Science

New process discovered for chemically storing solar energy

New process discovered for che...
An azobenzene-functionalized carbon nanotube molecule, which can store solar energy indefinitely (Image: Grossman/Kolpak)
An azobenzene-functionalized carbon nanotube molecule, which can store solar energy indefinitely (Image: Grossman/Kolpak)
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A new system for chemically storing solar energy is said to be less expensive and much more efficient than previous methods (Image: Grossman/Kolpak)
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A new system for chemically storing solar energy is said to be less expensive and much more efficient than previous methods (Image: Grossman/Kolpak)
An azobenzene-functionalized carbon nanotube molecule, which can store solar energy indefinitely (Image: Grossman/Kolpak)
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An azobenzene-functionalized carbon nanotube molecule, which can store solar energy indefinitely (Image: Grossman/Kolpak)

While solar panels are very useful at converting the sun's rays into electricity for immediate use, the storage of that energy for later use is ... well, it's still being figured out. The energy can be used to charge batteries, for instance, but that charge will wear off over time. Instead, scientists have been looking at thermo-chemical storage of solar energy. Last year, researchers from MIT discovered that the chemical fulvalene diruthenium was quite an effective storage medium. Unfortunately, the ruthenium element that it contains is rare and expensive. Now, however, one of those same scientists has created a new storage material that is cheaper, and is able to store much more energy.

The advantage of thermo-chemical storage in general is that the chemicals can be stored for long periods, without experiencing any energy loss. Suitable chemicals that don't contain the pricey ruthenium, however, have tended to degrade within just a few storage cycles.

MIT associate professor Jeffrey Grossman, who led the research last year, has now developed something better. He and postdoc Alexie Kolpak combined carbon nanotubes with the compound azobenzene, the result being a chemical that is less expensive than fulvalene diruthenium, and that has about 10,000 times the volumetric energy density - in other words, it can store more energy in less space.

Kolpak claims that its energy density is similar to that of a lithium-ion battery. By utilizing different methods of nanofabrication, it is also possible to independently control both how much energy can be stored, and how long it can be stored for.

A new system for chemically storing solar energy is said to be less expensive and much more efficient than previous methods (Image: Grossman/Kolpak)
A new system for chemically storing solar energy is said to be less expensive and much more efficient than previous methods (Image: Grossman/Kolpak)

The system works thanks to the azobenzene-functionalized carbon nanotube molecules, that change in structure when exposed to sunlight, and are capable of staying in that state indefinitely. When a stimulus such as a catalyst substance or a temperature change is applied, however, they revert to their previous form, releasing their stored energy as heat. That heat can be used directly in heating systems, or can be used to generate electricity. The molecules, meanwhile, are ready to be charged again.

"You've got a material that both converts and stores energy," said Grossman. "It's robust, it doesn't degrade, and it's cheap."

The MIT research was recently published in the journal Nano Letters.

17 comments
Michael Gene
A true game changer if true, cheap and direct storage of solar would relegate the ICE to the history books. I\'ve never been one to use the words \"game changer\" but a cheap direct storage medium for solar would allow the transportation of energy from sunny desert regions to anywhere it\'s needed just like refined petro is now and the locomotives could just as easily be powered from the same source.
Matthew Jacobs
The question that comes to mind is \" WHAT SURPLUS \" Power is produced during a few hours during the day time and the power is sent directly to the end users when demand during the day is high. Where does the surplus come from? It\'s not like you\'re producing excess Solar power at 2am in the morning when demand is low warranting storing the excess power. Is it me?
Wombat56
How much heat does it release and at what temperature? Does it get hot enough to be thermodynamically efficient at converting the heat into electricity without degrading the chemicals?
RichyRoo
Also whats the efficiency of this material, what percentage of incident solar energy does it capture and at what frequencies. I imagine you would need to arrange this on flat sheets, and once one sheet gets saturated with energy move a fresh one into the sunlight. But the real question, whats the efficiency? Is it better or worse than already fairly lame PV? So sick of these \'we can save the world with renewables\' stories promoting the CAGW agenda with no numbers attached! How cheap, how heavy, how efficient?!
Cesar Arzayus Jr
Cheap energy storage for Solar or any renewable energy source would be the catalyst that puts Solar panels on almost every roof in the US.
Shradhapati Singh
The question in my mind is that having stored vast energy in chemical bond form how will the reverse process of using t5his energy by conversion to other forms be possible.In case lots of energy is generated ,how will controls be effected that the devise does not explode like a bomb?What sort of future technology need to be devloed to be able to use this stored energy?Does anybody have suggestion on this matter?
alligator768
@Wombat56: You're asking the wrong people. Gizmag is a blog, not a scientific journal. The questions you and other pose are all valid, and I share many of them. Perhaps the answers you seek are in the original published article in Nano Letters. Or better yet, contact the researchers directly to discuss your concerns. In fact, I just typed in the phrase "Jeffrey Grossman MIT" into google, and found a more detailed article directly from MIT News. I'm sure you can even do better than that.
Simons Engineering
IF this technology is inexpensive AND easy to store w/o risk of serious volatility AND is easily transported (ie. fluid pumped via pipes) THEN it might be a step forward in putting solar thermal in our homes. That would significantly reduce home heating loads... when the sun shines AND when a method is implemented to eliminate snow blockage. This technology in no way will impact the ICE as commented previously. Comparing to Li batteries is suggestive and misleading. This technology will in no way replace batteries... unless you are referring to battery powered sock heaters. Converting the heat to useable electricity is not efficient, not cheap and isn\'t conveniently portable. Its interesting work that I hope we continue... but its uses may be limited to cold, sunny locations, like the high deserts of the American west where the day-night temperature delta is huge. PS. I\'m interested because I live in the Colorado mountains. This could be a fun home project to cut my heating & domestic hot water bills.
Muraculous
Great find, now, let\'s get it out of the lab and into real world testing before some Chinese government sponsored factory grabs it and beats us to the punch.
windykites
You can buy very cheaply, hand warmers, which use a chemical crystal reaction( is it sodium thiosulphate?) that you recharge in a microwave oven, or hot water. Or: solar heating. Perhaps this could be scaled up.