magnetic hydro dynamic

8/6/2019 Magnetic Hydro Dynamic

1/47

o

y ASSIGNMENT y O N

y MHD POW ER PLANT

y IN DIRECTION OF: - MR. J. SANDEEP SONI (Lect. In B. K. BIET)

-: INDEX:-


2/47

y C O NTENTS PAGE NO. y 1. HISTORY OF THE POWER PLANT 02-06

y 2. CONCEPT ON WHICH ITWORKS 06-09y 3. BASIC LAYOUT 09-1 3 y 4. VARIOUS PARTS 1 3-15y 5. WORKING PRINCIPLE 15-25

y 6. CLASSIFICATION 25-32y 7. SITE SELECTION . 32-35y 8. ADVANTAGES&DISADVANTAGES 35-37

o 9. IMPACT ON ENVIRONMENT 37 -41o 10.COMPARISION WITH OTHER POWER PLANT41-47 o 11.FUTURE CHALLENGE 47 -48

y HISTO RY OF THEPOW ER PLANT:-


3/47

y

y Magnetohydrodynamic power generation provides a way of

generating electricity directly from a fast moving stream of ionisedgases without the need for any moving mechanical parts - noturbines and no rotary generators. Several MHD projects wereinitiated in the 1960s but overcoming the technical challenges of making a practical system proved very expensive. Interestconsequently waned in favour of nuclear power which since that

time has seemed a more attractive option.y MHD power generation has also been studied as a method for

extracting electrical power from nuclear reactors and also frommore conventional fuel combustion systems

y Michael Faraday first proposed the idea in his "Bakerian lecture

for 1 83 2" to the Royal Society. He carried out experiments atWaterloo Bridge, measuring current from the flow of the Thamesin the Earth's magnetic field. The first practical MHD powerresearch was funded in 19 38 in the U.S. by Westinghouse in itsPittsburgh, Pennsylvania laboratories, headed by BelaKarlovitz.


4/47

The initial patent on MHD is by B. Karlovitz, U.S. Patent No.2,210,91 8, "Process for the Conversion of Energy", August 1 3,1940.

y World war II interrupted development. In 1962, the FirstInternational Conference on MHD Power was held in Newcastleon Tyne, UK by Dr. Brian C. Lindley of the International Researchand Development Company Ltd. The group set up a steeringcommittee to set up further conferences and disseminate ideas. In196 4, the group set up a second conference in Paris, France, inconsultation with the European Nuclear Energy Agency.

y Since membership in the ENEA was limited, the group persuaded

the International Atomic Energy Agency to sponsor a thirdconference, in Salzburg, Austria, July 1966. Negotiations at thismeeting converted the steering committee into a periodicreporting group, the ILG-MHD (international liaison group, MHD),under the ENEA, and later in 196 7, also under the InternationalAtomic Energy Agency. Further research in the 1960s by R. Rosa

established the practicality of MHD for fossil-fueled systems.y In the 1960s, AVCO Everett Aeronautical Research began a series

of experiments, ending with the Mk. V generator of 1965. Thisgenerated 35 MW, but used about 8MW to drive its magnet. In1966, the ILG-MHD had its first formal meeting in Paris, France. Itbegan issuing a

y periodic status report in 196 7. This pattern persisted, in thisinstitutional form, up until 19 76. Toward the end of the 1960s,interest in MHD declined because nuclear power was becomingmore widely available.


5/47

y In the late 19 70s, as interest in nuclear power declined, interest inMHD increased. In 19 75, UNESCO became persuaded the MHDmight be the most efficient way to utilise world coal reserves, andin 19 76, sponsored the ILG-MHD. In 19 76, it became clear that nonuclear reactor in the next 25 years would use MHD, so theInternational Atomic Energy Agency and ENEA (both nuclearagencies) withdrew support from the ILG-MHD, leaving UNESCOas the primary sponsor of the ILG-MHD.

y The MHD (magnetohydrodynamic) generator or dynamo transforms thermal energy or kinetic energy directly intoelectricity. MHD generators are different from traditional electric

generators in that they can operate at high temperatures withoutmoving parts. MHD was developed because the exhaust of aplasma MHD generator is a flame, still able to heat the boilers of asteampower plant. |

y So high-temperature MHD was developed as a topping cycle toincrease the efficiency of electric generation, especially when

burning coalnatural gas. It has also been applied to pump liquidmetals and for quiet submarine engines.

y The basic concept underlying the mechanical and fluid dynamos isthe same. The fluid dynamo, however, uses the motion of fluid orplasma to generate the currents which generate the electricalenergy. The mechanical dynamo, in contrast, uses the motion of mechanical

y devices to accomplish this. The functional difference between anMHD generator and an MHD dynamo is the path the chargedparticles follow.


