
Spherical Solar Cells Soak Up Scattered Sunlight - headalgorithm
https://spectrum.ieee.org/energywise/energy/renewables/spherical-solar-cells-soak-up-scattered-sunlight
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danans
My home's solar installation exhibits the curious behavior of producing its
maximum overall single day output when there is summer morning fog which burns
off around 9AM. This effect is clearly visible in the production graphs, which
show a steeper energy production increase earlier in the day when these
conditions are present.

My theory is that the fog moves the onset of generation earlier by reflecting
low angle morning sunlight from the east down to my solar panels. The 9AM fog
burnoff is critical to maximizing production because after that time, the fog
begins to inhibit the production of electricity rather than enhance it.

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hinkley
Long ago the World Solar Challenge competitors noticed that their cars had
peak power output not on clear days but on overcast days. They explained it as
having something to do with what frequencies get bounced back rather than
radiating out into space.

Later on while discussing a solar power result that sounded like Maxwell's
Demon, someone pointed out to me that solar cell performance is affected by
the temperature of the cell. Either or both could be in play here.

Did you plot temperature versus output by any chance?

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danans
I didn't, but this is just after sunrise in the Bay Area, so the temperature
is pretty low - not in the zone where solar panel efficiency starts to
decline.

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dmoy
Right, wouldn't lower morning temperature be better for solar cell efficiency?

It's been a long time since I took semiconductors, but I vaguely recall a
decrease in voltage at higher temperature.

You'd need to measure the temp of the actual cell, because it gets wonky. You
can't just look at air temp.

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danans
It would be surprising to see such huge difference in cell temperature in sun
vs fog when the ambient temperature itself is about only about 60F, which is
typical, or maybe even high for 7-9AM on the type of days I'm describing.

Even if the cells were 80F on the sunny mornings vs 60F on the foggy ones (or
a difference of roughly 10 Kelvin) that would result in about .5% to 1% drop
[1] in efficiency, so I should see only slightly lower output on sunny vs
foggy mornings.

Instead what I see is that initial production on foggy days is several times
higher than on sunny days. The only explanation I have for this is some kind
of local effect where the fog reflects light that would have otherwise gone
straight west in the morning down to my solar panels.

1\. [https://i2.wp.com/synergyfiles.com/wp-
content/uploads/2017/0...](https://i2.wp.com/synergyfiles.com/wp-
content/uploads/2017/01/Efficiency_PV_vs_Temperature2.png)

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hinkley
Morning fog means the dew point is being crossed. If you control for
temperature, as you have here, then the humidity is the deciding factor.

Can a hot solar panel shed heat faster into humid air than dry air? I'll bet
if we look it up that the answer is 'yes'.

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danans
Enough to cause a 2-3x increase in panel efficiency? Seems unlikely. Instead
the panels must be getting more light somehow.

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jpm_sd
Solyndra tried something similar (cylindrical cells) and it just wasn't worth
the effort. Flat cells are so, so cheap now.

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m463
I think it's pretty much a hallmark of engineering that the cheapest physical
solution will overcome 99% of all clever solutions that cost more than a
fraction more. This also goes for conventional solutions vs exotic ones.

It's like "better, faster, cheaper - pick cheaper"

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rozab
Alliterative articles are agreeable and alleviate anguish

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rini17
AFAIK large part of price of classical solar cells is attaching the leads (by
manual soldering). Tesla solar roof is one ingenious solution to this problem.

I suspect it could be a problem with these spheres.

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gpm
Genuinely ignorant, how does the solar roof reduce the need for manual
soldering?

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sandworm101
Connectors.... thousands of them. Small tiles On flexible structures like
roofs have connectivity issues too.

Tesla's only party trick is tiles that looks a little like roof shingles. They
look less intrusive than flat panels. Imho it is about as useful as painting
turbines green so they look like trees.

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Retric
The roof part of Tesla solar roof should presumably last a long time. It also
avoids drilling holes in your shingles, combined that could represent a
significant competitive advantage.

The solar part on the hand is overpriced and may limit how long the roofing
lasts. Which means it’s only really competitive if you’re already
constructing/replacing the roof and don’t yet have solar.

Aka best case is after ~25 years the roof reverts to a normal roof and then
goes on to last another 25+ years. The worst case on the other hand is if the
roof needs to be replace as soon as the solar panels reach end of life.

~~~
sandworm101
>> The roof part of Tesla solar roof should presumably last a long time.

Ya, but people aren't buying a tesla roof for the roof part. It is the solar
part that matters. Roofs move, they swell and shift with the seasons. Over 25
years at least some of those thousands of connectors between solar tiles will
have degraded and/or disconnected, leaving entire sections/rows of tiles
disconnected. That is why, when you need to make thousands of connections in
an electrical project meant to last many years, manual soldering is still the
preferred tactic.

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zatel
I worked in the Tesla factory making solar panels and I can attest that they
are more snazzy and lighter then normal panels I've bought for my home (the
wait list was to long for Tesla ones) I'm not sure they're much more durable.

They can take a hit straight on but if anything comes at the wrong angle the
top glass layer shatters. It was so common that we had a designated spot to go
dump the ones that would frequently break during the manufacturing process.

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blacksmith_tb
I have ~8yr old panels manufactured in China, one of them was shattered by
what I suspect was a falling bullet (must've been a wild party...). Since the
panels are wired in series, that reduced the output of the system by about
half (the shattered panel was in the middle). Ironically I couldn't easily
replace it, as new panels are higher output, so I would have to replace my
inverter. I opted to just bypass the dead panel and have 19 working instead of
20.

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zestyping
I want to know if they tested a hemisphere, and how well it did. Intuitively,
it seems like the lower half can't be as productive per unit of solar material
as the upper half.

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saeranv
Yeah, or even a quarter sphere since the sun only occupies the southern part
of the hemisphere (north of equator).

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skybrian
Why a sphere and not some other shape?

