Robert C. Svedberg

Design and Testing of AMTEC Mini‐Cells

The Alkali Metal Thermal to Electric Converter (AMTEC) technology is under development for both terrestrial and space power applications. System designs for these applications are compact and provide power at efficiencies between 20 and 35 %. Converter systems for space power applications have been designed that incorporate simple, compact AMTEC cells. A series of these cells, leading from the February 1993 state of the art to a flight qualified engineering prototype, are being designed and tested. Mechanical and thermal performance tests have been performed on the first four cells of this series. Testing is planned for another 12 cells. Mechanical testing demonstrated that the cell design is capable of worst case random vibration and shock loads of the launch environment. Measured cell efficiency is currently 10% at 923 K, and the cell mass is 110 g. Only a premature failure of a pressure boundary component prevented measured efficiencies from exceeding 14% in the fourth cell. The target cell efficiency ...

AMTEC Module Test Program

The Alkali Metal Thermal to Electric Converter (AMTEC) is a thermally regenerated sodium concentration cell that statically converts heat directly into electricity. The high efficiency of AMTEC will be useful for power generation in space and terrestrial applications. A series of 6 geometrically similar cells with identical wick structures has been fabricated by Advanced Modular Power Systems (AMPS). Three electrode/current collector designs have been included in the testing matrix. Two cells of each design were built. One cell in each set had a thermocouple installed at the electrode/current collector interface to measure the temperature of the beta‐alumina solid electrolyte (BASE) tube. This thermocouple can also be used to measure the voltage at the cathode since its sheath is electrically isolated from ground. The BASE tubes used to build the cells were all from the same production lot. This testing program represents a unique opportunity to comparatively evaluate the performance of geometrically iden...

AMTEC material studies

Texas A&M University, in conjunction with Advanced Modular Power Systems, is performing a series of material studies on key components of an alkali metal thermal to electric conversion (AMTEC) cell for the NASA outer planets power system program. These studies involve SEM, x-ray mapping, EDS, and WDS analysis of AMTEC components from unexposed (as built) samples, from sodium exposure tests, and from operating cells, specifically PX-4C and PX-5B run at the Air Force Research Lab’s Phillips Research Site. Findings are still prelimary, but indicate that recrystallization regions seen in the oven samples are an artifact of excess sodium and oxygen levels in those tests, more potassium is present than expected, and that diffusion bonding between the current collector and electrode takes place.

Enhancement of AMTEC electrodes and current collectors

An improved electrode deposition technique has been developed for a Alkali Metal Thermal to Electric Converter (AMTEC). The innovative Sodium Modulated Electrode (SME) deposition technique has been developed which selectively deposits the electrode on inactive Na sites and adjacent to active Na sites on the electrolyte surface. This program has demonstrated SME processing feasibility and achieved electrode performance enhancement. Power density was improved by 51 to 56% at 973 K and 19 to 26% at 1073 K at the start of electrode testing. Na+ has been conducted through the beta’’‐alumina solid electrolyte (BASE) during the deposition process. Electrode deposition has been a random process, covering both active and inactive sites on the BASE. This random process did not optimize electrode placement or provide pore openings at the Na active sites to permit Na+ easy access to electrons and a low resistance path for Na atoms to move to the condenser. Both Mo and TiN electrodes were evaluated. It has been demons...