- Dobrača 2238.18 21. Oktobar- Kamenica 1814.81 21. Oktobar- Rogojevac 773.42 Jovan Popović-Divostin 1050.68 0 5000 10000 15000 20000 25000 30000 kWh/user

Fig. 10  Annual specific CO2 emissions per user [kWh/user] for all small schools, up to 500 m2. 104 Energy Benchmarking in Educational Buildings in the City of Kragujevac…

2 Average annual specific CO2 emission per unit area [kWh/m ] for mid-sized schools, from 500 to 2000 m2, amounts to 58.9 kWh/m2.

Maximum and minimum annual specific CO2 emissions per unit area [kWh/m2] for mid-sized schools, from 500 to 2000 m2, amounts to 103.67 and 29.6 kWh/m2 respectively, as shown in Fig. 11. Average annual specific CO2 emission per user [kWh/user] for mid-sized schools, from 500 to 2000 m2, amounts to 665.1638 kWh/user.

Maximum and minimum annual specific CO2 emissions per user [kWh/user] for mid-sized schools, from 500 to 2000 m2, amount to 1463.23 and 139.9 kWh/user respectively, as shown in Fig. 12.

2 Annual specific CO2 emissions per unit area [kWh/m ] for all mid-sized schools, 500-2000m2

Natalija Nana Nedeljković- Veliko Polje 59.88 Sreten Maledenović- Lužnice 33.52 Jovan Popović-Šumarice 103.67 Sreten Maledenović 29.6 19.oktobar 75.03 Dragiša Mihajlović- Male Pčelice 45.67 Dositej Obradović 98.39 Julijana Ćatić- Ramaća 79.25 Sreten Maledenović- Cerovac 39.61

Name of the school the of Name Sreten Maledenović- Gornje Jarušice 93.18 Sreten Maledenović- Resnik 52.47 Svetozar Marković- Velike Pčelice 15.53 Svetozar Marković- Gornja Sabanta 41.84 Jovan Popović- Drača 58.39 Prota Stevan Popović 78.36 Natalija Nana Nedeljković- Grošnica 59.88 Miloje Simović 37.25

0 20406080100120 kWh/m2 2 Fig. 11  Annual specific CO2 emissions per unit area [kWh/m ] for all mid-sized schools 5002000m2.

Annual specific CO2 emissions per user [kWh/user] for all mid-sized schools, 500-2000m2

Natalija Nana Nedeljković- Veliko Polje 139.9 Sreten Maledenović-Lužnice 467.32 Jovan Popović-Šumarice 585.23 Sreten Maledenović 101.05 19.oktobar 227.87 Dragiša Mihajlović-Male Pčelice 257.8 Dositej Obradović 383.83 Julijana Ćatić-Ramaća 1320.78 Sreten Maledenović- Cerovac 1262.72 Sreten Maledenović- Gornje Jarušice 1177.02 Sreten Maledenović- Resnik 613.61 Name of the school Svetozar Marković-Velike Pčelice 1463.23 Svetozar Marković-Gornja Sabanta 646.77 Jovan Popović- Drača 597.78 Prota Stevan Popović 554.63 Natalija Nana Nedeljković- Grošnica 139.9 Miloje Simović 216.43

0 200 400 600 800 1000 1200 1400 1600 kWh/user

Fig. 12  Annual specific CO2 emissions per user [kWh/user] for all mid- sized schools, 5002000m2.

105 A. Radojević, D. Nikolić, J. Radulović, J. Skerlić

2 Average annual specific CO2 emission per unit area [kWh/m ] for big-sized schools, over 2000 m2, amounts to 81.23 kWh/m2.

Maximum and minimum annual specific CO2 emissions per unit area [kWh/m2] for big-sized schools, over 2000 m2, amount to 187.57 and 38.3 kWh/m2 respectively, as shown in Fig. 13.

Average annual specific CO2 emission per user [kWh/user] for big-sized schools, over 2000 m2, amounts to 692.82 kWh/user.

Maximum and minimum annual specific CO2 emissions per user [kWh/user] for big-sized schools, over 2000 m2, amount to 1018.15 and 197.8 kWh/user respectively, as shown in Fig. 14.

