Stanje I Perspektive Solarne Energetike U Srbiji Current State and Prospects of Solar Energy in Serbia

STANJE I PERSPEKTIVE SOLARNE ENERGETIKE U SRBIJI CURRENT STATE AND PROSPECTS OF SOLAR ENERGY IN SERBIA

Tomislav M. PAVLOVIĆ1, Dragana D. MILOSAVLJEVIĆ, Univeristy of Nis, Faculty of Science and Mathematics,Department of Physics

U radu će biti date informacije o razvoju, sadašnjem stanju i perspektivama solarne energetike u Srbiji. U vezi sa tim, pažnja je posvećena početnim istraživanjima i primeni uređaja za toplotnu i fotonaponsku konverziju sunčevog zračenja u Srbiji. Pored toga, dat je pregled sadašnjeg stanja istraživanja i primene uređaja za zagrevanje sanitarne vode, dobijanje električne energije, solarnom osvetljenju, itd. Na kraju su date informacije o perspektivama razvoja solarne energetike u Srbiji. Ključne reči: Sunčevo zračenje; solarni kolektori; solarne ćelije The paper gives information on development, current state and prospects of solar energy in Serbia. In addition, the focus of attention is on the initial research and application of the equipment for thermal and photovoltaic solar radiation conversion in Serbia. Moreover, the survey of the current research and application of the heating equipment for sanitary water, electricity generation, solar lighting is included as well. Finally, the information on the prospects of solar energy development in Serbia is provided. Key words: Solar radiatio;, solar collectors; solar cells

1 Introduction Energy plays the most vital role in the economic growth, progress and development, poverty eradication, and security of any nation. Uninterrupted energy supply is a vital issue for all countries today. Future economic growth crucially depends on the long-term availability of energy from sources that are affordable, accessible, and environmentally friendly. In recent decades, the overwhelming increase in development activities have triggered the increasing demand for energy, resulting in further contributions to green house gas (GHGs) emissions. The world had already experienced its first and second energy crises due to the oil and gas scarcities in 1973 and 1979, respectively. Because of the limited reserve of fossil fuel and the cost, from the beginning of the industrial age, renewable energy sources have been explored and the transition to renewable energy is inevitable [1-5].

2 Solar energy Solar radiation is the most important source of renewable energy and represents mankind's in- exhaustible energy source. The annual energy input of solar radiation on Earth exceeds the world's yearly energy consumption by several thousand times. The greatest advantage of solar energy compared with other forms of energy is that it is clean and can be supplied without environmental pollution. One of today's most promising tools to make use of solar energy is its direct conversion into thermal and/or electrical energy. The solar energy has been used by both nature and humankind throughout time in thousands of ways, from growing food to drying clothes; it has also been deliber- ately harnessed to perform a number of other jobs. Solar energy is used to heat and cool buildings (both actively and passively), heat water for domestic and industrial uses, heat swimming pools, power refrigerators, operate engines and pumps, desalinate water for drinking purposes, generate electricity, for chemistry applications, and many more operations. Solar energy devices available today can be put into two major classes: solar thermal collectors and photovoltaic (PV) cells and modules [1-7]. 2.1 Thermal conversion of solar radiation The thermal conversion of solar radiation means conversion of solar radiation into heat energy. Thermal conversion of solar radiation takes place in solar radiation collectors. Depending on the tem-

–––––––––– 1 Corresponding author, e-mail: [email protected]

