Infrared Photovoltaic Panels - A New Energy Source?

[metastable]

I know this will turn into a heated discussion about the 2nd Law of Thermodynamics, so I will just state the facts as I understand them.

The question is: can a battery be charged by any amount via the following method?

Facts:

1) This research paper about photovoltaic infrared detectors exists:

https://www.researchgate.net/publication/343856156_Higher_Operating_Temperature_IR_Detectors_of_the_MOCVD_Grown_HgCdTe_Heterostructures

2) All objects emit a spectrum of black body photons depending on temperature and for room temperature objects these are infrared wavelengths. This is part of the spectrum for 300k objects:

https://www.spectralcalc.com/blackbody_calculator/blackbody.php

3) The research paper shows a graph where the detector which is at 300k temperature generates 1.6 amps per watt of 3.5 micron infrared light on the detector. This is without any application of bias voltage.

Why not use the infrared emissions of the Earth at room temperature to charge a battery attached to the detector? Some will say this would violate the 2nd Law of Thermodynamics because you'd be generating useful power from a single temperature heat reservoir. Discuss.

 

[nwdiver]

I know this will turn into a heated discussion about the 2nd Law of Thermodynamics, so I will just state the facts as I understand them.

The question is: can a battery be charged by any amount via the following method?

Facts:

1) This research paper about photovoltaic infrared detectors exists:

https://www.researchgate.net/publication/343856156_Higher_Operating_Temperature_IR_Detectors_of_the_MOCVD_Grown_HgCdTe_Heterostructures

2) All objects emit a spectrum of black body photons depending on temperature and for room temperature objects these are infrared wavelengths. This is part of the spectrum for 300k objects:

View attachment 803293

https://www.spectralcalc.com/blackbody_calculator/blackbody.php

3) The research paper shows a graph where the detector which is at 300k temperature generates 1.6 amps per watt of 3.5 micron infrared light on the detector. This is without any application of bias voltage.

View attachment 803294

View attachment 803295

Why not use the infrared emissions of the Earth at room temperature to charge a battery attached to the detector? Some will say this would violate the 2nd Law of Thermodynamics because you'd be generating useful power from a single temperature heat reservoir. Discuss.

.... sure.... ~0.7w per m^2.... just like your graph says. But you'd get ~10x more energy from a Hamster running in a wheel and it would be ~100x more adorable.

 

[metastable]

.... sure.... ~0.7w per m^2.... just like your graph says. But you'd get ~10x more energy from a Hamster running in a wheel and it would be ~100x more adorable.

Right but since it would be running off of invisible infrared light from a room temperature thermal source like the ocean, not light directly from the sun, you could put the panels in stacks, so the power would be based on volume not surface area. There's also the possibility of tuning the band gap to capture multiple wavelengths or wavelengths at a different frequency with higher spectral power.

Then there's the issue where if you generate any useful power at all to store in a battery with a 300k (80F) heat source like an ocean and a 300k (80F) detector, it could be argued that it's tiptoeing or tapdancing around the 2nd Law of Thermodynamics, depending on how you analyze it. For example you can't power a stirling engine by simply lowering it into an 80F (300k) tank of water.

 

[nwdiver]

the power would be based on volume not surface area.

.... that's where conservation of energy says yeah, nah. You can't stack 100,000 and get 70kW of power. Don't work like that.

 

[metastable]

.... that's where conservation of energy says yeah, nah. You can't stack 100,000 and get 70kW of power. Don't work like that.

Well the power is proportional to the surface area, but in a stack the surface area is proportional to the volume, but the energy is proportional to the enthalpy of the Earth which is far larger in total than the world's oil reserves.

More interesting to me is if it works even slightly it suggests a possible 2nd Law of Thermodynamics violation. It would allow for the construction of a Maxwell's Demon type apparatus.

Maxwell's demon - Wikipedia

en.wikipedia.org

 

[metastable]

Lowering the temperature of the Earth's oceans by 1 degree C yields around 1.5*10^9 terawatt hours if I did my calculations correctly.

 

[nwdiver]

Well the power is proportional to the surface area, but in a stack the surface area is proportional to the volume,

Yes. The surface area not the volume and they're not directly proportional. Doubling the volume doesn't double the surface area.

