How to use solar energy to recapture Co2.

[William Gaatjes]

A week old already but interesting :

(PhysOrg.com) -- By using the sun's visible light and heat to power an electrolysis cell that captures and converts carbon dioxide from the air, a new technique could impressively clean the atmosphere and produce fuel feedstock at the same time. The key advantage of the new solar carbon capture process is that it simultaneously uses the solar visible and solar thermal components, whereas the latter is usually regarded as detrimental due to the degradation that heat causes to photovoltaic materials. However, the new method uses the sun’s heat to convert more solar energy into carbon than either photovoltaic or solar thermal processes alone.

The new process, called Solar Thermal Electrochemical Photo (STEP) carbon capture, was recently suggested theoretically by a team of scientists from George Washington University and Howard University, both in Washington, DC. Now, in a paper just published in The Journal of Physical Chemistry Letters, the scientists have experimentally demonstrated the STEP process for the first time.

“The significance of the study is twofold,” Stuart Licht, a chemistry professor at George Washington University, told PhysOrg.com. “Carbon dioxide, a non-reactive and normally difficult-to-remove compound, can be easily captured with solar energy using our new low-energy, lithium carbonate electrolysis STEP process, and with scale-up, sufficient resources exist for STEP to decrease carbon dioxide levels in the atmosphere to pre-industrial levels within 10 years.”

As the scientists explain, the process uses visible sunlight to power an electrolysis cell for splitting carbon dioxide, and also uses solar thermal energy to heat the cell in order to decrease the energy required for this conversion process. The electrolysis cell splits carbon dioxide into either solid carbon (when the reaction occurs at temperatures between 750°C and 850°C) or carbon monoxide (when the reaction occurs at temperatures above 950°C). These kinds of temperatures are much higher than those typically used for carbon-splitting electrolysis reactions (e.g., 25°C), but the advantage of reactions at higher temperatures is that they require less energy to power the reaction than at lower temperatures.

The STEP process is the first and only method that incorporates both visible and thermal energy from the sun for carbon capture. Radiation from the full solar spectrum - including heat - is not usually considered an advantage in solar technologies due to heat’s damage to photovoltaics. Even in the best solar cells, a large part of sunlight is discarded as intrinsically insufficient to drive solar cells as it is sub-bandgap, and so it is lost as waste heat.

By showing how to take advantage of both the sun’s heat and light for capturing and splitting carbon dioxide, the STEP process is fundamentally capable of converting more solar energy than either photovoltaic or solar thermal processes alone. The experiments in this study showed that the technique could capture carbon dioxide and convert it into carbon with a solar efficiency from 34% to 50%, depending on the thermal component. While carbon could be stored, the production of carbon monoxide could later be used to synthesize jet, kerosene, and diesel fuels, with the help of hydrogen generated by STEP water splitting.

“We are exploring the STEP generation of synthetic jet fuel and synthetic diesel,” Licht said, “and in addition to carbon capture, we are developing STEP processes to generate the staples predicted in our original theory, such as a variety of metals and bleach."

• Learn about becoming PhysOrg.com sponsor and ads-free website

More information: Stuart Licht, Baohui Wang, Susanta Ghosh, Hina Ayub, Dianlu Jiang, and Jason Ganley.” J. Phys. Chem. Lett. 2010. 11 2363-2368. DOI:10.1021/jz100829s

http://www.physorg.com/news199005915.html

 

[sandorski]

Interesting.

 

[PokerGuy]

That's really cool.... hopefully this can be used on a large scale!

 

[Throckmorton]

34% efficiency is incredible. I think that's much higher than photosynthesis

 

[PokerGuy]

Hypothetically speaking, if this was workable on a large scale and CO2 could be removed from the atmosphere to return the level to pre-industrial levels within 10 years, would that be the demise of the global warming religion, or would the true believers once again rename it and come up with a different angle?

 

[Patranus]

Its called a tree.

 

[sandorski]

Hypothetically speaking, if this was workable on a large scale and CO2 could be removed from the atmosphere to return the level to pre-industrial levels within 10 years, would that be the demise of the global warming religion, or would the true believers once again rename it and come up with a different angle?

No, because it is not a Religion. Yes, it would certainly lower the concern around CO2. Of course if this Technology works as theorized, it likely is going to Cost many $Billions and would have to be spread around the Globe.