5. MKOIEE • ICREPS 51 perature up to which working fluid may be heated, solar collectors can be divided into: low temperature (operating temperature 100°C), medium temperature (temperatures from 100°C to 400°C) and high temperature (temperatures from 400°C to 4000°C). For the low-temperature conversion of solar radiation, flat-plate solar collectors with water (water collectors) or air (air collectors) are used. Flat-plate collectors perform the thermal conversion of direct and diffuse solar radiation. For middle temperature solar energy conversion vacuum collectors with solar radiation (focusing) concentrators and solar furnaces are used. For high temperature solar radiation conversion solar systems with solar radiation concentrators are used. These systems use only direct solar radiation and must be facing the sun. In order to achieve higher temperatures, solar radiation by means of concentrators (lenses and mirrors) is concentrated towards the absorber vessel. This technique is called a concentrated solar power technique (Concen- trated Solar Power, CSP) and is used in solar thermal power plants. Solar systems with solar radiation concentrators can be of different design and purpose. Depending on their design, solar systems with solar radiation concentrators can be divided into: spherical concentrators, parabolic concentrators, focusing collectors with Fresnel lenses and Fresnel concentrators with mirrors. Depending on the application, solar systems with solar radiation concentrators can be divided into: heliostats, solar furnaces and solar thermal power plants [1-7]. 2.2 Photovoltaic conversion of solar radiation Photovoltaic (PV) conversion of the solar radiation implies conversion of solar radiation into the electrical energy. Photovoltaic conversion of the solar radiation takes place in PV solar cells which are made of semiconducting materials. PV cell technologies are generally categorized into three genera- tions, depending on the raw material used and the level of commercial maturity. First generation PV systems (fully commercial) that use the PV technology of crystalline silicon (c-Si) both in its simple crystalline form (sc-Si) as well as in the multicrystalline form (mc-Si). Second generation PV systems are based on thin film PV technologies and generally include three main families: (1) Amorphous silicon (a-Si) and micro amorphous silicon (a-Si/μcSi); (2) cadmium telluride (CdTe); and (3) copper indium selenide (CIS) and copper, indium gallium dieseline (CIGS). Third generation PV systems include organic photovoltaics technologies that are still in demonstration or have not been widely marketed and new concepts in development. The PV system means a system by which the solar radiation is converted into the electrical energy and is distributed to the direct (DC) and/or alternating (AC) current consumers. PV system can function independently of the electric power network (off grid) or it can be connected to it (on grid). Depending on the components that comprise it and its power, PV solar system can be ground mounted (PV solar plant) or building integrated (BIPV) [1-3,6-10]. 2.3 Solar architecture From the earliest days of the human civilization development, man has been skilful in choosing his place of residence and properly orienting his living habitat towards the Sun and adjusting it to the bioclimatic conditions of the environment in which it is located. Starting from the cave as the original place of residence and further on, man has observed the benefits of orienting the residential building to the south and the need for an additional thermal insulation on its north side. Modern solar architecture is based on a direct (passive), an indirect (active) and a combined (passive and active) solar radiation incidence. A direct (passive) solar radiation incidence means that an incidence takes place by means of a given object without any additional equipment for the solar radiation incidence and its transformation into the other forms of energy. An indirect (active) solar radiation incidence means an incidence that takes place on the equipment that is added to the object where it performs the heat (collectors), photovoltaic (solar cell) or thermal and photovoltaic (hybrid collectors) conversion of solar radiation. A combined (passive and active) intervention solar radiation incidence means an incidence that is carried out by a given object as a passive receiver and the additional equipment (collectors and solar cells) as the active receivers of solar radiation [6,7].

52 5. MKOIEE • ICREPS 3 Current state of solar energy use in Serbia Development of solar energy in Serbia is marked by the works of prof. dr Lalović (1928-1988) in Belgrade and prof. Živojin Ćulum (1911-1991) in Novi Sad. Since 1973 solar energy in Serbia has been the main research topic of several symposia and scientific meetings, first being held in 1978 in Belgrade (The International Solar Energy Symposium on Technical, Economical and Organizational Aspects), etc. Apart from the abovementioned scientific meetings our experts have presented their papers on solar energy at the international conferences featuring the topics of energy, techniques, environment protection, etc. Likewise, solar energy in Serbia was the research topic of several doctoral dissertations, master thesis, specialist and BA thesis, and a large number of books.Solar energy is being researched in Serbia in several university centres of Niš, Novi Sad, Kragujevac and Belgrade [6,7,11-15]. 3.1 Current state of thermal solar conversion in Serbia Previous research on low-temperature solar conversion in Serbia focused on the development of flat-plate collectors with a spectrally selective absorber (B. Lalović, T. Pavlović), air collectors (M. Lambić), hybrid collectors (B. Lalović, T. Pavlović), etc. Spanning the period from 1978 to 1985 there were several manufacturers of solar radiation flat- plate collectors in Serbia: Nissal in Nis, Sinvoz in Zrenjanin, Petar Drapsin in Novi Sad, Gosa in Smederevska Palanka, Jugoterm in Gnjilane, etc. However, after 1985 the manufacturers’ decline of interest seriously affected the production of solar collectors. Nowadays flat-plate collectors with water are produced by the following companies: Termovent in Belgrade, El-Sol in Pozarevac, Jugoterm in Nis, etc. Today the companies ETAZ, Viessmann and Conseko in Belgrade, Magmont in Pirot, Energo Pro-Teh in Zrenjanin, Termogas in Senta, El-Sol in Pozarevac, CIM Gas in Subotica etc., are designing and installing solar energy thermal systems. Solar water heaters and differential thermostats are produced by several private companies in Serbia. The biggest solar energy products trade companies in Serbia are ETAZ and Viessmann in Belgrade. Quality differential thermostats for low temperature conversion systems produce Enings Ltd. in Nis. Today solar flat-plate collectors with water are used to heat sanitary water in households, hotels, hospitals, military and other facilities in Serbia. Serbia got installed large number of solar systems with flat-plate collectors for water heating: on the building of the psychiatric hospital in Toponica, Health Center in Pirot, Hospital for Special Rehabilitation in Banja Koviljaca, swimming pool in Ba- busnica, ACC in Kragujevac, hospital in Subotica, Special hospital in Slankamen, Institute of Ortho- pedic Surgery Banjica in Belgrade, Gerontology Center in Pancevo, Hospital in Vrnjačka banja, home Heart in Jabuka, Gerontology Center in Kanjiža, Childrens’ Resort Golija in Zlatibor, General hospital Dr Djordje Jovanovic, Boarding school Angelina Kojic–Gina in Zrenjanin, Cradle -the disabled youth home in Subotica, hotel Danubia garni at Silver Lake near Veliko Gradiste, Food and Catering School in Cacak, kindergarten Lugovi in Cacak, Culture and Sports center, swimming pools and Disa- bled youth daycare in Obrenovac, etc. Vacuum collectors for water heating are being used in Serbia in several places such as hotels and residential households (e.g. Vojvodina hotel in Zrenjanin).