6/47

y MHD generators are now practical for fossil fuels, but have beenovertaken by other, less expensive technologies, such ascombined cycles in which a gas turbine's or molten carbonate fuel

cell's exhaust heats steam for steam turbine. The unique value of MHD is that it permits an older single-cycle fossil-fuel power plantto be upgraded to high efficiency.

y WO RKING CO NCEPT:-


7/47

y

y Under high pressure condition, an electrically conducting gas is

produced by burning a fossil fuel. Most of the MHD systems usecoal or natural gas as fossil fuel. However, inert gases like argonand helium are also used in some MHD systems. The gas is passedthrough a nozzle at a high speed of 1000 to 2000 meter persecond. The magnetohydrodynamic generators do not createelectric charge, it is inherent in the ionized fluid or gases. To

understand it better, think of a water pump that allows the waterto pass through but it is not the source of water. Conductivity of the fluid can be increased by adopting various methods. If thefluid is an inert gas, then suitable amounts of potassiumcarbonate can be added.The gas enters the channel or duct wherea strong magnetic field is applied with the help of


8/47

superconducting magnets. The magnetic intensity or magneticfield strength of the magnetic field inside the channel is usuallybetween 3 to 5 Tesla. As the gas passes through the channel, anelectromotive force is experienced by it. How does this forcearise? According to the Faraday's law of electromagnetic inductioncurrent/voltage (EMF) is induced in a coil/wire whenever there isa change in the magnetic flux linked with the coil. Here, theelectromagnets are stationary but the conductor fluid is movingconstantly. This causes the generation of electric field.

y As mentioned earlier the MHD systems consist of channel/ductthat are a bridge to the external circuit which will finally let the

electricity to flow to the load. The question that arises here is;what is an electrode? Electrodes are the plates, rods or wires thatact as a conductor to the flow of electricity. They act as aconnector to the external circuit. Here the channel acts as anelectrode. The external circuit is connected to the electrode andelectric power supply transferred to the desired path.The basic

mathematical equation governing the working of amagnetohydrodynamic generator is the Lorentz force law.Suppose, a particle is projected with certain velocity (v) in an areawhose magnetic field intensity is B, then the force acted on thecharged particle is given by Lorentz force law. The direction of motion of the charged particle is dependent on the charge of theparticle (positive, negative or neutral) and also on the direction of

the magnetic field. Here is the vector form of the Lorentz forcelaw.

F = Q (v B ), whereF = Force acting on the particle,


9/47

Q = Charge on the particle,v = Velocity of the particle,B = Magnetic field

The important thing to remember is that the direction of forcevector is perpendicular to the plane of velocity and magneticfield.However, in depth analysis requires the study of Navier-Stokes equation (included in fluid dynamics) and Maxwell's law of electromagnetism. The Navier-Stokes equations are differentialequations that determine the velocity of the fluid at any particularinstant of time. The Maxwell's law of electromagnetism are four

partial different equations that combine together to form complexequations involving either magnetic or electric field or both.Coupled with Navier-Stokes equations they are very useful instudying the working of magnetohydrodynamic generator.

y Magnetohydrodynamic generators were initially developed toheat the boilers of a steam power plant as they require very high

temperatures to function. This was not possible with conventionalelectric generators. Magnetohydrodynamic generators have highthermal efficiency required for power plants. MHD generators donot cause any significant harm to the environment. With moreresearch and innovation, MHD systems will lead to developmentin the work of thermonuclear fusion reactors.

y B ASIC SCHEMES:-


10/47

y In the report a brief account is gi v en of a large experimentalcomplex MHD - power plant for open - cycle operation withcombustion products of natural gas . The main distinguishingfeature of such a plant in comparison with existing ones consistsin the fact that with its help it is possible to in v estigate not onlythe MHD - generator itself but also other complicatedcomponents of MHD - power plants as well as to in v estigate theoperation of major components of the MHD - power plant . Presumably the question as to the prospecti v e application of open - cycle MHD - power plants for large - scale power generationcan be answered only after the solution of complicated research

and engineering problems associated with the de v elopment of alarge - scale commercial pilot plant .

y Another distinguishing feature of the described plant lies in thefact that it is intended for a long - period ser v ice .

y The report gi v es main parameters of the plant, describes thetechnological scheme and its major components : the combustionchamber, the MHD - channel, the magnet system, facilities forinjection and reco v ery of ionizing seeding, high - temperature airpreheaters, end heat - exchanger systems, current in v ertingsystems, etc .

y Also the report gi v es a summary of the obtained experimentalresults . The MHD - generator output power amounted to 30 k W.


