MHD power generation

magneto-hydrodynamics power generation(Thermal to electric conversion)

1. Magnetohydrodynamic Thermal to Electric Conversion Session 2016-2017 Department of Electrical Engineering University College of Engineering, RTU (Kota) Guided By :- Dr. Dhreeaj palwalia (Professor and Head) Department of Electrical Engg Submitted By :- Abhishek Dosaya 13/003 1

2. The word magneto hydro dynamics (MHD) is derived from   magn eto -  meaning magnetic field, and  hydro-meaning  liquid, and -dynamics meaning movement. For the conventional power plants thermal energy is converted in to kinetic energy which is then converted into electrical energy. For MHD, thermal energy is directly converted to electrical energy, hence know as direct energy conversion system. Magnetohydrodynamics power generation technology is the production of electrical power utilizing a high temperature conducting plasma moving through an intense magnetic field . 1 What is MHD Abhishek Dosaya 13/003

3. When an electric conductor moves across a magnetic field, a voltage is induced in it which produces an electric current. This is the principle of the conventional generator where the conductors consist of copper strips . In MHD generator, the solid conductors are replaced by a gaseous conductor, an ionized gas. If such a gas is passed at a high velocity through a powerful magnetic field, a current is generated and can be extracted by placing electrodes in suitable position in the stream 2 How it Works Abhishek Dosaya 13/003

4. Principle of MHD power generation 3 Abhishek Dosaya 13/003

5. Related equations Potential Difference is obtained by- U=V. B. d Where V= Average speed of plasma B= Magnetic flux density d= Distance between the electrodes Power generated by MHD generator- Where electrical conductivity of fluid , u= fluid velocity p= Density of fluid Pressure difference is created to force the gas.   4 Abhishek Dosaya 13/003

6. Ionization Method - Thermal ionization Working fluid - Gases from the combustor, ionized by intense temperature . A lower preheat temperature would be adequate if the air is enriched in oxygen . Conductivity of gases is too low at a temperature of 5000F to deal this difficulty seeded material like cesium, potassium nitrate, or potassium carbonate is added to reduce the temperature to 2000-3000F for adequate conductivity . Used as hybrid MHD-steam plant cycle to increase the efficiency . 5 Open Cycle MHD system Abhishek Dosaya 13/003

7. Open cycle MHd system 6 Abhishek Dosaya 13/003

8. Features of Open cycle MHD for efficient system Management of seed material. Combustion chamber must have low heat losses. Compressed air enriched in oxygen is used to reduce the preheater cost . 7 Abhishek Dosaya 13/003

9. Closed Cycle MHD system In a Closed Cycle MHD, Working gas is not mixed with combustor material. Gases like helium argon is heated by the regenerative heat exchanger. Hence the heat sources and the working fluid are independent. The working fluid is helium or argon with cesium seeding Major advantage of closed cycle MHD are simple operation and do not require seed processing facility. inert gas or liquid metal is used to transfer the heat. The liquid metal has typically the advantage of high electrical conductivity; hence the heat provided by the combustion material does not required too high . 8 Abhishek Dosaya 13/003

10. 10 Abhishek Dosaya 13/003

11. Seeder inert gas system Working fluid-inert gas like helium or argon . The complete system has three distinct but interlocking loops- On the left is the external heating loop. Coal is gasified and the gas is burnt in the combustor to provide heat. In the primary heat exchanger, this heat is transferred to a carrier gas argon or helium of the MHD cycle. The combustion products after passing through the air preheated and purifier are discharged to atmosphere . Because the combustion system is separate from the working fluid, so also are the ash and flue gases. Hence the problem of extracting the seed material from fly ash does not arise. 9 Abhishek Dosaya 13/003

12. Liquid metal system 11 Abhishek Dosaya 13/003

13. The liquid metal has typically the advantage of high electrical conductivity; hence the heat provided by the combustion material does not required too high. Working fluid-liquid lithium, liquid sodium and carrier gas like helium or argon gas with cesium seeding . Carrier gas provide high direct velocity to the liquid metal. Carrier gas works as thermodynamic electric fluid. Liquid metal works as electrodynamics fluid. 12 Liquid metal system Abhishek Dosaya 13/003

14. Generator Designs 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 . 13 Abhishek Dosaya 13/003

15. Faraday generator 14 Abhishek Dosaya 13/003

16. Hall generator In faraday generator, the issue is reduce the faraday current due to Hall effect(Hall current). In Hall generator first electrode of one wall and last electrode of opposite wall is connected, which reduce the hall effect . Another concept to reduce the Hall current is segmented Faraday generator. 15 Abhishek Dosaya 13/003

