A huge amount of infrared energy is sent back from Earth's surface into space. We're talk about 100,000 Terawatt here. There are some ideas on how to harness this vast source of renewable energy, which is also available at night - avoiding the disadvantages of photovoltaic mechanisms. What are your thoughts? Can it be done?
http://io9.com/is-earths-infrared-radiation-a-potential-energy-source-1536117294
There are many photovoltaic cells that work weel with infrared rays. At the moment they are still expensive but I think they can be used also with the Earth's infrared radiation.
So, could we have both in one device: sunlight collection and Earth's infrared radiation collection, @Davide?
The issue might be geometry though. The IR radiated at night is upwelling compared to the downwelling sunlight during the day, so what might be the optimum geometry for SW radiation may not be for IR. You say the available energy is 100,000 TW, but we would have to think what fraction of the daytime available energy this is, plus the efficiency of PV cells at those wavelengths (normally optimised for solar wavelengths).
As I understand, it's the energy emitted from Earth on a daily basis. And if you read the article carefully, the concern is about diodes not PV cells, although both could be merged (theoretically or practically?).
It is, indeed. The basics of the idea remind us, or can be found back to the Kardashev scales of civilization(s). The trouble, hence, is that so far the technology available is either too expensive or (therefore!) non-existent - at the daily level. But the possible use of the Earth's infrared radiation is one of the best gates to get out of the current Kardashev scale mealy scale 0. A meager layer, as it happens.
Why you do not commpare the energy emitted from the earth to the solar energy impinging on the earth ? Which is the largest and easiest to capture ?
Dear Giovanni, the point is to harness solar energy not only during daylight but also at night. So, a reasonable approach could be to use "solar energy" AND "earth energy" all day round. That's what I understand so far but I'm not an expert.
Dear Michael,
do not forget that energy exchange under the form of heat occurs because of a temperature difference.
The solar constant is about 1350W/m2. This is what we get from the sun.
Let us say now that I want to pick up the "earth energy" with the earth at a temperature of 20°C with a very low temperature device, say at 0°C. Let us also assume that the absorptivity of the device is unity and the air layer transmissivity is also unity, the energy you would collect by radiation heat transfer would be about 100 W/m2. But, of course, you should remove the device during the day, otherwise the earth would not heat up back also because you cannot rely on conduction with large devices. This prevents also all day operation The earth thermal conductivity is generally quite low.
You can now compare the above figures and decide feasibility of the energy capturing, that, in any case, it wold be a very low temperature energy.
Hope I was clear enough, if not, let me know.
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