No matter how abundant or renewable, solar power has a thorn in its side. There is still no cheap and efficient long-term storage for the energy that it generates.The solar industry has been snagged on this branch for a while, but in the past year alone, a series of four papers has ushered in an intriguing new solution.Scientists in Sweden have developed a specialised fluid, called a solar thermal fuel, that can store energy from the sun for well over a decade."A solar thermal fuel is like a rechargeable battery, but instead of electricity, you put sunlight in and get heat out, triggered on demand," Jeffrey Grossman, an engineer works with these materials at MIT explained to NBC News.The fluid is actually a molecule in liquid form that scientists from Chalmers University of Technology, Sweden have been working on improving for over a year.This molecule is composed of carbon, hydrogen and nitrogen, and when it is hit by sunlight, it does something unusual: the bonds between its atoms are rearranged and it turns into an energised new version of itself, called an isomer.Like prey caught in a trap, energy from the sun is thus captured between the isomer's strong chemical bonds, and it stays there even when the molecule cools down to room temperature.When the energy is needed - say at nighttime, or during winter - the fluid is simply drawn through a catalyst that returns the molecule to 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 team, nanomaterials scientist Kasper Moth-Poulsen from Chalmers University."And when we come to extract the energy and use it, we get a warmth increase which is greater than we dared hope for."A prototype of the energy system, placed on the roof of a university building, has put the new fluid to the test, and according to the researchers, the results have caught the attention of numerous investors.
