Physics and design methods of FGTM
L.I. Anatychuk, L.N. Vikhor
FGTM
(functionally graded thermoelectric material) is considered as one of the
promising methods improving the efficiency of thermoelectric energy conversion.
Physical meaning of FGTM lies in using for the operation of thermoelectric
generators and coolers not only contact, but also bulk effects. Maximum
opportunities of using these effects are achieved when creating materials with
programmable inhomogeneity. Magnetic or force fields affecting material can be
also optimally inhomogeneous. The search for optimal inhomogeneity functions of
both material itself and the fields affecting it is the main physical problem
in the design and creation of FGTM technologies.
The
method for computer design of FGTM for single-and multi-stage generators and
coolers based on the use of mathematical optimal control theory is presented.
The temperature dependencies of thermoelectric material properties and optimal
electric and thermal matching of stages are taken into account. The area of
permissible changes in kinetic material properties as a function of current
carrier concentration is selected with regard for real band structure of
material, energy spectra of phonons and current carriers, their scattering
mechanisms. The advantage of suggested method of seeking for FGTM over known
ones is demonstrated.
The
results of development of the method of seeking for two optimal inhomogeneity
functions simultaneously: of material and magnetic field affecting it for
low-temperature thermoelectric coolers are given. The efficiency of using FGTM
in thermoelectric energy converters is confirmed.