The article presents mathematical models and simulation programs, made in MATLAB - Simulink, of the main components within photovoltaic system. For the continuous supply of electricity to consumers, in addition to photovoltaic panels are used electric accumulators and static converters, which have the role of converting direct current into alternating current or alternating current into direct current and to monitor and control the charging–discharge batteries process. The assembly consisting of all the elements presented above, interconnected and dimensioned to operate in a single system, is modelled and simulated and the results obtained reflect the limits but especially offers the possibility of choosing the optimal solution for a park of energy production based on solar radiation.

The separation of particles with big inertial mass transported in the air, is most often done with the help of cyclones, due to their resistance to wear at contact with abrasive particles. However, pneumatic conveying of heavy and abrasive granular material mixed with fines, are problematic even for cyclone hardened inlets. The paper studies a new method of dividing the main airflow in two airstreams, one further divided in more smaller streams to achieve the laminar regime, by using a corrugated shaped inlet. Thus generating an improvement in impact resistance, overall cyclone grade efficiency and decreasing pressure drop.

The general topic of this paper is to study the possibilities of using renewable energy sources to supply urban consumers electricity, consumers located in areas affected by industrial restructuring. This carries out a comprehensive study on the possibilities of using renewable energy sources in the Motru Basin area. Moreover, creation a mix capable of producing the electricity needed by the inhabitants, in household consumption and not only, is being studied. The entry of free energy market has brought about the alignment with competitive conditions and observance of pollution regulations in force, and energy production has determined retrofitting or restriction of the activity of some thermal power plants due to non-competitive costs for primary energy resources. Our country has a diversified and balanced energy mix (hydropower, nuclear energy, coal and natural gas) but it must be complemented by renewable sources (wind, solar, biomass) to provide stability and energy safety prospects.

The paper approaches the theoretical and experimental analysis of the level of exhaust gas pollution in a protected nature environmental, located in the mountain area, for excavation a trench. Due to the legislative provisions prohibiting the use of explosives in the nature reservation or other protected nature environmental areas, the mechanized excavation solution remains the only viable option. Excavation the trench through the mechanized solution must be carried out, taking into account the maximum level of pollution with exhaust gases provided in the legislative norms. According to the geotechnical data, the rock composition to be excavated on the route will be of different hardness, which involves impactors of various powers to displace the rock, on the one hand, and on the other, different excavators and bulldozers for the handling the material resulted from excavation. The theoretical research required to solve the problem has several stages, of which we mention: choosing the correct mechanization solution for displacing the hard and very hard rock; determination of fuel consumption, and energy consumption, respectively, transformation of the energy consumed in the liquid fuel necessary for the tool driving engines, and which generate exhaust gases.