11/47

y The comparison of the results on thermal and gasdynamicinv estigation carried out in the MHD - channel with theoreticalcalculations made on a refined one - dimensional flow modelshowed that they agree

y After the in v estigations carried out on the described plantconditions were obtained not only for further wide - scalemagnetohydrodynamicthermophysical andelectrophysical investigations of MHD-power plants but also forthe continuation of the work for investigating a simultaneous

operation of the MHD-generator with other components of theplant as well as for developing more rational designs of thecomponents and conditions for their operation.

y In a fossil fuel power plant the chemical energy stored in fossilfuels (such as coal, fuel oil, natural gas or oil shale) and oxygen of the air is converted successively into thermal energy, mechanicalenergy and, finally, electrical energy for continuous use anddistribution across a wide geographic area. Each fossil fuel powerplant is a highly complex, custom-designed system. Constructioncosts, as of 200 4, run to US$1, 300 per kilowatt, or $650 million fora 500 MWe unit. Multiple generating units may be built at a singlesite for more efficient use of land, natural resources and labor.Most thermal power stations in the world use fossil fuel,

outnumbering nuclear, geothermal, biomass, or solar thermalplants.

y Con v ersion of chemical energy to heat :-


12/47

y

y wherestoichiometric coefficients x and y depend on the fuel type.A simple word equation for this chemical reaction is:

y

y Depending on temperature and flame parameters duringcombustion, however, some of the nitrogen can be oxidized,producing various nitrogen oxides. Other, unintended, products of combustion are sulfur dioxide coming from sulfur impurities(predominantly in coal).

y Heat into mechanical energy :- y The second law of thermodynamics states that any closed-loop

cycle can only convert a fraction of the heat produced duringcombustion into mechanical work. The rest of the heat, calledwaste heat, must be released into a cooler environment duringthe return portion of the cycle. The fraction of heat released into acooler medium must be equal or larger than the ratio of absolute

temperatures of the cooling system (environment) and the heatsource (combustion furnace). Raising the furnace temperatureimproves the efficiency but also increases the steam pressure,complicates the design and makes the furnace more expensive.The waste heat cannot be converted into mechanical energywithout an even cooler cooling system. However, it may be usedin cogeneration plants to heat buildings, produce hot water, or toheat materials on an industrial scale, such as in some oil refineries,plants, and chemical synthesis plants.

y VARIOU S PARTS O F POW ERPLANTS:-


13/47

y

y Si plifi d po pl nt :-

y 1 Cooling tow e y 10 Ste control

v lve y 19 S erh e ter

y 2 Cooling wat e rpump

y 11 High pr ess ur e steam turbin e

y 20 For ce draught(draft) fan

y 3. Thr ee-pha se tran smiss ion lin e

y 12 . Deaerator y 21 . Reheat er

y 4. Step-upTran sform er

y 13. Feedwat e rheat er

y 22 . Combu stion airintak e

y 5. Elec tri calgenerator

y 14. Coal con veyor y 23. Economi se r

y 6. Low pr ess ur e steam turbin e

y 15 . Coalhopp er/ silo

y 24. Air pr eheat e r

y 7. Boiler

f ee dwat erpump

y 16 . Coal pul verizer y 25 . Prec ipitator

y 8. Surfa ce cond ense r

y 17. Boiler steamdrum

y 26 . Indu ceddraught (draft) fan


14/47

y 9. Intermediatepressure steamtur.

y 18. Bottom ashhopper

y 27. Flue gas stack

y W O RKINGPRINCIPLE:-

y

When an electric conductor moves across a magnetic field avoltage is induced in it which produces a electric current.

y The electromagnetic induction principle is not limited to solidconductors. The movement of conducting fluid can also generateelectrical energy.

y When a fluid is used for energy conversion technique, it is called

the magneto hydrodynamic (MHD) energy conversion.


