In this paper two methods of highly efficient direct energy conversion are discussed: Beam Direct Conversion used in neutron beam irradiation and Pk Plasma Direct Conversion used in Tandem Mirror Reactor. Compared are the principles and current status of Beam Direct Converter (BDC) experiments in three nuclear laboratories: ORNL, LLNL and Fontenay-aux-Roses. The reasons of BDC efficiency loss are analyzed and the role of atomic processes, like ionization, charge exchange and reionization is evaluated. Efficiency of Plasma Direct Converter (PDC) is analyzed.