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Open-cycle magnetohydrodynamic electrical power generation: A review and future perspectives
Abstract
R and D activities in the fields of gas-fired and coal-fired MHD power generation now discontinued are reviewed and major technological problems are summarized. Most of the problems originate from the low conductivity feature in the gas-fired case and in the low conductivity plus slagging environments in the coal-fired counterpart. It is emphasized that the high efficiency and CO2 recovery capabilities of MHD power generation, which are much greater than those of other base-load-type fossil power technologies, could be realized by investigating the inherent features of the high temperature electromagnetic turbine, using such methods as thermo-chemical conversion of heat to chemical energy, high temperature fuel preheating, and oxygen combustion. In this respect, studies on alternative MHD topping combined systems are reviewed and the predominance of these systems over the gas turbine combined cycles is emphasized. The importance of a regeneration and recirculation scheme for an efficient thermal cycle is shown, and a stand-alone-scheme of open-cycle MHD power generation system is proposed wherein high efficiency, CO2 liquefaction and a wide range of combustion temperature selectivity are emphasized.
... Most developments related to MHD technology for electricity generation have been based on the conversion of thermal energy, which is mainly obtained from sources such as fossil fuels [2], nuclear [3], solar [4], and waste heat [5], involving a wide range of operating temperatures. Plasma MHD generation, which requires high operating temperatures, was the first to be developed for large-scale applications [6]. ...
... In the early plasma MHD generation systems, an open-cycle configuration was adopted where the gas heated by combustion flows through the MHD generator and is afterward rejected into the atmosphere [2]. In the 1980s, the closed-cycle MHD generator was proposed, which allowed the operation with low-temperature plasma through non-equilibrium ionization [25]. ...
... The power density in an MHD generator is proportional to the product σB 2 u 2 [24], where σ is the electrical conductivity of the fluid, B is the applied magnetic field strength, and u the average fluid velocity in the generator. Although high speeds can be achieved through the plasma expelled from gas turbines [2], obtaining reasonable power output depends largely on having a very strong magnetic field and an adequate conductivity of the working fluid. Therefore, plasma MHD generation requires high operating temperatures since suitable conductivity can be attained by thermal ionization at temperatures in the range of 2700-3000 K. ...
Magnetohydrodynamic (MHD) generators are direct energy conversion devices that transform the motion of an electrically conducting fluid into electricity through interaction with a magnetic field. Developed as an alternative to conventional turbine-generator systems, MHD generators evolved through the 20th century from large units, which are intended to transform thermal energy into electricity using plasma as a working fluid, to smaller units that can harness heat from a variety of sources. In the last few decades, an effort has been made to develop energy conversion systems that incorporate MHD generators to harvest renewable sources such as solar and ocean energy, strengthening the sustainability of this technology. This review briefly synthesizes the main steps in the evolution of MHD technology for electricity generation, starting by outlining its physical principles and the proposals to convert thermal energy into electricity, either using a high-temperature plasma as a working fluid or a liquid metal in a one- or two-phase flow at lower temperatures. The use of wave energy in the form of acoustic waves, which were obtained from the conversion of thermal energy through thermoacoustic devices coupled to liquid metal and plasma MHD generators, as well as alternatives for the transformation of environmental energy resources employing MHD transducers, is also assessed. Finally, proposals for the conversion of ocean energy, mainly in the form of waves and tides, into electric energy, through MHD generators using either seawater or liquid metal as working fluids, are presented along with some of the challenges of MHD conversion technology.
... The magnetic coils used for MHD generators (Fig. 34.6a) have been described by Kayukawa (2004). Kayukawa reported that the saddle-type coil shown as in Fig. 34.3a is the principal design for the linear channels including the Faraday-type MHD generators (Kayukawa 2004), the diagonal type (Kayukawa 2004) and the linear Hall geometries (Kayukawa 2004). ...
... The magnetic coils used for MHD generators (Fig. 34.6a) have been described by Kayukawa (2004). Kayukawa reported that the saddle-type coil shown as in Fig. 34.3a is the principal design for the linear channels including the Faraday-type MHD generators (Kayukawa 2004), the diagonal type (Kayukawa 2004) and the linear Hall geometries (Kayukawa 2004). In an MHD generator, generally, it is found as a basic need to minimize the eddy current losses at the entrance of the channel and at the exit of the channel where no load current is extracted. ...
... The magnetic coils used for MHD generators (Fig. 34.6a) have been described by Kayukawa (2004). Kayukawa reported that the saddle-type coil shown as in Fig. 34.3a is the principal design for the linear channels including the Faraday-type MHD generators (Kayukawa 2004), the diagonal type (Kayukawa 2004) and the linear Hall geometries (Kayukawa 2004). In an MHD generator, generally, it is found as a basic need to minimize the eddy current losses at the entrance of the channel and at the exit of the channel where no load current is extracted. ...
A hybrid system consists of conventional and nonconventional energy systems for the achievement of reliable operation to keep the balance between energy supply and load demand. Various methods have been employed for planning and sizing of the hybrid energy system to get optimal location. Due to weather conditions, some renewable energy sources such as solar and wind energy may be unable to provide continuous supply. In addition, stability is an important issue. This may be voltage stability, frequency stability, and rotor angle stability. Different optimization techniques have been developed for optimizing the parameters of the hybrid energy system. This manuscript deals with a review of different hybrid energy systems with optimization techniques to achieve their best optimal location and sizing. Some planning methods have been reviewed with in this manuscript and focused on the development of a new hybrid energy system with advanced techniques.KeywordsRenewable energy systemSolar systemWind powerParticle swarm optimizationGenetic algorithmArtificial bee colony algorithm
... The magnetic coils used for MHD generators (Fig. 34.6a) have been described by Kayukawa (2004). Kayukawa reported that the saddle-type coil shown as in Fig. 34.3a is the principal design for the linear channels including the Faraday-type MHD generators (Kayukawa 2004), the diagonal type (Kayukawa 2004) and the linear Hall geometries (Kayukawa 2004). ...
... The magnetic coils used for MHD generators (Fig. 34.6a) have been described by Kayukawa (2004). Kayukawa reported that the saddle-type coil shown as in Fig. 34.3a is the principal design for the linear channels including the Faraday-type MHD generators (Kayukawa 2004), the diagonal type (Kayukawa 2004) and the linear Hall geometries (Kayukawa 2004). In an MHD generator, generally, it is found as a basic need to minimize the eddy current losses at the entrance of the channel and at the exit of the channel where no load current is extracted. ...
... The magnetic coils used for MHD generators (Fig. 34.6a) have been described by Kayukawa (2004). Kayukawa reported that the saddle-type coil shown as in Fig. 34.3a is the principal design for the linear channels including the Faraday-type MHD generators (Kayukawa 2004), the diagonal type (Kayukawa 2004) and the linear Hall geometries (Kayukawa 2004). In an MHD generator, generally, it is found as a basic need to minimize the eddy current losses at the entrance of the channel and at the exit of the channel where no load current is extracted. ...
Though the available models cannot produce the efficiency or power as Horizontal Axis Wind Turbine (HAWT), the Vertical Axis Wind Turbine (VAWT) design in recent works was reviewed for its aesthetic value and efficiency. This review will be a useful guide to modify available design for any intended purpose or provide a futuristic design which can be efficient in power generation and be an ornamental device. Besides these, the overview of recent researches in the field of wind turbine technology is covered in this book chapter. The work provides the guide to design VAWT with the information about the implementation of farm, reduction of noise, and computational techniques used in recent researches. The review of this kind always has greater importance because of the up to date information about the ongoing researches.KeywordsVAWTAerodynamic designComputational analysisExperiment methodRenewable energy
... The magnetic coils used for MHD generators (Fig. 34.6a) have been described by Kayukawa (2004). Kayukawa reported that the saddle-type coil shown as in Fig. 34.3a is the principal design for the linear channels including the Faraday-type MHD generators (Kayukawa 2004), the diagonal type (Kayukawa 2004) and the linear Hall geometries (Kayukawa 2004). ...
... The magnetic coils used for MHD generators (Fig. 34.6a) have been described by Kayukawa (2004). Kayukawa reported that the saddle-type coil shown as in Fig. 34.3a is the principal design for the linear channels including the Faraday-type MHD generators (Kayukawa 2004), the diagonal type (Kayukawa 2004) and the linear Hall geometries (Kayukawa 2004). In an MHD generator, generally, it is found as a basic need to minimize the eddy current losses at the entrance of the channel and at the exit of the channel where no load current is extracted. ...
... The magnetic coils used for MHD generators (Fig. 34.6a) have been described by Kayukawa (2004). Kayukawa reported that the saddle-type coil shown as in Fig. 34.3a is the principal design for the linear channels including the Faraday-type MHD generators (Kayukawa 2004), the diagonal type (Kayukawa 2004) and the linear Hall geometries (Kayukawa 2004). In an MHD generator, generally, it is found as a basic need to minimize the eddy current losses at the entrance of the channel and at the exit of the channel where no load current is extracted. ...
In recent years, the market of the brushless Permanent Magnet (PM) motors, such as Permanent Magnet Synchronous Motor (PMSM) and Brushless Direct Current Motor (BLDCM) drives, has become huge due to demand of the Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs). However, brushless PM drives are less robust compared to other types of motor drives due to the high acoustic noise, vibrations, and de-magnetization risk of the PM (Chan. Proc IEEE 95:704–718, 2007; Report, Implementing Agreement for Co-operation on Hybrid and Electric Vehicle Technologies and Programmed. International Energy Agency, 2016). These shortcomings pose important restrictions for critical applications. Initially, to run PMSM, Sinusoidal Pulse Width Modulation (SPWM) is implemented. But this technique generates current harmonics and high torque ripples, which ultimately leads to Acoustic Noise and Vibration (ANV) in PMSM drive. Hence, for analysis purpose, a framework based on lumped model along with effective mass and mass participation factor technique for prediction of torsional vibration in case of SPWM technique is elaborated to show detailed methodology for vibration response caused by high torque ripples. This framework is generalized in a way that can be easily extended to any mechanical power transmission system having shaft-coupler or geared system especially for EV and HEV application. Also, vibration prediction modelling is integrated with optimum number of modes or degree of freedom selection technique, which help to enhance the accuracy of model along with computationally efficient, which is the novelty of present work, which usually researchers took earlier randomly based on their setup and mass distribution without any specific technical justification. The vibration analysis reveals high torsional twisting and untwisting of shaft in case of SPWM, because of high source torque ripple. Henceforth, a Random Pulse Width Modulation (RPWM) technique for reduction of ANV is discussed in this chapter. The proposed RPWM method brings a significant reduction in torque ripples which directly influence ANV in the motor, thereby enhancing the performance of the complete drive system under operation. The relationships between the stator current harmonics feed by drive and non-sinusoidal magnetic field flux distribution, with torque ripples is developed and detailed analysis is discussed in this chapter. An extensive simulation and experimental work are carried out on a 1.07- kW, 4-poles, 36-slots, 3-phase PMSM drive for validation of proposed control strategy. In the end, experimental validation part is presented for all analytical modelling and simulation results presented in this chapter.
... Superconducting materials are the materials which exhibit no electrical resistance at their superconducting state and hence they can conduct a considerably large amount of electric currents than conventional electrical conductors. Therefor the superconducting magnets can be supplied with a large amount of electrical current producing a huge amount of magnetic fields which can be very useful in many applications where a large magnetic field is required such as MHD generating system, magnetic resonance imaging system (MRI) etc. Different types of magnetic coils for MHD generators have been discussed by Kayukawa, N. (2004) [19]. ...
... Superconducting materials are the materials which exhibit no electrical resistance at their superconducting state and hence they can conduct a considerably large amount of electric currents than conventional electrical conductors. Therefor the superconducting magnets can be supplied with a large amount of electrical current producing a huge amount of magnetic fields which can be very useful in many applications where a large magnetic field is required such as MHD generating system, magnetic resonance imaging system (MRI) etc. Different types of magnetic coils for MHD generators have been discussed by Kayukawa, N. (2004) [19]. ...