15/47

y If the flow direction is right angle to magnetic field direction anelectromotive force is induced in the direction right angle to bothflow and field direction.

y

y This is the principle of CONVENTIONAL GENERATOR where the

conductor consists of a copper strip.

y In MHD generator solid conductor are replaced by gaseousconductor or ionized gas. if such a gas is passed at high velocitythrough a powerful magnetic field a current is generated & can beextracted by placing electrodes in suitable position in the stream.

y The principle can be explained as follows. An electric conductormoving through a magnetic field experiences a retarding force aswell as an induced electric field & current


16/47

y


17/47

y

y The conducting flow fluid is forced between the plates with akinetic energy and pressure differential sufficient to overcome themagnetic induction force F.

y An ionized gas is employed as the conducting fluid.

y Ionization is produced either by thermal means i.e. by an elevatedtemperature or by seeding with substance like cesium orpotassium vapours which ionze at relatively low temperature.

y The atoms of seed element split of electrons. The presence of negatively charged electrons makes the carrier gas an electricconductor.


18/47

y The MHD generator can be considered to be a fluid dynamo. Thisis similar to a mechanical dynamo in which the motion of a metal

o conductor through a magnetic field creates a current in theconductor except that in the MHD generator the metalconductor is replaced by a conducting gas plasma.

y When a conductor moves through a magnetic field it creates anelectrical field perpendicular to the magnetic field and thedirection of movement of the conductor. This is the principle,

discovered by Michael Faraday, behind the conventional rotaryelectricity generator. Dutch physicist AntoonLorentz provided themathematical theory to quantify its effects.

o


19/47

y The flow (motion) of the conducting plasma through a magneticfield causes a voltage to be generated (and an associated currentto flow) across the plasma, perpendicular to both the plasma flow

and the magnetic field according to Fleming's Right Hand Rule

y Lorentz Law describing the effects of a charged particle moving ina constant magnetic field can be stated as

y F = Q vB y Wherey F is the force acting on the charged particley Q is charge of particley v is velocity of particley B is magnetic field

y The MHD System y The MHD generator needs a high temperature gas source, which

could be the coolant from a nuclear reactor or more likely hightemperature combustion gases generated by burning fossil fuels,including coal, in a combustion chamber. The diagram below

shows possible system components.


20/47

y

y The expansion nozzle reduces the gas pressure and consequentlyincreases the plasma speed (Bernoulli's Law) through the

generator duct to increase the power output (See Power below).Unfortunately, at the same time, the pressure drop causes theplasma temperature to fall (Gay-Lussac's Law) which alsoincreases the plasma resistance, so a compromise betweenBernoulli and Gay-Lussac must be found.

y The exhaust heat from the working fluid is used to drive a

compressor to increase the fuel combustion rate but much of theheat will be wasted unless it can be used in another process.


21/47

y The Plasma y The prime system requirement is creating and managing the

conducting gas plasma since the system depends on the plasmahaving a high electrical conductivity. Suitable working fluids aregases derived from combustion, noble gases, and alkali metalvapours.


22/47

y

y The Faraday Current y A powerful electromagnet provides the magnetic field through

which the plasma flows, and perpendicular to this field areinstalled the two electrodes on opposite sides of the plasmaacross which the electrical output voltage is generated. Thecurrent flowing across the plasma between these electrodes iscalled the Faraday current. This provides the main electricaloutput of the MHD generat


23/47

y

y The Hall Effect Current y The very high Faraday output current which flows across the

plasma duct into the load itself reacts with the applied magneticfield creating a Hall Effect current perpendicular to the Faradaycurrent, in other words, a current along the axis of the plasma,resulting in lost energy. The total current generated will be the


24/47

vector sum of the transverse (Faraday) and axial (Hall effect)current components.

y Unless it can be captured in some way, the Hall effect current willconstitute an energy loss .

y Various configurations of electrodes have been devised to captureboth the Faraday and Hall effect components of the current inorder to improve the overall MHD conversion efficiency.

y One such method is to split the electrode pair into a series of segments physically side by side (parallel) but insulated fromeachother, with the segmented electrode pairs connected inseries to achieve a higher voltage but with a lower current.

