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Seminar and Project On Magnetohydrodynamic MHD Power Generation

Seminar and Project On Magnetohydrodynamic (MHD) Power Generation

INTRODUCTION

The whole world is already familiar with the conventional power generating resources like Hydra, thermal and nuclear resources etc. In all the conventional thermal and nuclear resources etc. In all the conventional systems the potential or thermal energy is first converted into mechanical energy and then this mechanical energy is converted into electrical energy. The conversion of potential energy into mechanical energy is significantly. This requires huge capital cost as well as maintenance cost. All across the world researches are trying to convert thermal energy directly into electrical energy by eradicating the mechanical process involved in energy conversions which have significant energy losses.

Research is now focusing its efforts on conversion process that do not involve mechanical energy conversion step. In the absence of moving mechanical part may allow in achieving the operating temperature much higher than the typical conventional processes to attain effective power generating systems. These processes are known as direct conversion systems in which primary or secondary
energy is directly converted into electrical energy without passing through the stage of mechanical energy. Some of the direct conversion methods are described below:
Magneto Hydrodynamics generation (MHD)
Photovoltaic generation system (solar cells)
Electrochemical energy conversion (Fuel cells)
Thermoelectric power generation
The reason for using new and direct energy conversion methods is to overcome the flaws in the conventional energy generating systems. The possibility of using new sources of energy seems enhanced by the development of new direct energy converters. There are many methods of converting direct thermal energy to electrical energy. In the following section one of the main
direct energy converting technology (magneto hydrodynamics) is discussed in detail.

Types of MHD Generators

A system with MHD generator has high potential of an ultimate efficiency i.e. 60 to 65% which is much improved than the efficiency of conventional thermal power station i.e. 30 to 35%. Output power of MHD generator for each cubic meter channel volume is directly proportional to square of gas velocity and gas conductivity and square of the strength of the magnetic field through which the gas flows. Moreover, forits competitive good performance the electrical conductivity of the plasma (ionized gas) must be above the temperature range of 2000K. Usually a number of issues like generator efficiency, economics, toxic products etc. are occurred during the working of MHD generator .MHD generator is classified in three different designs which are mentioned below:
  1. Faraday Generator
  2. Hall Generator
  3. Disk Generator
Faraday Generator
This type of generator consists of a non-conductive wedge-shaped pipe or tube. When ionized plasma (conductive fluid) flows through the tube in the presence of an intense magnetic field than current is induced, which can be extracted by placing electrodes on the sides of wedged shaped pipe or tube at
90-degree of magnetic field.
The main practical issue with faraday generator is differential voltages and currents in the fluid short through the electrodes on the sides of the tube.



Hall Generator
The electromagnetic induction principle is not limited to solid conductors. The movement of a conducting fluid through a magnetic field can also generate electrical energy. When a fluid is used for the energy conversion technique, it is called MAGNETO HYDRO DYNAMIC (MHD), energy conversion. The flow direction is right angles to the magnetic fields direction. An electromotive force
(or electric voltage) is induced in the direction at right angles to both flow and field directions. A number of generator configurations have been devised to accommodate the Hall Effect. In a Faraday generator, the electrode walls are segmented and insulated from each other to support the axial electric field and the electric power is taken out in a series of loads. In the alternate configuration known as a Hall generator, the Faraday field across each sector of the channel is short-circuited and the sectors are connected in series.

This allows the connection of a single electric load between the ends of the channel. Another major benefit of this design is that the magnet is more efficient.
Firstly, it has simple parallel field lines. Secondly, the fluid is processed in a disk, the magnet can be closer to the fluid and magnetic field strengths increase as the 7th power of distance. Finally, the generator is compact for its power, so the size of magnet is reduced. As a result magnet uses a much smaller percentage of the generated power.

 Disk Generator
The disc generator is the most efficient design. This design currently grasps the efficiency and energy concentration records for MHD generation. A disc generator has plasma (ionized gas) or fluid flowing between the center of a disc and a duct wrapped around the edge. The magnetic excitation field is made by a pair of circular Helmholtz coils above and under the disk. The Faraday currents flow in a perfect dead short around the edge of the disk. The Hall Effect currents flow between ring electrodes near the center and ring electrodes near the edge.

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