
Semi-transparent solar panels allow concurrent production of crops and power - rch
https://onlinelibrary.wiley.com/doi/full/10.1002/aenm.202001189
======
dghughes
My mother ayed tomatoes in the spring when it was still cool. She covered them
with clear plastic bags as she always has. But she needed one more bag so she
used a blue recycling bag on one of the plants. Blue tinged really it's almost
clear.

I pointed out to her one of the plants had yellow leaves. It was the plant
with the blue bag.

Later in the summer the blue bag plant produced fruit just like the other
plants. But the bottom of each tomato was disfigured and looked rotten but it
was dry to the touch. It's blossom rot due to low calcium. I have to wonder if
it was the blue bag or lack of/too much water. All the plants got the same
nutrients only this one had the blue bag. It got red light and green light
which plants don't need but no blue light.

Plants are seemingly very sensitive to sunlight quality. I'm sure the solar
panels are clear but even a slight colour blockage may be harmful.

It was an interesting result.

~~~
jws
The ratio of red and blue light controls various functions of a plant. In the
context of aquarium plants, more red light makes them get tall and leggy, more
blue light makes them be compact and bushy.

[https://gpnmag.com/article/effects-of-blue-light-on-
plants/](https://gpnmag.com/article/effects-of-blue-light-on-plants/) talks a
bit about it in the context of greenhouses and tomatoes, the picture in the
middle shows 6 plants grown with wildly different red/blue ratios.

If the balance of the light coming through your solar panel was problematic,
you could always filter out some of the overabundant light.

~~~
ballenf
Is that how they know how close to the surface of the water they are?

------
khawkins
Only people who spend most of their life in densely crowded cities could think
that the planet has so little space that you'd need to grow crops underneath
solar panels for efficiency's sake.

~~~
dTal
And only someone blind to the ecological damage that agriculture does would
regard all that land as free to use by humans, without consequences.

Here [0] is a map of the world's remaining wilderness. Notice how it's nearly
all desert, with the exception of the Amazon rainforest. And hey, guess what's
happening to that?

We _are_ short of space. And time.

[0]
[https://images.theconversation.com/files/256144/original/fil...](https://images.theconversation.com/files/256144/original/file-20190129-39344-xlctan.jpg)

~~~
samatman
Granted that the desert is effectively ideal for solar panels, and less useful
for agriculture.

An interesting application of this technology would be building solar arrays
along the edge of advancing deserts, with shade-tolerant plants with the sort
of root systems which have been shown to halt and reverse desertification.

It's easier to do good things (such as halting the inexorable spread of the
Sahara) if the operation is revenue-positive. Even though this would be more
labor and less energy than just putting up a panel farm and calling it a day,
it's more of a return on investment than the big old zero you'd get from just
planting to try and fix dunes.

------
Communitivity
Not just crops and power. I know a guy whose startup is using transparent
solar panels in Germany on eco-friendly buildings with grass on roofs, to get
power and eco-cooling, as well as Oxygen production - at least that is how he
explained it. The concept is called green-roofs. Unfortunately I don't
remember his startup's name.

A link with details about the concept, minus the use of transparent solar
panels: [https://buildingradar.com/construction-blog/green-
roofs/](https://buildingradar.com/construction-blog/green-roofs/)

~~~
BurningFrog
The oxygen claim doesn't inspire confidence.

Plants don't produce any useful amount of oxygen, and real scientists know
that.

~~~
atoav
A thing that they are good at however, is lowering temperatures in cities
(compared to e.g. stone surfaces which store the warmth of the sun) – this
alone might be a good reason to look into green roofs, given that we just
passed the point of no return for Greenland's ice sheet recently.

It takes the same amount of energy to melt 1kg of 0°C ice into 0°C water as it
takes to heat 1kg of 0°C water to 80°C.

~~~
BurningFrog
I wonder how that compares to white painted or even reflective roofs?

The paint solutions don't require a gardener at least.

~~~
rini17
Usual white painted surfaces get hot too. And if you use some superhigh-
reflectivity surface, you have to keep it clean.

