Researchers are developing molecules capable of harvesting and holding substantial amounts of solar energy, storing it for significant amounts of time and releasing it on demand.
The breakthrough may prove pivotal for technologies trying to capture the energy of the Sun, and saving it for a rainy day, researchers said.
The group is working with molecules known as the Dihydroazulene-Vinylheptafulvene system.
This stores energy by changing shape, but every time the group managed to design improved molecules, the molecules lost some of their ability to hold their "energy storage".
"Regardless of what we did to prevent it, the molecules would change their shape back and release the stored energy after just an hour or two," said Mogens Brondsted Nielsen from the University of Copenhagen.
Anders Bo Skova, student at Department of Chemistry, managed to double the energy density in a molecule that can hold its shape for a hundred years.
"Our only problem now is how we get it to release the energy again. The molecule does not seem to want to change its shape back again," Brondsted said.
"Regardless of method, when you store energy, there is a theoretical limit to the energy density," he said.
In theory, a kilogramme of the right molecules could store a megajoule of energy if they were perfectly designed.
With that amount of energy you can heat three litres of water from room temperature to boiling, researchers said.
A kilo of Skov's molecules can boil only 75 centilitres but it does that in just three minutes. This means that his molecules could bring 15 litres of water to boil per hour, and researchers are convinced that this is just the beginning.
"What Anders has achieved is an important breakthrough. Admittedly we do not have a good method to release the energy on demand, and we should increase the energy density further still. But now we know which path to take in order to succeed," said Brondsted.
Skov too is excited: Mostly because his molecules are sustainable on more levels than just the obvious one. Not only do they harvest sustainable solar energy. They are also completely non-toxic, he said.
The research was published in the journal Chemistry.