2 Annual specific CO2 emissions per unit area [kWh/m ] for all big- sized schools, over 2000m2 Julijana Ćatić 87.17

Sveti Sava 81.42

Dragiša Mihajlović 81.83

Milutin i Draginja Todorović 99.14

Vuk Stefanović Karadžić 42.54

Mirko Jovanović 68.2

Stanislav Sremčević 72.61

Dragiša Luković Španac 187.57

Jovan Popović 70.9

Treći kragujevački bataljon 96.91

Svetozar Marković 53.76

Name of the school the of Name Moma Stanojlović 107.83

Radoje Domanović 73.47

Đura Jakšić 56.77

Živadinka Divac 38.3

0 20 40 60 80 100 120 140 160 180 200 kWh/m2 2 Fig. 13  Annual specific CO2 emissions per unit area [kWh/m ] for all big-sized schools sized, over 2000 m2.

Annual specific CO2 emissions per user [kWh/user] for all big- sized schools, over 2000m2 Julijana Ćatić 3623.29

Sveti Sava 385.36

Dragiša Mihajlović 830.65

Milutin i Draginja Todorović 538.21

Vuk Stefanović Karadžić 197.8

Mirko Jovanović 243.38

Stanislav Sremčević 419.11

Dragiša Luković Španac 1018.15

Jovan Popović 272.42

Treći kragujevački bataljon 678.76 Name of the school the of Name Svetozar Marković 464.81

Moma Stanojlović 438.96

Radoje Domanović 432.98

Đura Jakšić 601.29

Živadinka Divac 247.24

0 500 1000 1500 2000 2500 3000 3500 4000 kWh/user

Fig. 14  Annual specific CO2 emissions, per user [kWh/user] for all big-schools sized, over 2000 m2.

106 Energy Benchmarking in Educational Buildings in the City of Kragujevac…

The highest CO2 emissions per user and per unit area in each school group are for coal-heated schools. Indicators for rural schools, less than 500 m2 in area, are the largest because they have the fewest students - users and cannot be compared with other indicators. Therefore, in the rest of the paper, only buildings with more than 500 m2 and a larger number of users were observed. For school facilities that are in these groups, the indicators can be compared.

4 Selection of Representative Facilities 4.1 Selection of groups based on the highest energy consumption Analysis of the indicators of the annual specific electricity consumption per unit area [kWh/m2] and per user [kWh/user] was done with the aim of selecting the facility on which the simulation of energy efficiency measures and installation of photovoltaic panels will be carried out.

The energy consumption and CO2 emission, depending on the period of construction and size of school facilities, was analyzed in order to select facilities on which energy efficiency measures would be implemented first. Analysis of the energy behavior of buildings under the city administration authority is necessary in order to form a city energy planning policy and make strategic decisions about which buildings need to be thermally improved and where there is a possibility of using renewable energy sources. After the initial analysis of the school buildings’ stock, energy modeling of representative buildings would be initiated. The modeling would estimate the current energy consumption, compare the calculated and actual values and then simulate the effects of improving energy efficiency - by measures on the building envelope, on mechanical and electrical systems and the use of renewable energy sources (photovoltaic panels). More than 60% of electric energy that is consumed in all schools with more 2 than 500 m area, is consumed in two groups of facilities. Over 70% of CO2 emission derives from electricity that is consumed in these same two groups of facilities: – big-sized schools, with over 2000 m2, constructed between 1971 and 1990; – big-sized schools, with over 2000 m2, constructed between 1946 and 1970. Most electricity (36.33%) is consumed in school buildings built in the period 1971-1990 and in the period 1946-1970: 32.04%, as shown in Fig. 15.

The highest CO2 emissions (40.39%) come from energy consumed in school buildings built in the period 1971-1990, and in the period 1946-1970: 34.14%, as shown in Fig. 16.

