Asri-unix.930 net.space utcsrgv!utzoo!decvax!ucbvax!C70:sri-unix!DIETZ@USC-ECL Tue Mar 9 12:22:38 1982 Sodium heat engine - SPS application? The following appeared in a recent (Feb. 27) Science News: ---------------------------------------- Electricity from a sodium heat engine Scientists at the Ford Motor Company are developing a new device capable of converting heat directly into electrical energy. This device, called a sodium heat engine, has no moving parts and uses a small quantity of liquid sodium as its working fluid. Hot liquid sodium fills one side of a closed container divided into two parts by a ceramic wall of the compound beta''-alumina. The wall allows passage of sodium ions but not electrons or sodium atoms. Thus, sodium ions go through the solid, ion-conducting electrolyte, while electrons travel an external circuit to provide a low voltage, high current electrical output. A sodium vapor pressure difference across the electrolyte generates the driving voltage. In the low temperature part of the system, the sodium vaporizes from the electrode surface and then condenses on a cooled wall. An electromagnetic pump returns the condensed sodium to the hot region. The device can use any source delivering heat at 700 degrees C or more. Its efficiency, potentially in the range of 30 to 40 percent, is independent of the heat engine's size. A model designed for long-term testing has reached 19 percent efficiency at an output of 22 watts. The pump siphons off less than 0.1 percent of the energy output. The major problem with the system is deterioration of the electrodes after several hundred hours of operation, which lowers the voltage and decreases power. Despite this problem, the sodium heat engine looks good more promising than many earlier thermionic devices. The researchers say, "An efficient, durable, low maintenance, thermoelectric energy converter with good power density, made of readily available materials and with efficiency independent of size would have substantial implications for solution of some of the nation's energy, transportation and defense problems." Potential applications include use in total energy systems for residences and factories, in remote locations and as part of solar energy installations the concentrate light. Even the rejected heat at the low temperature end of the cycle can be used. ---------------------------------------- If they can solve that electrode problem this thing could be useful in solar power satellites. ------- ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.