Self-Sustaining Solar Reactor Creates Clean Hydrogen

An anonymous reader writes "A mechanical engineer working out of the University of Delaware has come up with a way to produce hydrogen without any undesirable emissions such as carbon dioxide. The solar reactor is capable of using sunlight to increase the heat inside its cylindrical structure above 3,000 degrees Fahrenheit. Zinc oxide powder is then gravity fed through 15 hoppers into the ceramic interior where it converts to a zinc vapor. At that point the vapor is reacted with water separately, which in turn produces hydrogen. If the prototype gets through 6 weeks of testing at the Swiss Federal Institute of Technology located in Zurich, we could see it scaled up to industrial size, producing emission-free hydrogen."

Comments

Darn that dirty hydrogen

[retroworks]

Finally, a source of clean hydrogen.

Re:Darn that dirty hydrogen

[Fluffeh]

Finally, a source of clean hydrogen.

That is true, but isn't one of the big problems with Hydrogen storing it, not just producing it? I mean, don't get me wrong, it is excellent to see that part of this "we want to use hydrogen" problem solved, but a lot more still needs to be done.

Re:Darn that dirty hydrogen

[v1]

One reason storing it is such a big deal is because generating it can be expensive. Make hydrogen easier to produce and it lowers the demands on storage.

Re:Darn that dirty hydrogen

[Fluffeh]

Hydrogen stored under pressure has a considerably lower energy density compared to hydrocarbons that we use. Hydrogen is great when you look at the energy by weight, but if a tank is sitting in the back of a car, it doesn't matter whether it weighs an extra twenty kilos, what matters is how far a tank can make a car drive.

Like I said, don't get me wrong, I think it is a fantastic breakthrough to have - a cheap, clean and sustainable way to make Hydrogen gas, but a lot of work still needs to be done before we can all whizz around in clean cars and certainly before we have large scale power stations powered by burning Hydrogen.

Having said that, burning Hydrogen makes water, this process turns water into Hydrogen. It would make for a wonderful closed circuit...

Re:Darn that dirty hydrogen

[icebike]

You start with zink oxide. Apparently (not a chemist here) you de-ogygenate it via heat making zink vapor (releasing O2, which is vented) and that zink vapor grabs oxygen from the water, leaving you with your H2 product, and a clean supply of Zink Oxide again.

The byproduct is Oxygen.

Re:Darn that dirty hydrogen

[Solandri]

One reason storing it is such a big deal is because generating it can be expensive. Make hydrogen easier to produce and it lowers the demands on storage.

Eh? Those have nothing to do with each other. Hydrogen storage is a pain because of density and sealing. At STP, hydrogen is a very low density gas. To get decent energy density out of it, you either have to compress it to ridiculously high pressures, or chill it to ridiculously low temperatures. Di-atomic hydrogen gas molecules are about the smallest molecules that exist. They will leak through anything. A seal which is water-tight and air-tight is not necessarily hydrogen-tight. Couple this with high pressures and you have a major storage PITA.

Unless we discover some sort of hydrogen sponge which soaks up H2 gas and easily holds it at an energy density competitive with batteries and chemicals, I really doubt the hydrogen economy will take off. OTOH if someone can tweak this process so it can convert CO2 + 2 H2O ==> CH4 + 2 O2, then we have a winner. Methane, while not as ideal for storage as a liquid hydrocarbon (most oil wells and refineries just burn it off rather than try to capture and store it), is much easier to work with than H2 gas and has nearly 4x the volumetric energy density.

Long-term, I think alcohol biofuels will win out. Alcohol is nearly as good a storage medium as gasoline/diesel. First you use photosynthesis to create sugar: CO2 + H2O + sunlight ==> O2 + (CH2O)n. Plants are basically made of really long sugar molecules (cellulose). You then ferment the sugar to create alcohol: (CH2O)n ==> C(n)H(2n+1)OH. At some point we'll probably figure out a way to go straight from the raw ingredients (CO2 + H2O + sunlight) to alcohol, at which point you're converting solar energy straight into liquid fuel.

