Solar energy (photovoltaic and concentrated) can capture electromagnetic energy from the sun. If the use of this energy is very old, it is because the Greeks lit the Olympic flame thanks to a system of mirrors concentrated in the rays of the Sun; This renewable source is still marginal in our societies. The CNRS estimates that only 0.7% of the world’s final energy consumption is solar total. In Europe, the resource to renewable energy is more common, solar energy represents 6.3% of the total energy produced. And storing it for a long time was still difficult.
Swedish researchers have developed a molecular fluid capable of storing solar energy for 18 years.
The main reasons for this rather limited development are that the production of solar energy is irregular (it becomes zero at night and on days when the sky is cloudy) and that the conservation of the energy produced is very limited (which makes its storage to compensate for the irregularity of the difficult sunshine). A research team from the Chalmers University of Technology in Sweden may have found a way to get around this double limit by developing a liquid that can store solar energy sustainably. Kasper Moth-Poulsen, who led this work, presented these findings in the journal Energy & Environmental Science.
Swedish researchers have mixed molecules in liquid form (carbon, hydrogen and nitrogen). The organization of the atoms changes when it receives the sun’s rays (they are then called “isomers”) and the heat is “trapped” by the strong chemical bonds of the isomer.
This allows to use this liquid as a solar thermal fuel. “Solar thermal fuel is like a rechargeable battery, but instead of electricity, you store light and provide heat on demand,” says Jeffrey Grossman, MIT Materials Engineer.
To recover this energy, scientists put the fluid in a catalyst, so that the molecule returns to its original form and the energy is released as heat. “When we want to extract this energy and use it, we obtain a higher heat increase than we had hoped for,” the study notes.
The heat extraction cycle thus captured can already be repeated more than 125 times without the molecule being too degraded. “We have made significant progress in recent times, and today we now have a zero-emission energy system that runs all year round,” she continues.
A prototype of the energy system was placed on the roof of the university, and gave very encouraging results. “Energy can be contained in this isomer for 18 years,” says Kasper Moth-Poulsen. But there is still a lot of room for some improvements: “We have a system that works. We must now ensure that everything is optimally designed, “concedes the latter.
Researchers should therefore be able to improve the heat output of this system so that it reaches a temperature of at least 110 degrees Celsius.
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