
'Artificial leaf' concept inspires research into solar-powered fuel production - dnetesn
https://phys.org/news/2020-05-water-splitting-module-source-perpetual-energy.html
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dahfizz
What's the efficiency of using actual plants to produce fuel? Either through
refining e.g. corn oil directly or using plants to feed bacteria that produce
a fuel. That's a carbon neutral way to convert sunlight to fuel.

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entee
Algae and Cyanobacteria tend to be substantially more efficient than whole
plants (6-8% [1]). There are some caveats though. Generally the industry has
found it hard to grow algae at commercial scale cost-effectively for several
reasons including (but not limited to):

\- Contamination by outside organism kills your algal culture

\- If you create a closed system, the algae will stick to the glass, fouling
the surface and reducing light transmission

\- Extraction of materials from the algae is hard, you end up with a lot of
water weight you need to get rid of somehow

There are also some counterintuitive aspects in that apparently dropping the
efficiency of the antennae (light collection) actually makes the overall
culture more productive because excess light makes it past the initial cell
layer and therefore other cells can benefit from the light. Otherwise the
initial cells grab all the light they can, and waste whatever light energy
they don’t need.

I think it’s an interesting field, but so far it’s been a hard road to make it
actually work at scale cost effectively.

[1]
[https://www.sciencedirect.com/topics/chemistry/photosyntheti...](https://www.sciencedirect.com/topics/chemistry/photosynthetic-
efficiency)

~~~
samatman
I worked on phycology for an algae biofuels startup for the better part of a
year.

Just chiming in to say that this is a good post, and I don't even have much to
add to it.

I quit once I realized that paving over desert ecosystems with huge raceway
ponds filled with glyphosate, wasn't solving any problem I wanted solved.

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whatshisface
If we don't switch fuels, there will soon be no shortage of desert ecosystems
no matter how many we pave over...

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johnny99
I don't want to speak for anyone else, but the point might have been that
there may be other ways to get energy which accomplish the goal without
requiring that sacrifice.

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samatman
Correct, and while I work on developer tools these days, I had a satisfying
stint at a battery-analytics company after transitioning to software
development.

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Animats
_" Rice University researchers have created an efficient, low-cost device that
splits water to produce hydrogen fuel."_

We've heard that one before.

 _" The platform developed by the Brown School of Engineering lab of Rice
materials scientist Jun Lou integrates catalytic electrodes and perovskite
solar cells that, when triggered by sunlight, produce electricity. The current
flows to the catalysts that turn water into hydrogen and oxygen, with a
sunlight-to-hydrogen efficiency as high as 6.7%."_

OK. things like that have been built before. The usual problems:

\- Costs too much.

\- System only works for a while before filling up with crud from the water.
(This is also a big problem with fuel cells.)

\- Sunlight to hydrogen to fuel cells to electricity is _far_ less efficient
than solar cells.

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Symmetry
There _are_ a lot of industrial processes that need hydrogen as an input,
fertilizer production as possibly the most important. But yes, hydrogen to
electricity is silly and I'm pretty skeptical of its use for vehicles too.

~~~
sandworm101
At these efficiencies (6%) it would be better to use PVC panels and use that
electricity to make hydrogen.

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pacman83
Just last week I was thinking we need solar cells wired up in a tree structure
with batteries integrated into the tree so that we don't need to combine
series and parallel or have the drawbacks of either. Is anybody doing that? I
presume they would need to be connected with fluids, electrolyte in channels
instead of with wires. Or have I just reinvented the tree?

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p1mrx
What problem are you trying to solve?

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pacman83
That is always the most important question, isn't it?

I am looking at RV applications, thinking series would be ideal to reduce
wiring cost, but just learned that a small patch on one panel of shade lowers
current in the whole series, when wired that way. If there's some way they
could be wired as a tree, with the high amperage portion of the circuit fairly
short, that seems more efficient. But then I guess I have just reinvented the
power grid... I'm talking about residential scale, though, or smaller.

~~~
p1mrx
So you're trying to connect an array of solar panels in series, such that
shading one doesn't limit the current of the others. Isn't that normally
solved using bypass diodes?

~~~
pacman83
I guess you just solved my problem. This is a topic I'm just beginning to look
into. Thank you.

But now I'm wondering why are panels made this way? I mean internally they're
wired in series or at least substantially so. and I've read that shading a
small portion of one panel will drastically reduce the output of that one
panel. Is it possible to create a panel (e.g. nominally 12 volt system) with
bypass diodes inside it? If so then why wouldn't they have been doing this all
along?

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blackrock
Interesting. It’s a hydrogen generator.

As an alternative idea, is it possible to use a laser to break the bond
between hydrogen and oxygen, in a water molecule, to release the hydrogen?

Kind of how a laser was used to cool atoms, by knocking off energetic
electrons from the molecule. But this time, in reverse.

Asking for a laser physicist.

~~~
dredmorbius
Interesting suggestion.

Lasers themselves would likely be inefficient. An LED emitting at a speficic
frequency tuned to the H-O bond strength ... might ... work. First question
is: what is that frequency, if it exists at all?

