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Korvanacor t1_iy048w4 wrote

Reply to comment by blastradii in News Release: NREL Creates Highest Efficiency 1-Sun Solar Cell - 39.5% efficiency by TimeSpentWasting

Solar works by using the energy of photons to bump electrons from the valence bands up into the conductive band. These bands are separated by what is called the band gap. If the gap is 2 electron volts (eV) wide and the photon has 3 electron volts, the extra energy is “lost”. Photons with less than 2 eV don’t contribute anything. It’s possible to stack multiple layers with different band gaps to more efficiently capture a wider range of photons but there will still be losses due to interfacial physics that I don’t understand. Each layer adds to the cost of the cell as well

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a11en t1_iy2ijuk wrote

This and many others in this thread are great discussions of solar efficiency and limitations. Thank you for adding to the discussion! One other nasty bit is how the multijunctions are connected. In order to get good efficiency you basically need separate cells one atop the other without direct electrical connection- otherwise you are current limited to the smallest current cell - so they attempt to match the current output- but that’s not always possible (think AM1.5 intensity -v- frequency graph and trying to trap the area under the curve to be equal to the other cell’s conversion). It’s tricky business. It’s much easier just to treat them separately. I need to read the article more. I hope and pray it wasn’t MOCVD growth… that type of growth is so nasty and dangerous and dirty… work in the field. The environmental cost alone of MOCVD would tip the scales against this. Lol. So good for payloads perhaps- but please let’s not attempt to make all our roofs out of this. The environmental disaster alone wouldn’t be worth it. Lol

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LouSanous t1_iy45muh wrote

>solar efficiency and limitations

It's really important to note that this "limitation" isn't much of a limitation.

There is functionally infinite sun. The amount of energy reaching the earth at sea level from the sun every second is well over 100 times the total yearly energy consumption of the entire world.

Modern nuclear uses only 5% of the energy in the fuel. Then, the conversion to electricity is somewhere around 35%. So from the energy contained in the fuel, nuclear is about 1.75% efficient.

Coal plants are around 35% as well.

Combined cycle gas is 55-60%.

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a11en t1_iy4els3 wrote

Combustion is still the most energy efficient.

And Nuclear would be more efficient if they allowed refacing/recycling the rods.

Believe me- the MOCVD toll is huge and does play a factor. We don’t pay attention to cradle to grave, and it’s absurd not to. (Used to be the thing to do- for example for plastics- why ignore it for solar and wind?)

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LouSanous t1_iy4f2dz wrote

Everything not directly a part of profits in capitalism in an externality.

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Sprinkler-of-salt t1_iy05upz wrote

What if we don’t aim for the conductive band of electrons? What if there’s another way to harness the incoming energy?

Or what if there’s a way to “prime” the electrons in the cells such that the valence electrons are already at the conductive band, or somehow less than 2eV away?

If this requires a new atom, why not make one?

What if we forget about atoms altogether, and capture energy at the quarks and gluons?

What if we forget about photons, and harness dark energy instead?

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Haquestions4 t1_iy0cia2 wrote

What if we just forget all this science and get energy through our outlets?

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Sprinkler-of-salt t1_iy0ftr3 wrote

Nah, come on now, that’s unrealistic. The outlets have to get it from somewhere.

Maybe they should be fiber optic instead of electric… then we could send the light directly from the sun into devices!

Sun-powered blender would probably make even healthier smoothies!

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