No matter how rich or renewable, solar power has a thorn in her side. There is still no cheap and efficient long-term storage for the energy it generates.
The solar industry has been busy with this branch for some time, but only in the past year, a series of four labor sets up an intriguing new solution.
Scientists in Sweden have developed a specialized fluid, called solar thermal fuel, which can store energy from the sun for a decade.
"Solar thermal fuel is like a rechargeable battery, but instead of electricity you will put the sunlight on and warm up, causing it on demand," explained Geoffrey Grossman, an engineer with these materials at MIT.
The liquid is in fact a fluid in liquid form that scientists from the University of Technology in Chalmers, Sweden, have been working for more than a year.
This molecule is composed of carbon, hydrogen and nitrogen, and when it is affected by sunlight, it does something unusual: the links between its atoms are rearranged and transformed into an energetic new version of itself, called isomer.
As a captive caught in a trap, the sun's energy is trapped between the strong chemical bonds of the isomer and remains there even when the molecule is cooled to room temperature.
When the energy is needed – say at night or during the winter – the liquid is simply pulled through a catalyst that restores the molecule in its original form, releasing energy in the form of heat.
"The energy in this isomer can now be stored for up to 18 years," says one of the scientists, nanotechnology scientist Kasper Moth-Poulsen of Chalmers University.
"And when we come to extract energy and use it, we will get an increase in heat that is greater than we hoped."
The prototype of the energy system, set on the roof of the university building, put the new test fluid, and according to researchers, the results drew the attention of numerous investors.
The renewable energy release release device is made from a concave reflector with a tube at the center, which tracks the Sun as a type of satellite dish.
The system works circularly. Pumping through transparent tubes, the liquid is heated by sunlight, turning the molecule norborrenenidene into the isomer for retaining heat, quadricyclic. The liquid is then stored at room temperature with minimal energy loss.
When energy is required, the liquid is filtered through a separate catalyst that converts the molecules back into their original form, heating the liquid by 63 degrees Celsius (113 degrees Celsius).
We hope this heat can be used for household heating systems, boiler water supply, dishwasher, clothes dryer and much more, before you go back to the roof again.
The researchers put fluid through this cycle more than 125 times, taking heat and rejecting it without significant damage to the molecule.
"Recently, we have achieved many key achievements, and today we have an emission-free energy system that works all year," says Mol-Poulsen.
After a series of rapid development, the researchers claim that their liquid can now hold 250 watts of energy per kilogram, which is twice that of the Tesla's Powerwall's battery power, according to NBC.
But there is still much room for improvement. With real manipulations, researchers think they can get even greater heat from this system, at least 110 degrees Celsius (230 degrees Celsius).
"There are so many things that we need to do. We only have the work system. Now we have to make sure everything is optimally designed," says Mol-Poulsen.
If everything goes according to plan, Mott-Poulsen thinks technology can be available for commercial use within 10 years.
The latest study in the series is published in Energy and Environmental Science.
The version of this article was published in November 2018.