What are the components of thermionic generator?
Thermoelectric power generators consist of three major components: thermoelectric materials, thermoelectric modules and thermoelectric systems that interface with the heat source.
What is thermionic conversion?
Thermionic energy conversion (TEC) is the direct conversion of heat into electricity by the mechanism of thermionic emission, the spontaneous ejection of hot electrons from a surface.
What materials are used for thermionic emission?
Typically made of a mixture of barium, strontium, and calcium oxides, the coating is sputtered away through normal use, often eventually resulting in lamp failure. One of the bulbs with which Edison discovered thermionic emission.
How do you increase your thermionic emissions?
The large surface area provides more space for electrons to emit. Thus, if large surface area metals are used the rate of thermionic emission will increase proportionally.
Which metal is used in thermionic generator?
Cesium is used in the most efficient converters because of its low ionization potential (3.89 electron volts). Potassium, rubidium, and various other elements may also be used.
What are thermionic devices?
Thermionic devices convert thermal energy to electricity using the thermionic effect [3, p. 182]. A thermionic device consists of a vacuum tube with electrodes in it. The metal cathode is heated until electrons start evaporating off the metal. The electrons collect at the anode which is at a colder temperature.
How does a thermionic generator work?
Heating one end of a thermoelectric material causes the electrons to move away from the hot end toward the cold end. When the electrons go from the hot side to the cold side this causes an electrical current, which the PowerPot harnesses to charge USB devices.
Why tungsten is used for thermionic emission?
Tungsten is a suitable metal for Thermionic emission, has a high melting point of 3655 K but its work function is high at about 4.52 eV(electron volt-energy unit). It starts emission at 2500 K. If thoriated tungsten (coated with carbon and thorium) is used work function reduces to 2.6 eV and emission begins at 2000 K.
Why is tungsten filament used for thermionic emissions?
Tungsten was previously used as the materials for the thermionic emitter. It has high work function but still, it was used as the cathode because of its high melting point and the material is mechanically very strong.
How does a thermionic valve work?
The type known as a thermionic tube or thermionic valve utilizes thermionic emission of electrons from a hot cathode for fundamental electronic functions such as signal amplification and current rectification.
What is the use of thermionic emission?
Thermionic emission. Thermionic emitters are used in a variety of applications, including high-frequency vacuum transistors for electronics, electron guns for scientific instrumentation, power electronics, x-ray generation, and energy converters from high-temperature sources and solar energy.
What is inside a thermoelectric generator?
The basic building block of a thermoelectric generator is a thermocouple. A thermocouple is made up of one p-type semiconductor and one n-type semiconductor. The semiconductors are connected by a metal strip that connects them electrically in series. The semiconductors are also known as thermoelements, dice or pellets.
What is a thermionic converter?
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.
Why do thermionic converters need to be designed for space missions?
SUMMARY In order to provide design flexibility for space missions, thermionic converters must operate efficiently at reduced emitter temperatures. Maintaining converter efficiency while operating at reduced temperatures requires improved emitter and collector electrodes as well as decreased
Why do thermionic converters need an additional electrode?
High performance thermionic converters may require an additional electrode to minimize the arc drop, Vj. Such triodes (ignited and non- ignited) and pulsed diodes which require an auxiliary power input to provide ions for space charge neutralization can be characterized by
How do you supply oxygen to a thermionic converter?
The most satisfactory solution to supplying oxygen to a thermionic converter would be a cesium oxide reservoir that would supply an equilibrium cesium and oxygen atmosphere of the proper composition. Experiments by Pigford, et al., have indicated that such a reservoir