 

[PokerGuy]

No, because it is not a Religion. Yes, it would certainly lower the concern around CO2. Of course if this Technology works as theorized, it likely is going to Cost many $Billions and would have to be spread around the Globe.

More billions than what it's going to cost when the economy gets hit with carbon taxes and energy taxes and such? I don't think so.

It is a religion or cult, just listen to the true goron believers (shira, is that you?) proselytizing. They already renamed it from global warming to climate change when the public caught on to the whole warming scam, I wonder what they'll call it next.

 

[Fear No Evil]

Oil works for me. The left has convinced me there is no god and things like estate taxes don't impact the dead.. so why should I care what happens after I am gone? Its not my problem.

I'm actually looking at increasing my carbon footprint as much as possible. Hopefully turning it into a carbon ocean.

 

[sandorski]

More billions than what it's going to cost when the economy gets hit with carbon taxes and energy taxes and such? I don't think so.

It is a religion or cult, just listen to the true goron believers (shira, is that you?) proselytizing. They already renamed it from global warming to climate change when the public caught on to the whole warming scam, I wonder what they'll call it next.

Again, more Fail. You're no different than a 9/11 Conspiracy nut.

 

[Lemon law]

Sadly, global warming is not just about CO2 levels, not when CO2 may be just the fuse that causes the release of a 17 fold more effective greenhouse gas in methane.

But still, any bit helps, but can in be scaled up to a point where it helps?

In the case of the Petranus contention, the tree is basically carbon neutral, its great for sucking up CO2 when the tree is alive, but that CO2 is released right back when the tree decomposes.

What is needed is a way to lock the Carbon up in something stable, limestones, and fossil fuels do that for longer terms.

 

[William Gaatjes]

Sadly, global warming is not just about CO2 levels, not when CO2 may be just the fuse that causes the release of a 17 fold more effective greenhouse gas in methane.

But still, any bit helps, but can in be scaled up to a point where it helps?

In the case of the Petranus contention, the tree is basically carbon neutral, its great for sucking up CO2 when the tree is alive, but that CO2 is released right back when the tree decomposes.

What is needed is a way to lock the Carbon up in something stable, limestones, and fossil fuels do that for longer terms.

Fossil fuels do not lock it up, because these fuels will be used again.

There is only one clean option : automobiles with electric motors.
The only reason why electricity driven automobiles are not used is not because of the almost ideal efficiency of an electrical motor. It is a problem of energy storage and a whole industry making sure nothing that promises an increase in electrical storage capacity will ever hit the market. It is strange that the same people who try to frighten people with MMGW are also the people who are advocates of bio fuels as bio ethanol and carbon taxes.

 

[Lemon law]

Wille says, "Fossil fuels do not lock it up, because these fuels will be used again."

Wrong again, its man and man alone who is the decider, in terms of digging up or drilling up this locked away carbon or not. Its why we call it Man Made Global Warming,

And not part of the Earth's natural cycle.

But no doubt about it, man decided to dig up and burn all that locked up carbon in incredibly short period of time, and now we have things we have never seen before. Do you have a better explanation of why the charges we see are equally rapid?

If not, call a spade a spade, and call it man made.

Its sorta like being someone trapped in a Skinner's box, I push this button and get a nasty electric shock, I may be clueless on the precise mechanism that results in the shock, but its not hard to learn not to keep pressing the button.

 

[Throckmorton]

More billions than what it's going to cost when the economy gets hit with carbon taxes and energy taxes and such? I don't think so.

It is a religion or cult, just listen to the true goron believers (shira, is that you?) proselytizing. They already renamed it from global warming to climate change when the public caught on to the whole warming scam, I wonder what they'll call it next.

Blah blah blah.


What you are talking about is going to be NECESSARY, because we can't reverse the climate change we've done just by stopping emitting greenhouse gases. The real inconvenient truth is that geoengineering will be a necessity.

 

[ElFenix]

Blah blah blah.


What you are talking about is going to be NECESSARY, because we can't reverse the climate change we've done just by stopping emitting greenhouse gases. The real inconvenient truth is that geoengineering will be a necessity.

it'll be good practice for when we chrome the moon

 

[dammitgibs]

Sorry, it's already been done

 

[Elfear]

STEP sounds very interesting. I hope it is as successful as they claim.

 

[Throckmorton]

Sorry, it's already been done

This is more efficient than plants http://en.wikipedia.org/wiki/Photosynthetic_efficiency

 

[Jaskalas]

This is more efficient than plants http://en.wikipedia.org/wiki/Photosynthetic_efficiency

I'll take the tree, thanks.

