Majlesi Journal of Energy Management
Volume:2 Issue: 2, Jun 2013

Calculation of the load peak voltage, potential energy and power consumption of a Marx impulse generator, as a function of time, are presented. The equations are generalized and can be used to the design of any type of n-stage Marx impulse generator. The results were validated for a thyristor controlled Marx impulse generator with a maximum number of stages of 10 and 3 kV input DC voltage, which used 1 MΩ resistors and 33 nF capacitors in its topology.

A novel active clamp dual half bridge DC/DC converter with bidirectional power flow is proposed in this paper. By adding auxiliary active clamping circuits to both bridges, zero voltage and zero current switching are achieved to improve the performance of the bidirectional DC/DC converter. The principle of operation is analyzed and simulated. With the proposed active clamp ZVZCS concept, the MATLAB simulation results of the applications of the fuel cell and battery have been obtained and compared with those of ZVS-ZCS bidirectional converter. The simulation results of proposed converter is compared with the ZVS-ZCS bidirectional DC-DC converter, efficiency, switching losses are the key parameters compared.

In line with the demands to obtain energy from renewable energy resources, utilization of the wind turbines to convert the wind energy into the desired usable form with maximum efficiency has been faced with ever increasing research efforts. In this study taken a different approach with conventional systems, wind turbine with hydrostatic power train system is considered. Hydrostatic power train system characterized with high power and torque transmission along with significant efficiency, capable of reliably controlling the performance of the system, and persistent hydraulic components, has been replaced with the conventional mechanical power train system between the vane and electric generator. To explain the performance of the proposed system, a mathematical model of wind turbine with variable speed hydrostatic transmission in the MATLA/SIMULINK software has been established and the system control algorithm is presented. Based on the detailed mathematical model and using the information of hydraulic equipments from famous vendors and manufacturers to make the results ever realistic, simulation results showing the great performance compared to the today''s conventional wind turbines.

In this paper a novel zero-voltage-switching (ZVS) pulse-width-modulated (PWM) forward DC/DC converter with a simple auxiliary circuit is proposed. The auxiliary circuit switched at zero current (ZCS). The auxiliary circuit is configured in the presented ZVS-PWM forward converter to perform soft-switching in the semiconductor devices and soft commutation of the main switches without additional current stress. Eight transition states for describing the behavior of the ZVS-PWM forward converter in one switching period are described.

A series of low speed wind tunnel tests on a section of a 660 Kw wind turbine blade were conducted to examine the effects of frequency on its performance characteristics. The airfoil profile was NACA 63-617 and selected from the mid section of the turbines’ blade radius which generates the main part of the blade torque. Dynamic tests were performed for three cases of prestall, stall and post stall conditions. The domain of oscillations was 5 degrees and at 3 mean angles of attack which is 5, 10 and 18 degrees. The model was tested for four Reynolds number and for various reduced frequencies. In downstroke motion, it was obvious that oscillation had positive effect on aerodynamic characteristics at low angles of attack but negative effect happened post stall angles of attack that reduced lift coefficient. This phenomenon was in conflict with upstroke motion.

Providing electrical energy is one of the main concerns when constructing a new building for business, agricultural, or residential purposes in remote areas. On these occasions, an economic analysis should be done to make an appropriate decision for providing electrical energy to these areas. In this paper, an approach is proposed for economic evaluation of a plan to exploit solar energy in order to provide electricity for those consumers who have not access to the national electricity grid. On the other hand, those consumers who have access to the national grid may also use a variety of techniques and methods such as solar energy exploitation to manage their consumption and cut their electricity costs. Besides for generating electrical energy, solar energy may be used for direct provision of heat requirements, and this will lead to a cut in fossil fuel costs. In this paper, a method is also proposed for economic evaluation of using solar energy in buildings which are close to the national grid in order to manage electricity consumption and also to decrease fossil fuel costs. Related numerical studies are presented along with analysis of the sensitivity to changes in economic parameters.

20% of total world electricity consumption is approximately consumed by lighting. Researches show that, hospitals represent approximately 6% of total energy consumption in the utility buildings sector. Lighting systems in a hospital represents approximately 21% of the total energy consumption. In this paper, the research papers and practical studies on energy efficiency and energy saving potentials on lighting systems at the hospitals are presented. Under the following sections, the latest literatures including research articles, conferences, e-books, handbooks, reports, web pages, MSc and PhD theses interested in energy efficiency, energy saving and energy management are summarized. Payback period calculations of some lighting projects are also presented.