... The Hall Effect Disc Type MHD generator [19] is developed with a disc type MHD chamber through which the fluid can flow through between the centres of the disc exhausted through the ducts placed around the edge of the discs (Fig. 5). The magnetic field is produced by a two circular Helmholtz coils above and below the disk. ...
A magnetohydrodynamic (MHD) power generation technique is a nonconventional electric power harvesting modality in which the electricity is generated from an ionised fluid flow under a magnetic field. The ionized fluid moving under a magnetic field works as a moving electrical conductor and the MHD generator generates electrical energy according to the Faraday’s electromagnetic principle. The concept of MHD based electric power generation was first time introduced by Michael Faraday in 1832, and since then the MHD power generation method has been studied by several groups of researcher. In this paper the MHD technique has been discussed in details followed by a discussion on its components and instrumentation. A technical review on the research works conducted on MHD power generation has been presented and the major developments have been highlighted. The present scenario and the future trends are also discussed along with the challenges of the technology.
... 2-020-03280 -2) contains supplementary material, which is available to authorized users. high electrical conductivity metals; such as tungsten or copper, with extreme water cooling to avoid reaching melting temperatures [1,5]. With direct exposure to the seeded plasma, oxidation and potassium corrosion resulted in material failure. ...
... Alternative designs for use with coal combustion relied on a protective slag which would shield the electrodes from potassium and insulate the plasma to increase temperatures and improve efficiencies. The failure in this design was potassium diffusion through the slag, at which point the temperature at the surface of the electrodes was below the dewpoint of potassium resulting in a conductive liquid which shorted the electrode pairs [5][6][7]. A review of MHD technologies conducted in 2004 reports a more in-depth analysis of designs of MHD technologies [5]. ...
... The failure in this design was potassium diffusion through the slag, at which point the temperature at the surface of the electrodes was below the dewpoint of potassium resulting in a conductive liquid which shorted the electrode pairs [5][6][7]. A review of MHD technologies conducted in 2004 reports a more in-depth analysis of designs of MHD technologies [5]. ...
High temperature conducting ceramics are of current interest for use as electrode materials for magnetohydrodynamic (MHD) power generation systems for their high conductivity values and their excellent stability under extreme conditions including operating temperatures above 2000 °C. Ceria doped with Gd (GDC) has been extensively studied for intermediate temperature applications and shows promise as an efficient electrode material. A summary of the current understanding of the electrical properties of GDC is provided with an emphasis on the higher temperature limits. Experiments to further validate the conclusions drawn in the literature review confirm that with electrical conductivities near 10 S/m at 1100 °C make GDC a good candidate electrode material for an MHD power generator.
... The electrodes at CDIF were made of copper, as water cooled metallic electrodes became the material of choice for coal MHD due to the lack of any available hot ceramic-type electrodes which could withstand the electro-chemical attack within the MHD generator [19]. Platinum caps were used to protect the copper. ...
... Once at the cathode, the ions are neutralized and a metallic potassium layer can form causing leakage across electrode segments and "grouping" of the segments. At the gap between the newly formed electrode segment groups, the axial hall field can be exceeded, leading to electrode arcing and damage [19]. The possible solutions are 1) find a higher temperature electrode system that works for coal or 2) eliminate the slagging generator approach entirely. ...
In conventional oxy-fuel power generation scenarios, oxy-fuel combustion provides no significant advantage other than to simplify CO2 capture. So in terms of power production and efficiency, the energy and costs required to produce that oxygen are a burden. However, the high temperatures possible with oxy-fuel combustion can enable direct electric power extraction from high-temperature electrically-conductive gases using magnetohydrodynamic (MHD) principles, which would then be followed by a steam cycle also producing electricity. The combined system would produce a high CO2 exhaust stream - yet with efficiency that may exceed today's best coal power systems. The concept of adding an MHD topping unit to a coal fired power plant in order to directly extract electrical power is not new, and significant effort was made in this direction from about 1973 to 1993. During this time period, it was shown the MHD concept worked in the sense that power was generated, but ultimately development was discontinued due to the high cost of designing, constructing, and operating a complete MHD-steam plant. Additionally, there were a number of technical challenges associated with the technology. Some specific issues cited for coal MHD were slag removal problems, MHD channel operation problems, and cost effectiveness of seed utilization. In this paper, we revisit the use of MHD technology in the context of using it with oxy-combustion to enable cost effective carbon capture. Ongoing research activities within the National Energy Technology Laboratory - Regional University Alliance (NETL-RUA) to address legacy MHD power challenges, and apply new computational tools to MHD power systems are presented. Much has changed since earlier MHD studies: oxygen supplies have become less expensive (because of interest in oxy-fuel for CO2 control). Superconducting magnets have improved substantially. Perhaps the most dramatic technological improvement since previous MHD efforts is in the area of computational modeling. Today, we have three dimensional multi-physics models that could be utilized to design a more effective system (combustor and generator). To begin addressing the combustion issue, current work applies transported probability density function methods to solve the high-temperature combustion problem. An MHD generator model, which considers fluid dynamics and heat transfer, as well as relevant MHD equations involved in the process, is presented. The modeling efforts also address issues in using wall functions to bridge the laminar sublayer to the fully turbulent boundary layer when Lorentz force is dominant or equally important as compared to other forces.
... This alkali metal can be introduced into the combustor as an alkaline salt compound added to the reactants. For example, potassium carbonate (K 2 CO 3 ) can be used for potassium [5]. Alkali metals have low ionization energies, making them much more ionizable than conventional combustion gases (namely CO 2 and H 2 O), which in turn makes them practically the only source of electrons in the hot-gas plasma. ...
... An alternative term for this plasma class is thermal plasma, and quasi-equilibrium plasma. Examples include combustion-gas plasma [5] solar plasma, and arc discharge (electrical breakdown of a normally-nonconductive gas). We here focus on this class of plasma. ...
This work presents a multidisciplinary mathematical model, as a set of coupled governing equations and auxiliary relations describing the fluid-flow, thermal, and electric fields of partially-ionized plasma with low magnetic Reynolds numbers. The model is generic enough to handle three-dimensionality, Hall effect, compressibility, and variability of fluid, thermal, and electric properties of the plasma. The model can be of interest to computational modelers aiming to build a solver that quantitatively assesses direct extraction of electric energy from a plasma flow. Three different approaches are proposed to solve numerically for the electric fields with different levels of tolerance toward possible numerical instability encountered at a large Hall parameter, where the effective conductivity tensor loses diagonal dominance and becomes close to singular. A submodel for calculating the local electric properties of the plasma is presented in detail and is applied to demonstrate the effect of different factors on the electric conductivity, including the fuel's carbon/hydrogen ratio and the alkaline seed element that acts as the ionizing species. An analytical expression for the collision cross-section for argon is developed, such that this noble gas can be included as one of the gaseous species comprising the plasma.
... This alkali metal can be introduced into the combustor as an alkaline salt compound added to the reactants. For example, potassium carbonate (K 2 CO 3 ) can be used for potassium [5]. Alkali metals have low ionization energies, making them much more ionizable than conventional combustion gases (namely CO 2 and H 2 O), which in turn makes them practically the only source of electrons in the hot-gas plasma. ...
... An alternative term for this plasma class is thermal plasma, and quasi-equilibrium plasma. Examples include combustion-gas plasma [5] solar plasma, and arc discharge (electrical breakdown of a normally-nonconductive gas). We here focus on this class of plasma. ...
... An MHD power plant employing such an arrangement is known as an opencycle , or once-through, system. Figure 6: The typical open cycle scheme for a coal-firedMHD systems [9] The Figure 6 shows the typical open cycle scheme for a coalfired MHD systems for electric power production Coal combustion as a source of heat has several advantages [9]. For example, it results in coal slag, which under magnetohydrodynamic conditions is molten and provides a layer that covers all of the insulator and electrode walls The electrical conductivity of this layer is sufficient to provide conduction between the gas and the electrode structure but not so high as to cause significant leakage of electric currents and consequent power loss. ...
... An MHD power plant employing such an arrangement is known as an opencycle , or once-through, system. Figure 6: The typical open cycle scheme for a coal-firedMHD systems [9] The Figure 6 shows the typical open cycle scheme for a coalfired MHD systems for electric power production Coal combustion as a source of heat has several advantages [9]. For example, it results in coal slag, which under magnetohydrodynamic conditions is molten and provides a layer that covers all of the insulator and electrode walls The electrical conductivity of this layer is sufficient to provide conduction between the gas and the electrode structure but not so high as to cause significant leakage of electric currents and consequent power loss. ...
Magnetohydrodynamic (MHD) power generation process is basically based on the physics background of space plasma. The basic principle is the Faradays Law of electromagnetic induction. In this device plasma (Ionized gas) is the working fluid similar to the mechanism that happening in the magnetosphere of our earth's atmosphere. Except here the process is controlled and we increase the fluid density and pressure to get maximum efficiency in the generating power. Most problems come from the low conductivity feature in the gas at high temperature. High temperature gaseous conductor at high velocity is passed through a powerful magnetic field and a current is generated and extracted by placing electrodes at suitable position in the gas stream, and hence the thermal energy of gas is directly converted in to electrical energy. In this paper the process involved in MHD power generation will be discussed in detail along with the simplified analysis of MDH system and recent developments in magnetohydrodynamics and their related issues.
... The high-speed plasma loses part of its energy in reaction to an applied magnetic field, where an induced electric field allows collecting an induced electric current to power an external electric load [83][84][85]. This concept of hydrogen-powered magnetohydrodynamic power generation, which we refer to here as (H2MHD), can be combined with a classical power cycle [86][87][88] for better utilization of the input heat released from the zero-emission hydrogen combustion through a dual-cycle power plant, comprised of a higher-temperature open-cycle MHD (OCMHD) generator and either a lower-temperature closed-cycle Rankine system or a lower-temperature opencycle Brayton system [89][90][91]. A triple combined cycle that incorporates the open-cycle MHD (OCMHD) generator as a topping layer (high temperature) with an intermediate layer having an open-cycle Brayton gas turbine (intermediate temperature) and then a layer of a closed-cycle steam turbine (low temperature) is also possible, to recover part of the rejected heat containing in the stillhot plasma gas leaving the MHD generator [92][93][94]. ...
Hydrogen and some of its derivatives (such as e-methanol, e-methane, and e-ammonia) are promising energy carriers that have the potential to replace conventional fuels, thereby eliminating their harmful environmental impacts. An innovative use of hydrogen as a zero-emission fuel is being a source of weakly-ionized plasma through seeding its combustion products with a small amount of an alkali metal vapor (cesium or potassium). This plasma can be used as the working fluid in supersonic open-cycle magnetohydrodynamic (OCMHD) power generators. In such OCMHD generators, direct-current (DC) electricity is generated directly without moving turbogenerators. In the current study, we quantitatively and qualitatively explore the levels of electric conductivity and the resultant volumetric electric output power density in a typical OCMHD supersonic channel, where thermal equilibrium plasma is accelerated at a Mach number of two (Mach 2) while being subject to a strong applied magnetic field (applied magnetic-field flux density) of five teslas (5 T), and with the assumption of an isothermal temperature of 2,300 K (2,026.85 °C). We varied the total pressure of the pre-ionization seeded gas mixture between 1/16 atm and 16 atm. We varied the seed level between 0.0625% and 16% (pre-ionization mole fraction). We varied the seed type between cesium and potassium. We varied the oxidizer type between air (oxygen-nitrogen mixture, 21%-79% by mole) and pure oxygen. Our results suggest that the ideal power density can reach exceptional levels beyond 1,000 MW/m3 (or 1 kW/cm3). The power density can be enhanced using any of the following techniques: (1) lower total pressures, (2) using cesium instead of potassium for seeding, and (3) using air instead of oxygen as an oxidizer (if the temperature is unchanged). A seed level between 1% and 4% (pre-ionization mole fraction) is recommended (much lower or much higher seed levels are harmful to the OCMHD performance). The seed level that maximizes the electric power is not necessarily the same seed level that maximizes the electric conductivity due to additional thermochemical changes caused by the additive seed.
