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Posted: Jun 6 2012, 02:01 PM
Joined: 6-June 12
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I want to know if the known laws of physics, esp second law of thermodynamics, rules out any hope of making either a solar cell or an electric lamp that is 100% energy efficient.
The second law of thermodynamics rules out turning a less 'useful' type of energy into a more 'useful' type of energy without generating even more 'less useful' energy usually in the form of waste heat so that there cannot be any net increase in the overall 'usefulness' if the total energy from an energy conversion.
BUT, purely within this narrow thermodynamic context, is electric energy any more or less 'useful' than visible light energy?
Because if the answer is “no”, then surely it IS possible ( at least in theory ) to make BOTH a solar cell and an electric lamp that are both 100% energy efficient! -right?
But, even if the answer is “yes”, then which type of energy is the more 'useful' type? Electric or visible light?
If visible light is more 'useful' type of energy than electric then does that mean it IS possible ( at least in theory ) to make a solar cell that is 100% efficient but not an electric lamp that is 100% efficient?
And if electric energy is more 'useful' than visible light energy then does that mean it IS possible ( at least in theory ) to make an electric lamp that is 100% efficient but not a solar cell that is 100% efficient?
Does the answers of the above questions depend on the voltage of the electricity and, if so, what is the mathematical relationship between the two ? Does it depend on the frequency or wavelength of visible light?
I also want to know if how 'useful' ( in this narrow context ) visible light is is partly dependent on how broad the range of frequencies that light consists of.
Is, for example, light that just consists of one wavelength, say 550nm only ( which is monochromatic green light which I assume can only be produced by a laser ) , more 'useful' ( in this narrow context ) than white visible light consisting of many wavelengths but with an average wavelength of 550nm?
It is my understanding that visible light energy of lower frequencies i.e. longer wavelengths is less 'useful' ( in this narrow context ) than the same amount of light energy consisting of higher frequencies -is that correct?