Anode must be kept cool to avoid back emission of electrons. Adequate power supply is an unavoidable prerequisite to any nations development and electricity generation, transmission and distribution are capital intensive activities requiring huge resources of both funds and capacity. The goal is to achieve direct thermal to electric energy conversion with 20% efficiency and 1wcm2 power density at a hot side temperature of 300650c. This version of thermionic power conversion is called thermoelectronic power generation, as it is independent of the emission mechanism and furthermore uses only electrons, no ions, as active particles meir et al. Higher powered nuclearthermionic power systems driving electric propulsion qthruster, vasimr, etc. When there is an abundance of loads with poor power factor, this need for increased capacity will require that additional power generation and distribution capability will be needed. New highly efficient thermoelectronic generator by american institute of physics this is a view into the test generator, looking at the emitter 3 cm diameter. Because of its promise, researchers have been trying for more than half a century to develop a practical thermionic generator, with little luck.
Thermionic and thermoelectric power generators mona zebarjadi arpae workshop. Thermoelectric power a thermoelectric produces electrical power from heat flow across a temperature gradient. The design of a combustion heated thermionic energy converter. Thomas johann seebeck invented seebeck effect in 1822. A thermionic converter consists of a hot electrode which thermionically emits electrons over a potential energy barrier to a cooler electrode, producing a useful electric power output. A thermionic generator, in principle, can make use of any fuel may be fossil fuel, a nuclear fuel or solar energy subject to the condition that sufficiently high temperatures are obtainable. The electrical conductivity of metals indicates that at least some of the electrons in the metal are not bound to individual atoms, but are able to move more or less freely through the atomic lattice. This goal requires advances in thermionic converter technology. Thermionic power converter article about thermionic. The goal is to achieve direct thermal to electric energy conversion with 20% efficiency and 1wcm 2 power density at a hot side temperature of 300650c.
Power management and distribution system developed for thermionic power converters thermionic power management and distribution hardware. The closespaced highvacuum converter appears to have neared the limit of its development at a power output of 1 wattcm 2 and an efficiency of approximately 5%. Here, we study the potential of sigesi superlattices for power generation at high temperatures. Frontiers improving the efficiency of a thermionic energy. A thermionic energy converter using singlelayer graphene nanowerk spotlight heat energy can be converted into electricity with very high efficiency through a temperatureinduced electron flow process known as thermionic emission. Direct solar thermal power generation technologies, such as, thermoelectric, thermionic, magneto hydrodynamic, and alkalimetal thermoelectric methods, are among the most attractive ways to provide electric energy from solar heat. Through a process known as thermionic conversion, heat energysuch as light from the sun or heat from burned fossil fuelscan be converted into electricity with very high efficiency. The avenues to better thermionic performance are improved electrodes emitter and collector and reduced plasma arc drop. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Thermionic electron emission provides a means of direct energy conversion. Thermionic energy conversion tec is the direct conversion of heat into electricity by the mechanism of thermionic emission, the spontaneous. Thermionic power converter article about thermionic power. This chapter focuses on the thermionic energy conversion with description of idealized model of a thermionic converter a.
An elementary thermionic generator, or thermionic converter, consists of a hot metal surface emitter separated from a cooler electrode collector by an insulator seal. Thermionic power converter, also called thermionic generator, thermionic power generator, or thermoelectric engine, any of a class of devices that convert heat. Thermo electric power generation it is based on seebeck effect. Older seebeckbased devices used bimetallic junctions and were. Direct solar thermal power generation has been an attractive electricity generation technology. A device for converting heat into electricity through the use of thermionic emission and no working fluid other than electric charges. Terrestrial applications of thermionic energy conversion. Thermionic power systems were used in combination with various nuclear reactors bes5, topaz as electrical power supply on a number of soviet military surveillance satellites between 1967 and 1988. The conference is being cosponsored by the european nuclear energy agency of the oecd and by the iaea. Scientists look to thermionic energy conversion for clean and.
