The objective of the paper is to study the influence of certain shroud types suitable for horizontal axis hydrokinetic turbines using experimental testing in order to increase the energy conversion efficiency. The scale model of the shrouded hydrokinetic turbine is tested on a dedicated experimental bench for axial hydraulic turbine models. Two types of shrouds were tested in order to be compared: convergent shroud and divergent shroud. The rotor and shroud were made using 3D printer technology and were tested at a water velocity of 0.9 m/s on the closed-circuit testing bench. The testing facility allows the determination of the power extracted for each shroud at five distinct positions. Thus, the rotor can be moved within the shroud from inlet to outlet in order to establish the proper operating position. The mechanical power is measured using a torque transducer and an electromagnetic particle brake. The testing results will be analysed based on the variation of power curves obtained for different shroud types and operating positions. The optimum design and the best operating position will be recommended by comparing the testing result with the data collected from the bare turbine using the same rotor placed directly in free flow.

The paper presents theoretical considerations on gas bubbles behavior -analytic calculation of bubble time formation, extra pressure needed for the bubble formation and detachment, bubble size and correlation between the extra pressure and the liquid superficial tension.In order to evaluate the theoretical relation for extra pressure calculation, the results of the tests performed on different metallic perforated plates Ø 60, with a specific number of orifices of different diameters, were used. The extra pressure needed for bubble formation varies from approximately 171 Pa for the MPP with 0.9 mm orifices to 245 Pa for the MPP with 0.2 mm orifices.Index Terms-Bubble size, bubble detachment, extra pressure, orifice.

Integration of distributed generation units and other users within the low and medium voltage distribution grid induces a variety of problems related to the management and control of microgrids. These aspects can be solved by using significantly different Energy Management Systems for the operation of microgrids, comparing to those applied to conventional power systems. The main objective of the Energy Management System is to ensure the rational use of energy, while minimizing its costs. The secondary objectives relate to increasing energy efficiency and reducing energy consumption, but especially to assuring the power facilities security. Moreover, the management of power systems to which renewable sources are connected is one of the main concerns of Distribution System Operators in order to ensure the safe operation, security of power supply, and the operation optimization from the economic side. The chapter regards the LabVIEW design and testing of an Energy Management System for the interconnected or islanded operation of a microgrid to the electric public grid. Furthermore, the chapter leads to the microgrids development in terms of operation and efficiency by achieving an Energy Management System designed for a small mixed microgrid with separate AC and DC rings bidirectionally interconnected by static converters.

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