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The Magnetohydrodynamic power generation technology (MHD ) is the production of electrical power utilising a high temperature conducting plasma moving through an intense magnetic field.
Principle 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 force in a direction mutually perpendicular to the B field and to the velocity of the conductor. The negative charges tend to move in one direction, and the positive charges in the opposite direction. This induced electric field, or motional emf, provides the basis for converting mechanical energy into electrical energy. The production of electrical power through the use of a conducting fluid moving through a magnetic field is referred to as magnetohydrodynamic, or MHO, power generation. The principle was discovered by Michael Faraday.
The Lorentz Force Law describes the effects of a charged particle moving in a constant magnetic field. The simplest form of this law is given by the vector equation.
Principle 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 force in a direction mutually perpendicular to the B field and to the velocity of the conductor. The negative charges tend to move in one direction, and the positive charges in the opposite direction. This induced electric field, or motional emf, provides the basis for converting mechanical energy into electrical energy. The production of electrical power through the use of a conducting fluid moving through a magnetic field is referred to as magnetohydrodynamic, or MHO, power generation. The principle was discovered by Michael Faraday.
The Lorentz Force Law describes the effects of a charged particle moving in a constant magnetic field. The simplest form of this law is given by the vector equation.
F= Q.(v×B)
where
• F is the force acting on the particle.
• Q is the charge of the particle,
• v is the velocity of the particle, and
• B is the magnetic field.
The vector F is perpendicular to both v and B according to the right hand rule.
Systems using an MHD generator may operate in open or closed cycles. In the first case, products of combustion are the working fluid, and the exhaust gases are discharged into the atmosphere after removal of the alkali metal additives introduced into the working fluid to increase electric conductivity. In closed-cycle MHD generators the thermal energy produced by combustion of fuel is imparted to the working fluid in a heat exchanger. The working fluid then passes through the MHD generator and is returned through a compressor or pump, completing the cycle. Jet engines, nuclear reactors, or heat-exchange devices may be used as heat sources. The working fluids for MHD generators may be products of combustion of fossil fuels, inert gases with additives of alkali metals or their salts, vapors of alkali metals, and two-phase mixtures of liquid alkali metals and their vapors or liquid metals and electrolytes.
Advantages
• The conversion efficiency of a MHD system can be 50% as compared to less than 40 percent for the most efficient steam plants.
• Large amount of power is generated.
• It has no moving parts, so more reliable.
• It has ability to reach the full power level as soon as started.
• Because of higher efficiency, the overall generation cost of an MHD plant will be less.
• The more efficient heat utilization would efficient heat utilization would decreases the amount of heat discharged to environment and the cooling water requirements would also be lower.
• The higher efficiency means better fuel utilization. The reduce fuel consumption would offer additional economic and social benefits.
• The Closed cycle system produces power free of pollution
Disadvantages
• Simultaneous presence of high temperature and a highly corrosive and abrasive environment.
• MHD channel operates under extreme conditions of electric and magnetic field
•Initial installments are expensive.
where
• F is the force acting on the particle.
• Q is the charge of the particle,
• v is the velocity of the particle, and
• B is the magnetic field.
The vector F is perpendicular to both v and B according to the right hand rule.
Systems using an MHD generator may operate in open or closed cycles. In the first case, products of combustion are the working fluid, and the exhaust gases are discharged into the atmosphere after removal of the alkali metal additives introduced into the working fluid to increase electric conductivity. In closed-cycle MHD generators the thermal energy produced by combustion of fuel is imparted to the working fluid in a heat exchanger. The working fluid then passes through the MHD generator and is returned through a compressor or pump, completing the cycle. Jet engines, nuclear reactors, or heat-exchange devices may be used as heat sources. The working fluids for MHD generators may be products of combustion of fossil fuels, inert gases with additives of alkali metals or their salts, vapors of alkali metals, and two-phase mixtures of liquid alkali metals and their vapors or liquid metals and electrolytes.
Advantages
• The conversion efficiency of a MHD system can be 50% as compared to less than 40 percent for the most efficient steam plants.
• Large amount of power is generated.
• It has no moving parts, so more reliable.
• It has ability to reach the full power level as soon as started.
• Because of higher efficiency, the overall generation cost of an MHD plant will be less.
• The more efficient heat utilization would efficient heat utilization would decreases the amount of heat discharged to environment and the cooling water requirements would also be lower.
• The higher efficiency means better fuel utilization. The reduce fuel consumption would offer additional economic and social benefits.
• The Closed cycle system produces power free of pollution
Disadvantages
• Simultaneous presence of high temperature and a highly corrosive and abrasive environment.
• MHD channel operates under extreme conditions of electric and magnetic field
•Initial installments are expensive.
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