Magneto hydrodynamic (MHD) power generating system
Magneto hydrodynamic (MHD) power generating system
Magneto hydrodynamic is an academic discipline that studies the dynamic of electrically conducting fluids. Am MHD power generator is a device that generate electric power by means of the interaction of a moving conductive fluid (usually an ionized gas or plasma) and a magnetic field. As all direct energy conversion processes: the MHD generator can convert thermal energy of a fuel directly into electricity. In this way the static energy converter, with no moving mechanical parts, can improve the dynamic conversion and work at temperatures much higher than conventional energy conversion process can be the MHD power generation process can be directly coal fired. It accordingly opens up a temperature regime in which no competing process exists and thus offers a means of making more efficient use of coal resources beyond that offered by any other technology.
Principles of MHD power generation
When an electrical conductor is moved so as to cut lines of magnetic induction, the charged particles in the conductor experience a retarding force in the direction mutually perpendicular to the magnetic yield and to the velocity of the conductor. This effect is a result of faradays laws of electromagnetic induction. The negative charge tends to move in one direction, and the positive charges in the opposite direction. This undivided electric yield or motional BMF (electromotive force) provides the basis for converting mechanical energy into electrical energy. The electromagnetic induction principle is not limited to solid conductors. The movement of a conductivity fluid through a magnetic yield it can also generate a electrical energy. When a fluid is used for the energy conversion techniques, it is referred to as magneto hydrodynamic energy conversion in an MHD converter, the solid electrical conduction is replaced by an ionized gas or plasma.
Magneto hydrodynamic generation
The principle of the magneto hydrodynamic generator a hot electrically conductive gas is accelerated by a nozzle and is then injected into a channel at a high velocity. A powerful magnetic field s set up across the channel. The gas is forced through the channel with a kinetic energy and pressure differential sufficient to overcome the magnetic induction force
In accordance with faraday`s law of induction
‘An electric field is generated that acts in the direction perpendicular to both the gas and the magnetic field.’
The walls of the channel parallel to the magnetic field serve as electrodes and enable the generator to provide an electric current to an external circuit. Typically, the hot conducting gas is produced by the thermal ionization of the gas at high pressure by combustion of a fossil fuel. The power output of an MHD generator for each cubic meter of its channel volume is proportional to the product of the gas conductivity, the square of the gas velocity, and the square of the strength of the magnetic field through with the gas passes. An magneto hydrodynamic generator produces direct current output with needs of a high power inverter to convert the output into alternative current for connection to the grid.
Magneto hydrodynamic channel efficiency
physical attainable thermal efficiency of an magneto hydrodynamic generator is commonly referred to as the channel enthalpy extraction ratio, the net efficiency of a coal firing MHD power plant will depend on the plant configuration and the technologies adopted.
Challenges of magneto hydrodynamic power plant
Despite the considerable progress that was made during the 1980s and early 1990s towards the development of commercial scaled coal firing MHD power plants, several technological breakthroughs are required before magneto hydrodynamic power generating systems can be commercialized. Various technical challenges remain in coal fired MHD technology depending on the power generation cycle configuration among these are:
. High temperature heat exchange / air preheat.
. Cost effective seed recovery and regeneration system.
. High temperature resistant electrodes.
. Control of slag removal in magneto hydrodynamic combustor.
. Optional desym of magneto hydrodynamic generator and its components and durable operation of high temperature MHD challenge.
. Tail gasification process.