Scientists are trying to “bottle” solar energy and turn it into liquid fuel: “A solar thermal fuel is like a rechargeable battery, but instead of electricity, you expose it to the sun and release heat.

Whether abundant or renewable, solar energy has a weak point. Although there are many developments and solutions, such cheap and efficient long-term storage has yet to be found, this new technology could be a breakthrough in solar storage.

But now it looks like a solution may be near: Swedish scientists have developed a specific fluid, called thermal solar fuel, that can store the sun’s energy for more than a decade.

“A solar thermal fuel is like a rechargeable battery, but instead of electricity, you turn on sunlight and heat is removed, which is activated on demand,” explained Jeffrey Grossman, an engineer who works with these. materials at MIT.

The fluid is in fact a molecule in liquid form that scientists at Chalmers University of Technology in Sweden have been striving to improve for over a year.

This molecule is made up of carbon, hydrogen, and nitrogen, and when exposed to sunlight, it does something unusual: the bonds between its atoms reorganize and it becomes a new one. “live” version of itself, called an isomer.

Like prey caught in a trap, solar energy is captured between the strong bonds of the isomer, and it remains there even when the molecule cools to room temperature.

When energy is needed – for example at night or in winter – the fluid is simply sucked through a catalyst which returns the molecule to its original form, releasing energy in the form of heat.

“The energy of this isomer can now be stored for up to 18 yearsSays one of the team, Chalmers University nanomaterial scientist Kasper Moth-Poulsen. “And when we get to extract the energy and use it, we get an increase in heat that is greater than we expected.

A prototype of this energy system, placed on the roof of a university building, put the new fluid to the test and, according to the researchers, the results caught the attention of many investors.

The emission-free renewable energy device consists of a concave reflector with a tube in the center, which follows the Sun like a kind of parabolic antenna.

The system works in a circular fashion. By pumping through transparent tubes, the fluid is heated by sunlight, turning the molecule into its isomer. The liquid is stored at room temperature with minimal energy loss.

When energy is needed, the fluid is filtered through a catalyst that converts the molecules to their original form, heating the liquid to 63 degrees Celsius (113 degrees Fahrenheit).

The hope is that this heat can be used for home heating systems, to heat the water in the dishwasher or washing machine, before returning to the roof once again.

The researchers subjected the fluid to this cycle over 125 times, collecting the heat and recovering it without significantly damaging the molecule.

“We have recently made many important advances and today we have a zero emissions energy system that operates year round,” he added. said Moth-Poulsen.

After a series of rapid developments, researchers say their fluid can now hold 250 watt-hours of energy per kilogram – double the energy capacity of Tesla’s Powerwall batteries, for example.

But there is still a lot to improve, the researchers believe they can get even more heat from this system, at least 110 degrees Celsius (230 degrees Fahrenheit) more.

“There is a lot to do. We just got the system up and running. Now we need to make sure everything is optimally designed,” says Moth-Poulsen.

If all goes according to plan, Moth-Poulsen believes the technology could be available for commercial use within 10 years.

The most recent study in the series was published in Energy and environmental sciences.

More information: