Uninterruptible Power Supply | UPS
Fermi Dirac Distribution Function
Fault of Electric Cable
Energy Bands in Crystals
Gallium Arsenide Semiconductor
Atomic Energy Levels
Electric Power Generation
Power Plants and Types of Power Plant
Thermal Power Generation Plant or Thermal Power Station
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Nuclear Power Station or Nuclear Power Plant
Diesel Power Station
Why Supply Frequency is 50 Hz or 60 Hz?
Economiser in Thermal Power Plant | Economiser
MHD Generation or Magneto Hydro Dynamic Power Generation
Cogeneration | Combined Heat and Power
Thermoelectric Power Generators or Seebeck Power Generation
Cost of Electrical Energy
Gas Turbine Power Plant
Steam Boiler | Working principle and Types of Boiler
Methods of Firing Steam Boiler
Fire Tube Boiler | Operation and Types of Fire Tube Boiler
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Feed Water and Steam Circuit of Boiler
Boiler Feed Water Treatment Demineralization Reverse Osmosis Plant Deaerator
Coal Combustion Theory
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Steam Condenser of Turbine
Jet Condenser | Low Level High Level Ejector Jet Condenser
Surface Steam Condenser
Economics of Power Generation
Cooling Tower Useful Terms and Cooling Tower Performance
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Power Plant Fire Protection System
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Medium Velocity Water Spray or MVWS System for Fire Protection
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Solar Energy System | History of Solar Energy
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Staebler Wronski Effect
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Characteristics of a Solar Cell and Parameters of a Solar Cell
Solar Cell Manufacturing Technology
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What is Standalone Solar Electric System?
Steam Dryness Fraction
Superheated Steam and Steam Phase Diagram
Vapour Properties Mollier Chart Heat Capacities
What is Steam Flashing?
How to Calculate Steam Consumption During Plant Start Up
Effective Steam Distribution System
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Engineering Thermodynamics Part 1
Science of Engineering Thermodynamics Part 2
Basic Law of Conservation and First Law of Thermodynamics
Carnot Cycle and Reversed Carnot Cycle
Enthalpy Entropy and Second Law of Thermodynamics
Rankine Cycle and Regenerative Feed Heating
Rankine Cycle for Closed Feed Water Heaters and Rankine Cycle Cogeneration
Ideal Verses Actual Rankine Cycle
Rankine Cycle Efficiency Improvement Techniques
Basic Wind Energy
Wind Turbine | Working Types and History of Wind Turbine
Theory of Wind Turbine
MHD Generation or Magneto Hydro Dynamic Power Generation
History of MHD GenerationThe concept of MHD power generation was introduced for the very first time by Michael Faraday in the year 1832 in his Bakerian lecture to the Royal Society. He in fact carried out an experiment at the Waterloo Bridge in Great Britain for measuring the current, from the flow of the river Thames in earth's magnetic field.
This experiment in a way outlined the basic concept behind MHD generation over the years then, several research work had been conducted on this topic, and later in August 13, 1940 this concept of magneto hydro dynamic power generation, was imbibed as the most widely accepted process for the conversion of heat energy directly into electrical energy without a mechanical sub-link.
Principle of MHD GenerationThe principal of MHD power generation is very simple and is based on Faraday’s law of electromagnetic induction, which states that when a conductor and a magnetic field moves relative to each other, then voltage is induced in the conductor, which results in flow of current across the terminals. As the name implies,the magneto hydro dynamics generator shown in the figure below, is concerned with the flow of a conducting fluid in the presence of magnetic and electric fields. In conventional generator or alternator, the conductor consists of copper windings or stripswhile in an MHD generator the hot ionized gas or conducting fluid replaces the solid conductor. A pressurized, electrically conducting fluid flows through a transverse magnetic field in a channel or duct. Pair of electrodes are located on the channel walls at right angle to the magnetic field and connected through an external circuit to deliver power to a load connected to it. Electrodes in the MHD generator perform the same function as brushes in a conventional DC generator. The MHD generator develops DC power and the conversion to AC is done using an inverter.
The power generated per unit length by MHD generator is approximately given by, Where, u is the fluid velocity, B is the magnetic flux density, σ is the electrical conductivity of conducting fluid and P is the density of fluid. It is evident from the equation above, that for the higher power density of an MHD generator there must be a strong magnetic field of 4-5 tesla and high flow velocity of conducting fluid besides adequate conductivity.
MHD Cycles and Working FluidsThe MHD cycles can be of two types, namely
- Open Cycle MHD.
- Closed Cycle MHD.
Open Cycle MHD SystemIn open cycle MHD system, atmospheric air at very high temperature and pressure is passed through the strong magnetic field. Coal is first processed and burnet in the combustor at a high temperature of about 2700oC and pressure about 12 ATP with pre-heated air from the plasma. Then a seeding material such as potassium carbonate is injected to the plasma to increase the electrical conductivity. The resulting mixture having an electrical conductivity of about 10 Siemens/m is expanded through a nozzle, so as to have a high velocity and then passed through the magnetic field of MHD generator. During the expansion of the gas at high temperature, the positive and negative ions move to the electrodes and thus constitute an electric current. The gas is then made to exhaust through the generator. Since the same air cannot be reused again hence it forms an open cycle and thus is named as open cycle MHD.
Closed Cycle MHD SystemAs the name suggests the working fluid in a closed cycle MHD is circulated in a closed loop. Hence, in this case inert gas or liquid metal is used as the working fluid to transfer the heat. The liquid metal has typically the advantage of high electrical conductivity, hence the heat provided by the combustion material need not be too high. Contrary to the open loop system there is no inlet and outlet for the atmospheric air. Hence, the process is simplified to a great extent, as the same fluid is circulated time and again for effective heat transfer.
Advantages of MHD GenerationThe advantages of MHD generation over the other conventional methods of generation are given below.
- Here only working fluid is circulated, and there are no moving mechanical parts. This reduces the mechanical losses to nil and makes the operation more dependable.
- The temperature of working fluid is maintained by the walls of MHD.
- It has the ability to reach full power level almost directly.
- The price of MHD generators is much lower than conventional generators.
- MHD has very high efficiency, which is higher than most of the other conventional or non-conventional method of generation.