Figure 1. Solar system with flat-plate solar collectors at the disabled youth home Cradle in Subotica (left) and vacuum collectors at Vojvodina hotel in Zrenjanin (right) The first project on the high temperature solar energy conversion in Serbia was realized in Badnjevac, a village near Kragujevac (Figure 2).

5. MKOIEE • ICREPS 53 The project was implemented according to the design of full professor Vladan Petrovic, PhD, and solves two major solar energy prob- lems, the efficient conversion of the solar radiation into the thermal energy and the thermal energy storage for a longer period of time [6,7,11- 15]. 3.2 Current state of Photovoltaics in Serbia Photovoltaic conversion of solar radiation studies were conducted by M. Mihailović, Lj. Pešić in the Institute of Microelectronic Technol- ogies and Monocrystals (ICTM) in Belgrade, B. Lalović and M. Stojanović in the Institute of Nuclear Sciences Vinča in Belgrade, T. Pavlović in the Faculty of Sciences and Mathematics, Uni- Figure 2. Prototype of high temperature solar versity of Niš, Niš, etc. First solar cells were power plant in Badnjevac made of monocrystalline silicon having efficiency of 8% at the ICTM in Belgrade in 1963, whereas the satellites solar cells had an efficiency of 10%. In the period from 1978 to 1981 the company Radio cevi Ei (Radio tubes) in Niš manufactured monocrystalline silicon solar cells of low efficiency and low power solar modules. Solar cells and solar modules are not manufactured in Serbia. In Serbia solar modules, battery chargers, batteries and inverters are sold by several private companies such as Strukturcom Co. in Belgrade, Telephone engineering in Zemun, Elvet in Pirot, etc. In addition to the already mentioned companies, designing and installing of PV

systems are performed in Serbia by the following Figure 3. PV solar plant of 20 kW in Belgrade p companies: Alfatec (Niš), Elektrovat Ltd.(Čačak), (Telephone Engineering Ltd., Zemun) Energo Pro-The Ltd. (Zrenjanin), Vinča Solar (Belgrade), Netinvest (Belgrade), Conseko Ltd. (Belgrade), Plan-net-solar (Slovenia), etc. Lately, Serbia has begun construction of PV solar plants and PV systems of less power to generate electricity in private households. Up to now two larger PV solar plants of 2 MW (in Merdare and Velesnica), more than 200 independent PV solar plants of 1 - 60 kWp and larger number of small rooftop PV solar plants connected to the grid have been installed [6,7,11-15]. List of companies which are designing and installing some PV solar plants in Serbia is given in Table 1. Based on the Register of the Ministry of Mining and Energy of the Republic of Serbia (RMRERS), Table 2 shows the number of privileged and temporarily privileged PV solar plants generated electricity producers in Serbia, ending March 29, 2017. Overview of the installed power of the privileged and temporarily privileged PV solar plants generated electricity producers in Serbia, ending March 29, 2017, based on RMRERS is given in Ta- ble 3.

