Direct energy conversion of heat to electricity using AMTEC
Former renewable technologies, which did not prosper at that time due to engineering and material limitations, emerge once again, as in the case of the Alkali Metal Thermal to Electric Converter (AMTEC). This energy converter transforms heat to electricity through an electrochemical process at high temperature (700 - 1000 °C). At Karlsruhe Institute of Technology (KIT) an AMTEC test cell and an AMTEC TEst FAcility (ATEFA) have been designed and are under construction. The paper gives an overview of the history of AMTEC converter and its development; and presents the ATEFA facility included its latest progress in design and construction. In addition, a scoping study on the stability of PEEK polymer compound in liquid sodium environment was started and is reported.
Development of high temperature test facilities for material investigations in hot liquid metal flows
At the Karlsruhe Institute of Technology three high temperature liquid metal test facilities have been developed in the frame of the Helmholtz Energy Material Characterization Platform (HEMCP). The motivation for the usage of liquid metals is based on the innovative concept proposed for Concentrating Solar Power. The requirements for the qualification of new materials for high temperature applications on a long time basis could not be fulfilled by a facility with a single test section. Therefore, several universal scientific infrastructures, the SOdium Loop for TEst materials and Corrosion facilities (SOLTEC) have been designed, each facility having its specific test section. The core facility consists of two regions, the high temperature side with temperatures up to 1000 K connected to the test section and the low temperature side (up to ~773 K), where the pump and the main components are located. Nickel based steels are foreseen for the high temperature side, while conventional AISI 316Ti stainless steel is used for the low temperature side. At the interface between both regions a heat recuperator has been combined with a Na-air heat exchanger, providing a compact arrangement. All facilities have an electromagnetic pump that drives the sodium into the test section at a maximal mass flow rate of 300 kg/h. Several safety measures have been considered from the design phase and all facilities are designed to operate autonomously with passive fail safe option, allowing a fast emergency drainage and even component failure does not lead to large fire damages. SOLTEC 1 serves for a unique in situ low cycle fatigue investigation for new high temperature materials, such as tungsten laminated compounds. A universal test machine and a high temperature vacuum oven are considered to allow long term and fail safe experiments, even in the case of crack failures. SOLTEC 2 will be used for investigations of steel erosion and corrosion in flowing hot Na environment, while SOLTEC 3 facility will be employed for long term investigations of sodium based thermoelectrical devices. The design activities are finished and the SOLTEC facilities are currently in construction.
The failure of beta-alumina electrolyte by a dendritic penetration mechanism
Abstract A modified theory of beta-alumina breakdown is presented which takes into account factors not previously considered. Calculations show that whereas the population of critical surface flaws in a beta-alumina tube is likely to be initially zero, very small increases in the charge-transfer resistance at the sodium-electrolyte interface will result in previously sub-critical cracks attaining criticality. It is also shown that the time required for full penetration of the electrolyte tube is measured in minutes from the instant a crack achieves criticality. Thus electrolyte life is seen not as a continual process of degradation, but rather as an induction period, during which time changes are occurring at the sodium-electrolyte interface which ultimately lead to criticality and rapid electrolyte failure.