... Magnetohydrodynamic power generators (Messerle, 1995;Kayukawa, 2004;Woodside et al., 2012) are chambers where high-speed electrically-conducting hot plasma expands while subject to an applied magnetic field. This leads to the generation of direct-current electricity based on Faraday's law of induction without the conventional turbo-generators. ...
... Magnetohydrodynamic power generators (Messerle, 1995;Kayukawa, 2004;Woodside et al., 2012) are chambers where high-speed electrically-conducting hot plasma expands while subject to an applied magnetic field. This leads to the generation of direct-current electricity based on Faraday's law of induction without the conventional turbo-generators. ...
Oxy-fuel carbon capture in power plants is a relatively new concept aiming at reducing carbon dioxide emissions from the plants. This is achieved by burning the fossil fuel using oxygen as oxidizer with no nitrogen, thereby rendering the exhaust gases very rich in carbon dioxide (after condensing water vapor by cooling), which facilitates its capture for environmental or commercial purposes. Despite the worldwide interest in oxy-fuel carbon capture, its progress is at risk given the large energy needed to separate oxygen from air in order to provide the oxidizer, thereby hindering further progress of this concept toward large-scale applications. This paper focuses on alleviating this drawback of oxy-fuel combustion by making it more attractive through combining it with another concept, namely magnetohydrodynamic (MHD) power generators. The end product is a power plant operating on a combined cycle composed of a topping MHD ultra-high-temperature cycle with direct electricity extraction from plasma, followed by a bottoming steam cycle with conventional turbo-generators. Different design aspects and simplified technical analysis for the MHD generator are presented.
... A recovery process allows the reuse of the cesium leaving the MHD channel, which is then diverted to the MHD inlet stream. Despite the loss of energy contained in the plasma during the power extraction process and the drop in its temperature at the end of the supersonic MHD channel (this energy is transformed into electricity), its exit temperature and thermal energy are expected to be high enough to allow further extraction of this energy but as heat, rather than as electricity [119], [120], [121]. This takes place by first slowing down the still-supersonic exit plasma to subsonic speeds using a divergent diffuser; and then a heat recovery steam generator (HRSG) is used to transfer heat from the hot exhaust gases to liquid water for boiling and superheating it, to make it superheated steam that is suitable for operating one or more steam turbines, which are connected to conventional mechanical turbogenerators that generate alternating current (AC) electricity, which can be fed into the electric grid as a second stage of a magnetohydrodynamic (MHD) power plant [122], [123], [124], [125], [126]. ...
This study explores the suitability of hydrogen-based plasma in direct power extraction (DPE) as a non-conventional electricity generation method. We apply computational modeling and principles in physics and chemistry to estimate different thermal and electric properties of a water-vapor/nitrogen/cesium-vapor (H2O/N2/Cs) gas mixture with different levels of cesium (Cs) at a fixed temperature of 2300 K (2026.85 {\deg}C). This gas mixture and temperature are selected because they resemble the stoichiometric combustion of hydrogen with air, followed by the addition of the alkali metal element cesium to allow ionization, thus converting the gas mixture into electrically conducting plasma. We vary the cesium mole fraction in the gas mixture by two orders of magnitude, from a minute amount of 0.0625% (1/1600) to a major amount of 16% (0.16). We use these results to further estimate the theoretical upper limit of the electric power output from a unit volume of a high-speed magnetohydrodynamic (MHD) channel, with the plasma accelerated inside it to twice the local speed of sound (Mach number 2) while subject to an applied magnetic field of 5 T (5 teslas). We report that there is an optimum cesium mole fraction of 3%, at which the power output is maximized. Per 1 m3 of plasma volume, the estimated theoretical electric power generation at 1 atm (101.325 kPa) pressure of the hydrogen-combustion mixture is extraordinarily high at 360 MW/m3, and the plasma electric conductivity is 17.5 S/m. This estimated power generation even reaches an impressive level of 1.15 GW/m3 (11500 MW/m3) if the absolute pressure can be decreased to 0.0625 atm (6.333 kPa), at which the electric conductivity exceeds 55 S/m (more than 10 times the electric conductivity of seawater).
... A recovery process allows reusing the cesium leaving the MHD channel, which is then diverted to the MHD inlet stream. Despite the loss of energy contained in the plasma during the power extraction process and the drop in its temperature at the end of the supersonic MHD channel (this energy is transformed into electricity), its exit temperature and thermal energy are expected to be high enough to allow further extraction of this energy but as heat, rather than as electricity [119]- [121]. This takes place by first slowing down the still-supersonic exit plasma to subsonic speeds using a divergent diffuser; and then a heat recovery steam generator (HRSG) is used to transfer heat from the hot exhaust gases to liquid water for boiling and superheating it, to make it superheated steam that is suitable for operating one or more steam turbines, which are connected to conventional mechanical turbogenerators that generate alternating current (AC) electricity, which can be fed into the electric grid as a second stage of a magnetohydrodynamic (MHD) power plant [122]- [126]. ...
This study explores the suitability of hydrogen-based plasma in direct power extraction (DPE) as a non-conventional electricity generation method. We apply computational modeling and principles in physics and chemistry to estimate different thermal and electric properties of a water-vapor/nitrogen/cesium-vapor (H
2
O/N2/Cs) gas mixture with different levels of cesium (Cs) at a fixed temperature of 2300 K (2026.85 °C). This gas mixture and temperature are selected because they resemble the stoichiometric combustion of hydrogen with air, followed by the addition of the alkali metal element cesium to allow ionization, thus converting the gas mixture into electrically conducting plasma. We vary the cesium mole fraction in the gas mixture by two orders of magnitude, from a minute amount of 0.0625% (1/1600) to a major amount of 16% (0.16). We use these results to further estimate the theoretical upper limit of the electric power output from a unit volume of a high-speed magnetohydrodynamic (MHD) channel, with the plasma accelerated inside it to twice the local speed of sound (Mach number 2) while subject to an applied magnetic field of 5 T (5 teslas). We report that there is an optimum cesium mole fraction of 3%, at which the power output is maximized. Per 1 m
3
of plasma volume, the estimated theoretical electric power generation at 1 atm (101.325 kPa) pressure of the hydrogen-combustion mixture is extraordinarily high at 360 MW/m
3
, and the plasma electric conductivity is 17.5 S/m. This estimated power generation even reaches an impressive level of 1.15 GW/m
3
(11500 MW/m
3
) if the absolute pressure can be decreased to 0.0625 atm (6.333 kPa), at which the electric conductivity exceeds 55 S/m (more than 10 times the electric conductivity of seawater).
... This is unlike ionization established by electric glow discharge in fluorescent lighting tubes [62,63], where p ʹ s Partial static pressure of the seeded alkali metal vapor before ionization, the "seeding pressure", p ʹ s = X electrons have a temperature that is higher than the temperature of ions and other heavy particles. In MHD plasma based on combustion product gases (flue gases), electrons and heavy particles are in thermal equilibrium due to high collision frequencies and energy exchange per collision [64], leading to a "thermalization" process by which the temperature becomes uniformly distributed [65]. ...
A complete model for estimating the electric conductivity of combustion product gases, with added cesium (Cs) or potassium (K) vapor for ionization, is presented. Neutral carrier gases serve as the bulk fluid that carries the seed material, as well as the electrons generated by the partial thermal (equilibrium) ionization of the seed alkali metal. The model accounts for electron-neutral scattering, as well as electron-ion and electron-electron scattering. The model is tested through comparison with published data. The model is aimed at being utilized for the plasma within magnetohydrodynamic (MHD) channels, where direct power extraction from passing electrically conducting plasma gas enables electric power generation. The thermal ionization model is then used to estimate the electric conductivity of seeded combustion gases under complete combustion of three selected fuels, namely: hydrogen (H2), methane (CH4), and carbon (C). For each of these three fuels, two options for the oxidizer were applied, namely: air (21 % molecular oxygen, 79 % molecular nitrogen by mole), and pure oxygen (oxy-combustion). Two types of seeds (with 1 % mole fraction, based on the composition before ionization) were also applied for each of the six combinations of (fuel-oxidizer), leading to a total of 12 different MHD plasma cases. For each of these cases, the electric conductivity was computed for a range of temperatures from 2000 K to 3000 K. The smallest estimated electric conductivity was 0.35 S/m for oxy-hydrogen combustion at 2000 K, with potassium seeding. The largest estimated electric conductivity was 180.30 S/m for oxy-carbon combustion at 3000 K, with cesium seeding. At 2000 K, replacing potassium with cesium causes a gain in the electric conductivity by a multiplicative gain factor of about 3.6 regardless of the fuel and oxidizer. This gain factor declines to between 1.77 and 2.07 at 3000 K.
... This is unlike ionization established by electric glow discharge in fluorescent lighting tubes [62,63], where p ʹ s Partial static pressure of the seeded alkali metal vapor before ionization, the "seeding pressure", p ʹ s = X electrons have a temperature that is higher than the temperature of ions and other heavy particles. In MHD plasma based on combustion product gases (flue gases), electrons and heavy particles are in thermal equilibrium due to high collision frequencies and energy exchange per collision [64], leading to a "thermalization" process by which the temperature becomes uniformly distributed [65]. ...
A complete model for estimating the electric conductivity of combustion product gases, with added cesium (Cs) or potassium (K) vapor for ionization, is presented. Neutral carrier gases serve as the bulk fluid that carries the seed material, as well as the electrons generated by the partial thermal (equilibrium) ionization of the seed alkali metal. The model accounts for electron-neutral scattering, as well as electron-ion and electron-electron scattering. The model is tested through comparison with published data. The model is aimed at being utilized for the plasma within magnetohydrodynamic (MHD) channels, where direct power extraction from passing electrically conducting plasma gas enables electric power generation.
The thermal ionization model is then used to estimate the electric conductivity of seeded combustion gases under complete combustion of three selected fuels, namely: hydrogen (H2), methane (CH4), and carbon (C). For each of these three fuels, two options for the oxidizer were applied, namely: air (21 % molecular oxygen, 79 % molecular nitrogen by mole), and pure oxygen (oxy-combustion). Two types of seeds (with 1 % mole fraction, based on the composition before ionization) were also applied for each of the six combinations of (fuel-oxidizer), leading to a total of 12 different MHD plasma cases. For each of these cases, the electric conductivity was computed for a range of temperatures from 2000 K to 3000 K.
The smallest estimated electric conductivity was 0.35 S/m for oxy-hydrogen combustion at 2000 K, with potassium seeding. The largest estimated electric conductivity was 180.30 S/m for oxy-carbon combustion at 3000 K, with cesium seeding. At 2000 K, replacing potassium with cesium causes a gain in the electric conductivity by a multiplicative gain factor of about 3.6 regardless of the fuel and oxidizer. This gain factor declines to between 1.77 and 2.07 at 3000 K.
Based on the findings of this research study, the four analyzed factors to increase the electric conductivity of MHD plasma can be listed by their significance (descending order) as (1) type of additive seed type (cesium is better than potassium), (2) temperature (the higher the better), (3) carbon-to-hydrogen ratio of the fuel (the higher the better), and finally (4) the oxidizer type (air is generally better than pure oxygen).
The relative size of the two electric conductivity components (due to neutrals scattering and Coulomb scattering) at various plasma conditions are discussed, and a threshold of 10⁻⁵ (0.001 %) electrons mole fraction is suggested to safely neglect Coulomb scattering.
