One of the biggest challenges faced by solar energy is how to store it for use when the sun goes down. The leading solar storage technology is batteries that store electricity generated by a solar system for later use. But a newly developed ‘molecular photoswitch’ takes solar energy storage to a whole new level by storing sunlight within its chemical bonds. Once stored, the sunlight can be released later to generate electricity whenever needed.
How a molecular photoswitch works
A molecular photoswitch is a molecule that can exist in two different forms, called isomers, which vary in their chemical structure. Isomers are compounds that have identical chemical formulas, but the atoms that make up the compounds are structured differently. With molecular photoswitches, the structure of the atoms is changed by adding light energy to them.
To enable the molecule to store large amounts of energy, researchers worked to make the energy variation between both isomers as large as possible. Before storing energy, the molecular photoswitch is considered to be in parent form. In that form, the molecule is highly stable. In organic chemistry, a molecule that is highly stable is described as ‘aromatic’
In its standard parent form, the molecular photoswitch contains three rings made up of atoms, each of which is aromatic. But when the molecule is charged with light, the aromaticity vanishes, and the molecule is charged with abundant energy.
How molecular switches were developed
Molecular photoswitches that can store sunlight were developed by a research team at Linkoping University (LiU) in Hungary. The team, led by Professor Bo Dureej, used advanced computer simulations to model the type of chemical reaction needed to store useful amounts of sunlight within a novel molecule. According to Professor Bo Dureej
“Our molecule can take on two different forms: a parent form that can absorb energy from sunlight, and an alternative form in which the structure of the parent form has been changed and become much more energy-rich while remaining stable. This makes it possible to store the energy in sunlight in the molecule efficiently.”
Computer models revealed that the new molecule would go through the chemical reaction required to store sunlight very quickly, in less than 200 femtoseconds (a femtosecond is one-trillionth of a second). Subsequently, a team at the Research Center for Natural Sciences was able to construct the molecule and perform subsequent tests that confirmed the molecules’ ability to store sunlight.
Future research on molecular photoswitches
The next step in molecular photoswitches is to find the ideal way to discharge the stored light energy from the molecule. Professor Durbeej and his team believe that molecular photoswitches are the long-term solution to storing energy from sunlight and will be conducting further research to find the best way to release the stored solar energy from the molecules. No timeframe has been given as to how long it will take to bring this technology to market.