Pdf thermionic energy conversion in the twentyfirst century. Inside the material it has some kinetic energy and some potential energy, but we dont really care exactly what those are since we know their sum. The stirling engine power conversion concept is a candidate to provide electrical power for deep space missions. Thermoelectric and thermionic generators slideshare. Pdf thermionic energy conversion tec is the direct conversion of. Enhanced thermionic energy conversion and thermionic emission.
Direct energy conversion gang chen mechanical engineering department massachusetts institute of technology office. A hot wire will be surrounded by evaporated electrons. Rohsenow heat and mass transfer laboratory, mit direct thermaltoelectric energy conversion technologies thermoelectric converter thermionic converter. The simplest type of thermionic converter consists of two electrodes separated by a vacuum gap a simple cesium thermionic converter is shown in. The simplest type of thermionic converter consists of two electrodes separated by a vacuum gap a simple cesium thermionic converter is shown in figure 1 on page 604.
The fundamentals of electron emission from electrodes and electron transport in vacuum gap are presented, as well as the state of the art of solar thermionic energy conversion technologies, including heatinduced thermionics and photonenhanced thermionics. Thermionic energy converters tec can function as topping cycle devices for combustion systems or serve as. Ang1, 1sutdmit international design center, singapore university of technology and design, singapore 8682. In this article, the conceptual model of a hybrid energy converter consisting of a thermoradiative cell trc and a thermionic cell tic is established, where the trc is made of ptype and ntype. T1 enhanced thermionic energy conversion and thermionic emission from doped diamond films through methane exposure. Thermionic converter article about thermionic converter by. The analysis applies to all vacuum converters, and to gas. Pdf prototype rhenium component for stirling engine. One of these is raised to a sufficiently high temperature to. Thermionic power converters can convert heat energy directly to electrical. The point is, once it enters the vacuum, its total energy is still made up of kinetic and potential energy.
In the ideal case, when the electrons strike the collector, they will give up their kinetic energy plus energy equal to the collector work function. 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. The journal energy conversion and management provides a forum for publishing original contributions. The concept of a vacuum thermoelement is attractive as it removes one of the problems in thermoelectric energy conversion, namely heat conduction through a solid. Nov 30, 20 thermoelectric and thermionic generators 1. Scientists look to thermionic energy conversion for clean and efficient power generation. A brief overview of the research activities at the thermionic energy conversion tec center is given. The current density associated with this process is obtained from.
Proofs of this development are the existing thermionic reactor projects in. We derive richardsons law that describes emission of electrons from a metal at given temperature. A key element for qualifying potential flight hardware is the longterm durability. Theoretical efficiency of the thermionic energy converter. Thermionic energy conversion for concentrating solar power. Thermionic emission of electrons from metal at high temperature is discussed. The conversion efficiency and high temperature of heat rejection minimize the size and weight of the radiator. Mar 01, 2016 scientists look to thermionic energy conversion for clean and efficient power generation. Researchers will perform systems analysis and smallscale experimental performance verification of an optically modulated thermionic energy converter omtec. Mcdonald, received 23 october 1966 abstractthe transfer of electrons from the emitter or space charge region to the collector in a thermionic energy convertor by negative ions has been. It is shown that efficient thermionic generation in a vacuum device might be possible if improved thermionic emitters become available.
Thermionic energy conversion how is thermionic energy. Childs law that describes relation between anode current at given cathodeanode potential is also derived. Electron emission thermal energy conversion a thesis. A thermionic energy converter using singlelayer graphene. The charge carriers can be electrons or ions, and in older literature are sometimes referred to as thermions. Thermionic energy conversion, volume 1 the mit press. Efficiency and cop in vacuum diodes used as energy convertors. Thermionic emission article about thermionic emission by. Unlike the conventional indirect methods for generating electricity from heat sources, no intermediate form of energy is required, and no working fluid except the flow of the electrical charges themselvesare involved in the process. For that reason, the author developed the general theory of the plasma diode energy converter. Thermionic emission energy distribution from nanocrystalline diamond.
Thermionic conversion is a method for converting heat directly into electrical energy. An analysis of the efficiency of the thermionic energy converter is given in terms of vc and va, which represent the potential differences between the top of the potential barrier between the electrodes and the fermi levels of cathode and anode, respectively. Pdf thermionic energy converter tec is a heat engine that generates. Advanced energy conversion thermionic power conversion. Schematic representation of an energy conversion device. This chapter focuses on the thermionic energy conversion with description of idealized model of a thermionic converter and work function of various surfaces. This type of emission uses a high electric field produced by a gate electrode to. Mannhart2,b 1experimental physics vi, center for electronic correlations and magnetism. Thermionic energy converter tec has recently received significant attention, for it. The possibility of transfer of electricity in a thermionic. Weiner,1,3 and gerardo morell1,2 1institute for functional nanomaterials, university of puerto rico, san juan, puerto rico 00931, usa 2department of physics, university of puerto rico. The driving force of this process is the thermal energy which provides a nonzero density of carriers at energies larger than the confining barrier.
An international journal energy conversion and management. Enhanced thermionic energy conversion and thermionic. 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. The basic plasma types associated with various modes of con. Energy conversion device energy input energy output energy output energy input 1st law useful energy output energy input 2nd law figure 41. Thermionic energy conversion is one of the promising technologies for transforming thermal energy into electrical energy. Vacuum thermionic energy converter construction of a thermionic energy converter sulfur doped nanocrystalline diamond films as field enhancement based. Review on thermionic energy converters ieee journals. Thermionic energy conversion is the direct conversion of heat into electricity by the mechanism of thermionic emission, the spontaneous ejection of hot electrons. Thermionic conversions is a method for converting heat directly into electrical energy. Thermionic energy conversion is intended for scientists and engineers working in the field of energy conversion. Starting in 1901, owen richardson studied this phenomenon and in 1929 he received the nobel prize in physics for his work. Thermionic power converter article about thermionic power.