... Since the beginning of the twentieth century, the applicability of Magnetohydrodynamic (MHD) Generators for the replacement of gas turbine-based energy conversion has been widely investigated [1][2][3][4][5][6][7][8]. Without the utilization of any mechanically moving part, the MHD power generation can convert thermal energy into electrical energy, and so this energy conversion system has attracted much attention [9][10][11][12]. ...
This study presents the supersonic inductive Magnetohydrodynamic (SIMHD) generator and simulates its model through the use of COSMOL Multiphysics. This generator, as an inductive MHD generator, is suggested to address the problems associated with the conventional MHD generator. Since the proposed generator does not require a moving part to convert thermal energy to electrical energy, it is categorized as a direct energy convertor. The SIMHD generator consists of a converging-diverging duct and is divided into two sections at the diverging part by means of a diaphragm. Both of these sections are diverging, which makes it possible to obtain a high Mach number. In this regard, the performance of the SIMHD generator is studied by its mathematical modeling and numerical simulation using the finite element method. In addition, a sensitivity analysis is carried out on the design parameters. The results indicate that the proposed SIMHD duct design will increase the speed from 160 to 1300 m⁄s, and decrease the temperature from 2100 to 1300 K. Moreover, considering a charge generation equation, the produced power for the resistive load 50 Ω equals 25.3 kW. This generator also has the potential to be used in scramjets and ramjets.
... The idea of MHD plasma power generation is not new and has been studied experimentally, analytically, or computationally for years (Blackman et al., 1961;Wright, 1963;Jones, 1985;Rosa et al., 1991;Borghi et al., 1992;Davidson, 2001;Panchenko, 2002;Kayukawa, 2004;Ishikwa et al., 2007;Sarkar, 2017). Despite this, the concept of plasma power plant has not been used practically at commercial levels because economically it is not favorable compared to other technologies of power plants that have comparable efficiency but with less initial and operational cost, such as combined cycle gas turbines (CCGT) power plants, whose LHV (lower heating value) efficiency can reach nearly 50% (Takeishi and Krewinkel, 2023). ...
Magnetohydrodynamics (MHD) is a subject concerned with the dynamics of electrically conducting fluids (plasma) and can be applied in electric power generation. As a unique technology for producing direct-current electricity without moving parts, it can be utilized within a high-temperature topping power cycle to be combined with a traditional bottoming power cycle, forming a combined-cycle MHD system. This study presents governing equations for the electric field and current density field within a moving plasma subject to an applied magnetic field. The modeling equations are described at four descending levels of complexity. Starting with the first level of modeling, which is the most general case, where no assumptions are made regarding the electric field, plasma velocity field, applied magnetic field, or electrode geometry. In the second level of modeling, the magnetic field is treated as one-dimensional. In the third level of modeling, a specific Faraday-type magnetohydrodynamics plasma generator channel is considered, having two continuous electrodes acting as parallel constant-voltage terminals. In the fourth (and simplest) level of modeling, an additional approximation is made by setting the Hall parameter to zero and replacing all vector fields with scalar quantities. For that simplest model, a representative set of operation conditions (electric conductivity 20 S/m, temperature 2800 K, supersonic plasma gas speed 2000 m/s with Mach 2.134, and magnetic flux density 5 T) shows that the optimum idealized electric power that can be extracted from a unit volume of plasma is estimated as 500 MW/m3. This is a much larger volumetric power density than typical values encountered in reciprocating piston-type engines (0.2 MW/m3) or rotary gas turbine engines (0.5 MW/m3). Such an extremely high power density enables very compact power generation units.
... This additive ionizable substance (also called the seed) can be cesium vapor, potassium vapor, or a compound containing either of them. Some of the electrons in the seed atoms are liberated under the influence of the high temperature of the carrier combustion product gases, making the gaseous mixture electrically conductive, thus making it a plasma gas [23]. Knowing the chemical composition and the electric conductivity of this plasma gas is an important step during the CFD modeling, which eventually allows for predicting the electric power output that can be extracted from the flowing plasma gas inside the MHD system, which acts as a very powerful source of electricity. ...
The collision cross sections (CCS), momentum transfer cross sections (MTCS), or scattering cross sections (SCS) of an electron–neutral pair are important components for computing the electric conductivity of a plasma gas. Larger collision cross sections for electrons moving freely within neutral particles (molecules or atoms) cause more scattering of these electrons by the neutral particles, which leads to degraded electron mobility, and thus reduced electric conductivity of the plasma gas that consists of electrons, neutral particles, and ions. The present work aimed to identify the level of disagreement between four different methods for describing how electron–neutral collision cross sections vary when they are treated as a function of electron temperature alone. These four methods are based on data or models previously reported in the literature. The analysis covered six selected gaseous species that are relevant to combustion plasma, which are as follows: carbon monoxide (CO), carbon dioxide (CO2), molecular hydrogen (H2), water vapor (H2O), potassium vapor (K), and molecular oxygen (O2). The temperature dependence of the collision cross sections for these species was investigated in the range from 2000 K to 3000 K, which is suitable for both conventional air–fuel combustion and elevated-temperature oxygen–fuel (oxy-fuel) combustion. The findings of the present study suggest that linear functions are enough to describe the variations in the collision cross sections of the considered species in the temperature range of interest for combustion plasma. Also, the values of the coefficient of variation (defined as the sample standard deviation divided by the mean) in the collision cross sections using the four methods were approximately 27% for CO, 42% for CO2, 13% for H2, 39% for H2O, 44% for K, and 19% for O2. The information provided herein can assist in simulating magnetohydrodynamic (MHD) power generators using computational fluid dynamics (CFD) models for combustion plasma flows.
... There are three fundamental methods to MHD power generation: open cycle, closed cycle plasma and closed liquid-metal systems. In open cycle MHD systems, the working fluid is emitted in the atmosphere after the electricity generation [30][31][32][33][34], the closed cycle MHD system does an extra step, it recycles the working fluid in order to make use of the thermal energy present in the fluid as it exits the MHD chamber (after the electricity has generated by MHD system) [35] whereas closed liquid-metal MHD systems, the liquid metals is used as the electrically conducting fluids and that is why it is called liquid-metal MHD generators [36,37]. The liquid metals can be used as conducting fluids in MHD generators because the metals have extremely high electrical conductivity. ...
A layout of urban waste fired zero emission power plant is described in this paper. The principle of layout, which comes from similar coal-fired plants retrieved from the literature, integrates gasification with a power generation section, and implements two parallel conversion processes, one supplied by the heat of the gasifier consisting of a thermoacousticmagnetohydrodynamic (TAMHD) generator, while in the second one the syngas is treated in order to obtain almost pure hydrogen, which is fed to fuel cells. The CO2 deriving from the oxidation of Carbon base is stocked in liquid form. The novelty of the proposed layout lies in the fact that the entire conversion is performed without solid moving parts. The resulting plant avoids any type of emissions in the atmosphere, increases mechanical efficiency as compared to traditional plants, thanks to the absence of moving parts, nonetheless, resolving at its root the ever-increasing waste-related pollution problems.
... Magnetohydrodynamic (MHD) power generation is quickly becoming a key power generation system because it has the highest theoretical thermodynamic efficiency of any other electrical generation method [1]. Magnetohydrodynamic generators (MHDG) directly convert heat into electricity, making them reliable as both a mechanical system and a power plant [2]. ...
... In an MHD generator, thermal plasma is moving across a magnetic field generating electric power (Salvatore and Alessandra, 2014). Open-cycle and Closed-cycle MHD generators are the two of MHD systems under consideration in Fig.11 and 12, classified on the basis of the working fluid and the heat source [72]. MHD generator is classified in three different designs which are Faraday generator, Hall generator and Disk generator. ...
The primary objective of this study is to investigate economic freedom of access to energy, energy utilization and consumption, improve energy security, mitigate climate change and ignite interest in various renewable energy sources in developing countries. Sustainable development is the benefit that meet the needs of the people without compromising access to affordability, reliability, sustainability and modern quality of human satisfaction of its citizens within the limitation of the environment. It has become widely recognized that the rising environmental hazards, depletion threatened the unreliable supply of electricity with huge economic cost associated with fossil fuel has made renewable energy issue a significant sustainability resource as the basic requirements for development in developing countries. This paper aims to present review and promote access to harnessing, harvesting, storage, conversion and technology of renewable energy sources for generating electricity in developing nations by 2050. In this review, we have identified the various renewable energy sources, challenges and benefits. The recommendation on this investigation shows greatly our contributions to the aspiration of citizens in developing countries for alleviating struggles to overcome the epileptic power supply that has harassed the economy of the nation in jeopardy for long time.
... The e ciency of such systems is, however, subject to fundamental limitations, as dictated by the laws of thermodynamics and other scienti c principles. In recent years, considerable attention has been devoted to certain direct energyconversion devices that bypass the intermediate step of conversion to heat energy in electrical power generation [23,24]. Although the total amount of energy in an isolated system remains unchanged, there may be a great difference in the quality of different forms of energy. ...
Many attempts have been made to understand the underlying principles of design and operation for portable hydrogen production systems. However, the mechanisms for the effects of design factors on heat transfer characteristics are still not fully understood. This study relates to a thermochemical process for producing hydrogen by the catalytic endothermic reaction of methanol with steam in a thermally integrated microchannel reforming reactor. Computational fluid dynamics simulations are conducted to better understand the consumption, generation, and exchange of thermal energy between endothermic and exothermic processes in the reactor. The effects of wall heat conduction properties and channel dimensions on heat transfer characteristics and reactor performance are investigated. Coupling of steam reforming of methanol with methanol catalytic combustion in a thermally integrated microchannel reforming reactor is simulated for both co-current and counter-current operation, using identical parameters of the mathematical model. A direct comparison between the reactor behavior and performance under different flow arrangements is made. The results indicate that reactor performance and thermal behavior is strongly affected by overall and local balance between heat generated on the exothermic side and heat consumed on the endothermic one, which in turn is influenced by flow arrangement. The thermal conductivity of the channel walls is fundamentally important. Reaction heat flux profiles are considerably affected by channel dimensions. The peak reaction heat flux increases with the channel dimensions while maintaining the flow rates. Design recommendations are made to improve thermal performance for the reactor. The reactor is better balanced thermally for co-current operation. For counter-current arrangement, higher conversions and better utilization of the overall heat generated in the exothermic process are achieved at the expense of pronounced temperature extremes. This increases the chances of the reactor running away and of homogeneous combustion being initiated. Utilization of a non-uniform catalyst distribution can overcome the heat imbalance by inducing favorable reactant depletion along the reactor during counter-current flow.
... The generator exhaust gases which are still at a higher temperature but insufficient for MHD power generation can be passed through a suitable heat exchanger for heat recoveries such as the air preheater and some kind of heat recovery steam generators (HRSGs). A standalone MHD plant by itself is less efficient due to the irreversibility present in the system and perform well in combination with other power generating systems [7][8]. Hence, it is extremely necessary to find the real position, causes and amount of irreversibility for the improvement of the MHD system. ...
Sustainable and environmental friendly energy extraction and utilization is the foremost priority of the energy sector to meet the present and near future energy demands. The need of the day is to have efficient and eco-friendly energy conversion technologies either through the enhancement of the existing technologies or the development of some all-new technology. The present study investigates a standalone open-cycle Magnetohydrodynamic (MHD) power generation system using the advanced exergy analysis analytically. The effects of distributing the exergy destruction into endogenous/exogenous and avoidable/unavoidable on the improvement possibilities and the mutual interlinkages among the different units of the MHD system have been studied. The results showed that the MHD system has a higher possibility of its further development due to low unavoidable (36.82%) and high avoidable (63.18%) exergy desolation rates. The interlinkages among various units of the MHD system were found to be reasonably stronger due to the higher rate of exergy destruction of the endogenous type as compared to the exogenous portion. In the present study, the combustion chamber is found to have the highest possibility of upgradation as it possesses the largest value of avoidable exergy destruction rate together with the maximum rate of avoidable endogenous portion of the exergy destruction.
