MadSci Network: Physics

Re: Is the Peltier effect the most efficient way to convert heat to electricity

Date: Fri Feb 2 19:37:48 2001
Posted By: Michael L. Roginsky, Staff, Avionics, Honeywell Defense Avionics
Area of science: Physics
ID: 979023801.Ph

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:,5716,108546+3+106047,00.html?

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:

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):

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:

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.

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