54 5. MKOIEE • ICREPS Table 1. List of companies which are designing and installing some PV solar plants in Serbia Company PV solar plants Power Year (kWp) Alfatec Ltd. in Niš On the building of the private company Domit in Leskovac 34.32 2012 (www.alfatec.rs) On the building of the Faculty of Electronic Engineering in Niš 1.2 2011 On the building of the Technical School in Pirot 4.59 2013 On the building of the Faculty of Sciences and Mathematics in Niš 2.08 2012 Telephone Engineering Ltd. in On the residential house in Batušinac 10 2012 Zemun (www.telephone- On the building of the private house in Belgrade 20 - engineering.co.rs) In the village of Čortanovci 10 2012 In Backa Topola 7.5 - In Ralja 4.5 - Netinvest Ltd. in Belgrade In the yard in village Blace near Kuršumlija 10 2011 (www.netinvest.rs) On the roof of headquarter building of Electrical Power Company of 6.75 2013 Republic of Srpska On the building of the secondary school in Varvarin 5 2010 On the building of the secondary electrotechnical school Rade Kon- 5 2010 čar in Belgrade On the building of the secondary technical school Mihajlo Pupin in 5 2010 Kula On the roof of the daycare center in Bežanijska kosa 3 2012 Elektrovat Ltd. in Čačak On the building Elektrovat Ltd. in Čačak 54.72 2012 Institute Mihajlo Pupin in On the building of the Institute Mihajlo Pupin in Belgrade 50 2013 Belgrade (www.imp.bg.ac.rs) Energo Pro-Teh Ltd. in Zre- On the roof of the Faculty of Technical Sciences in ČaČak 1.050 2008 njanin Faculty of Technical Sciences On the building of Faculty of Technical Sciences in Novi Sad FTS1 9.6 2011 in Novi Sad On the building of Faculty of Technical Sciences in Novi Sad FTS2 15.9 2015 Elektromehanika Ltd. in Niš On the building of Elektromehanika Ltd. in Niš 30 2014 Hemofrigo Ltd. in Leskovac On the building of Hemofrigo Ltd. in Leskovac 60 2012 Vinca Solar in Belgrade On the building of Primary school Dušan Jerković in Ruma 3 2004 Conseko Ltd. in Belgrade On the private house in Avala, Belgrade 11 - (www.conseko.rs) On the gas station MOL in Batrovci 1.5 - On the grange in Bački Petrovac 4 - On the private house in Irig 7 - On the private house in Melenci 4 - On the cottage in Kopaonik 0.56 - On the cottage in Mala Remeta 2 - On the cottage in Lazarevac 4.5 - On the private farm in Tršić 6.5 - On the bank Societe General in New Belgrade 2.5 - Plan-net-solar, Slovenia PV solar plant Anitex, Bosilegrad 40.32 2013 (www.plan-net-solar.si) PV solar plant Konvojtrans, Kragujevac 29.835 2014 PV solar plant Šumadija, Kragujevac 29.835 2014 On the private house in Čačak 9.36 2014 On the private house in Dupci, Municipality of Brus 9.86 2014 PV solar plant in Dupci, Municipality of Brus 29.75 2014 PV solar plant in Beloljin 17.25 2014 PV solar plant Snek bar Aleksandar, Ćićevac 29.89 2014

Table 2. Number of privileged and temporarily privileged PV solar plants generated electricity producers in Serbia, ending March 29, 2017. Status Ground-mounted PV Roof-top PV solar plants of and Roof-top PV solar plants of 30- solar plants up to 30 kW 500 kW Privileged 8 84 11 Temporarily privileged 9 81 10 Total 17 165 21

Table 3. Overview of the installed power of the privileged and temporarily privileged PV solar plants generated electricity producers in Serbia, ending March 29, 2017. Installed power Ground-mounted PV Roof-top PV solar plants of and Roof-top PV solar plants of 30- solar plants up to 30 kW 500 kW Privileged 5.34 MW 1941.9 kW 1504.1 kW Temporarily privileged - - -

