Researchers: Solar energy can be stored for eighteen years with isomers

Swedish researchers at Chalmers University of Technology have developed a molecule that is suitable for storing energy generated by solar panels. These are special isomers, in which the energy can be stored for up to eighteen years.

The researchers have developed a modified solar energy system called Molecular Solar Thermal Energy Storage. It uses a special molecule that can store solar energy and release it at a later time. The molecules are made of carbon, hydrogen and nitrogen, also known as norbornadienes. When exposed to sunlight, these change into energy-rich isomers, quadricyclanes. Isomers are molecules with the same atoms, but a different structural formula, where the atoms are arranged differently. The molecules are used in liquid form in the solar energy system.

Normally, half of the norbornadienes revert to quadricyclanes in a month, but the scientists have increased this half-life to eighteen years. According to the researchers, the isomers they have developed can store solar energy for a very long time and, when the energy is extracted, much more heat is released than they had hoped.

In the fourth and final publication on this system, they describe a catalyst that can best control the release of energy. It concerns the substance cobalt phthalocyanine, which serves as a filter through which the liquid flows. This causes a reaction that heats up the liquid by 63 degrees Celsius. If the liquid is already at room temperature, it will warm up to 83 degrees Celsius. Moreover, the reaction returns the molecules to their original shape, so that they can be reused and are suitable for a circular heating system.

In this case, it concerns the substance norbornadienes that is formed into quadricyclanes, whereby the quadricyclanes are returned to norbornadienes by means of a catalyst, whereby energy is released.

The researchers recognize that much remains to be done. They only recently got their invention working, so they still have to optimize many things and, above all, combine everything to arrive at a coherent system. It is hoped in due course to be able to extract even more energy and to reach temperatures of up to 110 degrees Celsius. According to the scientists, the technology can be used commercially within ten years. This is based on the prediction that the norbornadienes can in principle be made on a large scale. In addition, the system should be relatively safe, partly because the researchers were able to liquefy the norbornadienes without the potentially flammable liquid toluene.