... From Equation 22, when the load factor (0 ≤ k ≤ 1) is approximately 0.5, the internal resistance of the generator equals the external load resistance. Hence, the maximum power, Pmax, that can be extracted is given by (Kayukawa 2004;Sivaram et al. 2015), ...
In many developing countries,the use of conventional power plants to generate electricity is not meeting the increasing demands. Therefore, it has become important to find sustainable alternatives. In the present study, a solar hybrid combined cycle power plant consisting of a solar thermal plant, large-scale gas and steam turbines, and a magnetohydrodynamic generator has been investigated under oxy-fuel combustion. The performance analysis of this system under fuel pressure rate varying from 10 to 25 bar was conducted using Cycle Tempo software. The analysis of the gas and steam combined cycle shows that the net powers and the net efficiencies obtained ranged from 98 MWe to 134 MWe and 30.5% to 40%, respectively. In addition, the integration of the magnetohydrodynamic generator to the combined cycle led to an increase in the overall power from 169 MWe to 205 MWe. Moreover, it is seen that the fuel mass rate (2.81 kg/s) obtained in the gas turbine system under oxy-fuel combustion is significantly reduced when compared to conventional systems. The incorporation of solar energy and oxy-fuel combustion in the gas turbine system has increased the combustor inlet and outlet temperature and reduced the fuel consumption. From these observations, the solar hybrid system proposed in this study does not only generates electric power but also reduce the turbine exhaust fumes and CO2 emissions, which is a key factor in minimizing environment pollution.
... [2][3][4] Most of the research in this field has focused on boundary layer flow control. 5,6 In MHD, a magnetic fluid is used and this technology has been used in power generation, aviation, navigation, and other fields; [7][8][9] the main focus has been on MHD flow control, 10,11 MHD acceleration, 12,13 MHD power generation, [14][15][16][17] and MHD combined engines. 18 Sun 19 and Luo 20 et al. conducted experimental studies on the deflection of a gas plasma jet by injecting Cs 2 CO 3 ionization seed into a combustion chamber under an external magnetic field. ...
This paper presents an integrated research scheme for vector deflection and energy extraction in a gas plasma jet under Magneto-Hydrodynamic (MHD) control. A MHD-controlled thrust-vector test rig was used to conduct the experimental research. A gas plasma was obtained by injecting ionization seeds of Cs2CO3 into the combustion chamber via artificially forced ionization. The effects of the gas temperature and ionization seed mass fraction on the plasma jet deflection and energy extraction were experimentally verified under an applied magnetic field. The experimental results were analyzed theoretically. The results showed that the deflection amplitude of the gas plasma jet and the extracted voltage signal intensity increased with increasing gas temperature and the ionization seed mass fraction. The extracted dynamic voltage signals proved that the ionization seeds of Cs2CO3 induced gas ionization at 1173 K. The experiment verified that it is feasible to simultaneously achieve jet deflection and extract energy under the action of an external magnetic field.
... Magnetohydrodynamic power generators (Messerle, 1995;Kayukawa, 2004;Woodside et al., 2012) are chambers where high-speed electrically-conducting hot plasma expands while subject to an applied magnetic field. This leads to the generation of direct-current electricity based on Faraday's law of induction without the conventional turbo-generators. ...
Oxy-fuel carbon capture in power plants is a relatively new concept aiming at reducing carbon dioxide emissions from the plants. This is achieved by burning the fossil fuel using oxygen as oxidizer with no nitrogen, thereby rendering the exhaust gases very rich in carbon dioxide (after condensing water vapor by cooling), which facilitates its capture for environmental or commercial purposes. Despite the worldwide interest in oxy-fuel carbon capture, its progress is at risk given the large energy needed to separate oxygen from air in order to provide the oxidizer, thereby hindering further progress of this concept toward large-scale applications. This paper focuses on alleviating this drawback of oxy-fuel combustion by making it more attractive through combining it with another concept, namely magnetohydrodynamic (MHD) power generators. The end product is a power plant operating on a combined cycle composed of a topping MHD ultra-high-temperature cycle with direct electricity extraction from plasma, followed by a bottoming steam cycle with conventional turbo-generators. Different design aspects and simplified technical analysis for the MHD generator are presented.
... Although ionization seeds can be used to lower this temperature, it still exceeds 2000~2500 K [6,7]. In addition, there is another crucial technical problem to overcome-the slagging [8]. ...
Liquid metal MHD (Magneto-Hydro-Dynamic) systems can be employed to produce electricity from a wide range of heat resources. In such a system, a low-boiling organic fluid and a high-temperature liquid metal fluid mix. The former evaporates, and carries the latter to flow through an MHD channel, where the electricity is generated. The mixing process and the gas-liquid flow characteristics will have a significant effect on the power generating efficiency. In the present work, trifluorotrichloroethane (R113) was chosen as the organic fluid, and gallium (Ga) as the liquid metal, respectively. Numerical study was subsequently carried out on the gas-liquid flow and heat transfer in a self-designed spherical mixer. The effects of the main factors, including the inlet velocities and inlet temperatures of Ga and R113, were separately determined, with suggested values or ranges discussed in detail.
... Open-cycle magneto-hydrodynamic (MHD) electrical power generation has been considered as an option for hydrogen production [105]. A high-efficiency MHD system with regeneration and recirculation of the high-temperature exhaust is used to provide heat to produce chemical energy thermo-chemically and to preheat fuel. ...
Solid fuels such as coal, biomass and solid waste are increasingly used with water to produce hydrogen, and the conversion processes have been enhanced through recent developments. An extended review of selected research and recent advances into hydrogen production from solid fuels is presented in this paper, focusing on novelty, understanding and application. Suggestions from the review include increasing attention on minimization of waste (material and energy) in processes through proper sizing of unit operations, especially those involving catalysts and rare chemical compounds; minimizing the number of components in solid fuels-to-hydrogen processes; increasing flexibility regarding demand-based operation of the system; proper integration of the benefits of new processes; adding multi-product capability to satisfy hydrogen demand; and coordinating the use of waste heat within systems.
Hydrogen and some of its derivatives (such as e-methanol, e-methane, and e-ammonia) are promising energy carriers that have the potential to replace conventional fuels, thereby eliminating their harmful environmental impacts. An innovative use of hydrogen as a zero-emission fuel is forming weakly ionized plasma by seeding the combustion products of hydrogen with a small amount of an alkali metal vapor (cesium or potassium). This formed plasma can be used as a working fluid in supersonic open-cycle magnetohydrodynamic (OCMHD) power generators. In these OCMHD generators, direct-current (DC) electricity is generated straightforwardly without rotary turbogenerators. In the current study, we quantitatively and qualitatively explore the levels of electric conductivity and the resultant volumetric electric output power density in a typical OCMHD supersonic channel, where thermal equilibrium plasma is accelerated at a Mach number of two (Mach 2) while being subject to a strong applied magnetic field (applied magnetic-field flux density) of five teslas (5 T), and a temperature of 2300 K (2026.85 °C). We varied the total pressure of the pre-ionization seeded gas mixture between 1/16 atm and 16 atm. We also varied the seed level between 0.0625% and 16% (pre-ionization mole fraction). We also varied the seed type between cesium and potassium. We also varied the oxidizer type between air (oxygen–nitrogen mixture, 21–79% by mole) and pure oxygen. Our results suggest that the ideal power density can reach exceptional levels beyond 1000 MW/m3 (or 1 kW/cm3) provided that the total absolute pressure can be reduced to about 0.1 atm only and cesium is used for seeding rather than potassium. Under atmospheric air–hydrogen combustion (1 atm total absolute pressure) and 1% mole fraction of seed alkali metal vapor, the theoretical volumetric power density is 410.828 MW/m3 in the case of cesium and 104.486 MW/m3 in the case of potassium. The power density can be enhanced using any of the following techniques: (1) reducing the total pressure, (2) using cesium instead of potassium for seeding, and (3) using air instead of oxygen as an oxidizer (if the temperature is unchanged). A seed level between 1% and 4% (pre-ionization mole fraction) is recommended. Much lower or much higher seed levels may harm the OCMHD performance. The seed level that maximizes the electric power is not necessarily the same seed level that maximizes the electric conductivity, and this is due to additional thermochemical changes caused by the additive seed. For example, in the case of potassium seeding and air combustion, the electric conductivity is maximized with about 6% seed mole fraction, while the output power is maximized at a lower potassium level of about 5%. We also present a comprehensive set of computed thermochemical properties of the seeded combustion gases, such as the molecular weight and the speed of sound.
Magnetohydrodynamics (MHD) is usually used in energy harvesting. Application of MHD power generators can be seen at sea, chimneys, and industry for large-scale energy harvesting. MHD produces an electromotive force by using a fluid conductor, such as plasma gas, liquid metal, or saltwater, to generate a magnetic field (e.m.f.). The electromagnetic field will be captured using an electrode made of aluminium, copper, or another conducting metal. For this project, the MHD system has been seen to have the potential to become a sensor for detecting water flow inside underground drains. This MHD sensor could help to prevent floods from occurring. Many factors has been found and most commonly that the flood incident occurred due to the overflow of rivers and clogged underground drains. Therefore, flood prevention measures must be taken immediately. This work contains a study of the MHD system and MHD generator with different number of magnets and output power as a signal. It can be found that the more magnet used give a better signal in output power as well as a sign of a good drainage flow in underground drains.
The power generation characteristics of a disk-shaped magnetohydrodynamic generator driven by rotating detonation with potassium-seeded hydrogen–air mixture are examined via quasi-two-dimensional numerical simulations. For unburned gas injection in the outward and inward directions, the rotating direction of the detonation wave is set so that the azimuthal velocity enhances the radial electromotive force. The simulation results show that the power output in the outward flow configuration exceeds that of the inward flow configuration. In the outward flow configuration, the radial gas velocity around the contact surface is the main contributor to the power generation, while in the inward flow configuration, the low gas velocity in almost the entire region and the vortices around the contact surface lead to poor power output. The characteristics in not only the power output mode but also the power input mode in which the voltage is applied externally between the electrodes are investigated. Under the positive load voltage, high enough for providing negative current, the Lorentz force occurs in the same direction as the propagation of the detonation wave; otherwise, the Lorentz force is induced in the opposite direction of the detonation wave.
In this study, the performance of magnetohydrodynamic (MHD) generators working with seawater and with hot exhaust gas in a combined cycle was computationally investigated. The flow and electric potential coupled governing equations were solved using a commercial computational fluid dynamics code. For seawater applications, 2 geometries were studied: square-cross-section duct and helical channel. For both geometries, the influence of the magnetic field intensity, the flow rate and external electric circuit resistance on the device performance were analyzed. The energy structure of the MHD flow for the helical MHD generator was also analyzed. Finally, a combined power cycle equipped with the investigated MHD generators was studied to evaluate its effects on the thermal efficiency of the combined cycle. The results showed that the helical geometry resulted in 10, 30 and 44 times more electric power produced than the square-cross-section duct for Reynolds numbers of 104, 105 and 106, respectively. An analysis of the energy structure in the helical MHD flow indicated that variations in the magnetic field modified the conversion of mechanical energy into electrical power and lost due to viscous and turbulence effects. It is also shown that for Reynolds numbers of 105 and 106, viscous and turbulence effects dissipate 60% of the mechanical energy lost in the MHD generator, independently of the Hartman number. The results of the MHD-based combined power cycle analysis revealed that the use of the MHD generator improved the thermal efficiency of the combined cycle around 24%, reaching values of 67.5% and 67.3%.