107 A. Radojević, D. Nikolić, J. Radulović, J. Skerlić

Table 2 Matrix of typology of school buildings in Kragujevac (based on the National typology of school buildings in Serbia). Gross floor area Year Smaller than 500m2 from 500 to 2000m2 larger than 2000 m2 Electricity consumption Electricity consumption Electricity consumption share – 2.42% share – 8.45% share – 3.3% Before Heat consumption share Heat consumption share Heat consumption share 1945 3.45% 2.32% 9.03% CO2 emission share CO2 emission share CO2 emission share 3.08% 3.26% 5.1% Electricity consumption Electricity consumption Electricity consumption share – 1.44% share – 2.32% share – 32.04% 1946– Heat consumption share Heat consumption share Heat consumption share 1970 2.43% 2.63% 28.89% CO2 emission share CO2 emission share CO2 emission share 2.06% 2.3% 34.14% Electricity consumption Electricity consumption Electricity consumption share – 0.72% share – 7.83% share – 36.33% 1971- Heat consumption share Heat consumption share Heat consumption share 1990 0.77% 4.92% 41.42% CO2 emission share CO2 emission share CO2 emission share 0.59% 2.6% 40.39% Electricity consumption Electricity consumption share – 0.72% share – 7.83% After Heat consumption share Heat consumption share

1991 1.2% 4.92% CO2 emission share CO2 emission share 1.02% 4.99% Electricity consumption share – 1.65% NA Heat consumption share 0.09% CO2 emission share - 0.47%

Fig. 15  Distribution of electricity consumption [%]. 108 Energy Benchmarking in Educational Buildings in the City of Kragujevac…

Fig. 16  Distribution of CO2 emissions [%].

Based on all the above, representative facilities from these two groups, that have the largest share in electricity consumption and CO2 emissions, will be selected for the facilities on which the simulation of energy efficiency measures and installation of photovoltaic panels will be done. 4.2 Selection of representative facilities from selected groups After this, representative facilities were selected from these groups using two criteria: indicators of annual specific electricity consumption per unit area [kWh/m2] and per user [kWh/user] that are closest to average annual specific electricity consumption per unit area [kWh/m2] and per user [kWh/user] for the analyzed group, and the buildings that have the largest area of flat roofs or roofs with the smallest slope, most favorable for the installation of photovoltaic panels. Mean electricity consumption indicators for each of the two groups are as shown in the Figs. 17  20. Annual specific electricity consumption per unit area [kWh/m2] for big-sized schools, constructed 1945-1970 45

0 Radoje Domanović Moma Stanojlović Svetozar Marković Treći kragujevački Jovan Popović Dragiša Luković bataljon Španac Specific electricity consumption Average specific electricity consumption Fig. 17  Annual specific electricity consumption per unit area [kWh/m2] for big-sized schools, constructed 19451970. 109 A. Radojević, D. Nikolić, J. Radulović, J. Skerlić

Annual specific electricity consumption per user [kWh/user] for big- sized schools, constructed 1945-1970 250

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0 Radoje Domanović Moma Stanojlović Svetozar Marković Treći kragujevački Jovan Popović Dragiša Luković bataljon Španac Specific electricity consumption Average specific electricity consumption Fig. 18  Annual specific electricity consumption per user [kWh/user] for big-sized schools, constructed 1945  1970.

Annual specific electricity consumption per unit area [kWh/m2] for big-sized schools, constructed 1971-1990 30

0 Stanislav 21. Oktobar Mirko Vuk Stefanović Milutin i Dragiša Sveti Sava Julijana Ćatić Sremčević Jovanović Karadžić Draginja Mihajlović Todorović Specific electricity consumption Average specific electricity consumption Fig. 19  Annual specific electricity consumption per unit area [kWh/m2] for big-sized schools, constructed 1971  1990.

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0 Stanislav 21. Oktobar Mirko Vuk Stefanović Milutin i Dragiša Sveti Sava Julijana Ćatić Sremčević Jovanović Karadžić Draginja Mihajlović Todorović Specific electricity consumption Average specific electricity consumption Fig. 20 – Annual specific electricity consumption per user [kWh/user] for big-sized schools, constructed 1971  1990.

110 Energy Benchmarking in Educational Buildings in the City of Kragujevac…

Mean CO2 emission indicators for each of the two groups are as shown in the Figs. 21  24.

