Search Results

The Alkali Metal Thermal to Electric Converter (AMTEC) technology can provide static energy conversion at efficiencies between 15 and 30%. Most of these devices reach this efficiency by operating at temperatures near 1100 K or above. High efficiency at lower temperatures is, however, feasible. Experiments and supporting analysis show that 15-20% could be achieved at 925 K by minimizing parasitic losses and using sodium molybdate enhanced electrodes. The sodium molybdate in these enhanced electrodes evaporates from the electrode within 10 to 100 hours at 1100 K, but the molybdate enhancement may last for several years at 925 K.

AMTEC systems have historically been operated with sodium as the working fluid, in large part because fabrication of beta”-alumina solid electrolyte (BASE) membranes has been substantially easier with sodium than with potassium or other alkali metals1. It has been anticipated that because potassium has a substantially higher vapor pressure for a given temperature, and because the best K-BASE conductivity falls only marginally below that for Na-BASE, potassium AMTEC cells could produce higher power at a given temperature or comparable power at a lower temperature than similar sodium cells. Operation at lower temperatures can reduce materials lifetime or compatibility problems, and for severely heat input constrained systems it could enhance efficiency by reducing parasitic thermal conduction losses. Recently K-BASE tubes have become available as a commercial product2 and conventional experiments to evaluate the performance of complete KAMTEC cells have become much more feasible.