3 edition of Thermionic energy conversion found in the catalog.
Thermionic energy conversion
George Nickolas Hatsopoulos
|Statement||[by] G.N. Hatsopoulos and E.P. Gyftopoulos ; prepared under the auspices ofthe U.S. Department of Energy, Division of Power Systems.|
|Contributions||Gyftopoulos, E P.|
It includes in-depth discussions not only of better efficient energy management in buildings and industry, but also of how to plan and design for efficient use and management from the ground up. It appears that the close-spaced converter project has been carried out with great competence and skill. This program should be funded separately from the thermionics research program. Schematic of a basic thermionic converter.
That year another American scientist, George N. These factors are all available in planar converter geometries. These issues must be addressed before benefits of oxygenation can be conclusively established, and the committee believes that the benefits are difficult to justify. Evaporation and redeposition of even a few atomic layers could change the single-crystal nature of the surfaces. A thermionic converter consists of a hot emitter electrode from which electrons are vaporized by thermionic emission and a colder collector electrode into which they are condensed after conduction through the inter-electrode plasma.
Researchers were able to grow layers of pure tungsten on molybdenum substrates using both reactions. During the period from tohowever, significant research on advanced low-temperature thermionic converter technology for fossil-fueled industrial and commercial electric power production was conducted in the US, and continued until for possible space reactor and naval reactor applications. This power density value is less than conventional thermionic technology capability by a factor of approximately This is sometimes collectively referred to as a "sea of electrons".
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By the early s the American chemist Irving Langmuir had developed sufficient understanding of thermionic emission to build basic devices, but little progress was made until From toJulius Elster and Hans Geitel of Germany developed a sealed device containing two electrodes, one of which could be heated while the other one was cooled.
Stephanos, T. The vacuum converter must have very clean electrodes at all times. Edison built several experimental lamp bulbs with an extra wire, metal plate, or foil inside the bulb that was separate from the filament and thus could serve as an electrode.
The current modeling work does not appear to extend theoretical understanding. From band theorythere are one or two electrons per atom in a solid that are free to move from atom to atom. PbTe is one of the best materials for this purpose.
The work function is less than 1. When the foil was raised to a positive potential relative to the filament, there could be a significant current between the filament through the vacuum to the foil if the filament was heated sufficiently by its own external power source.
Thermoelectric converters use a semiconductor with a high thermoelectromotive force. 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 themselves—are involved in the process.
However, even given the fairly large number of projects for the modest yearly funding available, the program does not sustain thermionic science and basic research related to electrode materials, plasma physics, and surface physics. The book also gives a comprehensive description of the direct energy conversion methods, including, Photovoltaics, Fuel Cells, Thermoelectric conversion, Thermionics and MHD It briefly reviews the physics of PV electrical generation, discusses the PV system design process, presents several PV system examples, summarizes the latest developments in crystalline silicon PV, and explores some of the present challenges facing the large scale deployment of PV energy sources.
In cylindrical geometries, a single-crystal electrode will provide enhanced mechanical properties, but the work function will vary around the circumference. The purpose of this volume — the first of two — is to summarize what is known about the process for the benefit of a wide audience of technical readers who are not familiar with its potentials as well as to serve as a reference for those already in the field.
The theoretical predictions for our thermoelectronic generators reach about 40 percent, although this is theory only," noted Mannhart. Sb-doped highly oriented diamond and low electron affinity AlGaN are investigated for collectors.
It is hoped that MTCs would be able to operate at high efficiency using a relatively low temperature heat source. In the case of solid-state devices, hot electron filtering using heterostructure barriers is used to increase the thermoelectric power factor.
Ultimately they envision a small device that can fit on a desk and easily scale depending on the application. Two axial measurements will be made periodically to determine creep rates. Mannhart appears in the Journal of Renewable and Sustainable Energy: dx.
They discovered that, at fairly low temperatures, electric current flows with little resistance if the hot electrode is positively charged. Finding: Without stable, multiyear funding, university researchers hesitate to take part in thermionics research efforts, and the thermionics community misses the opportunity to leverage university-based research.
His work led to rapid advances in thermionic power conversion. The proportion depends on the temperature. Integrated circuit fabrication techniques are used to transfer the n- and p-type thin films on AlN substrates and make power generation modules with hundreds of thin film elements.
Substantial thermionic space reactor development programs were conducted in the U. It is the opinion of the committee that, at this time, program funding should not be spent on electrode analysis validation, particularly when no method to correct performance problems is available.
University research must be supported not only to provide technical knowledge continuity but also to gain advocates, now and in the future, for the complex and wide ranging technologies associated with thermionic energy conversion.
And unlike other direct conversions methods, there is no need for access to natural light as required for photocells or special chemicals as required for fuel cells —there are many available sources of thermal energy that can be utilized.
Mechanism for electron escape in thermionic power conversion A The electric field lines for an electron near the surface of a metal. Part of this energy is converted to heat that must be removed to maintain the collector at a suitably low temperature.
These losses can occur by radiative transfer across the gap and by parasitic thermal conduction transfer around the converter edges from the hot side to the cold side of the system as a whole.c.
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 thermionic conversion can be utilized in several different situations—remote locations on the earth and in space. Proceedings of the 13th Intersociety Energy Conversion Engineering - Direct energy conversion - pages. 0 Reviews. From inside the book. What people are saying - Write a review.
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Contents. Chapter Title Page. Thermionic Energy Conversion. Thermoelectric Energy. Visit atlasbowling.com to get more information about this book, to buy it in print, or to download it as a free PDF.
The National Academies Press. doi: / be more successful if it were to emphasize a basic research program in electrode and materials. The emphasis of the review is placed both on the available tools for the analysis of thermionic emission and on the problems that remain to be solved.
Transport of low-energy particles through a vapor, of the type encountered in thermionic conversion, is discussed. Oct 22, · The book contains 10 chapters and opens with a discussion of forms of energy, energy sources and storage, and energy conversion.
This is followed by separate chapters on thermal properties and relations, heat engines, chemical energy, electrochemical processes, and solar energy. Subsequent chapters deal with thermoelectricity, thermionic Book Edition: 1.
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.
This minimal energy, called the work function, is characteristic of the emitting material and the state of contamination of its surface. See also field emission.