Re:Darn that dirty hydrogen

[TheInternetGuy]

Or even use the hydrogen in a Carbon-monoxide/dioxide capture scheme and produce methanol that could be used in today's engines with minor conversions.
The cars would of course re release that carbon dioxide when driving, so it wouldn't really be sequestering.

See syn-gas to methanol process from the 1920's by Alwin Mittasch and Mathias Pier. Or alternatively the newer processes involving a copper catalyst.

Re:Darn that dirty hydrogen

[gstrickler]

Hydrogen exceeding ~4.5% in air is explosive, so a slow leak in a ventilated area just escapes into the atmosphere. A faster leak, or a poorly ventilated area presents a tremendous explosion potential. Remember the reactor buildings in Fukushima? Those were from hydrogen building up inside the building.

Re:Darn that dirty hydrogen

[ThreeKelvin]

But why would you build a power plant like that?

You're proposing a cycle that goes something like:
solar mirrors -> zinc reactor -> hydrogen furnace -> turbine

Why not just use the old and tried method of:
solar mirrors -> hot steam -> turbine

It would be simpler and far more efficient.

Now, the story is interesting because it's about creating hydrogen using sunlight, without converting the sunlight to electricity first.

Re:Darn that dirty hydrogen

[azalin]

Are you out of your mind? Shipping dihydrogenmonoxide in trucks on regular roads. Do you have any idea how many people die each year because of dihydrogenmonoxide overexposure? Dihydrogenmonoxide was the main reason for the Fukushima disaster. It can already be detected in drinking water supplies of all mayor US cities. This stuff is dangerous!

How down-scalable is it?

[sirlark]

Could it effectively be mass produced so that it could become a household item, every house having it's own hydrogen generator and turbine which can contribute to the grid? I've always thought that decentralising power production would make it greener, if only because there's less loss to long distance transmission. Either way, I'm holding thumbs for the six week trial.

Global Warming!

[sehlat]

But if you burn hydrogen, it creates dihydrogen monoxide, a known greenhouse gas!

This is terrible!

Re:so...

[pushing-robot]

As well as a lack of emissions, the other good news is that the zinc oxide can apparently be reused, meaning the solar reactor is theoretically self sustaining as it only relies on materials and energy that are renewable.

TFAs: Read one today!

not any more, read about formic acid

[Anonymous Coward]

it can be stored in vast quantities in the form of formic acid and then released and restored in a continual cycle. there is obviously efficiency losses but apparently its very practical as it allow storage of large amount of hydrogen at a very high density in a room temperature atmospheric pressure liquid,
that is basically as safe as vinegar.

I was thinking this clean hydrogen would be perfect in so many parts of the world where their is plenty of sunlight but the land is otherwise of low value.

ps: its the nail polish like odor that gets released when ants die, and more specifically when they get crushed. its probably something they are sensitive to, so hopefully our green cars in the future dont get covered with ants in because of the pheromone.

Re:so...

[pushing-robot]

The recovery could be pretty close to 100%; the reactor's only products are oxygen and hydrogen, both of which are gases, so capturing zinc should be simple enough.

Zinc is usually found in conjunction with other metals like copper, so we get most of it "for free". Zinc oxide is actually a lot easier to produce than pure zinc, so refinement costs should be relatively low. The most common ore of Zinc, Sphalerite, is ZnS, and converting it to ZnO just involves adding oxygen and heat:

ZnS + (3)O2 = ZnO + SO2

The sulphur dioxide can be converted to sulphuric acid (H2SO4).

No carbon involved.

Besides, we already use >10 million tons of the stuff per year, and have at least a couple centuries more deposits to mine (to say nothing of recycling), so using a bit for this solar plant wouldn't even be noticed.