Thermoelectric power generator is a device that converts the heat energy into electrical energy based on the principles of seebeck effect. Thermionic energy conversion is well suited for space applications. An electric force can pull these electrons away from the wire the larger the electric force, the larger the resulting current of electrons. A stable cathode electrode with high conductivity and low work function is. The second design concept investigated in this thesis utilizes the transition region between field emission and thermionic emission known as thermalfield.
Thermionic emission underlies the operation of many electrical vacuum and gas discharge instruments and devices. From a physical electronic viewpoint, thermionic energy conversion is the direct production of electric power from heat by thermionic electron emission. The design of a combustion heated thermionic energy converter. It is shown that efficient thermionic generation in a vacuum device might be possible if. To date, this potential remains unrealized because of difficulties with the materials, designs, and manufacturing methods historically used in thermionic energy conversion technology. Thermionic energy conversion in the twentyfirst century. The basic operating principle of thermionic energy converters is that electrons are evaporated from a heated. Thermionic energy converters are uniquely suited for such topping cycle applications because of their high operating temperatures. Scientists look to thermionic energy conversion for clean and.
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. Electron thermionic emission from graphene and thermionic energy converter shijun liang1 and l. Good thermionic emission is also exhibited by some metallic film cathodes, such as refractorymetal cathodes coated with a film of an alkali, alkalineearth, or rareearth metal. A thermionic converter is a device which converts heat energy into electrical energy by utilizing the thermionic emission of electrons. Despite having a huge potential as an efficient direct energy conversion device, the progress in vacuumbased thermionic energy. Highlyefficient thermoelectronic conversion of solar energy and heat into electric power s. The topics considered include energy generation, utilization, conversion, storage. Sustainable energy science and engineering center energy conversion concerned with the transformation of energy from sources such as fossil fuel and radiation from sun into conveniently used forms such as electrical energy, propulsive energy, heating and cooling. Highlyefficient thermoelectronic conversion of solar energy. Nextgeneration thermionic solar energy conversion fact sheet, sunshot, solar energy technologies program setp, u.
From a thermodynamic viewpoint, it is the use of electron vapor as the working fluid in a powerproducing cycle. A thermionic converter is a static device that converts heat into electricity by boiling electrons from a hot emitter. Energy conversion and management has an open access mirror journal energy conversion and management. Rohsenow heat and mass transfer laboratory, mit thermionic power. With lower material work functions, low temperature. Thermoelectric power generator is a device that converts the heat energy into electrical energy based on the principles of seebeck effect the pioneer in thermoelectric was a german scientist thomas johann seebeck 17701831 later, in 1834, french scientist, peltier and in 1851, thomson. Thermionic emission energy distribution from nanocrystalline. The thermionic conversion can be utilized in several different situationsremote locations on the earth and in space. Unlike the conventional indirect methods for generating electricity from heat sources, no intermediate form of energy is required, and no working fluidexcept the flow of the electrical charges themselvesare involved in the process. Thermionic energy conversion how is thermionic energy conversion abbreviated. Kinetic, potential, thermal, chemical, electromagnetic etc. Highlyefficient thermoelectronic conversion of solar. 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.
Scientists look to thermionic energy conversion for clean. This minimal energy, called the work function, is characteristic of the emitting material and the state of contamination of its surface. January 22, 2015 abstract in this paper, we propose a model to investigate the electron thermionic emission from a single. Thermionic power converter article about thermionic. Thermionic emission is the process where electrons are emitted across a barrier. In thermionic energy conversion a vacuum is applied as the active material between the electrodes, rather than the. Direct energy conversion global climate and energy project. The efficiency of an energy conversion device is a quantitative expression of this balance between energy input and energy output. Other effects at thermionic emission are mentioned. In thermionic emission, the heat supplies some electrons with at least the minimal energy required to overcome the attractive force holding them in the structure of the metal.
Direct thermaltoelectric energy conversion technologies thermoelectric converter thermionic converter thermophotovoltaic converter warren m. Thermionic energy conversion tec is the direct conversion of heat into electricity by the. Efficient low temperature thermionic energy conversion is currently not viable due to the high temperatures required to excite electrons above the material work function. 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. Thermionic energy conversion plasmas plasma science. With increased interest in maximizing the efficiency of present energy conversion systems, it is an important reference for scientific and engineering libraries as well. This occurs because the thermal energy given to the carrier overcomes the work function of the material. Thermionic energy conversion plasmas plasma science, ieee. Lecture 6 thermionic engines i t mit opencourseware. 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. Consequently, thermionic systems with high powertoweight ratios are possible. 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. Printed in great britain the possibility of transfer of electricity in a thermionic convertor by negative ions k.
Thermoelectric conversion is, in essence, similar to thermionic conversion, but without a vacuum gap separating the emitter and collector. Thermionic emission is the liberation of electrons from an electrode by virtue of its temperature releasing of energy supplied by heat. Volume i of thermionic energy conversion dealt with processes and devices mit press. Highly improved thermionic energy converter iopscience. Electron thermionic emission from graphene and thermionic. Dec 03, 20 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. At least 90 per cent of the development effort is now going into the cesium diode as a thermionic energy converter.
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