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## Could Earth's Infrared Emissions Be a New Renewable Energy Source?78

Zothecula (1870348) writes "Could it one day be possible to generate electricity from the loss of heat from Earth to outer space? A group of Harvard engineers believe so and have theorized something of a reverse photovoltaic cell to do just this. The key is using the flow of energy away from our planet to generate voltage, rather than using incoming energy as in existing solar technologies."
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## Could Earth's Infrared Emissions Be a New Renewable Energy Source?

• #### Not New (Score:4, Informative)

on Friday March 21, 2014 @03:16AM (#46541349)
This is not a new idea. http://web.mit.edu/newsoffice/... [mit.edu]
• #### Re:Power density? (Score:3, Informative)

on Friday March 21, 2014 @06:24AM (#46541913)

Score 5: Interesting/Insightful. WTF?

*) Diurnal. Does it mean what you think it means?
*) Energy received and energy emitted by the Earth aren't equal. You might have heard of global warming.
*) The energy emitted by the Earth isn't all infrared radiation.( http://en.wikipedia.org/wiki/F... [wikipedia.org] and http://www.eoearth.org/view/ar... [eoearth.org] )
*) Temperature doesn't have color, pressure doesn't have speed and energy doesn't have entropy. You can only define entropy for a thermodynamic system (i.e. Earth, or Earth + atmosphere).
*) Entropy more or less describes the disorder of a system. All oher things being equal, the entropy goes up with the temperature (0 at 0K, higher at 6000K than at 300K)
*) You're probably talking about exergy : http://en.wikipedia.org/wiki/E... [wikipedia.org]

Thermodynamics is hard. You have to define everything and understand the underlying mathematical concepts.

• #### Re:Power density? (Score:5, Informative)

on Friday March 21, 2014 @07:38AM (#46542209)

Energy received and energy emitted by the Earth aren't equal. You might have heard of global warming.

True, they're not equal. To a reasonable approximation, they are equal: the heat picked up via global warming is tiny compared to the amount of heat added by the Sun each day (and subsequently lost to space by radiation).

The energy emitted by the Earth isn't all infrared radiation.( http://en.wikipedia.org/wiki/F [wikipedia.org]... [wikipedia.org] and http://www.eoearth.org/view/ar [eoearth.org]... [eoearth.org] )

True, though it's mostly infrared and albedo.

Temperature doesn't have color

No, but a distribution of radiation does. When, in physics, someone says that radiation is "X Kelvin", it's shorthand for "a distribution of radiation very close to the ideal black-body radiation at X Kelvin". The great bulk of the Sun's and Earth's radiation is black-body radiation.

You can only define entropy for a thermodynamic system (i.e. Earth, or Earth + atmosphere).

Radiation certainly does have entropy. See, for example, Planck's "the Theory of Heat Radiation" or some more modern text.

All oher things being equal, the entropy goes up with the temperature (0 at 0K, higher at 6000K than at 300K)

This is just a misunderstanding of the meaning of 6000K vs. 300K light. Though it's incorrect to just assume zero entropy at 0K.

Entropy more or less describes the disorder of a system.

It's enormously more complicated than that. That's a Brian-Greene-level description.

... Are you an engineer?

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