AMTEC requires energy input at modest elevated temperatures and thus is easily adapted to any heat source, including radioisotope, concentrated solar power, external combustion, or a nuclear reactor. A solar thermal power conversion system based on an AMTEC could have advantages over other technologies for some applications including (thermal energy storage with phase-change material) and power conversion in a compact unit. The overall system could achieve as high as 14 W/ kg with present collector technology and future AMTEC conversion efficiencies. The energy storage system has the potential to batteries, and the temperatures at which the system operates allows long life and reduced radiator size (heat-reject temperature of 600 K).