Thermoelectricity is phenomena of direct heat conversion into electricity in solid and liquid conducting materials and inverse effect of direct heating and cooling of junctions of conducting materials with let-through current. The term ‘thermoelectricity��™ comprises three interrelated effects: Seebek thermoelectric effect and Pelletier and Thomson electrochemical effects.� All of them are characterized with corresponding coefficients which are different for different materials. These coefficients are connected with each other by so-called Kelvin relations. They are determined by characteristics of junctions and by properties of materials. Other phenomena, in which heat energy and electricity participate, like thermionic emission and heating effect of current, described by Joule-Lenz’s law, differ essentially from thermoelectric and electrochemical effects and they are not discussed here**.**

**In such a way, these effects allow us having one type of energy (heat or electric) to get another, necessary to solve different problems.**