| MadSci Network: Physics |
Hello Chris: The Peltier effect consists of two dissimilar metals joined together. When electricity is applied to the circuit, heat is transferred across the junction cooling one side while heating the opposite. The opposite phenomena occur when applying heat to the bonded dissimilar metals: electricity is generated. This is called the Seebek effect. Look- up the Internet: www.britannica.com/bcom/eb/article/6/0,5716,108546+3+106047,00.html? query=peltier%20efect www.funkandwagnalls.com/encyclopedia/getpage.asp? abspage=/articles/025000b/025000870.asp The current capacity of Peltier junctions can be increased by using semiconductors instead of metals, and a few watts of power can be produced at efficiencies of 5 up to 7 percent. These devices are used in remote places using kerosene heat to produce enough electric power for radios to operate. In distant and isolated places like in Russia and China where generators are not practical for use, Peltier devices are the only means for radio communications with other areas of the world. Typical utility power plants using natural gas attain efficiencies above 52% and coal around 35 to 42%. Here is a website you might look-up: http://www.greenhouse.gov.au/markets/gen_eff/qa.html Conversion efficiency from turbine to generator is much higher, up to 98%. Here is another website that illustrates the internals of a power plant. Just click the mouse over the area of interest and a page will pop-up discussing that process (neat): http://www.pert.hu/eng_noframe/techn_an.htm Peltier devices find very specialized applications in industry because of the small size that can practically be produced. One manufacturer’s website discusses the practical applications: http://www.electracool.com/install.htm Probably the most worthwhile contribution of Peltier and Seebek is called thermal junction, or thermocouple. It is a temperature-measuring device consisting of two wires of different metals joined at each end. One junction is placed where the temperature is to be measured, and the other is kept at a constant lower temperature. A measuring instrument is connected in the circuit. The temperature difference causes the development of an electromotive force that is approximately proportional to the difference between the temperatures of the two junctions. Thermocouples are very practical for the measurement of temperatures. However, only a select few dissimilar metal junctions are actually practical: copper and constantan (a copper-nickel alloy) for temperatures below 500° F and platinum-rhodium alloy for high-temperature measurements. Your MAD.SCI Micro.
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