The aim of the article is to study the magneto-convective laminar incompressible flow within a differentially heated square enclosure partly filled with porous medium saturated with ionized helium gas in the presence of a transverse magnetic flux, as a model for emerging fuel cell designs. A Darcy model is utilized for porous medium bulk drag effects. Visualization of heat line and energy flux vectors is computed via Bejan's heat line approach and the Hooman energy flux vector method. The horizontal (i.e., bottom and top) wall boundaries are considered adiabatic and impermeable, while the side walls (cold and hot walls) are maintained at different but constant temperatures. The nonlinear coupled conservation equations under prescribed boundary conditions are solved with a finite difference-based vorticity-stream function approach. Appropriate convergence criteria factors are deployed. Furthermore, validation with earlier studies for the purely fluid, non-magnetic case i. e. in the absence of porous medium (Da) and Hartmann number (Ha) effects, is included. A parametric examination of the impact of Rayleigh number (Ra), Darcy number (Da) and Hartmann number (Ha) on temperature contours, heat lines, energy flux vectors and streamline patterns for ionized helium gas (Prandtl number, Pr = 0.71) is conducted. An increment in Hartmann magnetic number decreases the magnitudes of heat lines, suppresses heat transmission in the enclosure and curtails flow circulation. Enhancing the magnetic parameter and Rayleigh number however boosts the average heat transfer rate. Average Nusselt number at the left hot wall is elevated with increasing permeability of the porous medium and Rayleigh number. Mid-section velocities are enhanced in the porous layer but depleted in the non-porous layer of the enclosure with greater Rayleigh number. The simulations find provide some insight into applications in emerging hybrid electromagnetic fuel cells enabling better visualization of the thermal/fluid characteristics via the novel heat flow visualization heat-function and energy flux vectors analogy.
This paper presents a new method of extracting electric energy in the process of realizing thrust vector by magnetron gas plasma. Based on the model scramjet, the combustion plasma scheme is adopted, during the experiment, Cs2CO3 was put into a high-temperature environment to excite its own properties, so as to obtain the product Under the action of external magnetic field, it is verified that electric energy can be extracted in the process of plasma jet deflection, and the results are analyzed from the mechanism. Finally, the specific numerical results of magnetic field intensity and outgoing gas temperature are obtained, the average extraction voltage is 600 mV, indicating that ionized seeds enhance the ionization degree of gas. In the process of gas plasma jet of magnetic control scramjet, the scheme of extracting energy is feasible.
We develop a quasi-one-dimensional theoretical model describing the oscillatory plasma MHD conversion in a channel with parallel electrodes. Based on the model, a thermoacoustic plasma MHD generation system with a looped configuration is proposed and the characteristics of the operation of the system are investigated. Our results show that, for efficient oscillatory MHD generation, the channel dimension of the MHD duct should be much larger than the penetration depth (a proper Womersley number is above 100), otherwise the thermoacoustic effect will play a major role and consume considerable energy. Further, the electromagnetic induction parameter should be larger than 100ST2/m, so that a majority of the kinetic energy of the oscillatory plasma can be harnessed for energy conversion. Moreover, a load ratio between 0.6 to 0.8 is suggested for the presented system, with which an efficiency above 20% can be achieved when the electromagnetic induction parameter is 500ST2/m. In the optimal case, an efficiency of 24% can be obtained, with the corresponding output electricity of 1644 W. These results shed light on the feasibility of the closed-cycle MHD generation without any moving part, which endows the system with advantages of high reliability and long lifetime.
DESCRIPTION
Harvesting solar and ocean wave energy is a longstanding challenge that has been revisited in recent years. Currently, indirect power conversion systems based on rotatory generators are the dominant technology for harvesting thermal and mechanical energy. However, owing to their complex structure comprising turbines and gearboxes, indirect systems afford low energy conversion efficiency in low-grade thermal and ocean energy utilization.
A magnetohydrodynamic (MHD) power generation system is an electrical power generating system which generates the electricity utilizing the MHD principle. MHD power generation technique generates the electric power directly from a moving stream of ionized fluid flowing through a magnetic field. Therefore, the MHD power generation systems are found as the non-conventional electric power generation modality which is considered as the green energy harvesting procedures. The MHD generators utilizes the electromagnetic interaction of an ionized fluid flow and a magnetic field. The ionized fluids in MHD generators work as the moving electrical conductor and hence the electromotive force (e.m.f.) could be generated across the ionized conductor due to the Faraday’s electromagnetic principle. An MHD system, therefore, can act as a fluid dynamo or MHD power converter. In MHD, as the flow (motion) of the conducting fluid (conductor) under a magnetic field causes an induced voltage across the fluid, the e.m.f. would be found at the perpendicular direction to both the magnetic field and the fluid flow according to Fleming's right-hand rule. The concept of MHD power generation technique was first introduced by Michael Faraday in 1832 during his lecture at the Royal Society, UK. Since then, the MHD systems have been developed and studied by several research groups. Different types of MHD generator geometries have been proposed with different channel geometries, different electrode configurations, different magnetic coil structures, and different working fluids or plasmas. Though a typical coal-fired MHD generator converts about 20% of the thermal input power to the output electricity but, using the combined MHD/steam cycle systems, an energy conversion efficiency up to 60% of the coal’s energy can be converted into the electrical energy. In recent time, the green energy harvesting processes are found extremely important to reduce the pollution and to save the fossil fuel in the world for its sustainable development. In this direction, the MHD power generation technique could be utilized for green energy generation without any environmental pollution. In this chapter, The MHD technology has been discussed in detail followed by a discussion on its components, system design issues, and crucial design aspects. A detail review on the historical developments and the associated research works conducted on the MHD power generation process has been presented highlighting the major developments. Along with the limitations and challenges of the MHD power generation method, the present scenario and the future trends are also discussed.KeywordsElectric powerElectric power generationNon-conventional power generating systemsGreen energyMagnetohydrodynamic (MHD) power generationMHD GeneratorsPlasma
This chapter presents the state of art of conventional and nonconventional heat engines. It deals with the basic principles of the main thermodynamic cycles, showing plant layouts, thermodynamic analyses, and design guidelines. In particular, these engines can convert heat—mainly obtained by the thermal energy produced by the combustion of any fuel or by waste heat recovery—into mechanical energy. The chapter analyzes both air and steam cycles. The Rankine cycle is analyzed in detail, presenting the main configurations: basic, superheated, resuperheated, and regenerated. Similarly, a detailed analysis is also provided for the Bryton cycle, investigating the following arrangements: open and closed cycles, regeneration and interrefrigeration, and postcombustion. Finally, combined cycles are also presented. This technology exhibits the highest energy efficiency and is based on the combination of Rankine and Bryton cycles. For all the analyzed cycles, the chapter presents guidelines for maximizing their energy efficiency. In addition, an overview of some of the most advanced cycles (organic Rankine cycle, ORCs, Stirling engine, Kalina cycle, etc.) is also presented. A comparison among the analyzed heat engines is also included.
In the present study, the performance of an open cycle magneto hydrodynamics (MHD)-gas turbine (GT) combined plant has been analysed by considering the combustion products of MHD in partially ionized state and through the application of exergy. The combustor in the MHD system uses preheated air and coal mix and potassium carbonate as seed material to release the combustion products as partially ionized gases together with the undissociated product gases. The GT unit burns a mixture of methane and preheated air. Both MHD and the GT components have been modelled for computing energy rates and exergy destruction rates and the combined power generated. The ionization fraction is taken as 0.4 which is significant only up to the MHD generator due to temperature reduction below ionization beyond the generator. The exergy model of the GT plant is validated with a known model and the overall efficiency of the combined plant is determined. The exergy analysis which is partly based upon the effect of gas ionization shows the MHD combustor to have maximum exergy destruction followed by the process heater. Using partial ionization during combustion process in MHD, a more realistic attempt has been made to measure the power output and efficiency of the plant.
The hydrodynamics of immiscible micropolar fluids are important in a variety of engineering problems, including biofluid dynamics of arterial blood flows, pharmacodynamics, Principle of Boundary layers, lubrication technology , short waves for heat-conducting fluids, sediment transportation, magnetohydrodynamics, multicompo-nent hydrodynamics, and electrohydrodynamic. Motivated by the development of biological fluid modeling and medical diagnosis instrumentation, this article examines the collective impacts of ion slip, viscous dissipation, Joule heating, and Hall current on unsteady generalized magnetohydrodynamic (MHD) Couette flow of two immiscible fluids. Two non-Newtonian incompressible magnetohydrodynamic micropolar and micropolar dusty (fluid-particle suspension) fluids are considered in a horizontal duct with heat transfer. No-slip boundary conditions are assumed at the channel walls and constant pressure gradient. Continuous shear stress and fluid velocity are considered across the interface between the two immiscible fluids. The coupled partial differential equations are formulated for fluids and particle phases and the velocities, temperatures, and microrotation profiles are obtained. Under the physically realistic boundary and interfacial conditions, the Modified cubic-B-spline differential quadrature approach (MCB-DQM) is deployed to obtain numerical results. The influence of the magnetic, thermal, and other pertinent parameters, i.e. Hartmann magnetic number, Eckert (dissipation) number, Reynolds number, Prandtl number, micropolar material parameters, Hall and ion-slip parameters, particle concentration parameter, viscosity ratio, density ratio, and time on velocity, microrotation, and temperature characteristics are illustrated through graphs. The MCB-DQM is found to be in good agreement with accuracy and the skin friction coefficient and Nusselt number are also explored. It is found that fluids and particle velocities are reduced with increasing Hartmann numbers whereas they are elevated with increment in ion-slip and Hall parameters. Temperatures are generally enhanced with increasing Eckert number and viscosity ratio. The simulations are relevant to nuclear heat transfer control, MHD energy generators, and electromagnetic multiphase systems in chemical engineering.
The generation of the electric power through magnetohydrodynamic is one of the most advanced high -temperature energy conversions as it directly turns the heat into electricity. In this study, a quadruple cycle with magnetohydrodynamic generator was considered as the upstream cycle and a Brayton cycle was taken as the middle cycle through heating and an organic Rankine cycle and steam cycle were regarded as the downstream cycles using the heat loss of the magnetohydrodynamic generator and gas turbine, respectively. Energy, exergy, exergoeconomic, exergoenvironmental, emergoeconomic, and emergoenvironmental (6E) analyses were done in the proposed system simultaneously for the first time. In addition, advanced exergy, exergoeconomic, and exergoenvironmental analyses were performed for the proposed system to show the effect of irreversibility accurately and deeply. Despite the slight difference between the results of the emergoeconomic and emergoenvironmental sector with the exergoeconomic and exergoenvironmental sector, the obtained qualitative results were very similar showing that the emergoeconomic and emergoenvironmental analyses can be proper alternatives to the conventional exergoeconomic and exergoenvironmental analyses. The temperature of the heat source is one of the most important criteria for fluid selection in the organic Rankin cycles. Five organic fluids were selected and evaluated according to the desired hot source temperature for the Rankin organic cycle (262 °C). The results showed that the R141b with energy and efficiency of 15.25 and 58.05%, respectively had the best thermodynamic and exergy performance with the least amount of total costs using this fluid.
In solar power generation, not only does the heat transfer significantly affect the energy conversion efficiency, but it also determines the stability and durability of the optoelectronic materials. Therefore, special attention has been given to the development of advanced heat transfer materials and methods to achieve more efficient energy conversion. Recently, low-melting-point liquid metal materials have emerged as an attractive heat transfer medium, owing to their unique properties, such as, low melting point, high thermal conductivity, high latent heat, nonflammability, and non-toxic characteristics. Various heat transfer systems based on liquid metals have been investigated, and consequently, significant advances in liquid metal material properties, industrial thermal management, and solar power generation have been achieved. This paper presents a thorough review on basics and applications of liquid metal technology in solar power generation. Specifically, three typical liquid metal materials, including liquid metal fluids, liquid metal thermal interface materials, and liquid metal phase change materials are introduced. Some typical liquid metal based solar power applications, including the liquid metal cooling enhanced photovoltaic power generation, the liquid metal based solar thermal power generation, the liquid metal based solar thermal magnetohydrodynamic (MHD) power generation, the liquid metal thermal interface material enhanced heat transfer in solar energy system, and the liquid metal based solar thermal storage system are illustrated and interpreted. Both these fundamental issues and their latest application researches are elaborated and critical issues are discussed. Eventually, the paper concludes with a description of future developments and challenges in these areas.