Instead of the electrodes being directly opposite eachother,perpendicular to the plasma stream, they are skewed at a slightangle from perpendicular to be in line with the vector sum of theFaraday and Hall effect currents, as shown in the diagram below,thus allowing the maximum energy to be extracted from theplasma.

y


25/47

y Power Output :- y The output power is proportional to the cross sectional area and

the flow rate of the ionised plasma. The conductive substance isalso cooled and slowed in this process. MHD generators typicallyreduce the temperature of the conductive substance from plasmatemperatures to just over 1000 C.

y An MHD generator produces a direct current output which needsan expensive high power inverter to convert the output intoalternating current for connection to the grid.

y Effici en cy:-

y Typical efficiencies of MHD generators are around 10 to 20percent mainly due to the heat lost through the high temperatureexhaust.

y This limits the MHD's potential applications as a stand alonedevice but they were originally designed to be used incombination with other energy converters in hybrid applicationswhere the output gases (flames) are used as the energy source toraise steam in a steam turbine plant. Total plant efficiencies of 65%could be possible in such arrangements


26/47

CLASSIF ICATIO N POW ER PLANTS: - y MHD system can be classified as follows

y Open cycle systemy Closed cycle system

o Seeded inert gas systemo Liquid metal system

y Open

Cycle System

:-


27/47

y Fuel used may be oil through an oil tank or gasified coal through acoal gasification plant.

y The fuel (coal, oil or natural gas) is burnt in the combustor orcombustion chamber.

y The hot gas from the combustor is then seeded with a smallamount of an ionized alkali metal (cesium or potasium) toincrease the electrical conductivity of the gas.


28/47

y The seed material potassium carbonate is injected into thecombustion chamber, the potassium is then ionized by the hotcombustion gases at temperature roughly(2 300-2 700deg)

y To attain such high temperatue,the compressed air used to burn

the coal in the combustion chamber must be adequate to at least1100 c.A lower preheat temperature would be adequate if the airwhere enriched is oxygen. An alternative is to use compressedoxygen alone for combustion of fuel, little or no preheating isrequired. The additional cost of oxygen might be balanced bysaving thepreheater.

y The hot pressurized working fluid living the combustor flowsthrough a convergent divergent nozzle.In passing through thenozzle the random motion energy of the molecules in the hot gasis largely converted into thus directed mass of energy. the gasemerges from the nozzle & enters the MHD generator unit at a

high velocity.y The MHD generator is divergent channel made of a heat resistant

alloy with external water cooling. the hot gas expands through therocket like generator surrounded by powerful magnet. duringmotion of the gas the +ve& - ve ions move to the electrodes &constitute electric current.

y The arrangement of the electrode connections is determined bythe need to reduce losses arising from the Hall effect. By thiseffect magnetic field acts on the MHD generated current &


29/47

produces a voltage in flow direction of the working fluid ratherthan at right angle to it.

y C losed Cycle System :-

y

y Two general types of closed cycle system are being investigated.

y 1 > electrical conductivity is maintained in the working fluid byionization of a seed material as in open cycle system.

y 2 > A liquid metal provides the conductivity.


30/47

y The carrier is usually a chemically inert gas,although a liquidcarrier is been used with a liquid metal conductor.The workingfluid is circulated in closed loop & is heated by the combustion gasusing a heat exchanger.Hence the heat sources & working fluidare independent. The working fluid is helium or argon with cesiumseeding.

y Seeded Inert Gas System :- y In a closed cycle system the carrier gas operates in the form of

Brayton cycle.in a closed system the gas is compressed & heats issupplied by the source at essentially constant pressure, thecompressed gas then expand in the MHD generator & its pressureand temperature falls. After leaving the generator, heat isremoved from the gas by a cooler, this is the heat rejection stageof he cycle. Finally the gas is recompressed & returned forreheating.

y The complete system has three distinct but interlocking loops. Onthe left it is external heating loop. Coal is gasified and the gas burnin a combustor to provide heat. IN the primary heat exchanger theheat uis transferred to a carrier gas argon or helium of the MHDcycle. the combustion product after passing through the airpreheated & purified are discharged to atmosphere.

y Because the combustion system is separate from the working fluidso also are ash & flue gases. Hence the problem of extracting theseed material from fly ash doesn t arise. The fuel gases are used topreheat the incoming combustion air & then treated for fly ash &


31/47

sulphur dioxide removal, if necessary prior to discharge through astack to the atmosphere.

y The loop in the centre is the MHD loop. The hot argon gas isseeding with cesium and resulting working fluid is passed throughthe MHD generator at high speed. The dc power out of MHDgenerator is converted in ac by the inverter and is then fed intothe grid.

o Liquid Metal System :-


32/47

y

y When the liquid metal provides the electrical conductivity, aninert gas is a convenient carrier.

y The carrier gas is pressurized and heated by passage through aheat exchanger within combustion chamber. the hot gas is thenincorporated into the liquid metal usually hot sodium to form theworking fluid. the latter the consist of gas bubble uniformlydispersed in an approximately equal volume of liquid sodium.

y The working fluid is introduced into the MHD generator through anozzle in the usual ways, the carrier gas then provides therequired high direct velocity of the electrical conductor.


