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 com- pared with other forms of energy is that it is clean and can be supplied without environmental pollu- tion. 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 temperatu- re (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 (focus- ing) 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 ap- plication, solar systems with solar radiation concentrators can be divided into: heliostats, solar furnac- es 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 sili- con (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 radia- tion 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 equip- ment 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, envi- ronment 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 be- ing 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