The characterization of nozzle heat flux at extreme conditions has been a subject of investigation for a long time. Because of the complexity of the multiple processes involved, including a coupling of turbulent fluid flow, heat transfer, and combustion, designers of similar systems have largely relied on empirical and semi-empirical correlations. However, some of these correlations lead to inaccuracies in the design process. The current study presents the analysis of a combustor that could be used in a direct power extraction (DPE) configuration. The combustor produces flame temperatures of 3300 K and heat fluxes greater than 7 MW/m2. In this paper, analytical and two-dimensional numerical heat flux values and temperatures are compared with experimental results. Results show that analytical methods using Bartz correlation with a 40% reduction of the heat transfer coefficient produce similar results to a much more complicated coupled Navier–Stokes–based model. Both methods match with experimental results to within 2.8% for coolant heat absorption and 2.5% for the chamber-region channel wall temperature prediction. The analytical model presented in this paper can be employed in other scenarios that use incompressible fluids as coolants, where stratification effects are reduced.
Liquid metal magneto-hydro-dynamic (LMMHD) system is a promising power generation converter for a variety of heat sources. This paper presents a novel concept of self-evaporating-driving LMMHD system, in which the liquid metal is driven by the vapor from its own evaporation. It has advantages of safety, higher electrical conductivity, a simplified structure without mixer and separator, and therefore a more reliable and higher efficiency. Firstly, the basic principle of this system was introduced, in comparison with that of a conventional LMMHD system. Secondly, simulations were conducted to study the physical process of the evaporation of liquid metal in the heater and the characteristics of vapor-liquid flow in the following tube. Finally, three main impacting factors, namely inlet velocity, inlet temperature of liquid sodium, and temperature of pipe wall were discussed respectively. The findings verify the feasibility of the proposed self-evaporating-driving LMMHD system, and present the outlook for future research.
The accurate modeling of coal combustion requires detailed radiative heat transfer models for both gaseous combustion products and solid coal particles. A multiphase Monte Carlo ray tracing (MCRT) radiation solver is developed in this work to simulate a laboratory-scale pulverized coal flame. The MCRT solver considers radiative interactions between coal particles and three major combustion products (CO2, H2O, and CO). A line-by-line spectral database for the gas phase and a size-dependent nongray correlation for the solid phase are employed to account for the nongray effects. The flame structure is significantly altered by considering nongray radiation and the lift-off height of the flame increases by approximately 35%, compared to the simulation without radiation. Radiation is also found to affect the evolution of coal particles considerably as it takes over as the dominant mode of heat transfer for medium-to-large coal particles downstream of the flame. To investigate the respective effects of spectral models for the gas and solid phases, a Planck-mean-based gray gas model and a size-independent gray particle model are applied in a frozen-field analysis of a steady-state snapshot of the flame. The gray gas approximation considerably underestimates the radiative source terms for both the gas phase and the solid phase. The gray coal approximation also leads to under-prediction of the particle emission and absorption. However, the level of under-prediction is not as significant as that resulting from the employment of the gray gas model. Finally, the effect of the spectral property of ash on radiation is also investigated and found to be insignificant for the present target flame.
The sulfur-iodine water-splitting cycle is characterized by the following three reactions: 2HâO + SOâ + Iâ ..-->.. HâSOâ + 2HI; HâSOâ ..-->.. HâO + SOâ + 1/2 Oâ; and 2HI ..-->.. Hâ + Iâ. This cycle was developed at General Atomic after several critical features in the above reactions were discovered. These involved phase separations, catalytic reactions, etc. Estimates of the energy efficiency of this economically reasonable advanced state-of-the-art processing unit produced sufficiently high values (to approx.47%) to warrant cycle development effort. The DOE contract was largely directed toward the engineering development of this cycle, including a small demonstration unit (CLCD), a bench-scale unit, engineering design, and costing. The work has resulted in a design that is projected to produce Hâ at prices not yet generally competitive with fossil-fuel-produced Hâ but are projected to be favorably competitive with respect to Hâ from fossil fuels in the future.
The basic elements in the design of the MHD generator channel of the U-25 are described, as well as improvements in the design made on the basis of measurements. Results are given from electrical measurements, together with estimates of the electric conductivity of the plasma and the potential drop near the electrodes.
This study presents a new design, and thermodynamic and engineering analyses of the H2SO4 decomposition section of the sulphur-iodine thermochemical cycle for producing hydrogen. Excess oxygen is used as an energy vector in various direct contact adiabatic equipment and shell and tube heat exchangers are eliminated as much as possible. Thermodynamic (energy and energy) and cost analyses have been carried out. The results show that energetic and exergetic efficiencies are 64.2% and 64.0% respectively and typical cost is 3.3(1990)/GJ nuclear heat cost.
The applicability of the concept of the rapid devolatilization of coal to the MHD power cycle is experimentally and analytically investigated. In addition to providing an ashless fuel for the generator, utilization of the concept could reduce the size of the gasification reactor by an order of magnitude. For the experimental investigation, an entrained bed gasifier capable of handling up to 100 lbs of coal per hour has been constructed. An analytical model for the reaction under investigation has been formulated.
Stand-alone scheme of open-cycle magnetohydrodynamic power generation system was discussed. The coal combustion gas containing slag vapor radiated a large radiation continuum resulting in decrease in temperature. A distinctive feature of the system was that a considerable amount of energy can be recirculated to the combustor as chemical energy.
A laboratory scale demonstration experiment was carried out for an iodine-sulfur thermochemical hydrogen production process. The material balance is determined by considering the experimental results of the acid formation, separation of the two phases and the acid decomposition. In a 24-hour continuous hydrogen production experiment with the rate of 1.2 dm3/h S.T.P., stoichiometric and stable production of hydrogen and oxygen was achieved. Little change of the composition of the process solution was confirmed by comparison before and after the experiment. Key words: thermochemical hydrogen production, iodine-sulfur cycle, closed cycle demonstration, material balance. © 1998, The Society of Chemical Engineers, Japan. All rights reserved.
A regenerative and recirculation-type coal power system is proposed that works at high efficiencies with a stand-alone magnetohydrodynamic generator under complete CO2 liquefaction. The open-cycle MHD generator is almost a unique power generation unit for the proposed cycle because combustion temperatures become far beyond the working region of any gas turbines due to both high fractional energy recirculation and oxygen combustion required for an efficient CO2 liquefaction process. The MHD exhaust heat is regenerated sequentially through three processes, including thermochemical coal gasification, high temperature syngas preheating and an iodine-sulphur water splitting process. The mass and energy balances in each elementary process are calculated on the basis of Gibbs' energy minimization principle. It is shown that the system efficiency can attain much higher values than those of the coal gasification gas turbine combined cycle and the direct coal-fired MHD combined counterpart estimated under the same evaluation criteria. © 2003 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Various anode electrodes for MHD channels were recently operated successfully for over 1000 hours under the same electrical, thermal and chemical stress conditions as would exist in a commercial MHD power plant, including the requisite fractions of sulfur and coal ash carry-over. The most successful electrodes were made of water-cooled copper with platinum and/or stainless steel cladding in critical areas. Based on measured erosion rates for the 1000 hours of operation actually achieved, an ultimate lifetime in the range 5000 to 8000 hours can be extrapolated for these electrodes.
Results of the POC testing at the DOE Coal Fired Flow Facility (CFFF) during calendar year 1988 are summarized. Emphasis is on the development of technology for the steam bottoming plant for the MHD Steam Combined Cycle power plant. The first 500 hours of corrosion testing on candidate boiler tubes were completed and preliminary results are discussed. Ash deposition and efforts to improve the removal of deposits by sootblowers are outlined. Results of testing the particulate control devices (baghouse and ESP) are included. Finally, plans for future testing are presented. 9 figs.
The results of MHD generator studies are presented. These include channel modeling and performance, non-rectangular (V-wall) cross-sections and channel loading and faults. An analytical model aimed at predicting the overall performance of channels is presented. The results of theoretical calculations are compared with experimental measurements. These include electrical conductivity measurements, pressure distribution, current and voltage distribution and overall performance. The salient construction features of a V-wall channel are described. Preliminary performance characteristics are presented. Also presented are the results of loading experiments which include diagonal and Faraday loading, nonuniform local loading and fault simulation studies.
Under conditions that result in strong Hall or ion‐slip effects, a uniform and a nonuniform gas can behave much differently as conductors of electricity. An Ohm's law for a nonuniform gas is derived. It is used to study the performance of normal‐current and Hall‐current magnetohydrodynamic devices and also the possibility for obtaining significant electron heating or ``extrathermal'' ionization.
When an electric current flows through an expanse of fluid, the flow of charge may be distributed over the entire expanse of the conduction domain or it may be intensely confined to a locally narrow path through the fluid. The former mode of conduction is referred to as a diffuse discharge and the latter is termed a constricted or arc discharge. In this paper we attempt to show one of the conditions under which a diffuse discharge in an MHD plasma will transit to a constricted discharge. We then show the characteristic features of the steady state arc into which the diffuse discharge may develop.
The high performance demonstration experiment (HPDE) is in progress with the objective of demonstrating that an MHD generator, simulating a commercial scale device, can convert 15% of the available thermal energy into electrical power. Operation of the facility was initiated in the fall of 1979. Preliminary experimental results have been obtained with the channel in the Faraday configuration and magnetic field strengths from 1. 5-3. 5 T. A maximum Faraday power of 23 MW has been generated which represents an enthalpy extraction of 9%. A detailed analysis of the electrical power and aerodynamic characteristics of the channel, including the voltage drop in the relatively cold plasma layers near the electrode walls is presented.
The development of the three-dimensional flow and temperature fields in an MHD channel is studied. The partial-differential equations for the three momenta, the enthalpy, and the electrical fields are solved by a finite-difference calculation procedure. The turbulence phenomenon is represented by a two-equation turbulence model, in which additional equations are solved for the kinetic energy of turbulence and its dissipaton rate. Calculations have been made for typical MHD channel conditions in the subsonic flow regime. Interesting secondary flow patterns have been observed to develop along the duct as the flow and electrical fields interact with each other. The detailed development of the three-dimensional flow, temperature, and electrical fields is presented.
Two scenarios for achieving CO2-free fossil fuel utilization in electric power systems are proposed, and the role of the open-cycle magnetohydrodynamics (MHD) power generation is discussed, taking into account the current trends of power generation systems and fossil fuel utilization. It is emphasized that the oxygen combustion of synthetic fuels, synthesis of primary fuels with exhaust gases and heat with additional steam, and separation of carbon dioxide from a syngas mixture should be performed in the central power stations to provide concentrated CO2 recovery and hydrogen supply capability for dispersed-type power units. It is shown that MHD power generation driven by plasmas from oxygen-fired synthetic fuel might be the only possible candidate for a topping system in the ultimate base-load power station with the highest efficiency. Four models of central power generation systems were considered on the basis of the presumably attainable performance of the components, and the effects of the proposed scenarios were evaluated in terms of power generation efficiencies with the assumed fractional dependence on the dispersed-type power systems.
Internal surface-leakage effects on magnetohydrodynamic power generator performance were studied using a combined experimental and analytical approach. A method to determine the wall resistance and slag layer conductivity distributions from seed shutoff test data is introduced. These measured resistance values were then utilized in generator performance analyses. Calculated generator variables were compared with measured data to verify the modeling approach. Finally, these calculated results were used to investigate the distribution of internal leakage currents as a function of generator size, generator operating conditions, and iron oxide injection rates, An advantage of this analysis methodology is the ability to differentiate wall leakage from apparent leakage effects in the measured test data.
