This pa per pres ents the ex per i men tal in ves ti ga tion of tur bu lent struc tures of flow around a sphere. The mean ve loc ity field and the tur bu lence quan ti ties are ob tained in a small low speed wind tun nel us ing, la ser-Dopp ler anemometry, for the flow around a sphere at subcritical Reynolds num ber of 50,000. The re sults of la ser-Dopp ler mea sure ments are com pared with results ob tained by large eddy sim u la tion. In this pa per also flow vi su al iza tion around sphere in the big ger wind tun nel and wa ter chan nel for Reynolds num bers be tween 22,000 and 400,000 have been done.

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Although the countries of the Western Balkans are mostly electrified, there are still regions which do not have access to the electricity network or where the network capacity is insufficient. For the most part such areas are under special care of the state (i. e. underdeveloped, devastated by war, depopulated), on islands or in mountainous regions. Since the decentralized energy generation covers a broad range of technologies, including many renewable energy technologies that provide small-scale power at sites close to the users, such concept could be of interest for these locations. This paper identifies the areas in Western Balkans where such systems could be applied. Consideration is given to geographical locations as well as possible applications. Wind, hydro, solar photovoltaic, and biomass conversion systems were taken into consideration. Since the renewable energy sources data for Western Balkans region are rather scarce, the intention was to give a survey of the present situation and an estimate of future potential for decentralized energy generation based on renewable energy sources. The decentralized energy generation based on renewable energy sources in Western Balkans will find its niche easier for the users that will produce electricity for their own needs and for the users located in remote rural areas (off-grid applications).

The technical analysis of a hybrid wind-photovoltaic energy system with hydrogen gas storage was studied. The market for the distributed power generation based on renewable energy is increasing, particularly for the standalone mini-grid applications. The main design components of PV/Wind hybrid system are the PV panels, the wind turbine and an alkaline electrolyzer with tank. The technical analysis is based on the transient system simulation program TRNSYS 16. The study is realized using the meteorological data for a Typical Metrological Year (TMY) for region of Novi Sad, Belgrade cities and Kopaonik national park in Serbia. The purpose of the study is to design a realistic energy system that maximizes the use of renewable energy and minimizes the use of fossil fuels. The reduction in the CO2 emissions is also analyzed in the paper. [Acknowledgment. This paper is the result of the investigations carried out within the scientific project TR33036 supported by the Ministry of Science of the Republic of Serbia.

This paper presents the experimental results for the flow around a sphere: a smooth sphere in flow with low inlet turbulence, a sphere with trip wire and a sphere in flow with high free stream turbulence, at sub critical Reynolds number. The mean velocity field and the turbulence quantities are obtained using laser-Doppler anemometry. Comparison of velocity field and turbulence character is tics for different flow configuration are given.