33/47

y 7)SITE SELECTIO N OF POW ER PLANT:- y Points that should be taken care of while selecting a site for

MHD POW ER PLANT is giv en below : y Difficult gelogy : much of the region in or near the electric

company s service area is seismically active or has other naturalfeatures that might make it unacceptable for a nuclear powerplant.

y Limited water : the power plant would require large quantities of water for cooling purposes, and water is in short supply in thearea.

y

Significant uncertainties:

these include uncertainties aboutgeology. Water availability and future socioeconomicdeveloments in the area.

y Multiple siting concenns : in addition to system costs, other sitingconcerns include licensing requirements,public health and safety ,environmental and socioeconomic effects and public acceptance.

y Multiple interest groups : the electric company has responsibilitiesto both its share-holders and its rate payers , and a variety of other groups are interested in nuclear power.

y Data limitations : there were many data that could not be collectedwithin a realistic budget and schedule or that were not available.

y 7 . regulatoryrequirements : regulations of the U.S.nuclearregulatory commission and other government bodies impose

requirements on the selection of sites for nuclear power plants. y Points that should be gi v en importance while selecting a site for

MHD POW ER PLANT is giv en below : y 1 . a v ailabilty of water :


34/47

y Since the primary reqirement for a hydro electric power stationis the a v ailability of huge amount of water such plants should bebuilt at a place (example : riv er,canel ) where adequate water isa v ailable at a good head .

y 2 . storage of water : y There are wide v ariations in water supply from a ri v er or canal

during the year . this makes its necessary to store water byconstructing a dam inorder to ensure the generation of powerthrough out the year . the storage helps in equalising the flow of water so that any excess quantity of water at a certain period of the year can be made a v ailable during of v ery low flow in the

riv er . The leads to the conclusion that site selected for hydroelectric plant should pro v ide adequate facalities for erecting adam and storage of water .

y 3. cost and type of land : y The land for the construction of plant shoud be a v ailable at a

reasonable price . further the bearing capacity of the soil should

be adequate to withstand the installation of hea v y equipment . y 4 . transportation facilities : y The site selected for the hydro electric plant should be accessible

by rail and road so that necessary equipment and machinerycould be easily transported .

y 8 )Adv antages of Power Plant :- y The conversion efficiency of a MHD system can be 50% as

compared to less than 40 percent for the most efficient steamplants.

y Large amount of power is generated.


35/47

y It has no moving parts, so more reliable.

y It has ability to reach the full power level as soon as started.

y 5) Because of higher efficiency, the overall generation cost of anMHD plant will be less.

y 6) The more efficient heat utilization would efficient heatutilization would decreases the amount of heat discharged toenvironment and the cooling water requirements would also belower.

y 7) The higher efficiency means better fuel utilization. The reducefuel

y consumption would offer additional economic and social benefits.y 8) The Closed cycle system produces power free of pollution.y 9) Power generation in space craft.

10) Hypersonic wind tunnel experiments.y 11) Defense application.

y Disad v antages of power plant :- y Toxic byproductsy 1)MHD reduces overall production of hazardous fossil fuel wastes

because it increases plant efficiency.y 2) In MHD coal plants, the patented commercial "Econoseed"

process developed by the U.S. recycles potassium ionization seedfrom the fly ash captured by the stack-gas scrubber. 3)this

equipment is an additional expense. If molten metal is thearmature fluid of an MHD generator, care must be taken with thecoolant of the electromagnetics and channel.

y 4) The alkali metals commonly used as MHD fluids react violentlywith water. Also, the chemical byproducts of heated, electrified


36/47

alkali metals and channel ceramics may be poisonous andenvironmentally persistent.

y 5 ) Activists have long chosen to picket power plants that producetoxic waste or create other bad side effects. They urge a Greenapproach to producing electricity for an ever growing population.

y 6)Nuclear power has long been targetted for the deadly hazards itinvolves. Coal creates its own pollutants and mining dangers.Hydroelectric dams are considered bad for the surroundinghabitat. And many claim windmill towers are eyesores and oftenpoorly located to produce adequate electricty.

y 7)a new method of harnessing energy has been completely

overlooked in AmericaMagnetohydrodynamics or MHD power.MHD uses a powerful magnetic field to move fluids.