5. MKOIEE • ICREPS 55 4 Solar architecture Solar architecture was the main research focus of B. Lalovic, M. Lambic, M. Jovanovic- Popovic, M. Pajevic, M. Pucar, M. Lukic and many others in Serbia. In this connection Serbia has up to now built several houses with passive solar incidence in Boljevci, Kac, Mladenovac, Belgrade, Sombor, Zajecar, Ljig, Novi Sad, etc [6,7,11-15]. In Boljevci there is an ecology glass dome sha- ped house diameter of 18.5 m, front side glass covered and back side earthbased. The ecology house is cons- tructed as a double shell enabling air circulation through the house interior and the heat battery. Maximal solar radiation incidence is realized by the combination of the active system (solar collectors) and passive (solar radiation incidence on the south, glass covered side of the house). At the bottom of the house there is a battery heat of 600 tons of stone and concrete. Ground floor locates residential area and the swimming pool Figure 4. Solar house in Boljevci with the water heated by the solar radiaton falling on the glass facade and the heat battery. The house is heated by the air circulation from the basement heat store. The house saves around 50% of the energy needed for its heating [6,7,11-15].

5 Prospects of solar energy use in Serbia In most developed countries the law regulates the possibility of production and sale of the thermal energy and electricity generated by the renewable energy sources. In Serbia, there are clearly defined laws, conditions and incentives for investing in the construction and sale of electricity from the power plants using renewable energy sources. Serbia has in 2006 ratified a contract on the establishment of the energy association of EU and Albania, Bulgaria, Bosnia and Herzegovina, Croatia, Former Yugoslav Republic of Macedonia, Montenegro, Rumania and Interim Mission of the United Nations in Kosova. In September 2008 European parliament has adopted a legislature on climate changes with the aim to provide for less greenhouse effect of 20%, to increase the energy efficiency by 20% and the incorporation of the renewables of 20% in the total energy consumption in EU-to 2020, as compared to 1990. Serbia has accepted the Directions of the EU on the use of the renewable sources of energy and is putting all efforts to realize them. The European Energy Law has a great impact on Serbia and its renewable energy sector. Serbia has on 26 January, 2009 become a member and the founder of the International Agency for the renewable sources of energy (IRENA). In accordance with the mentioned above in Serbia there is strong interest to invest in the energy sector of the Republic of Serbia. In the coming period it is expected to use more intensively solar thermal and PV systems for water heating and electricity generation in Serbia. Serbia is taking measures to raise awareness of the environmental and economic value and importance of the energy efficiency within the public, consumer, business and industry sectors. Besides, it is necessary to con- tinue to strengthen the state efforts to promote the development of solar industry, with the emphasis on the cost effectiveness and capturing the benefits of the solar energy potential to meet future energy needs. The development of a transparent approach to setting feed-in tariffs by the government, including rate impact analysis, will help ensure optimal long term outcomes, including a better return on investment in the energy efficiency [6,7,11-16]. The incentive purchase prices of electricity produced from the solar energy expressed in euro- cents per kilowatt hour (c€/kWh) in Serbia, based on the Directive on the incentive measures for the subsidized manufacturers of electrical energy (Official Gazzette of Republic of Serbia, no.8/2013), are given in Table 4 [16]. Further on, attracting investment in the energy education sector through cooperation projects with industry and establishment of the cooperation with international bodies and organizations in the energy sector aiming at the additional education of experts, are expected in the upcoming period [6,7,11- 15].

56 5. MKOIEE • ICREPS Table 4. The incentive purchase prices of electricity produced from the renewable energy sources expressed in euro-cents per kilowatt hour (c€/kWh) in Serbia, based on the Directive on the incentive measures for the subsidized manufacturers of electrical energy [16]. Type of power plants Installed power The incentive purchase prices P (MW) (c€/kWh) Solar power plants On the object (Roof-top PV solar plant) up to 0.03 20.66 On the object (Roof-top PVB solar plant) 0.03-0.05 20.941-9.383*P Ground-mounted 16.25

6 Conclusion To sum up, by geographical location and climate conditions Serbia appears to be a very favour- able country in Europe to utilize solar energy for water heating, electricity generation and houses and other buildings heating by passive solar energy. In Serbia, the increasing number of solar systems with flat plate solar collectors to heat water were installed on the public and private facilities. Vacuum collectors for water heating are being used in Serbia in several places such as hotels and residential households. The first project on the high temperature solar energy conversion in Serbia was realized in Badnjevac. Recently, Serbia has begun construction of PV plants and PV systems of less power to generate electricity in private households. Up to now two larger PV solar plants of 2 MW, more than 200 independent PV solar plants of 1 - 60 kWp and several small rooftop PV solar plants connected to the grid have been installed. Based on the Register of the Ministry of Mining and Energy of the Republic of Serbia which gives the overview of the installed power of the privileged and temporarily privileged PV solar plants generated electricity producers in Serbia, ending March 29, 2017, there were installed total 5.34 MW ground-mounted PV solar plants, 1941.9 kW roof-top PV solar plants up to 30 kW and 1504.1 kW Roof-top PV solar plants of 30-500 kW. In Serbia, there are clearly defined laws, conditions and incentives for investing in the construction and sale of thermal and electrical energy from the power plants using solar energy. Therefore, Serbia works hard to apply solar systems for commercial purposes and to raise awareness of the importance of education and international cooperation as the key strategic areas as well as funding agen- cies/counseling and organizing campaigns for better information of the public. In the coming period the Republic of Serbia is also expected to use more intensively solar systems for water heating, electricity generation.