 

[metastable]

Well if you lowered 1 square meter (m^2) panel into the 80F (300k) ocean at night (horizontally), and it generates a certain amount of power (W), voltage (V) and current (I) from the water's 3.5 micron infrared black body radiation to charge a battery connected across the terminals of the 80F (300k) panel, and then you lower a second one beneath it, charging a 2nd battery, you've doubled the power and current and doubled the volume, and doubled the surface area of the panels (although the footprint area on the ocean remains unchanged if the 2nd panel is beneath the 1st one).

 

[ItsNotAboutTheMoney]

Well if you lowered 1 square meter (m^2) panel into the 80F (300k) ocean at night (horizontally), and it generates a certain amount of power (W), voltage (V) and current (I) from the water's 3.5 micron infrared black body radiation to charge a battery connected across the terminals of the 80F (300k) panel, and then you lower a second one beneath it, charging a 2nd battery, you've doubled the power and current and doubled the volume, and doubled the surface area of the panels (although the footprint area on the ocean remains unchanged if the 2nd panel is beneath the 1st one).

The concept isn't the problem. Cost is the problem. Energy-density and efficiency are huge cost factors. They're why it took so long for PV to be commercially viable.

As noted above by @nwdiver, it's very low energy-density.

Something like this could, however, be useful for sensors with low energy requirements.

PS If it's infrared, it's not photvoltaic.

 

[metastable]

PS If it's infrared, it's not photvoltaic.

It is actually photovoltaic since it's a photodiode operating with zero bias voltage...

Photodiode article from wikipedia:

 

[metastable]

The concept isn't the problem. Cost is the problem.

If you talk to a thermodynamics professor they'll likely say the concept is the problem because extracting usable energy from a single temperature reservoir is considered a violation of the 2nd Law of Thermodynamics and it's also considered a perpetual motion machine of the 2nd kind...

Perpetual motion machine of the second kind

Perpetual motion machine of the second kind

www.futurelearn.com

UY1: Definition of second law of thermodynamics

The second law of thermodynamics is based on experimental observations. It places constraints on the direction of heat flow the attainable efficiencies of heat engines and heat pumps, beyond the fi…

www.miniphysics.com

 

[metastable]

For example if it works as I described then I could charge a battery with an 80F (300K) heat source like the ocean for a long time day or night (depending on the area of the panel) and then use the stored energy from the battery to boil some water in an espresso machine. Boiling water 373K (211F) spontaneously with a 300K (80F) ambient heat source (like the ocean) is a violation of the 2nd Law of Thermodynamics as I understand it.

 

[ItsNotAboutTheMoney]

For example if it works as I described then I could charge a battery with an 80F (300K) heat source like the ocean for a long time day or night (depending on the area of the panel) and then use the stored energy from the battery to boil some water in an espresso machine. Boiling water 373K (211F) spontaneously with a 300K (80F) ambient heat source (like the ocean) is a violation of the 2nd Law of Thermodynamics as I understand it.

You don't understand it.
Temperature is irrelevant.
Energy is what matters.
You're moving energy from once place to another.

Microwaves are very cold. Microwave ovens make things hot.
Heat pumps can take energy from lower temperature environments and heat up hotter environments.

 

[metastable]

You don't understand it.
Temperature is irrelevant.
Energy is what matters.
You're moving energy from once place to another.

Microwaves are very cold. Microwave ovens make things hot.
Heat pumps can take energy from lower temperature environments and heat up hotter environments.

I sat down with a thermodynamics professor at Chico State University a week or two ago to discuss the idea, and he insisted it wouldn't work because it would violate the 2nd Law of Thermodynamics.

If it works one could achieve the same outcome as Maxwell's Demon by putting the 3.5 micron infrared photovoltaic panel in Chamber A and a resistive heating element in Chamber B with everything having a starting temperature of 300K (80F)...

"Maxwell's demon is a thought experiment that would hypothetically violate the second law of thermodynamics."

"the demon's actions cause one chamber to warm up and the other to cool down"

Maxwell's demon - Wikipedia

en.wikipedia.org

 

[metastable]

It seems with enough vertical layers underwater in the ocean, you could get more power for the same surface footprint (W/m^2 ocean surface area) than with solar which can only use 1 layer on the surface.

Also since it would be running off thermal radiation from the water rather than sunlight it could work 24hr/7dy so could be considered baseload power and might eliminate the need for costly energy storage batteries (wind and solar don't work on calm nights so needs storage to achieve a 100% renewable grid).

Also the thermal energy extractable from the oceans exceeds the planet's fossil fuel reserves... so there seems to be a lot of reasons to explore this power source as a future means of extracting heat energy from the planet.