The simplest thermoelectric power generator consists of a thermocouple, comprising a ptype and ntype material connected electrically in series and thermally in parallel. Construction of a thermionic energy converter sulfur doped nanocrystalline diamond films as field enhancement based thermionic emitters and their role in energy conversion 1183. Discussions of generation, transmission, and utilization are complemented by environmental and energy resources topics as well as electromechanical conversion, power electronics, electric safety, renewable energy, and electricity blackouts. Thermoelectric and thermionic generators slideshare. Thermionic emission in vacuum could be a highly efficient cooler or power generator if the work function, the minimum work for electrons to go into vacuum, is around 0. Higher powered nuclear thermionic power systems driving electric propulsion qthruster, vasimr, etc. Thermionic energy conversion plasmas plasma science, ieee. A thermionic generator of electricity is essentially a diode valve in which electrons emitted from a hot cathode3ow to a cooler anode, producing an electric.
A thermionic energy converter using singlelayer graphene. An integrated solar upper stage isus provides orbital. Direct power generation using tunneling and thermionic. The electrons are still bound to the lattice as a whole by a characteristic binding.
One of these is raised to a sufficiently high temperature to. This occurs because the thermal energy given to the carrier overcomes the work function of the material. The current emphasis is on outofcore thermionic conversion tec. The basic operating principle of thermionic energy converters is that electrons are evaporated from a heated. Electrical energy systems power applications of electricity. Fuji electric has a track record of many successful applications including pure power generation and cogeneration plants based mainly on coalfired power generation, and combined cycle power generation. Frontiers improving the efficiency of a thermionic. Thermoelectric power generator ppt pdf seminar report. A detailed theory based on boltzmann transport equation is. Experiments have been conducted on a dual electric grid thermionic device to investigate an alternative method of space charge mitigation in a thermionic energy convertor tec.
In addition to ferrotecs thermoelectric modules for power generation, ferrotec acquired the telan line of power generation modules and systems in 2003 and the company continues to supply replacement parts for these systems. A spacecraft solar, bimodal system combines propulsion and power generation into a single integrated system. The charge carriers can be electrons or ions, and in older literature are sometimes referred to as thermions. Thermoelectrics have even been miniaturized to harvest body heat for powering a wristwatch. Many countries are producing the power against its opportunies and wrong methods. An international conference on thermionic electrical power generation is being organized by the government of the federal republic of germany, in collaboration with the german nuclear research centre at jlilich, to be held in june this year. The thermionic conversion can be utilized in several different situationsremote locations on the earth and in space. Concentrating solar thermal power, a method of using heat collected by a solar concentrator to drive a heat engine to generate elec. Scientists look to thermionic energy conversion for clean and efficient power generation. Thermionic emission in both vacuum and solidstate devices is investigated. Thermionic emission energy distributions from nanocrystalline. Thermionic energy conversion how is thermionic energy. Thermionic energy conversion for concentrating solar power.
The additional degrees of freedom offer new potentialities, but hightemperature material. Conservation of lateral momentum in heterostructure. Thermionic energy conversion in the twentyfirst century. The research team is using device and system modeling to design and test a nextgeneration solarthermal energy converter proofofconcept that is capable of 15% thermaltoelectricity efficiency. Thermionic power converter, any of a class of devices that convert heat directly into electricity using thermionic emission rather than first changing it to some other form of energy. A thermionic convertergenerator comprises a heated cathode electron emitter and an anode electron collector separated by vacuum, the electrical output circuit being connected between the two as shown in the fig. Thermionic power generation at high temperatures using sige. Introduction thermoelectricity refers to a class of phenomena in which a temperature difference creates an electric potential or an electric potential creates a temperature difference. Apr 19, 2016 thermionic emissions occur at high temperature without need for external heater source thermionic technology diodes, triodes, tetrodes, etc amplifier, oscillators, power generation parc 3 heat sensor project concept the 1946 eniac computer used 17,468 vacuum tubes and consumed 150 kw 32of power. The basic principle of thermionic power generation is the same as that of the thermionic valve once before the advent of transistors at the heart of all electronic equipment. Thermionic power generator accessscience from mcgraw. Thermionic emission is the liberation of electrons from an electrode by virtue of its temperature releasing of energy supplied by heat. Two electric grids, the attractor and deflector grids, provide opposing electric fields to overcome space charge while minimizing power losses to the attractor grid.
Because the accelerating electrons constitute a steady current i. Solar photovoltaic power production generates another con ict between ac and dc standards. Unfortunately, the work function of existing materials is currently above 1 ev. This cost increase will, to a first approximation, be directly proportional the inverse of the power factor. A vacuumtype thermionic diode, designed for student laboratory use, is described which features variable electrode spacing, interchangeable electrodes, and a guardring structure. The electrical conductivity of metals indicates that at least some of the electrons in the metal are not bound to individual atoms, but are able to move more or less freely through the atomic lattice of the metal. Thermionic emission 103 where vx is the potential di. The magnitude of voltage generated is proportional to temperature difference and depended on type of the conducting material seebeck.
