- Engineered wood stores solar heat and releases it to generate electricity
- Nanoscale modifications turn balsa into a heat-driven power material
- Phosphorene coating enables broad-spectrum sunlight absorption and efficient heat conversion
Ordinary balsa wood can now absorb sunlight, store heat, and generate electricity even in the dark after a team of Chinese scientists reengineered its cellular architecture.
A team from Kunming University of Science and Technology and Guangdong University of Technology says the wood's internal structure was transformed at the nanoscale to achieve this result.
They chose balsa not for its strength but for its natural alignment of microchannels, which guide heat and hold other materials in place.
How the wood-based system actually works
The scientists first stripped away lignin, the component that gives wood its color and rigidity, boosting the material's porosity above 93%.
They then coated the channel walls with ultrathin sheets of black phosphorene, a material that absorbs sunlight across ultraviolet, visible, and infrared wavelengths and converts it directly into heat.
Each phosphorene nanosheet received a protective layer made from tannic acid and iron ions, creating a molecular shield that prevents oxidation.
Even after 150 days of solar exposure, the coated material remained stable.
Silver nanoparticles were added to enhance light absorption via plasmonic effects, while long hydrocarbon chains were grafted onto the surface to make it water repellent.
The finished structure had a contact angle of 153 degrees, meaning water simply rolls off.
The channels were filled with stearic acid, a bio-based phase-change material that stores heat when melted and releases it upon solidifying.
The material stored approximately 175 kJ of heat per kilogram and converted 91.27% of incoming sunlight into usable heat.
It conducted heat about 3.9 times more efficiently along the grain of the wood. When paired with a thermoelectric generator, it produced up to 0.65 V under standard sunlight.
When sunlight hits the material, it melts the stearic acid, and the heat is released gradually after dark to maintain a temperature difference across the generator.
This allows the system to keep producing electricity even after the light source is gone.
After 100 heating and cooling cycles, the material's performance barely changed. It also resisted burning by self-extinguishing within two minutes.
The scientists note their design is flame-retardant, superhydrophobic, and antimicrobial, preventing dust and microbes from degrading outdoor performance.
Similar designs could help manage heat in electronics, improve energy efficiency in building materials, or support small off-grid power systems.
The research is published in Advanced Energy Materials, but the gap between a lab-tested prototype and a commercially viable product remains substantial.
The team avoided high-temperature carbonization to preserve the wood's chemical features, which is promising for scalability.
However, producing this material at scale while maintaining its complex layered structure will not be easy.
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