This expression is called the Wiedemann—Franz—Lorenz law, and the constant, L = 2.44 X 10-8 (V/K)2, is the Lorenz number.
In the above derivation, we assumed that the only mechanism of heat conduction is electronic. This is approximately true for metals. We are going to show that in semiconductors the major heat transport is not by electrons but, rather, by phonons. In such materials, the heat conductivity is the sum of AC, the conductivity owing to conduction electrons plus AL, the conductivity owing to lattice vibrations or phonons. However, the Lorenz number is related only to AC:
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The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.