According to the International Energy Agency (IEA), heating represents approximately 50% of global final energy consumption. Most of it depends on fossil fuels, and the use of solar energy is limited. This is because sunlight requires the climate and the supply is unstable. Molecular solar thermal energy storage (MOST) systems are attracting attention as a solution to this problem.
In most cases, thermal energy can only be temporarily stored in the form of hot water. On the other hand, a MOST uses specific molecules known as photoswitches, which change their chemical properties and structure when exposed to electromagnetic radiation: infrared, visible and ultraviolet light, to convert solar energy into chemicals by storing them as bonds. Through this mechanism thermal energy can be retained for weeks or months.
However, the rigor of MOST is limited by the need to balance sunlight absorption efficiency. A group of German researchers used photosensitizers to separate the process of absorption and transfer of energy obtained to other substances, drastically increasing the storage rate. Their study was published in the magazine german chemistry Angewandte Chemie.
How does MOST work?
Most use an organic compound called norbornadiene; This is converted into a quadrocyclane in a high energy state through a photoreaction. The MOST system works by releasing energy as heat as needed. The photoswitch was first proposed by a research team at the University of Siegen, Germany; It had energy storage capacity comparable to that of a typical lithium-ion battery. However, it could only be excited by ultraviolet light, which represents only a small part of the spectrum of sunlight.
Therefore, the team from the University of Siegen, together with the Johannes Gutenberg University of Mainz (JGU), combined a sensitizer that efficiently absorbs visible light to create a complete indirect light harvester similar to that used in algae and others. plants during photosynthesis.
It is a paradox: seagrasses are among the ecosystems that bury the most tons of CO2, but also among those most affected by climate change.
A mechanism similar to plant photosynthesis
“The sensitizer absorbs light and transfers energy to the photoswitch, which cannot be directly excited,” explains Christoph Kelzig, lead author of the study and professor of chemistry at JGU. By separating the energy absorption and storage processes in this way, the efficiency of solar energy storage improved more than 10 times compared to conventional MOST.
The research team was also able to minimize energy loss by spectroscopically analyzing the reaction mechanisms at each step, including the energy transfer of sunlight and the chemical conversion of the photoswitches. Additionally, testing of repeated energy storage and release cycles using sunlight demonstrated the durability and practicality of the system. The technology can be applied at a wide range of scales, from home heating equipment to large-scale energy storage facilitiesand researchers hope it will become a sustainable energy source for the future.
Article originally published in WIRED Japan. Adapted by Alondra Flores.
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