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In respect to increasing demand for energy in the world and limited fossil fuel resources, there is a great need for using renewable energies (REs). One of the most attractive applications of RE technology is the application of hybrid energy systems in remote areas. An alternative to overcoming the intermittence of RE sources, such as the sun and wind (are freely available and environmental friendly), is to develop the hybrid energy system where excess electrical energy could be converted and stored. These sources combined with energy storage would provide a better system reliability making it suitable for stand-alone applications. They have been integrated and worked at the Taleghan renewable energies site in Iran. The National Renewable Energy Laboratory's hybrid optimization model for electric renewables simulation software has been used to carry out the optimal design and techno-economic viability of energy system in this study. The simulation results demonstrate that for hybrid energy system is consists of 0.8 kW PV modules, two wind turbines (0.4 kW each), 2.5 kW inverter, and 8 batteries (200 Ah and 12 V). The cost of energy is 1.655 US$/kWh, whereas the initial capital required, and net present costs are, 22998 US$ and 24623 US$, respectively.

This paper presents the study of the dynamic analysis of a rigid rotor supported by a twolobe non-circular gas-lubricated journal bearing. A finite element method has been employed to solve the Reynolds equation in static and dynamical states and the dynamical equations have been solved using Runge-Kutta method. To analyze the behavior of the rotor center in horizontal and vertical directions under the different operating conditions, the dynamic trajectory, the power spectra, the Poincare maps, and the bifurcation diagrams are used. Results of this study indicates that by considering bearing number and rotor mass as the parameters of the system, complex dynamic behavior comprising periodic, KT -periodic, and quasi-periodic responses of the rotor center has occurred.

This paper presents the effect of preload, as one of the design parameters, on nonlinear dynamic behavior of a rigid rotor supported by gas-lubricated noncircular journal bearings. A finite element method has been employed to solve the Reynolds equation in static and dynamical states and the dynamical equations are solved using the Runge-Kutta method. To analyze the behavior of the rotor center in horizontal and vertical directions under different operating conditions, dynamic trajectory, power spectra, Poincare maps, and bifurcation diagrams are used. Results of this study reveal how the complex dynamic behavior of two types of noncircular bearing systems comprising periodic, KT-periodic, and quasi-periodic responses of the rotor center varies with changes in preload value. NomenclaturēC Conventional radial clearance (m) C m Minor clearance when rotor and bearing geometric centers are coincident (m) D Rotor diameter (m) F X 0 ,F Y 0 Components of the fluid film force on the rotor in the steady state (N) F X ,F Y Components of the fluid film force on the rotor in the dynamical state (N) W 0 Static load (N) h Film thickness (m) L Bearing length (m) m r Rotor mass (Kg) N i Shape function n e Number of nodes in an element n f Number of nodes in fluid domain P * Absolute gas pressure (N/m 2 ) P Partial gas pressure (N/m 2 ) P a Ambient pressure (N/m 2 ) R Rotor radius (m) t Time (s) U Peripheral speed of the rotor in dynamical state (m/s) X,Ȳ Cartesian axes with origin at the bearing geometric center (m) X j 0 ,Ȳ j 0 Coordinates of the rotor center in steady state (m) X j ,Ȳ j Coordinates of the rotor center in dynamical state (m) 232 R. Rashidi et al.