Ozawa and Kayukawa (1975) have proposed the design of an MHD generator employing the Shaped B-Field Configuration ('SFC'), in which the applied magnetic field is greatly diminished near the electrode walls by keeping the core magnetic field at approximately the same level as the conventional MHD generator. Attention is presently given to the experimental results obtained for an SFC MHD generator incorporating an improved magnetic field design, under shock tube operating conditions. These results are compared with those for a previous SFC MHD device and a conventional MHD generator with uniform B-field configuration.
The electrical characteristics of segmented Z-bar insulator walls for magnetohydrodynamic power generators have been investigated. Experiments were carried out, using a 20-MW (thermal input) power generator, to compare the performance of the Z-bar sidewall design to that of the conventional straight-bar configuration. Electrical properties were measured for clean-fuel (bare-wall) and simulated coal-fired (slagged-wall) test conditions. The Z-bar sidewall design was found to be superior for its ability to adjust to varying generator load and operating conditions. The wear-inducing electrical stresses were much lower and more uniformly distributed in the Z-shaped configuration than in the straight-bar design. The effects of bar segmentation on the interbar voltage and fault power distributions were also studied. The selection of sidewall design for several recent power generators was based in part on the results of this study.
In this paper, the main objectives for the present development of gas fired MHD power generation are considered. The state of the world-wide natural gas consumption and its utilization for electricity production is analyzed. The experimental efforts in gas-fired MHD studies are briefly described. The essential features of the two major world gas-fired MHD project - the Ryazan MHDES-580 (U-500) power plant and the Italian 230 MWt retrofit are presented. New suggestions for improving the efficiency of MHD systems and the theoretical and experimental aspects of MHD development are discussed.
A review of the design of the CFFF LMF upstream test train and its subsystems is presented. This review details major components of the upstream from an historical perspective and summarizes the design that has been used in POC testing. Modifications to upstream hardware that were made in preparation for the 1992 western coal POC test program are detailed. Past operation of the CFFF is revisited to define the capabilities of the LMF upstream. Characterizations of the combustion plasma are given to compare eastern with western coal operation. Analyses and data on the plasma-dynamic and heat transfer throughout the upstream are also presented. The operation and demonstrated performance of the LMF upstream during the Montana Rosebud coal shakedown tests of 1991 is presented and compared to past eastern coal tests.
Preparation for the Proof-of-Concept (POC) tests began at the University of Tennessee Space Institute (CFFF) with development of magnetohydrodynamic technology in the early 1960s. Historical aspects of the POC are given. Work is underway now to complete the necessary analyses, such as metallurgical analyses of corrosion specimens, data analysis and report preparation. Therefore, this summary is a preliminary assessment of the results obtained during the 2000-hour POC test program. (VC)
Practical and theoretical problems in the industrial-scale conversion of thermal energy to electrical power by the MHD processes are discussed in a review (originally published in Russian in 1983) comprising individual chapters by Soviet MHD experts. Chapters are devoted to engineering and technical problems of developing MHD power plants, calculation of MHD power flows, the characteristics of a nonideal MHD generator, plasma diagnostics in MHD generators, and phenomena in the near-electrode region of a constricted discharge. Graphs, diagrams, drawings, and photographs are provided.
A series of experiments was conducted on a slagging MHD generator to investigate the loss in channel performance brought about by slag polarization phenomena in which large reductions in slag resistivity are observed on the cathode wall. However, tests in which the seed was discontinued resulted in relatively no change in generated Hall voltage (about 500 volts) while power levels dropped to less than 1 kW, demonstrating minimal leakage in the slag layer. It is concluded that the cathode slag layer is not continuous but is periodically ''broken''. Shorting of Faraday currents in the presence of a Hall field results in increasing current concentrations at the downstream edge of the shorted group until sufficient joule heating is produced to locally remove or thin the slag layer and create an open insulator gap capable of sustaining the Hall voltage. The net effect was a resegmentation of the cathode wall from a design pitch of 1.5 cm to a pitch of between 4 and 10 cm depending on the iron oxide concentration in the ash.
Various types of MHD generators are examined, viz. Faraday generator,
Hall generator, and diagonal generator. The critical generator fluid
mechanics, which affects efficiency and influences design and
performance limitations, is discussed. The all-important
electrode-insulator problem and MHD channel design considerations are
reviewed. Finally, instrumentation and control of MHD generators are
considered from an operating standpoint. The present status of generator
development is highlighted, and critical design criteria and limitations
for building a commercial-scale MHD plant are established.
A theoretical and experimental study of electrode phenomena as they
relate to the interfacial current transport in slagging MHD channels is
presented. An analytical study of the stability of the current transport
in the vicinity of electrode walls is given. The critical current
density for arcing is shown to depend on the temperature of the plasma
or slag-wall interface as well as the unperturbed temperature gradient.
Generator studies of the current transport process include voltage drop
measurements and visual studies of the current transport to anodes and
cathodes. The effect of slag and of the magnetic field are discussed.
The wall processes in generators are studied. The degradation
characteristics of various anode and cathode materials and designs are
evaluated. Long duration MHD channel tests indicate that massive, low
temperature metallic current collectors of sufficient thermal
diffusivity can operate as cathodes in the arcing regime without any
appreciable degradation. Materials of low thermal diffusivity exhibit
substantial arc erosion in the absence of slag. Oxidation rather than
arc damage is the main degradation process for anode elements. The use
of high thermal diffusivity materials appears to minimize the
degradation process.
The performance characteristics of disk MHD generators are analyzed for
the combustion products of a western coal at typical baseload
conditions. Three disk generator configurations - radial outflow, radial
inflow, and radial inflow-outflow - are considered for both impulse and
reaction modes of operation. It is shown that for enthalpy extraction,
generator isentropic efficiency, and electric fields to be sustained
along the generator channel and the reaction mode radial inflow
configuration is preferable for the baseload disk generator. The radial
inflow-outflow configuration, which is a combination of the inflow and
outflow geometries, could attain higher performance than the radial
inflow configuration with substantially reduced generator size.
Comparisons of disk generators with linear generators show that the
performance of the disk generator is comparable to that of the diagonal
generator, while the magnet cost for the disk generator is expected to
be less than for linear generators. In view of these results, together
with the advantages associated with simple channel construction, it is
concluded that the disk generator is a potentially effective alternative
to linear generators for baseload power generations.
The concepts and goals of a dual cycle commercial size MHD topping-steam
bottoming power plant have been translated into a reference design
within the limits of present or reasonably projected technology.
Trade-offs involving the chosen design characteristics and major
parametric evaluations have been performed to select the reference
system configuration. This paper defines the system to date, the basis
for selection of the subsystems, the viable alternatives and the power
plant economics. Many of the factors governing choice of equipment or
techniques are not conclusive because of uncertainties which presently
exist in design and construction. A parametric analysis of the reference
system design was made based upon predicted operating characteristics of
the staged coal combustor, the MHD generator-diffuser and the
directly-fired air heaters. Equipment has been selected to provide the
best compromise between economic and technical aspects.
The water splitting reaction by a thermo-chemical cycle using ferrites was investigated for H2 production. In the first step (activation step), ferrites were thermally reduced at 1200 °C to form an oxygen-deficient ferrite. In the second step (water splitting step), the activated ferrites were oxidized by water at 800 °C to produce hydrogen. Among the prepared ferrites, Ni-ferrite was found to be the most suitable for H2 production. NiFe2O4 produced an average of 0.442 cm3/g cycle of H2. The H2 productivity of the Ni-ferrite was much higher than that of the other ferrites at the same temperature. XRD showed that the crystal structure of NiFe2O4 during the redox reaction was not changed during the repeated cycles, indicating that NiFe2O4 was an excellent material in terms of structural stability and durability.
The potential is examined of various advanced power plant concepts using coal and coal-derived fuel. The results indicate that open cycle coal fired direct preheat MHD systems have potentially one of the highest coal-pile-to-bus-bar efficiencies and also one of the lowest costs of electricity (COE) of the systems studied. Closed cycle MHD systems may have the potential to approach the efficiency and COE of open cycle MHD. The 1200-1500 F liquid metal MHD systems studied do not appear to have the potential of exceeding the efficiency or competing with the COE of advanced steam plants.
Experimental studies on the performance of closed-cycle MHD generator with fully-ionized seed
- N Harada
- H Yamasaki
- T Oyake
- M Watanabe
- E Shimizu
- T Osogai
- Shioda
Harada N, Yamasaki H, Oyake T, Watanabe M, Shimizu E, Osogai T, Shioda S. Experimental studies on the performance of closed-cycle MHD generator with fully-ionized seed. Proceedings of the 22nd SEAM, Mississippi State University, Starkville; June 1984. Paper 3.1.
Thermo-chemical water-splitting for hydrogen production
- K Ohnuki
- H Nakajima
- M Futakawa
- I Ioka
- Shimizu
Ohnuki K, Nakajima H, Futakawa M, Ioka I, Shimizu S. Thermo-chemical water-splitting for hydrogen production. Proc Int Topical Meeting Nucl Reactor Thermal-Hydraulics, Kyoto 1998;3:1803 –8.
High current arc discharge rise on open-cycle MHD generator electrodes
- Buznikov
Buznikov AE, Reshetov EP. High current arc discharge rise on open-cycle MHD generator electrodes. Proc 11th ICMHD, Beijing 1992;1:159–62.
Comparison of three-dimensional, constricted electric current near anode and cathode of open-cycle MHD generator. Proceedings of the 14th ICMHD and HTT, Maui
- M Ishikawa
- K Itho
- Takeuchi
Ishikawa M, Itho K, Takeuchi K. Comparison of three-dimensional, constricted electric current near anode and cathode of open-cycle MHD generator. Proceedings of the 14th ICMHD and HTT, Maui; May 2002. Paper AIAA-2002-2237.
Cathode wall nonuniformities in MHD generators—modeling and comparison with experiments
- I Sadovnik
- Pian
- Ccp
Sadovnik I, Pian CCP. Cathode wall nonuniformities in MHD generators—modeling and comparison with experiments. Proceedings of the 23rd SEAM, Hidden Valley Conference Center, Somerset; June 1985. p. 392– 406.
Results on the U-25 MHD power plant
- Kirillin Va
- Sheindlin
- Ae
Kirillin VA, Sheindlin AE. Results on the U-25 MHD power plant. High Temperature 1974;12(2):325 –37.
Stability analysis of coal-oxygen fired transonic disk MHD generqator
- Matsuo
Matsuo T, Ishikawa M, Umoto J. Stability analysis of coal-oxygen fired transonic disk MHD generqator. Proc ICMHD HTT, Beijing 1999;1:105.
Closed cycle continuous hydrogen production test by thermo-chemical IS process
- H Nakajima
- K Ikenoya
- K Ohnuki
- Shimizu
Nakajima H, Ikenoya K, Ohnuki K, Shimizu S. Closed cycle continuous hydrogen production test by thermo-chemical IS process. Kagaku Kogaku Ronbunshu 1998;24(2):352–5. in Japanese.
Achievement of highest performance in disk MHD generator with Ar/Cs
- H Yamasaki
- Y Okuno
- S Torii
- J Masuda
- M Tsutsumi
- N Oda
- K Uchiyama
- H Kouka
- T Fujimoto
- H Suzuki
- Ohgaki
Yamasaki H, Okuno Y, Torii S, Masuda J, Tsutsumi M, Oda N, Uchiyama K, Kouka H, Fujimoto T, Suzuki H, Ohgaki K. Achievement of highest performance in disk MHD generator with Ar/Cs. Proc ICMHD HTT, Beijing October 1999;1: 233 –41.
Coal-fired MHD channel parametric studies aspects of power generation with iron oxide addition
- Petty
- Sw
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