17. Hall generator 16 Abhishek Dosaya 13/003

18. 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 . 17 Abhishek Dosaya 13/003

19. Disk generator 18 Abhishek Dosaya 13/003

20. Disk generator 19 Abhishek Dosaya 13/003

21. Selection of seed material Seed material has atoms which ionize easily, for example, cesium, potassium and calcium, and by supplying electrons causes an increase in the electrical conductivity of the gas. However , it is not possible to raise the electrical conductivity by increasing the concentration of the seed material . The electrical conductivity carrier gas mixed with appropriate quantity of seed depends upon- 1.Collison profile 2.Molecular weight 20 Abhishek Dosaya 13/003

22. Collision Profile :- The collision profile of a gas stream is defined as a value that is proportional to the probability of collisions of gas atoms with an electron. Since these collisions of gas atoms with the electrons reduce the mobility of the electrons within an electrical field, a high collision profile is synonymous to a low electrical conductivity. Molecular weight :- The power density is inversely proportional to the molecular weight of the gas, therefore, in order to attain a high power density it will be advantageous to select a carrier gas with a low molecular weight. Hence, hydrogen as a carrier gas and potassium as a seed is used 21 Abhishek Dosaya 13/003

23. Plasma Physics Experiments on High temperature Xenon plasma :- High temperature Xe plasma is generated by shock tunnel. This Xenon Plasma flows into a linear shaped segmented type faraday generator. The channel width is constant at 20mm,and the height variable. Variable temperature and variable flux density is applied. 22 Abhishek Dosaya 13/003

24. 23 Effect of inlet total temperature on enthalpy extraction ratio Abhishek Dosaya 13/003

25. Relation between stream-wise length and the power output density 24 Abhishek Dosaya 13/003

26. Effect of magnetic flux density on enthalpy extraction ratio 25 Abhishek Dosaya 13/003

27. Result In this experiment, however, the maximum enthalpy ratio remains only remains only 8%,smaller than the target performance of a CCMHD generator(enthalpy extraction ratio=30%). High enthalpy extraction ratio should be achieved with a long channel generator or a high magnetic flux density . For MHD generators to operate with good performance and the reasonable physical dimensions, the electrical conductivity lies 10 semen's per meter of plasma lies must be lie in temperature 1500-2800 F about 1800 K. 26 Abhishek Dosaya 13/003

28. Why Is need of MHD Conventional Coal Fired Generators achieve a max. efficiency of about 35%.MHD generators have the potential to reach 50%-60% efficiency. utilization of heat. The MHD process is industrial attractive because of reduced cooling requirements It has been estimated the overall operational costs of MHD plants would be about 20% less than conventional steam plants. Use MHD fluid in some nuclear reactors as coolant for Directly MHD electricity generation. 27 Abhishek Dosaya 13/003

29. Why is it not commerci al ize d Material corrosion problem created by the presence of high temperatures. Maximum enthalpy ratio remains only 8%, smaller than the target performance (30%) of a CCMHD generator. Seed material attacks insulating materials and make them conducting. The gases used as flow media are ionized only to a limited degree because their temperature must be kept within tolerance by the components of the generator. 28 Abhishek Dosaya 13/003

30. Why is it not commercialized Working temperature is very high as about 2000 k to 3000 k. Construction of generator is uneconomical due to its high cost . Selection of carrier gas, channel problem, predominant fuel. Construction of Heat resistant and non conducting ducts of generator and large superconducting magnets. 29 Abhishek Dosaya 13/003

31. Related work The first “commercial” plant will be the U-500 Ryazan Power Station. Construction on site has been initiated, the design of the plant components has been completed and consultation by U.S.S.R. industries on the manufacturing of the components is taking place. In India , it is still under construction, this construction work in in progress at TRICHI in TAMIL NADU 5MW, under the joint efforts of BARC (Bhabha atomic research center), Associated cement corporation (ACC) and Russian technologists 30 Abhishek Dosaya 13/003

32. Conclusion These systems permit better fuel utilization. The reduced fuel consumption would offer additional economic and special benefits and would also lead to conservation of energy resources. The MHD power generation is in advanced stage today and closer to commercial utilization significant process has been made in development of all critical component and subsystem technologies coal burning MHD combined steam power plant promise significant economic. Aim will be to increase enthalpy extraction ratio. 31 Abhishek Dosaya 13/003

33. Thank you 33 Abhishek Dosaya 13/003