A liquid that remembers sunlight and gives it back when asked
At the intersection of biology and energy science, researchers at UC Santa Barbara have drawn inspiration from the architecture of DNA to create a liquid that captures sunlight and holds it—patiently, stably—for months or years before releasing it as heat on demand. The pyrimidone molecule at the heart of this system stores nearly twice the energy of a lithium-ion battery without degrading, suggesting that the next chapter in renewable energy storage may look less like a battery and more like a living thing. In a world straining under the weight of grid infrastructure and the mounting demands of an electrified civilization, this quiet molecular coil may represent a genuinely different path forward.
- A molecule modeled on DNA can absorb sunlight, lock into a high-energy twisted state, and hold that energy indefinitely—releasing it as intense heat only when triggered, with no degradation over repeated cycles.
- At 1.65 MJ/kg, the pyrimidone system nearly doubles the energy density of lithium-ion batteries and has already demonstrated enough thermal output to rapidly boil water in laboratory conditions.
- The technology bypasses the electrical grid entirely, offering a portable, emissions-free thermal energy source for home heating, off-grid cooking, industrial defrosting, and applications where wiring infrastructure is impractical or impossible.
- The global battery storage market is racing toward $100 billion by 2030, driven by AI infrastructure and energy transition demands—and this liquid solar system could carve out a distinct niche that conventional grid-scale batteries cannot fill.
- Researchers are now coupling the thermal storage with thermoelectric chips to generate electricity as well as heat, pointing toward self-charging consumer electronics and continuous off-grid power from a single liquid system.
At UC Santa Barbara, a research team led by Associate Professor Grace Han has engineered a liquid battery unlike anything powering today's devices. Rather than storing charge electrochemically, it stores sunlight as chemical potential inside a molecule called pyrimidone—a structure modeled on a component naturally found in DNA. When light strikes the liquid, the molecules twist into a strained, high-energy form and stay locked there, stable for months or years, until a small trigger causes them to snap back and release their stored energy as heat. The team calls this the "Coiled Spring Effect," and because the molecular cycle is fully reversible, the system can be charged and discharged indefinitely without any loss of capacity.
The performance figures are difficult to ignore. Pyrimidone delivers an energy density of 1.65 megajoules per kilogram—nearly double the roughly 0.9 MJ/kg offered by standard lithium-ion batteries. In the lab, the material released enough heat to rapidly boil water, a threshold that molecular solar thermal systems have historically struggled to reach. The findings were published in the journal Science.
The practical implications span from the domestic to the industrial. A homeowner could charge the liquid through rooftop solar collectors by day, store it in a tank, and draw heat from it at night for water or space heating—no grid connection required. For off-grid users, the liquid offers portable, emissions-free thermal energy for cooking or equipment, sidestepping the infrastructure demands that are pushing the global battery storage market toward a projected value exceeding $100 billion by 2030.
The deeper ambition lies in hybrid systems. Building on earlier work by Sweden's Chalmers University—where photoswitchable molecules stored solar energy for up to 18 years before releasing it through a thermoelectric chip as electricity—the UC Santa Barbara team is pursuing a similar dual-output approach. By pairing their molecular thermal storage with thermoelectric generators, they aim to produce both heat and electricity simultaneously from a single liquid system, opening pathways to self-charging wearables and continuous off-grid power. What emerged from a search for better battery materials is something more unexpected: a liquid that holds sunlight in memory and returns it, precisely, when asked.
At UC Santa Barbara, researchers have engineered a battery that works nothing like the lithium-ion cells powering your phone. It stores sunlight as chemical potential in a liquid, holds that energy stable for months or years, and releases it as heat whenever you need it—all without touching an electrical grid or requiring the massive infrastructure of conventional battery systems.
