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News >> The material that can generate electricity by temperature difference

 Often concerned about some of the new electronic products, should be seen to promote their own electronic products never need to charge, alone the body can advertise. And regardless of one of the water, alone can the body can generate electricity? The answer is yes, thermoelectric material can be.

 
As the name implies, thermoelectric materials are a functional material that can achieve direct conversion of thermal and electrical energy.
 
Speaking of thermoelectric materials this unique performance found, you have to mention three people, as well as their name in the name of the three effects.
 
In 1821, the German scientist Seebeck connected two different metal wires together to form a current loop and maintained a different temperature at both nodes, and found that the compass around the wire had deflected. Thus, the effect of the potential due to the temperature difference is called the Seebeck effect. And the ratio of the voltage difference between the two ends of the wire to the temperature difference is called the Seebeck coefficient.
 
In 1834, the French scientist Peltier discovered the inverse effect of the Seebeck effect. He connected the two metal wires together and passed the current, and found that the joints at the water into the ice, this phenomenon for the Peltier effect.
 
In 1856, the British physicist Thomson found that if the temperature gradient in a uniform conductor through the current, the conductor in addition to produce irreversible Joule heat, but also to absorb or release a certain amount of heat, this phenomenon known as Thomson effect The
 
 
 
So why is this thermoelectric phenomenon? The figure above is a schematic representation of the plug-in effect of the semiconductor material (left) and the Peltier effect (pictured right).
 
When the temperature difference between the two ends of the semiconductor, the hot side carriers (electrons or holes) has a higher kinetic energy than the carrier near the cold end, and the hot end is excited into the conduction band or valence band carriers More, resulting in the diffusion of carriers from the hot end to the cold end. While the accumulation of carriers will form an electric field, thus hindering the diffusion. When a balance is reached, the carriers are no longer diffused and the electromotive force is generated at both ends of the semiconductor. This is the thermoelectric power generation.
 
So what is its reverse process? The potential energy of the carriers in different semiconductors is different, so the energy exchange between the dissimilar materials and the lattice occurs, and the endothermic or exothermic phenomena near the interface are generated macroscopically.
 
See here, I believe many people will think of thermoelectric materials can be used to generate electricity or cooling.
 
Thermoelectric materials Thermoelectric power generation technology began in the early 1940s. Compared with other power generation technology, the thermoelectric power generation has the advantages of simple structure, strong and durable, no moving parts, no noise, long service life and so on. It is suitable in the fields of aerospace, aviation and military. With the development of technology, thermoelectric power generation in the use of solar energy, geothermal energy, industrial waste heat, car exhaust waste heat, the body also has the application of heat.
 
The main application of thermal refrigeration has a civilian field of automotive refrigerators, dehumidifiers, small beverage machines, car cold cups, cold caps, car seats, cosmetic storage boxes, as well as electronic field CPU test platform, cold air device, High-power LED radiator, projector cooling and so on.
 
The same is the temperature of electricity or electricity cooling, which material is better? German scientist Altenkirch (Altenkirch) pointed out that a good thermoelectric material must have a larger Sebeck coefficient, higher conductivity, lower thermal conductivity. So the thermoelectric properties of the material can be expressed by a uniform ZT value. The higher the ZT value, the higher the maximum conversion efficiency of the material. In general, the ZT value is greater than 1, the party has practical value.
 
It is difficult to achieve a significant increase in the ZT value by independently regulating a parameter by independently determining the three parameters (conductivity, sebeck coefficient and thermal conductivity) of the ZT value. Increasing the carrier concentration increases the conductivity, but at the same time reduces the Seebeck coefficient and increases the carrier thermal conductivity. Increasing the effective mass of the carrier increases the Seebeck coefficient, but theoretically has an adverse effect on the mobility.
 
At present, ZT has been found greater than 2 thermoelectric materials, but still need to be further improved.