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.
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.
Speaking from experience (DIY foundry mishap involving brass), even small amounts of airborne zinc fumes are sufficient to knock a healthy adult flat on their ass for four days with superflu style symptoms.
Nitpick: 3.6 times hotter than a home oven, not 6. Fahrenheit is not a linear scale, you must subtract absolute zero (about -460°F) from measurements (or convert to Kelvin) before computing ratios.
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?
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.
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?
This is basically a combination of the two things - use a lot of heat to make the reaction easier, and use solar catalyzed reactions to take it the rest of the way.
It's one of many, many research projects in thermochemical hydrogen production -- the idea of splitting water using only heat (thermal decomposition), indirectly through longer chemical processes. It's been going on since at least 1977 [1], and there's 352 known thermochemical cycles for splitting water [2] (including zinc/zinc oxide), including the 14 listed [2] on wikipedia. The news today is that a grad student in Delaware built a small lab version of one of these, which he plans to run experiments with. His school media office wrote a press release for him [3], which was cloned by Physorg and written about on a few blogs.
In general, the idea (thermochemical hydrogen production) is just what you say -- heat in (solar, nuclear also researched), hydrogen out. No byproducts, as the chemical intermediates form a closed cycle.
Is thermochemical production much more efficient that say simple electrolysis of water using electricity (which could be produced by photovoltaic solar panels) without the extreme temperatures.
"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."
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."
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:
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.
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[ 4.3 ms ] story [ 54.1 ms ] threadI'm having trouble seeing why it would take long for a startup to start baking the clay for one of these in every home.
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.
2700lbs is ~1200 kg
Thats great, but who is going to use it if it isn't cheaper than alternatives?
The general idea is well known: http://en.wikipedia.org/wiki/Photocatalytic_water_splitting
This specific method is also well known: http://en.wikipedia.org/wiki/Zinc_zinc-oxide_cycle
And there are many other possible cycles: http://en.wikipedia.org/wiki/Water_splitting
At 2500c water will split into hydrogen without any help at all: http://en.wikipedia.org/wiki/High-temperature_electrolysis This reactor runs at 1600c.
This is basically a combination of the two things - use a lot of heat to make the reaction easier, and use solar catalyzed reactions to take it the rest of the way.
In general, the idea (thermochemical hydrogen production) is just what you say -- heat in (solar, nuclear also researched), hydrogen out. No byproducts, as the chemical intermediates form a closed cycle.
[1] http://www.osti.gov/energycitations/product.biblio.jsp?osti_...
[2] http://en.wikipedia.org/wiki/Water_splitting
[3] http://www.udel.edu/udaily/2012/apr/solar-reactor-040312.htm...
"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."
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
Zn + 2 H2O → Zn(OH)2 + H2
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.
ZnO + energy → Zn + O
Zn + 2 H2O → Zn(OH)2 + H2
SCNR