SOLAR ENERGY STORED IN A MOLECULE IS THE NEW FUTURE

Nothing is more valuable to us on earth than the sun. We are able to survive because of the radiant energy yielded by the sun. Without exposure, life on Earth might blackout. Solar Energy acts as the ultimate primary power source for all the different forms of energy. But, the sun isn’t always shining!

The progress hitherto carried out during the past decades enable us to transform radiant energy as per our need but the biggest challenge arises when it comes to firm renewables, that is, ensuring continual solar energy in demand, no matter the time of day or weather- SOLAR ENERGY WITH STORAGE.

Lithium batteries are the most used form of solar energy storage while further options include lead ion batteries for off-grid energy systems. Unlike both, aquion or saltwater batteries use electrolytes and retain higher longevity. However, The future of energy storage is beyond batteries.

It is, indeed fascinating to note that solar energy can presently be stored in a molecule, referred to as molecular photoswitches, mainly, Azobenzene photoswitches. This process is known as Molecular Solar Thermal Energy Storage which represents a favourable avenue for harvesting and storing solar energy.

Recent advances in diverse azobenzene materials for solar thermal fuels include pure azobenzene derivatives, nanocarbon-templated azobenzene, and polymer- templated azobenzene.

Photoswitches act as molecular sensors which isomerize, change their shape, after absorbing light and can liberate the stored energy when irradiated or heated. In order to store huge amount of solar energy, a suitable energy profile is attained for these metastable molecules in a thermodynamically closed operative way.

Synthetic approaches for the preparation of high-performance Azobenzene photoswitches requires a large difference in the free energies of the two isomers separated by a large kinetic barrier; quantum yield of the photoisomerisation reaction to be as close to unity; storage half-life at room temperature should be long enough to fulfil application-relevant storage times; the energy of the metastable photoisomer have to be significantly higher than the ground state of the parent isomer; highly selective isomerizations that allow charging and discharging cycles without favouring the formation of side products at high discharge temperatures.

The energy is indefinitely stored in these organic chromophores in a chemical potential form. Besides, They are attached to Multi-wall Carbon Nanotube (MWCNT) to increase the stored energy per azobenzene molecule. After the absorption of sunlight, the aromaticity of the molecule is lost, however, its energy rises. Generally, during chemical reactions cis-isomer being less stable changes into trans-isomer. Here, we execute the opposite, photoisomerisation of trans- azobenzene to cis azobenzene is performed, which has been regarded as a promising reaction for long term energy storage. The system features several striking properties, such as a long energy storage half-life (40 h) at room temperature, as well as an excellent robustness affirmed by optically charging and discharging the molecule over 203 cycles without any trace of degradation.

However, the release of stored energy from these molecules is still under examination.

In conclusion, some potential future directions could be expected with ongoing analysis. In view of the exciting recent achievements in the field, the future emergence and further development by researchers in solar storage are eagerly anticipated.

Reference : Friedrich Alexander University,Erlangen-Nuremberg

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