Permeablethermoelement based on the use of heat transfer by liquids or gases passingthrough thermoelement legs has been studied. Various models of suchthermoelements and their physical descriptions are given. The procedure forcalculation and optimization of basic parameters based on optimal controltheory and computer simulation methods has been presented. The advantages ofpermeable thermoelements over conventional ones containing legs of solidmaterial have been shown. Experimental results proving the basic concepts of theoryand results of calculating permeable thermoelements are given. The prospects ofusing such thermoelements in thermoelectric generators are analyzed.