Energy Conversion Systems B. V., a joint venture of ADENCO advanced energy conversion in the Netherlands and the Institute of Physics and Power Engineering (IPPE) in Russia is making good progress in the commercialization of terrestrial thermionics. A survey is given of recent results, including the design of a prototype TECTEM®. This is a central heating facility equipped with thermionic converters. This prototype will serve as a test vehicle for various TECTEM concepts. The TECTEM consists of an array of Thermionic Energy Converters (TEC's), each equipped with it's own radiative burner recuperator, a boiler and an invertor which converts the low voltage DC electricity into 220 V/50 Hz AC electricity. Some preliminary test results of combustion heated TEC's are presented, as well as some data about improved performance of TEC's with modified electrodes as compared to the standard Mo-Ni electrode pair.