MOST: The New Science of Molecular Solar Thermal

When the sun sets, solar panels stop capturing energy. This nightly shutdown is one of renewable energy’s biggest challenges: how to store sunlight efficiently for use after dark. Researchers believe they have found an elegant, alternative solution to batteries.

New way to capture the sun's energy

To date, of course, the answer to overnight storage of the sun's energy has been bulky battery packs. But now, researchers at California's UC Santa Barbara believe they have found an elegant alternative solution - inside a small, carefully engineered molecule.

In a new study, Associate Professor Grace Han and her team describe a new material that captures solar energy, locks it into chemical bonds, and releases it later as heat on demand. The innovation offers a promising alternative energy solution and belongs to a growing field known as molecular solar thermal (MOST) energy storage. A lightweight, recyclable alternative to conventional batteries.

Unlike solar panels, which convert light into electricity, this system converts sunlight into chemical energy. The molecule behaves like a tiny mechanical spring. When sunlight strikes it, the structure twists into a high-energy configuration and remains locked in that strained state. It stays that way until triggered by a small amount of heat or a catalyst, and then it snaps back into its relaxed form, releasing the stored energy as heat.

“The concept is reusable and recyclable,” said Han Nguyen, a doctoral student in the Han Group and lead author of the paper.

To explain it, Nguyen uses an everyday analogy. “Think of photochromic sunglasses. When you’re inside, they’re just clear lenses. You walk out into the sun, and they darken on their own. Come back inside, and the lenses become clear again,” Nguyen said. “That kind of reversible change is what we’re interested in. Only instead of changing color, we want to use the same idea to store energy, release it when we need it, and then reuse the material over and over.”

By creating a compact, high-density molecular system that can capture, store, and release heat on demand, the UCSB team offers a new pathway for solar energy that may reduce reliance on traditional batteries and heavy infrastructure.