  Thermoelectrics involves both the generation of electrical power from heat
flow, and the efficient refrigeration using electricity, which has been
intensively focused on for two decades. The performance of thermoelectric power
generation and refrigeration has been improved by many proposals since 1993,
which is, however, the currently not yet in an industrially competitive level.
The development of the entire filed has come to a puzzling point, where the
physical reason of why this energy conversion efficiency enhancing problem is
barely soluble, and the physical answer of how it should be re-formed to be
soluble are the most urgent questions in this field. We here answer these
questions and provide the guidance on how to design the of thermoelectric
figure of merit enhancement in various systems using different approaches for
future researches. We start from criticizing the current way of expression the
thermoelectric figure of merit ZT and then introduce the new concept of
pseudo-ZT, which can finally make it clear what variables really decides ZT,
and clarify the historical misunderstanding of many thermoelectric performance
enhancing proposals. Then we explore the most important question on what
variables really enhance ZT, and give the contemporary researchers a new
guidance on what is the correct direction of thermoelectric performance
improving for various systems.
