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80% solar cells
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raptor1956:
Yep, this has got to be click-bait, sure looks like it to me.

Actually, according to some research at Rice University, they appear to be indicating that they've found a way to convert the large percentage of wasted energy in typical solar cells by a process, if I understand it properly, that is able to convert the waste heat into photo-electrons that can come from any direction but are channeled in only one direction via carbon nano tubes and this channeling squeezes them into useful electricity.  OK, this has my bullshit detector going off but I'll link the article for your own perusal. 

https://www.sciencealert.com/device-that-channels-heat-into-light-could-boost-solar-efficiency-to-80-percent

https://news.rice.edu/2019/07/12/rice-device-channels-heat-into-light/?T=AU


The thing is, as improbable as this seems if there is any there-there to this and they are able to up the efficiency to anything near 80% its game over for all other energy source and the game isn't even close.  We've seen about 44% with triple junction cells that would never be commercially viable and consumer grade cells are now about 18% for the better ones, but getting anywhere near 80% would end the debate and put Texas out of business.


Brian
Kleinstein:
There is a rather general thermodynamic based limit to the possible efficiency of a PV (or other solar light to power converter). Without concentration the limit is quite a bit lower than 50% AFAIR. For non concentrated PV it's more like a round 35%.

https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limit

So the BS detector goes to full over-unity.
Once converted to thermal energy, there is not much power to get back unless the temperature is really high.

AFAIK good commercial cells can reach some 22% under standard condition and maybe 20% real world (higher temperature).

The triple junction cells get there high efficiency with concentration. Under suitable conditions (AFIAK in Spain) such installations with concentrated PV were actually build at quite some scale. So it is not that far off to take this system into consideration for suitable places.
With concentration the actual cell is tiny (some 2% AFIAR) and may allow more exotic materials.
CatalinaWOW:
As a Rice alumni, the BS comment forced me to read this closely.  It appears to me that the original Rice release has potential for credibility, saying that they could convert the heat from "very hot" sources to narrow band light.  They do claim 80% conversion, but again only for very hot sources.  With no other stipulations on the operating conditions or how efficiency is measured.

This process bypasses the Shockley limit mentioned earlier, as that involves direct interaction of the solar spectrum (photon energy distribution) with the band gap.  The Rice process changes that distribution and thus changes the Shockley calculation.

The science writer further removes the claim from any discussion of the circumstances and limitations, and thus into BS territory.

This whole discussion reminds me of one of my favorite SF stories where one protagonist proves something impossible by demonstrating instability of a (science fiction) force field for durations longer than a few microseconds.  Another protagonist says, "Sure, I found that experimentally."  And put a high speed switcher on the generator, resulting in a force field that never reaches its instability limit but is for all practical purposes always there. 

A real world example of the same thing is Lord Kelvin's analysis of heat flow from the Earth and the heat capacity and temperature of the material in the Earth's interior.  The conclusion was that the Earth could not possibly be more than a few tens of thousands of years old.  The discovery of radioactivity made those calculations irrelevant.

I don't know if the Rice work is a breakthrough or just a wild claim, but it is too soon to push the proven BS button.

                                                                                                                                                                                                                                                                                                                                                             
raptor1956:

--- Quote from: Kleinstein on July 29, 2019, 08:50:36 pm ---There is a rather general thermodynamic based limit to the possible efficiency of a PV (or other solar light to power converter). Without concentration the limit is quite a bit lower than 50% AFAIR. For non concentrated PV it's more like a round 35%.

https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limit

So the BS detector goes to full over-unity.
Once converted to thermal energy, there is not much power to get back unless the temperature is really high.

AFAIK good commercial cells can reach some 22% under standard condition and maybe 20% real world (higher temperature).

The triple junction cells get there high efficiency with concentration. Under suitable conditions (AFIAK in Spain) such installations with concentrated PV were actually build at quite some scale. So it is not that far off to take this system into consideration for suitable places.
With concentration the actual cell is tiny (some 2% AFIAR) and may allow more exotic materials.

--- End quote ---


There are triple junction cells in operation at over 43% so that's well above the 35% value you listed.  I may be mistaken but the 35% value may be the theoretical limit for single junction cells. 

I didn't mention in my first post but it appears this may work in co-generation situations by converting waste heat into electricity.  OTH, if it really is in the 80% range, and that point just seems impossible, but if it is true why do co-generation -- just use whatever heat source you have and use that heat directly with this technique. 

As for commercial cells ... the range is about 13%-16% for CIGS based really cheap cells to the 16%-20% for lower cost silicon cells to 35% or so for space grade cells at much higher price on up to the 43% cells that I don't think have made it out of the lab just yet.

It appears that solar can now produce at around $0.02/KWHr though that is still limited to daylight hours, obviously.  One of the advantages of molten salts based concentrating solar is that the energy can be stored and then produce electricity at night, generally in the hours after sunset when demand is still high but the Sun is no longer shining.  I believe concentrating solar is now about $0.06/KWHr or there abouts.   The person or company that cracks the storage problem and can utilize solar 24/7/365 will be an instant billionaire and hugely impact the climate debate in a favorable way.


Brian
NiHaoMike:
One easy way to boost solar panel efficiency is to make the back side out of heatsink. Problem is that would increase the cost per watt by a lot, so it's only used in special applications.

--- Quote from: raptor1956 on July 29, 2019, 10:54:32 pm ---It appears that solar can now produce at around $0.02/KWHr though that is still limited to daylight hours, obviously.  One of the advantages of molten salts based concentrating solar is that the energy can be stored and then produce electricity at night, generally in the hours after sunset when demand is still high but the Sun is no longer shining.  I believe concentrating solar is now about $0.06/KWHr or there abouts.   The person or company that cracks the storage problem and can utilize solar 24/7/365 will be an instant billionaire and hugely impact the climate debate in a favorable way.

--- End quote ---
Considering that the majority of home energy use is thermal in nature - HVAC and hot water, thermal storage can work very well. What's lacking is incentive to invest.
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