------
chrisco255
So this technique reduces the sunlight the plants receive by about 57% but
only reduces biomass growth by about 30%. It's very interesting. I imagine you
could enclose the sides with glass or plastic and make a greenhouse from it.
That makes me wonder if the reduction in growth wouldn't be offset by the
ability to extend the growing season.

~~~
conscion
> I imagine you could enclose the sides with glass or plastic and make a
> greenhouse from it

FTA - that's why they tested on basil and spinach. Both crops are commonly
grown in greenhouses

------
Grakel
There's no shortage of open area to put solar panels. If we put a (nearly)
continuous strip in every highway median, that would be a huge step forward,
and still take up practically zero useable space. Even 1% of the federally
owned land in the sun belt would generate an enormous amount of power.

~~~
hirundo
"if the government were to take over the Sahara Desert, there would be a
shortage of sand in five year" \-- Milton Friedman (exaggerating, somewhat)

Better to put them on home roofs, and arrange for them to be owned by the
homeowners, designed so that the occupants are (literally) empowered when the
grid is mismanaged, as in California.

On highway medians control is more centralized, and they would require more
maintenance and cleaning, which would be more disruptive in that location.

~~~
Retric
Rooftop photovoltaic is currently more expensive, less efficient, and
surprisingly dangerous to install. Solar _thermal_ designs actually benefit
from being on rooftops.

As to dust, economies of scale make a huge difference. It’s rarely worth it,
but using a farm truck to spray water across miles of panels is much more
efficient than tens of thousands of homeowners doing the same.

~~~
samatman
It's also unattractive, which should matter to us.

Much of the distinctive beauty of traditional building in sunny areas comes
from the roofs.

Solar tiling, which is still not a mature technology, doesn't add danger: we
have to put _something_ on a roof, and if installing solar tile takes extra
time, it isn't by much. And it looks good.

Less efficient and more expensive? Sure. But as the meme would have it, it's
free real estate. And since we're living through a grotesque failure of
robustness on a civilizational scale, let me point out that it's more robust
as well, particularly combined with on-site batteries.

~~~
Nasrudith
Why do they count as unattractive? It seems that the "definition" of eyesore
is wholey independent of aesthetics and entirely based upon if it is
functional and new. Old windmills, steam engine trains, and canals are
considered quaint, wind turbines, shipping canals and modern trains are
considered "visual pollution". Modern art fixtures often deliberately defy all
rules of structure and aesthetics and don't get tarred with this. I only have
weird hypothesises as for why.

------
newyankee
I cannot imagine the revolution that solar power will produce if it can fall
another 3-5x in the next 10 years. It is already at grid parity.

Although my personal hope is for storage, inverters, controllers and other
technologies to get cheaper. Especially longer term storage beyond 4 hours.

~~~
toomuchtodo
I think it’s unlikely you see any fossil generation in the mix in 10 years
except in the most remote of locations (with no solar or wind potential).

Wind and solar are already around 2 cents/kWh utility scale, and batteries are
catching up. No fossil or nuclear generation can compete with that.

~~~
manfredo
> Batteries are catching up.

Are they? The US consumes 11.5TWh of electricity daily. It's estimated that it
needs 3 weeks if storage to get to 100% carbon free [1]. By comparison global
battery production in 2019 was 300GWh [2]. Even if you factor in the fact that
the curve of battery production is rising, it'd take decades to fullfil just
the US's storage demands with batteries. There are other storage options like
hydroelectricity and pumping air into mineshafts, but those are geographically
limited.

1\. [https://pv-magazine-usa.com/2018/03/01/12-hours-energy-
stora...](https://pv-magazine-usa.com/2018/03/01/12-hours-energy-
storage-80-percent-wind-solar/)

2\. [https://cleantechnica.com/2019/04/14/global-lithium-ion-
batt...](https://cleantechnica.com/2019/04/14/global-lithium-ion-battery-
planned-capacity-update-9-growth-in-a-single-month-march-charts/amp/)

~~~
christkv
Or stacking blocks

[https://qz.com/1355672/stacking-concrete-blocks-is-a-
surpris...](https://qz.com/1355672/stacking-concrete-blocks-is-a-surprisingly-
efficient-way-to-store-energy/)

~~~
manfredo
Apparently each of these structures stores 20 MWh of energy. By comparison,
the US consumes 11.5 TWh of electricity daily. To reach the 12 hours of
storage estimated to be necessary to reach 80% renewable generation we'd need
287,500 of these towers. To reach the 3 weeks of storage necessary for 100%
renewable generation we'd need 12,075,000 of these towers.