 

[bigdog1218]

Blah blah blah.


What you are talking about is going to be NECESSARY, because we can't reverse the climate change we've done just by stopping emitting greenhouse gases. The real inconvenient truth is that geoengineering will be a necessity.

Are you actually saying that no warming or cooling trend in the history of Earth has ever been reversed? What data can you provide to show that we're at the point where the Earth can't correct itself?

I'm sure you can find something somewhere that says at xxxppm of CO2 all is lost, and if you can't you can just make it up and call it science.

 

[Moonbeam]

34% efficiency is incredible. I think that's much higher than photosynthesis

Photosynthesis is 3 to 6 %

The real significance of this potential technology would be the potential for jet fuel, it would seem to me. It would mean, in effect, that all the fuel could be recycled.

It would be interesting to see if a blimp could be covered with this kind of thing, making it's own fuel as it flies.

This is an interesting development too:


An unexpected discovery could yield a full spectrum solar cell

BERKELEY, CA � Researchers in the Materials Sciences Division (MSD) of Lawrence Berkeley National Laboratory, working with crystal-growing teams at Cornell University and Japan's Ritsumeikan University, have learned that the band gap of the semiconductor indium nitride is not 2 electron volts (2 eV) as previously thought, but instead is a much lower 0.7 eV.



A newly established low band gap for indium nitride means that the indium gallium nitride system of alloys (In1-xGaxN) covers the full solar spectrum.

The serendipitous discovery means that a single system of alloys incorporating indium, gallium, and nitrogen can convert virtually the full spectrum of sunlight -- from the near infrared to the far ultraviolet -- to electrical current.

"It's as if nature designed this material on purpose to match the solar spectrum," says MSD's Wladek Walukiewicz, who led the collaborators in making the discovery.

What began as a basic research question points to a potential practical application of great value. For if solar cells can be made with this alloy, they promise to be rugged, relatively inexpensive -- and the most efficient ever created.

In search of better efficiency

Many factors limit the efficiency of photovoltaic cells. Silicon is cheap, for example, but in converting light to electricity it wastes most of the energy as heat. The most efficient semiconductors in solar cells are alloys made from elements from group III of the periodic table, like aluminum, gallium, and indium, with elements from group V, like nitrogen and arsenic.

One of the most fundamental limitations on solar cell efficiency is the band gap of the semiconductor from which the cell is made. In a photovoltaic cell, negatively doped (n-type) material, with extra electrons in its otherwise empty conduction band, makes a junction with positively doped (p-type) material, with extra holes in the band otherwise filled with valence electrons. Incoming photons of the right energy -- that is, the right color of light -- knock electrons loose and leave holes; both migrate in the junction's electric field to form a current.

Photons with less energy than the band gap slip right through. For example, red light photons are not absorbed by high-band-gap semiconductors. While photons with energy higher than the band gap are absorbed -- for example, blue light photons in a low-band gap semiconductor -- their excess energy is wasted as heat.

The maximum efficiency a solar cell made from a single material can achieve in converting light to electrical power is about 30 percent; the best efficiency actually achieved is about 25 percent. To do better, researchers and manufacturers stack different band gap materials in multijunction cells.

Dozens of different layers could be stacked to catch photons at all energies, reaching efficiencies better than 70 percent, but too many problems intervene. When crystal lattices differ too much, for example, strain damages the crystals. The most efficient multijunction solar cell yet made -- 30 percent, out of a possible 50 percent efficiency -- has just two layers.

A tantalizing lead

The first clue to an easier and better route came when Walukiewicz and his colleagues were studying the opposite problem -- not how semiconductors absorb light to create electrical power, but how they use electricity to emit light.

"We were studying the properties of indium nitride as a component of LEDs," says Walukiewicz. In light-emitting diodes and lasers, photons are emitted when holes recombine with electrons. Red-light LEDs have been familiar for decades, but it was only in the 1990s that a new generation of wide-band gap LEDs emerged, capable of radiating light at the blue end of the spectrum.



Light emitting diodes made of indium gallium nitride held clues to the potential new solar cell material.

The new LEDs were made from indium gallium nitride. With a band gap of 3.4 eV, gallium nitride emits invisible ultraviolet light, but when some of the gallium is exchanged for indium, colors like violet, blue, and green are produced. The Berkeley Lab researchers surmised that the same alloy might emit even longer wavelengths if the proportion of indium was increased.