Annual specific CO2 emission per area unit [kWh/m2] for big-sized schools, constructed 1945-1970 200

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0 Radoje Domanović Moma Stanojlović Svetozar Marković Treći kragujevački Jovan Popović Dragiša Luković bataljon Španac Specific CO2 emission Average specific CO2 emission 2 Fig. 21  Annual specific CO2 emission per unit area [kWh/m ] for big-sized schools, constructed 1945  1970.

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0 Radoje Domanović Moma Stanojlović Svetozar Marković Treći kragujevački Jovan Popović Dragiša Luković bataljon Španac Specific CO2 emission Average specific CO2 emission

Fig. 22  Annual specific CO2 emission per user [kWh/user] for big-sized schools constructed 19451970.

Annual specific CO2 emission per area unit [kWh/m2] for big-sized schools, constructed 1971-1990 120

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0 Stanislav Mirko Vuk Stefanović Milutin i Dragiša Sveti Sava Julijana Ćatić Sremčević Jovanović Karadžić Draginja Mihajlović Todorović Specific CO2 emisssion Average specific CO2 emission 2 Fig. 23  Annual specific CO2 emission per unit area [kWh/m ] for big-sized schools, constructed 1971  1990.

111 A. Radojević, D. Nikolić, J. Radulović, J. Skerlić

Annual specific CO2 emission per user [kWh/user] for big-sized schools, constructed 1971-1990 4000

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0 Stanislav Mirko Jovanović Vuk Stefanović Milutin i Dragiša Sveti Sava Julijana Ćatić Sremčević Karadžić Draginja Mihajlović Todorović Specific CO2 emission Average specific CO2 emission

Fig. 24  Annual specific CO2 emission per user [kWh/user] for big-sized schools, constructed 19711990.

Thus, based on previously presented data, the following facilities were selected: – From the group big-sized schools, over 2000 m2, constructed between 1971 and 1990 – ”Milutin i Draginja Todorović” Elementary School; – From the group big-sized schools, over 2000 m2, constructed between 1946 and 1970 – ”Treći kragujevački bataljon” Elementary School.

5 Conclusion The paper presents the process of benchmarking of energy consumption indicators for 61 Kragujevac elementary school buildings. These school buildings have previously been divided in 12 groups, according to the period of construction and size. This benchmarking process will produce data to be implemented in a subsequent study on how and where to use the energy efficiency measures and, especially, renewable energy sources. The implementation of energy efficiency measures and renewable energy sources in educational buildings, such as schools, can significantly contribute to reducing energy consumption, but also to reducing CO2 emissions in the entire public sector of the city.

Indicators of annual specific electricity consumption and CO2 emission per unit area [kWh/m2] and per user [kWh/user]. After that, from two groups (in which the highest electricity consumption and CO2 emissions are 68.37% and 74.53% of the total consumption/emissions), one representative facility was selected. Those two groups of facilities are: – big-sized schools, over 2000 m2, constructed between 1971 and 1990; – big-sized schools, over 2000 m2, constructed between 1946 and 1970. 112 Energy Benchmarking in Educational Buildings in the City of Kragujevac…

Schools in these two groups participate with 36.33% and 32.04% in total electricity consumption and with 40.39% and 34.14% in total CO2 emissions. Then, the indicators in these two groups of facilities were analyzed and, based on the mean specific annual electricity consumption per user, two representative facilities were selected. In the further work, the possibilities for the installation of photovoltaic panels on these two facilities will be additionally analyzed. The part of the paper analyzing which school buildings consume the most electricity is significant for other cities located in the same climate zone as well, because it is possible for them to implement the final results of the paper, stating that the most energy consuming school buildings are those larger than 2000 m2 in area and constructed from 1971-1990 and from 1946-1970. The paper shows that the comparison of energy indicators can play a significant role in the selection of facilities where energy efficiency measures will be implemented and renewable energy sources will be used. The results of the paper can also benefit decision-makers when deciding which buildings will be the first to be energetically renovated, as they clearly show which schools consume the most electricity and as a result have the highest CO2 emissions.

6 Acknowledgment This investigation is part of the projects TR 33015 and III 42006. The authors would like to thank to the Ministry of Education and Science of Republic of Serbia for the financial support during this investigation.

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