~~~
samatman
The former is easily achievable, if the towers are profitable to install. We
only have to build them one at a time, and if a collection of 10-50 is cheaper
than a peaker gas plant, then the utility decommissions the latter and builds
the former.

The latter is simply not necessary. There are a number of ways to solve the
last few percent, including leaving a few peaker plants running; presumably,
we'll do all of them.

Those peakers can be carbon-neutral, because it's possible to run CO2
extractors. One implication of our renewables is that there are times when
they generate power considerably in excess of requirements: using that energy
to sequester carbon is plausible.

Of course, if we got over our civilizational horror of nuclear energy, we
could solve this problem in a thorough and boring way. I'm not holding my
breath.

~~~
christkv
Thorium reactors or pebble bed reactors might be options. The only reason we
have the current designs is due to the us navies need to build a reactor that
would fit on submarines and ships. That technology became the basis for our
deployed reactors. Since then nothing else has been tried outside of small
experimental plants from what I understand.

------
peter_d_sherman
This is very interesting!

A few related questions come to mind:

1) What happens when two or more semi-transparent solar panels are stacked one
behind the other? Is output power then comparable to the highest efficiency
solar panel, do you get more, do you get less, and if so, how much less?

2) Polarization of light and solar panels -- what happens if light is
polarized by a filter before going to a solar panel? And then, what happens
(in terms of overall energy production) when that polarization filter is
turned to an angle? And then the same question, applied to both regular solar
panels, and these semi-transparent solar panels.

3) While I'm on the topic, has any researcher out there found a way to get
even so much as a single millivolt/milliwatt (microvolt/microwatt?) from solar
power coupled with a fully transparent surface, like let's say, glass, or some
other crystal? I seem to recall some researcher somewhere that showed that
very small charge regions occur at boundaries when sunlight hits plain
transparent water -- but I do not recall the details...

------
gdubs
Our area of Oregon recently banned new solar farms on the grounds that it
detracts from the beauty of the landscape – a wine region with lots of
tourism. Ironically, that very beauty is threatened by the changing climate,
which clean energy could help mitigate.

~~~
quotemstr
Let's be real for a second. Climate change isn't going to destroy Oregon's
wine-growing regions within our lifetimes. A solar farm will change it within
months. You can support or oppose solar farm bans according to your liking,
but you should do so on the basis of facts. The two forces aren't even close
to equal in magnitude and timing.

~~~
orev
The “not within my lifetime so who cares” trope has been around for decades,
and guess what? Climate change is happening faster than anyone imagined,
mostly because scientists can only present findings on things they are certain
about, which makes the predictions conservative. Most people are already
seeing the impact of climate change, and if it’s not visible to you
personally, it has never been easier to seek out information on those that
are. If you really can’t see past your own lifetime and feel that you should
be able to take whatever you want from the planet simply because you don’t
need to deal with the repercussions, then you are not part of human society
and are free to leave the planet at any time.

~~~
jodrellblank
No matter how you try to write it politely, "I don't agree with your position,
kill yourself" is a shitty comment.

------
mrfusion
Could we design one to mostly get energy from green light which plants reject
anyway?

~~~
everybodyknows
From the abstract:

>selective utilization of different light wavelengths

~~~
hobofan
Yes, it says it in the abstract, but isn't really given special attention to
in the article itself.

Looking at the graphic it looks like a fairly normal absorption spectrum for a
solar panel without it being specifically tailored to this use-case. It seems
like there might still be something won by specifically tailoring it to be
complementary to the plant absorption spectrum. On the other hand it might
also not be economically viable due to lack of scale and varying requirements
for wavelengths between plant species and stages of plant development, which
makes some optimizations moot.