Publishers pdf, also known as version of record includes final page, issue and. Thermionic generator article about thermionic generator. Thermionic power generation at high temperatures using. Nearfield enhanced thermionic energy conversion for. Thermionic energy conversion plasmas plasma science. Thermionic emissions occur at high temperature without need for external heater source thermionic technology diodes, triodes, tetrodes, etc amplifier, oscillators, power generation parc 3 heat sensor project concept the 1946 eniac computer used 17,468 vacuum tubes and consumed 150 kw 32of power. Energy analyses of thermoelectric renewable energy sources. A thermionic converter is a device which converts heat energy into electrical energy by utilizing the thermionic emission of electrons. Scientists look to thermionic energy conversion for clean. Caesium vapor is used to optimize the electrode work functions and provide an ion supply by surface ionization or electron impact ionization in a plasma to neutralize the electron space charge. Basics on electricity and electrical generation ej moyer, u. Heat is applied to a circuit at junction of different conductors a current will be generated. Pdf in the present world of latest researches, a very hot domain of research is power generation.
The simplest thermoelectric power generator consists of a thermocouple, comprising a ptype and ntype material connected electrically in series and. This process is crucially important in the operation of a variety of electronic devices and can be used for power generation or cooling. The interelectrode gap is usually a fraction of a millimeter in width. Construction thermoelectric power generation teg devices typically use special semiconductor materials, which are optimized for the seebeck effect. Pdf general overview of thermionic power generation. A detailed theory based on boltzmann transport equation is developed which takes into account multiple valleys. Mar 01, 2016 scientists look to thermionic energy conversion for clean and efficient power generation.
Power management and distribution system developed for. Nov 30, 20 thermoelectric and thermionic generators 1. A brief overview of the research activities at the thermionic energy conversion tec center is given. In this article we will discuss about the construction and working of thermionic generator with the help of a suitable diagram. Power generation on earth could benefit from simpler, moe economical nuclear plants, and topping of more fuel and emission efficient fossilfuel plants. Every country can produce the power denpen upon its own local opportunits and resoucres under the guidlines of this article and its recoomendations. Some of the benefits of thermionic power generation include. While we know johnson for water gun technology, he also has 60 patents 20 pending to his name, for everything from a thermionic generator to a wet diaper detector. Dec 03, 20 new highly efficient thermoelectronic generator by american institute of physics this is a view into the test generator, looking at the emitter 3 cm diameter. Apr 04, 2015 thermo electric power generation it is based on seebeck effect.
However, the term thermionic emission is now used to refer to any thermally excited charge emission process, even when the charge is emitted from one solidstate region into another. Thermoelectric power generator is a device that converts the heat energy into electrical energy based on the principles of seebeck effect. In such a system electrons are boiled off an emitting electrode, the cathode, by heating it, and collected by a second electrode, the anode, placed nearby. Frontiers thermionic energy conversion in the twenty. Small thermoelectric generators electrochemical society. Since the broad band of the photon energy absorbed by the cathode is used for thermionic power generation, photonenhanced thermionic energy conversion has a significantly higher efficiency than conventional thermionic energy conversion. Thermionic power generator accessscience from mcgrawhill. Because of this high rejection temperature, thermionic converters may be useful as top ping devices for steam turbines. In a thermionic device, electrons evaporate from a hot cathode into a vacuum and are collected by a cooler anode, generating current.
Solidstate and vacuum thermionic energy conversion mrs. Since a thermionic converter is essentially a heat engine whose working fluid is an electron gas the electrons evaporate from the heated emitter and condense on the cooled collector, the efficiency of a thermionic converter cannot exceed that of the carnot cycle. We find the relation between the optimum load resistance and the internal resistance and. Thermionics is a method for converting heat to electricity that was developed in the 1960s and 1970s, primarily for use in the spacenuclear program. Thermionic and thermoelectric power generators arpae. The improvement in the effective power factor through thermionic emission can be combined with the other methods to reduce the phonon thermal conductivity in superlattices and thus obtain higher thermoelectric figureofmerit zt.
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