Credit:
NASA
When the sun goes down, solar
panels stop working. This is the fundamental hurdle of renewable energy: how to
save the sun's power for a rainy day—or a cold night. Chemists at UC Santa
Barbara have developed a solution that doesn't require bulky batteries or
electrical grids. In a paper published in the journal Science, Associate Professor Grace Han and her team detail a
new material that captures sunlight, stores it within chemical bonds and
releases it as heat on demand.
The material, a modified organic
molecule called pyrimidone, is the latest advancement in molecular solar thermal
(MOST) energy storage.
"The concept is reusable and
recyclable," said Han Nguyen, a doctoral student in the Han Group and the
paper's lead author.
"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 continued.
"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."
Bio-inspired design
To create this molecule, the team
looked to a surprising source: DNA. The pyrimidone structure is similar to a
component found in DNA that, when exposed to UV light, can undergo reversible
structural changes.
By engineering a synthetic version
of this structure, the team created a molecule that stores and releases energy
reversibly. They collaborated with Ken Houk, a distinguished research professor
at UCLA, to use computational modeling to understand why the molecule was able
to store energy and remain stable for years without losing the stored energy.
"We prioritized a lightweight,
compact molecule design," Nguyen said. "For this project, we cut
everything we didn't need. Anything that was unnecessary, we removed to make
the molecule as compact as possible."
A 'rechargeable battery' for heat
Traditional solar panels convert
light into electricity; however, most systems convert light into chemical
energy. The molecule acts like a mechanical spring: when hit with sunlight, it
twists into a strained, high-energy shape. It stays locked in that shape until
a trigger—such as a small amount of heat or a catalyst—snaps it back to its
relaxed state, releasing the stored energy as heat.
"We typically describe it as a
rechargeable solar battery," Nguyen said. "It stores sunlight, and it
can be recharged."
The team's new molecule is a heavy
hitter. It boasts an energy density of more than 1.6 megajoules per kilogram. That
is roughly double the energy density of a standard lithium-ion battery—which
comes in at around 0.9 MJ/kg—and significantly higher than previous generations
of optical switches.
From theory to boiling water
The critical breakthrough for Han's
group was translating high energy density into a tangible result. In the study,
the researchers demonstrated that the heat released from the material was
intense enough to boil water—a feat previously difficult to achieve in this
field.
"Boiling water is an
energy-intensive process," Nguyen said. "The fact that we can boil
water under ambient conditions is a big achievement."
This capability opens the door for
practical applications ranging from off-grid heating for camping to residential
water heating. Because the material is soluble in water, it could potentially
be pumped through roof-mounted solar collectors to charge during the day and
stored in tanks to provide heat at night.
"With solar panels, you need an additional battery system to store the energy," said co-author Benjamin Baker, a doctoral student in the Han Lab. "With molecular solar thermal energy storage, the material itself is able to store that energy from sunlight."
Source: Organic molecule stores solar energy for years, then releases it as heat on demand
No comments:
Post a Comment