------
adrianmonk
There is a LOT of low-hanging fruit when it comes to where to install plain
old regular solar.

We could probably spend the next 50-100 years installing as many (regular)
solar panels as possible and still have plenty of places left to put more of
them.

Obviously it's not bad to develop these technologies, but I think they'll only
be useful in niche applications.

------
csours
I'm imagining a green-greenhouse which covers all of it's energy usage with
these panels.

Edit: heck, what about auto-glass?

------
jugg1es
This is fascinating but you have to wonder how it would work with current
harvesting techniques. New harvesting machines would have to be invented to
work around the support infrastructure for the panels if they were to be
deployed at scale.

------
richardrk
"Maximizing the generation of electricity is a desirable goal, but might be at
the expense of biomass production. For example, for lettuce, the total biomass
yield under agrivoltaic installation in Montpellier (France) was 15–30% less
than the control conditions (i.e., full‐sun conditions).[28, 29] When growth
of tomato was tested in Japan, the yield in an agrivoltaic regime was about
10% lower than for conventional agriculture."

------
tiku
I always wondered why you could not just place the panels a bit higher. So
that the sun can pass on certain times etc.

~~~
kube-system
Yeah, people are treating this solar panel like a hammer and finding any use-
case that looks like a nail.

Instead of a entire roof of panels that pass 50% of the light, it’s is more
simple to make a roof of half covered in panels that pass 0% of light... like
a pergola.

------
xwdv
Alternatively, dust build up on the solar panels can prevent production of
both.

~~~
agumonkey
automated panel cleaning is probably solved by now

------
quotemstr
Besides: nuclear power plants take up very little space. I really can't
seriously people pushing solar, wind, and so on while they eschew nuclear
power (and increasingly hydropower too).

Fake environmentalists: "We have an existential crisis! We must change our
energy strategy to save humanity!"

Engineers: "That's quite a problem. Here's a way to solve it. It's called
fission. Here are some power plant designs."

Fake environmentalists: "Nooo! Not _that_ plan! This existential problem can
be solved using only those technologies that agree with my aesthetics!"

It gets old after a while. If carbon-induced anthropogenic climate is a
problem --- and I think _it is_ \--- then we shouldn't disparage good
solutions on weak grounds in favor of solutions with serious problems. We
don't need to devote swaths of land to solar and wind if we just build nice
compact nuclear power stations.

~~~
codefreakxff
The tone of your post (being simultaneously dismissive and insulting to those
who have a different view than you) is very trollish. The problem many people
have with nuclear power are things like accidents making areas uninhabitable,
radiation making people sick, disposal of waste rods is difficult, some
materials can be used to make weapons, and the cost to make a safe plant are
staggering and leading to cancellation of projects.

Renewable sources don’t have these downsides. Are they ugly? Not any uglier
than a concrete dome and cooling systems of a nuclear power plant. You can bet
wine country does not want a nuclear plant in their valley either. I think
it’s perfectly reasonable to zone land usage appropriately.

~~~
skriticos2
Agree.

Compared to renewables - nuclear is a big risk (financial and operational).
Also nuclear needs a lot of water, which is getting to be a serious problem.
Compared to coal/gas/biomass they look great though in our current
terraforming predicament.

There is no way we could build enough of them in the near term to matter, so
that makes this discussion moot anyway. There is simply not enough expertise
and production capacity left. Very few nuclear plants have been completed
recently and the institutional knowlege is fading. It takes a lot of time and
effort to reinvigorate that, especially since the nuclear industry is so
extremely conservative.

Also the conversation is not being done on technical merits - but political
inertia, an unwillingness to change and special interests by established
energy companies (coal, gas).

As you say, renewables are still winning (slowly) because of the low risk
profile and generally being price competitive.

Not that it matters much, we are mostly over the point of no return. It's just
a matter of time before this ball is getting very unpleasant, sadly. We are
just playing with the dial on how quickly that happens.

------
aaron695
I was just thinking farmers had it to easy harvesting their crops.

If we take the solar panels off the 1% of roof space they are on and move them
far away from the place we use the actual power, we could do this.

The attention span of the environmental movement is quite amazing at times.

