Electrode testing in simple vapor-vapor AMTEC cells

Alkali metal thermoelectric conversion (AMTEC) is under consideration for a range of applications from solar and radioisotope spacecraft power systems to micro-cogeneration in residential furnaces. AMTEC cells designed for many applications require series connection of individual beta"-alumina solid electrolyte (BASE) tubes. In order to prevent short circuit conditions due to liquid sodium bridging to the metallic cell structure, this generally demands cell operation in a vapor-anode mode. The authors report here the results of a series of AMTEC experiments carried out in a simple vapor-vapor mini-electrode test cell (METC). The cell provides for a once-through sodium supply, in order to provide rapid turnaround and avoid the assembly complications of providing for Na recirculation. This test cell design also provides a simple method to allow for operating a given electrode and current collector combination in both vapor-vapor and liquid-vapor states in a single experimental run. This capability allows a direct comparison between the larger body of historical data on liquid-vapor cells and the vapor-vapor systems now required.