Key words: Renewable energy resources, technologies, sustainable development, environment.

Abstract: The move towards a de-carbonised world, driven partly by climate science and partly by the business opportunities it offers, will need the promotion of environmentally friendly alternatives, if an acceptable stabilisation level of atmospheric carbon dioxide is to be achieved. This requires the harnessing and use of natural resources that produce no air pollution or greenhouse gases and provides comfortable coexistence of human, livestock, and plants. This article presents a comprehensive review of energy sources, and the development of sustainable technologies to explore these energy sources. It also includes potential renewable energy technologies, efficient energy systems, energy savings techniques and other mitigation measures necessary to reduce climate changes. The article concludes with the technical status of the ground source heat pumps (GSHP) technologies.

Key words: hybrid system, modeling, optimal sizing, simulation algorithm.

Abstract: This paper presents an optimal sizing method of an autonomous hybrid wind photovoltaic system. The main objective of this study is to determine the optimal characteristics of a system able to cover the energy demands of a consumer for a given specific location. This method is essentially based on two main phases. The modeling of the autonomous hybrid system is considered the first phase in the process of optimal sizing. The second phase is to optimize the dimensioning of the system based on the lack of energy to generate probability (LEGP), percentage of the surplus of energy produced (PSEP) and the cost of the kilowatt-hour produced (CkWh). From these two phases, a simulation code has been developed as a working tool able to perform the analysis and optimization of a hybrid system for given load and location. Therefore, a case study that uses this code was presented to determine the optimal configuration of a system that meets the energy requirements (5kWh/jour) of a house located in Sfax, Tunisia.

The aim of this paper is a presentation of a new solar air conditioning unit for office spaces at Tunisia and a simulation study of the behaviour of two stages. The first one is the dehumidification stage which is mainly composed of desiccant wheel. The second one is the regeneration stage which is mainly composed of flat plate solar collector, storage tank and heat exchanger. Thus, mathematical models for each of those components are developed which are based mainly on thermal and mass balances. A finite differences method is applied to the partial differential equations. The simulation study shows that minimizing the value of the distributed hot water mass flow for the storage tank is very interesting. This can be beneficial as it reduces thermal losses and makes the heating of the inlet cold water entering the storage tank effective. In addition, increasing the value of the hot water temperature produced by flat plate solar collector is interesting because it ensures an efficient heating of the water contained in the storage tank. Finally, the studied regeneration stage can successfully ensure the regeneration of the hygroscopic wheel used in the corresponding solar air conditioning unit.

Key words: Streamfunction-vorticity formulation, Control volume based on finite element method, NACA 23015, POD analysis.

Abstract: To study the flow dynamic behavior of the NACA 23015 airfoil, used in many commercialized wind turbine, a computational fluid dynamic solving the streamfunction-vorticity formulation of Navier-Stokes equations using the Control Volume Method based on Finite Element (CVMFE) have been made to simulate the flow over the NACA 23015 at high angle of attack equal to 14° for Reynolds number equal to 1000. The Proper Orthogonal Decomposition (POD) method is adopted to analyze and extract the coherent motion structures in the flow behind the airfoil and the first two modes are used to determine the phase of the vortex shedding.

Key words: Savonius rotor, wind tunnel, incidence angle, aerodynamic structure.

Abstract: The study of the incidence angle effect around a Savonius wind rotor on the numerical results was obtained using "SolidWorks Flow Simulation" softaware. The objective of this study is to observe the effect of the incidence angle on the aerodynamic structure characteristics. These results are presented in different transverse and longitudinal planes of the considered control volume. To validate the numerical results, we have developed an experimental approach to measure the flow velocity in
different positions of the test vein of our wind tunnel.