MIT associate professor Jeffrey Grossman had previously found out how expensive fulvalene diruthenium was able to store solar energy which led to this years discovery that carbon nanotubes combined with azobenzene work. Not only do they work but they are much cheaper to produce and use.
According to Massachusetts Institute of Technology (MIT), Grossman and postdoc Alexie Kolpak published their findings in Nano Letters. The azobenzene carbon nanotubes are able to store solar energy in a stable chemical form until needed. It also is able to store about 10,000 times more energy in the same amount of space than fulvalene diruthenium would use.
Thermo-chemical storage of solar energy uses a molecule whose structure changes when exposed to sunlight, and can remain stable in that form indefinitely. Then, when nudged by a stimulus — a catalyst, a small temperature change, a flash of light — it can quickly snap back to its other form, releasing its stored energy in a burst of heat. Grossman describes it as creating a rechargeable heat battery with a long shelf life, like a conventional battery.
Another positive aspect of the azobenzene carbon nanotubes is that they can work as both a solar energy harvester and a storage system, a one step process. Unfortunately, if you want to turn the energy into electricity and not heat, you have to add another step to the system. You can either use the heat to produce steam to run a generator or you have to use a “thermoelectric device”.
Grossman and Kopak’s discovery is more than just finding that carbon nanotubes and azobenzene will work well for solar energy storage, they developed a concept that can be used to turn other materials into chemical energy storage batteries. Some of those materials have been synthesized by other scientists.
In order for solar thermal storage to work, the proper energy barrier has to be found. The energy barrier has to provide enough of a block to allow long term storage while also allowing an easy method for release of the energy in the right amount at the right time. As ‘Grossman says, “The barrier has to be optimized.”’
The search for new materials is underway. While the current azobenzene carbon nanotubes are a breakthrough, there may be better materials for solar thermal batteries or for use with other types of chemical energy storage and unless they keep looking, they will never know. Who knows they may come up with storage that doesn’t require a thermoelectric device to turn it into electricity.