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.
A dual-stage sodium thermal electrochemical converter (Na-TEC)
Abstract The sodium thermal electrochemical converter (Na-TEC) is a heat engine that generates electricity through the isothermal expansion of sodium ions. The Na-TEC is a closed system that can theoretically achieve conversion efficiencies above 45% when operating between thermal reservoirs at 1150 K and 550 K. However, thermal designs have confined previous single-stage devices to thermal efficiencies below 20%. To mitigate some of these limitations, we consider dividing the isothermal expansion into two stages; one at the evaporator temperature (1150 K) and another at an intermediate temperature (650 K–1050 K). This dual-stage Na-TEC takes advantage of regeneration and reheating, and could be amenable to better thermal management. Herein, we demonstrate how the dual-stage device can improve the efficiency by up to 8% points over the best performing single-stage device. We also establish an application regime map for the single- and dual-stage Na-TEC in terms of the power density and the total thermal parasitic loss. Generally, a single-stage Na-TEC should be used for applications requiring high power densities, whereas a dual-stage Na-TEC should be used for applications requiring high efficiency.
Spin label motion in fatty acids.
Spin labels dissolved in highly purified fatty acid systems exhibit nearly identical tumbling rates in liquid and solid phases. Even though the spin labels do not have the same molecular geometry as the lipid matrix the melting point of the matrix can be inferred by measurements of the temperature dependency of molecular motion.