Performance characteristics and thermal design of alkali metal thermoelectric conversion system

Experimental studies to improve the performance of the alkali metal thermoelectric converter (AMTEC) have been conducted. A new method for supplying thermal energy to the beta-aluminum solid electrolyte (BASE) is proposed. A porous metal thermal conductor inserted between the thermal source and the BASE tubes reduces the large temperature drop without disturbing the sodium vapor flow from the electrodes to the condenser surfaces. The current-voltage characteristics of three different types of BASE tubes were measured, and the highest power density achieved was 0.6 W/cm² at 1100 K. A preliminary 7-kW AMTEC system integrated with a space solar receiver (SSR) has been designed based on the state-of-the-art AMTEC performance. The AMTEC-SSR system has achieved a specified mass of approximately 130 kg/kWe, resulting in an expected mass reduction of 20-50% as compared with solar dynamic power systems or solar photovoltaic systems.