7 Acknowledgement This paper was done with the financial support of the project TR 33009 approved by the Ministry of Education and Science of the Republic of Serbia.

8 References [1] Kalogirou, S.A., Solar Energy Engineering - Processes and Systems (Second Edition), Elsevier Academic Press, 2014. [2] Sen, Z., Solar Energy Fundamentals and Modeling Techniques - Atmosphere, Environment, Cli- mate Change and Renewable Energy, Springer, 2008. [3] Masters, G.M., Renewable and Efficient Electric Power Systems, John Wiley & Sons, Inc., Ho- boken, New Jersey, 2004. [4] Timilsina, G.R., Kurdgelashvili L., Narbel P.A., Solar energy: Markets, economics and policies, Renewable and Sustainable Energy Reviews, 16 (2012), 449– 465. [5] Mekhilef, S., Saidur R., Safari A., A review on solar energy use in industries, Renewable and Sustainable Energy Reviews, 15 (2011) 4, 1777-1790. [6] Pavlović, T.M., Tripanagnostopoulos Y., Mirjanić D.Lj., Milosavljević D.D., SOLAR ENERGY in Serbia, Greece and the Republic of Srpska, Monographs Vol. XXVI, Department of Natural- mathematical and Technical Sciences Vol. 26, Academy of Sciences and Arts of the Republic of Srpska, 694 p., Banja Luka, 2015., ISBN:978-99938-21-70-0

5. MKOIEE • ICREPS 57 [7] Pavlović, T.M., Milosavljevic D.D., Mirjanic D.Lj., Renewable energy sources , Academy of Sciences and Arts of the Republic of Srpska, Monographs-Book XVII, Department of Natural- mathematical and Technical Sciences - Book 18, Banja Luka, 2013, 365p. [8] Green, M.A., Wenham S.R., Watt M.E., Applied Photovoltaics (2nd Edition), Editors: Richard Corkish and Stuart R. Wenham, Earthscan Ltd., 2006, 335 p. [9] Practical Handbook of Photovoltaics: Fundamentals andApplications, Editors: Tom Markvart, Luis Castafier, Elsevier Science Ltd., 2003, ISBN 1856173909. [10] Tiwari, G.N., Dubey S., Fundamentals of Photovoltaic Modules and Their Applications, RSC Publishing Energy Series No. 2, 2010. [11] Milosavljević, D., Pavlović T., Mirjanić D., Piršl D., Current state of the Renewable Sources of Energy use in Serbia, Contemporary Materials (Renewable energy sources), VI (2015) 2, pp. 170- 180. [12] Radivojević, A., Pavlović T.M., Milosavljević D.D., Djordjević A., Pavlović M., Filipović I., Pantić L.S., Radovanović M., Influence of climate and air pollution on solar energy development in Serbia, Thermal Science, 19 (2015) 2, pp. S311-S322. [13] Pavlović, T., Milosavljević D., Lambić M., Stefanović V., Mančić D., Pirsl D., Solar energy in Serbia, Contemporary Materials (Renewable energy sources), II (2011) 2, pp. 204-220 [14] Pavlović, T., Milosavljević D., Radonjić I., Pantić L., Radivojević A., Pavlović M., Possibility of electricity generation using PV solar plants in Serbia, Renewable and Sustainable energy Review, 20 (2013), pp. 201-218. [15] Milosavljević, D., Pavlović T., Piršl D., Performance analysis of a grid-connected solar PV plant in Niš, Republic of Serbia, Renewable and Sustainable Energy Reviews, 44 (2015), pp. 423-435. [16] *** Official Gazzette of Republic of Serbia, no.8/2013

This is an open access article distributed under the CC BY-NC-ND 4.0 terms and conditions. The Proceedings is available at https://izdanja.smeits.rs

58 5. MKOIEE • ICREPS