8)The concept of MHD was first popularized by the Hollywoodmotion picture "The Hunt for Red October" which depicted asubmarine using the technology for its propulsion system. In real

life, Japan created an MHD-driven sea vessel, the Yamato series.y 9)an MHD power plant was built in Israel. Proponents claim that

the Etgar 3 system is up to 30 percent more efficient thantraditional generators.

y 9 )Impact on En v iroment :-


37/47

y

y The Mohave Power Station, a 1,5 80 MW coal power station nearLaughlin, Nevada, out of service since 2005 due to environmentalrestrictions

y The world's power demands are expected to rise 60% by 20 30.With the worldwide total of active coal plants over 50,000 andrising, the International Energy Agency (IEA) estimates that fossil

fuels will account for 85% of the energy market by 20 30.y World organizations and international agencies, like the IEA, are

concerned about the environmental impact of burning fossil fuels,and coal in particular. The combustion of coal contributes themost to acid rain and air pollution, and has been connected withglobal warming. Due to the chemical composition of coal there are


38/47

difficulties in removing impurities from the solid fuel prior to itscombustion. Modern day coal power plants pollute very little dueto new technologies in "scrubber" designs that filter the exhaustair in smoke stacks.

y Nowadays, the only pollution caused from coal-fired power plantscomes from the emission of gases carbon dioxide, nitrogenoxides, and sulfur dioxide into the air. Acid rain is caused by theemission of nitrogen oxides and sulfur dioxide into the air. Thesethemselves may be only mildly acidic, yet when they react withthe atmosphere, they create acidic compounds (such as sulfurousacid, nitric acid and sulfuric acid) that fall as rain, hence the term

acid rain. In Europe and the U.S.A., stricter emission laws anddecline in heavy industries have reduced the environmentalhazards associated with this problem, leading to lower emissionsafter their peak in 1960s.

y European Environment Agency (EEA) gives fuel-dependentemission factors based on actual emissions from power plants in

EU.

y

y Pollutant

y

y Hardcoal

y

y B rowncoal

y

y Fuel oil

y

y O ther oil

y

y Gas

y C O2 (g/GJ ) y 94600 y 101000 y 774 00 y 74100 y 56100

y SO 2 (g/GJ ) y 765 y 1361 y 1350 y 228 y 0.68


39/47

y NO x (g/GJ ) y 292 y 183 y 195 y 129 y 93.3

y C O (g/GJ ) y 89.1 y 89.1 y 15.7 y 15.7 y 14.5

y Nonmethaneorganic

compounds(g/GJ )

y 4.92 y 7.78 y 3.70 y 3.24 y 1.58

y Particulatematter (g/GJ )

y 1203 y 3254 y 16 y 1.91 y 0.1

y F lue gasv olume total

(m3/GJ )

y 360 y 444 y 279 y 276 y 272

y Carbon dioxide y Electricity generation using carbon based fuels is responsible for a

large fraction of carbon dioxide (CO 2) emissions worldwide and for41% of U.S. man-made carbon dioxide emissions. Of fossil fuels,coal combustion in thermal power stations result in greateramounts of carbon dioxide emissions per unit of electricitygenerated (22 49 lbs/MWh [15]) while oil produces less(1672 lb/(MWh) or 211 kg/GJ) and natural gas produces the least11 35 lb/(MWh) (1 43 kg/GJ).U S EPA Clean Energ y G as )

y The Intergovernmental Panel on Climate Change (see IPCC) states

that carbon dioxide is a greenhouse gas and that increasedquantities within the atmosphere will "very likely" lead to higheraverage temperatures on a global scale (global warming);concerns regarding the potential for such warming to change the


40/47

global climate prompted IPCC recommendations calling for largecuts to CO 2 emissions worldwide.

y Emissions may be reduced through more efficient and highercombustion temperature and through more efficient productionof electricity within the cycle. Carbon capture and storage (CCS) of emissions from coal fired power stations is another alternative butthe technology is still being developed and will increase the costof fossil fuel-based production of electricity. CCS may not beeconomically viable, unless the price of emitting CO 2 to the

atmosphere rises.

y 1 0)Comparisons of v arious energy sources :-

y As the world's population increases and there is continued comparison to the current western European, Japanese, and North

American living standards, there is likel y to be demand for moreelectrical power. Energ y sources available in the world include

coal, nuclear, h y droelectric, gas, wind, solar, refuse-based, and biomass. In addition, fusion had been originall y proposed as thelong-term source.

y Ever y form of energ y generation has advantages and disadvantages as shown in the table below.


