
Self-sustaining solar reactor creates clean hydrogen fuel - ukdm
http://www.geek.com/articles/geek-pick/self-sustaining-solar-reactor-creates-clean-hydrogen-fuel-2012044/
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stephengillie
[http://www.udel.edu/udaily/2012/apr/solar-
reactor-040312.htm...](http://www.udel.edu/udaily/2012/apr/solar-
reactor-040312.html)

 _"The reactor, which resembles a large cylinder, is comprised of layers of
advanced, ultra-high temperature insulation and ceramic materials. It measures
roughly 2 feet by 3 feet and weighs a hefty 1,750 pounds.

The conical geometry of the reactor’ design uses gravity to feed zinc oxide
powder (the reactant) into the system through 15 hoppers.."_

(From TFA) "...where it converts to a zinc vapor. At that point the vapor is
reacted with water separately, which in turn produces hydrogen."

(Linked article) _"During testing, light concentrated to simulate the energy
of 10,000 suns will be focused down into the reactor, sending the temperature
within soaring to over 3,000 degrees Fahrenheit, nearly one-third the
temperature of the sun’s surface."

...

One interesting feature of the reactor is that, in theory, the zinc oxide
byproduct created during the reaction will be re-usable, making the project
self-sustaining."_

~~~
rch
Don't worry about the '10000 suns' requirement...

The High-Flux Solar Furnace "can nominally provide flux at 2,000 suns but,
when required, can use specialized secondary optics to generate concentrations
greater than 20,000 suns."

\-- <http://www.nrel.gov/docs/legosti/fy97/23377.pdf>

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jessriedel
This article is completely lacking any info which would allow the reader to
judge how news-worthy this story is. Is this supposed to be a primary energy
source (e.g., sunlight goes in, hydrogen for fueling cars comes out)? If so,
what advantages does it have over existing technology? Does it have hope of
being economically competitive?

~~~
ukdm
Sunlight, zinc oxide, and water goes in, hydrogen comes out. This is a
prototype about to undergo 6 weeks of testing to answer the very question you
pose about it being economically competitive. The main advantage this has? No
emissions such as carbon dioxide.

~~~
jessriedel
Do any solar-powered generators of hydrogen produce carbon dioxide? Is the
idea here that this would be a primary source of hydrogen for cars? Or is it
only competitive in certain restricted applications?

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gizzardguts
The part that is missing is the energy costs of reprocessing the zinc. I
didn't pay attention in chemistry 30 years ago, but I assume the zinc is
reacting with the water and isn't just a catalyst. Hmm, a little googling
shows:

Zn + 2 H2O → Zn(OH)2 + H2

~~~
sliverstorm
It's supposed to be zinc oxide going in, so it probably looks more like this:

ZnO + energy → Zn + O Zn + 2 H2O → Zn(OH)2 + H2

(I know that's not balanced, but yours isn't either)

Maybe you can then get the zinc hydroxide back into oxide without too much
trouble. It disassociates in water, leaving you with hydroxide and zinc ions.

~~~
sliverstorm
Correction, there needs to be a newline there.

ZnO + energy → Zn + O

Zn + 2 H2O → Zn(OH)2 + H2

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alexchamberlain
That is really cool! How long before people start hacking these in their
garage?

~~~
stephengillie
This is a ceramic furnace as large as a washing machine, as heavy as a Honda
Civic, that needs to be 6 times hotter inside than their home
stove/oven/range, and the fuel (ZnO) is safe to eat in small quantities
(breakfast cereal) but is toxic(?) to breathe.

I'm having trouble seeing why it would take long for a startup to start baking
the clay for one of these in every home.

~~~
Someone
Zinc boils at just over 900 degrees centigrade. I guess that might make this a
bit risky as a device. If, as you say, Zinc in gas form is toxic, that might
be a problem.

Two by three feet and 10000 suns translates to "on a perfectly sunny day,
needs a 200 by 300 feet solar collector" to produce the required heat. Actual
numbers for a machine operating throughout the year will be quite a bit
higher.

~~~
stephengillie
While the goal of the project was to create a 100% renewable energy source
based on sunlight, another energy source could probably be used.

~~~
sliverstorm
This is a heat engine. Your options for renewable heat are mostly geothermal
or solar.

~~~
alexchamberlain
The question is... if we connected the hydrogen to a fuel cell, is it more
efficient than a steam generator?

~~~
sliverstorm
I am skeptical. Large steam generators are very, very good.

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jsilence
"Don't look into concentrated sunbeam with remaning eye."

SCNR