"But even though indium nitride's band gap was reported to be 2 eV, nobody could get light out of it at 2 eV," Walukiewicz says. "All our efforts failed."

Previously the band gap had been measured on samples created by sputtering, a technique in which atoms of the components are knocked off a solid target by a beam of hot plasma. If such a sample were to be contaminated with impurities like oxygen, the band gap would be displaced.

To get the best possible samples of indium nitride, the Berkeley Lab researchers worked with a group at Cornell University headed by William Schaff, renowned for their expertise at molecular beam epitaxy (MBE), and also with a group at Ritsumeikan University headed by Yasushi Nanishi. In MBE the components are deposited as pure gases in high vacuum at moderate temperatures under clean conditions.

When the Berkeley Lab researchers studied these exquisitely pure crystals, there was still no light emission at 2 eV. "But when we looked at a lower band gap, all of a sudden there was lots of light," Walukiewicz says.

The collaborators soon established that the alloy's band-gap width increases smoothly and continuously as the proportions shift from indium toward gallium, until -- having covered every part of the solar spectrum -- it reaches the well-established value of 3.4 eV for simple gallium nitride.

Promising signs

At first glance, indium gallium nitride is not an obvious choice for solar cells. Its crystals are riddled with defects, hundreds of millions or even tens of billions per square centimeter. Ordinarily, defects ruin the optical properties of a semiconductor, trapping charge carriers and dissipating their energy as heat.

In studying LEDs, however, the Berkeley Lab researchers found that the way indium joins with gallium in the alloy leaves indium-rich concentrations that, remarkably, emit light efficiently. Such defect-tolerance in LEDs holds out hope for similar performance in solar cells.

To exploit the alloy's near-perfect correspondence to the spectrum of sunlight will require a multijunction cell with layers of different composition. Walukiewicz explains that "lattice matching is normally a killer" in multijunction cells, "but not here. These materials can accommodate very large lattice mismatches without any significant effect on their optoelectronic properties."

Two layers of indium gallium nitride, one tuned to a band gap of 1.7 eV and the other to 1.1 eV, could attain the theoretical 50 percent maximum efficiency for a two-layer multijunction cell. (Currently, no materials with these band gaps can be grown together.) Or a great many layers with only small differences in their band gaps could be stacked to approach the maximum theoretical efficiency of better than 70 percent.

It remains to be seen if a p-type version of indium gallium nitride suitable for solar cells can be made. Here too success with LEDs made of the same alloy gives hope. A number of other parameters also remain to be settled, like how far charge carriers can travel in the material before being reabsorbed.

Indium gallium nitride's advantages are many. It has tremendous heat capacity and, like other group III nitrides, is extremely resist to radiation. These properties are ideal for the solar arrays that power communications satellites and other spacecraft. But what about cost?

"If it works, the cost should be on the same order of magnitude as traffic lights," Walukiewicz says. "Maybe less." Solar cells so efficient and so relatively cheap could revolutionize the use of solar power not just in space but on Earth.

The Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.

 

[JohnOfSheffield]

If co2 causes warming it's because of a natural cycle, and if it's not then it's because of solar flares and if it's not then it's because of other natural events and if it's not then it doesn't exist and if it does then it's not man made and if it is, i'll deny it anyway...

So what possible use could this tech have?

 

[Throckmorton]

Are you actually saying that no warming or cooling trend in the history of Earth has ever been reversed? What data can you provide to show that we're at the point where the Earth can't correct itself?

I'm sure you can find something somewhere that says at xxxppm of CO2 all is lost, and if you can't you can just make it up and call it science.

Previous warming has always been due to something other than CO2, with CO2 just being a feedback. So whatever the factor was, be it orbital or biological or cosmic, the factor would start pushing the other way. There's nothing like that this time.

 

[JohnOfSheffield]

Previous warming has always been due to something other than CO2, with CO2 just being a feedback. So whatever the factor was, be it orbital or biological or cosmic, the factor would start pushing the other way. There's nothing like that this time.

Actually, the release of CO2 from the lakes and rivers in the north (it's trapped because of lower temperatures in the past) is another problem.

When we come to the point where the ocean bottoms do the same thing... that is when we'll truly be fucked.

 

[Fear No Evil]

nvm