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- A new molecule that can capture and store sunlight has been created
- It has twice the energy density of a standard solar storage battery
- The molecule could be used to as a residential water heating alternative
Scientists in California have invented a liquid solar battery that they claim can capture and store a record amount of energy, and make it easier to live off grid.
The team of chemists at UC Santa Barbara made the new material organic molecule out of a modified molecule called pyrimidone, the structure of which is similar to that of a component found in DNA. They said it has twice the energy density of a standard solar battery, meaning it can store twice as much.
When exposed to UV light, the modified molecule can undergo reversible structural changes and store energy for up to three years.
Associate professor, Grace Han, who led the team, said this breakthrough in storage can help generate energy when solar panels stop working at night.
Writing in the journal Science, Han said that once the liquid battery is charged with light, it can store the energy for three years. The material is also entirely reusable and recyclable, working in the same way as sunglasses where the lenses darken or become clear depending on sunlight.
The molecule has been described as a mechanical spring, twisting into a high-energy shape when hit by sunlight, and remaining locked in that position until a trigger – either a small amount of heat or a catalyst – forces it to snap back into its original form and release the stored energy as heat.
Doctoral student and the paper’s lead author, Han Nguyen, described the breakthrough as “a rechargeable solar battery” that stores sunlight that can be recharged.
Nguyen said that the team “prioritised a lightweight, compact molecule design” and that they “cut everything [they] didn’t need.
“Anything that was unnecessary, we removed to make the molecule as compact as possible.”
While being a lot smaller than a standard battery, the molecule has an energy density of 1.6 megajoules per kilogram (MJ/kg). This is double the energy density of a standard lithium-ion battery, which averages around 0.9MJ/kg.
The most significant breakthrough for the research team came when they were able to offer tangible results as to the potential of the molecule. They were able to mix 107mg of the material in about 0.5ml of water, charge the material using UV light, and then, when they added hydrochloric acid, heat was released so fast that the water boiled in 0.5 seconds.
It opens the door for practical applications, from long-term off-grid heating to sustainable residential water heating.
The material is water soluble, meaning it could technically be pumped through roof-mounted solar collectors, letting it charge during the day and collect in tanks to provide heat overnight.
Nguyen said: “Boiling water is an energy-intensive process. The fact that we can boil water under ambient conditions is a big achievement.”
Co-author of the paper, Benjamin Baker, said: “With solar panels, you need an additional battery system to store the energy.”
“With molecular solar thermal energy storage, the material itself is able to store that energy from sunlight.”
The research was supported by the Moore Inventor Fellowship, which Han received in 2025.