41/47

y Source y Advantag es y Di sadvantag es

y C oal

y Ine x pensivey Easy to recover

(in U .S. and Russia)

y Requirese x pensive air

pollution controls

(e.g. mercur y ,sulfur dio x ide)

y Significant contributor toacid rain and global warming

y Requirese x tensivetransportationsy stem

y N uc l ea r

y Fuel isine x pensive

y Energ y generation is the

most concentrated source

y W aste is morecompact than an y source

y E x tensive

scientific basis for the c y cley Easy to transport

as new fuel y No greenhouse or

acid rain effects

y Requires larger capital cost because of emergenc y ,containment,radioactive wasteand storagesy stems

y Requiresresolution of thelong-term high

level wastestorage issue inmost countries

y Potential nuclear proliferation issue


42/47

y Hy d roe l ec t r i c

y V er y ine x pensiveonce dam is built

y Government hasinvested heavil y in building dams,

particularl y in theW estern U .S.

y V er y limited source sincedepends on water elevation

y Man y dams

available arecurrentl y e x ist (not much of a

futuresource[dependson countr y] )

y Dam collapse

usuall y leads toloss of lifey Dams have

affected fish (e.g.salmon runs)

y Environmental damage for areas

flooded (backed up) and downstream

y G a s / O i l

y Good distributionsy stem for current use levels

y Easy to obtain(sometimes)

y Better as spaceheating energ y source

y V er y limited availabilit y asshown b y shortages during

winters several y ears ago

y Could be major contributor toglobal warming

y V er y e x pensive


43/47

for energ y generation

y Large priceswings withsuppl y and

demand y Liquified Natural

Gas storage facilities and gastransmissionsy stems have met opposition from

environmentalists.

y W i nd

y W ind is free if available. As it turns out, the U Shas man y areasavailable.

y Good source for periodic water pumpingdemands of

farms as used earlier in 1900's

y Generation and

maintenancecosts havedecreased significantl y .W ind is provingto be a

y Need 3 x theamount of installed generation tomeet demand

y Limited to wind y areas.

y Limited to small generator size;need man y towers.

y H ighl y climate

dependent - wind can damageequipment duringwindstorms or not turn duringstill summer da y s.


44/47

reasonable cost renewablesource.

y W ell suited torural areas.

E x amples includeMid-Columbiaareas of Oregonand W ashington,westernMinnesota,

Atlantic Ocean off Cape Cod.

y Ma y affect endangered birds,however tower design can reduceimpact..

y Sola r

y Sunlight is freewhen available

y Costs aredropping.

y Limited tosouthern areas of U .S. and other sunn y areasthroughout theworld (demand can be highest when least available, e.g.winter solar heating)

y Does requirespecial materials

for

mirrors/panelsthat can affect environment

y Current technolog y requires large


45/47

amounts of land for small amounts of energ y generation

y B i om a ss

y Industr y in itsinfanc y

y Could create jobsbecause smaller

plants would be

used

y Inefficient if small plants are used

y Could besignificant contributor toglobal warmingbecause fuel haslow heat content

y R efuse B a se d Fue l

y Fuel can have low

cost y Could create jobs

because smaller plants would beused

y Low sulfur dio x ideemissions

y Inefficient if small plants are used

y Could besignificant contributor to

global warmingbecause fuel haslow heat content

y Fl y ash cancontain metals ascadmium and lead

y

Contain dio x insand furans in air and ash releases

y Hy d ro g en y Combines easil y

with o xy gen toy V er y costl y to

produce


46/47

produce water and energ y

y Takes moreenerg y to

producehy drogen thenenerg y that could

be recovered.

y Fus i on

y H y drogen and tritium could beused as fuel source

y H igher energ y output per unit mass than fission

y Low radiationlevels associated with process than

fission-based reactors

y Breakeven point has not beenreached after ~40y ears of e x pensiveresearch and commerciall y available plantsnot e x pected for at least 35 y ears.

y 11 )Future Challanges : y With the increased industrial and agricultural activities, power

demand is also highly increased. In the country is sure to fall shortof the energy demand by the first decade of next century. Thismeans an additional capacity of power is required next 10 year.

The answer to this is in non conventional energy.y The MHD power generation is in advanced stage today and closer

to commercial utilization significant progress has been made indevelopment of all critical component and sub systemtechnologies coal burning MHD combined steam power plant


47/47

promise significant economic and environmental advantagescompared to other coal burning power generate technologies. Itwill not be long before the technological problem of MHDgenerate are overcome and MHD power generation transformitself from non- conventional to conventional energy sources

magnetic hydro dynamic

Documents