The breakthrough centers on a molecule called pyrimidone, designed by Associate Professor Grace Han's team and modeled after a structure found naturally in DNA. When sunlight strikes the liquid, the molecules absorb that light and twist into a highly strained, high-energy configuration known as a Dewar isomer. They stay locked in this coiled state indefinitely. Apply a small trigger—a catalyst or a flash of heat—and the molecule snaps back to its relaxed form, releasing the stored energy as pure thermal energy. The team calls this the "Coiled Spring Effect," and it works because the molecular cycle is highly reversible. Unlike conventional batteries that degrade through physical wear, this system can be charged and discharged indefinitely without losing capacity.
The numbers are striking. The pyrimidone molecule delivers an energy density of 1.65 megajoules per kilogram, nearly double that of a standard lithium-ion battery at roughly 0.9 MJ/kg. In the lab, the material released enough intense heat to rapidly boil water under normal conditions—a threshold that has historically been difficult for molecular solar thermal systems to reach. The research, published in the journal Science, represents a genuine leap forward in how we might store renewable energy.
The practical applications are immediate and varied. A homeowner could circulate the liquid through rooftop solar collectors during the day to charge it, then store it in a tank until evening, when it pumps heat into water boilers or home heating systems. For off-grid and industrial use, the liquid offers emissions-free, portable thermal energy for cooking, camping equipment, or defrosting surfaces—all without electrical connections. The technology sidesteps the need for the massive battery systems now scaling up to support AI servers and hyperscale data centers, which are driving explosive growth in the grid storage market. Global battery energy storage capacity is projected to surge up to 15 times over the current decade, with market value expected to exceed $100 billion by 2030.
But the real frontier lies in hybrid systems. Researchers are already coupling molecular solar thermal storage with thermoelectric generators—ultra-thin chips that convert heat into electricity via the Seebeck effect, the same principle that creates voltage from a temperature difference. Four years ago, scientists at Sweden's Chalmers University of Technology demonstrated photoswitchable molecules that absorbed sunlight and stored the energy for up to 18 years. When a catalyst triggered the molecules to revert, the released heat passed through a thermoelectric chip and generated electricity on demand. This dual-output approach opens doors to self-charging consumer electronics like smartwatches and headphones, as well as continuous off-grid power generation. The UC Santa Barbara team is exploring similar pathways, aiming to produce both heat and electricity simultaneously from a single system. What began as a hunt for advanced materials to push battery technology forward has yielded something stranger and more elegant: a liquid that remembers sunlight and gives it back when asked.
Notable Quotes
The system can be charged and discharged indefinitely without losing capacity, unlike conventional batteries that degrade through physical wear.— UC Santa Barbara research findings
The Hearth Conversation Another angle on the story
Why does a molecule that stores heat matter more than another incremental improvement to lithium-ion?
Because it decouples energy storage from electricity. Most of the grid is built around converting everything to electrons. This stores energy as molecular structure—it's stable for years, doesn't degrade, and comes out as heat, which is what most buildings actually need.
The "Coiled Spring Effect"—is that just marketing language, or does it describe something real?
It's real. The molecule physically twists into a strained state when it absorbs light, then snaps back when triggered. It's not metaphorical. The strain is what holds the energy, the same way a compressed spring holds mechanical energy.
You said it can boil water. That seems almost mundane compared to powering a data center.
Exactly. That's the point. Most of what we need energy for is heat—space heating, water heating, industrial processes. We've been forcing everything through electricity because that's what the grid does. This lets you store solar energy as heat directly, which is more efficient for those applications.
What's the catch? Why isn't this everywhere already?
It's brand new. Published in Science just now. The molecules work, the energy density is proven, but scaling production, finding the right catalysts for different applications, integrating it into existing systems—that's years of engineering away. And the thermoelectric conversion to electricity is still being refined.
So someone could theoretically have a tank of this liquid in their basement and heat their house all winter from summer sun?
In theory, yes. The molecules stay stable for months or years, so you could charge it all summer and draw heat all winter. You'd need the right tank, the right circulation system, and a catalyst to trigger release. But the core physics works.
What happens if you trigger it and don't use the heat?
The molecule snaps back and releases the energy as heat anyway. You can't really "hold" it once triggered. So you'd need to design the system so the heat goes somewhere useful—into water, into air, into a space you're trying to warm.