- Engineered wood stores solar heat and releases it to generate electricity
- Nanoscale modifications make balsa a heat-driven power material
- Phosphor 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 conduct heat and hold other materials in place.
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How the wood-based system actually works
The researchers first removed lignin, the component that gives wood its color and stiffness, increasing the material’s porosity to over 93%.
They then coated the channel walls with ultra-thin sheets of black phosphorus, 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 of tannic acid and iron ions, creating a molecular shield that prevents oxidation.
Even after 150 days of sun exposure, the coated material remained stable.
Silver nanoparticles were added to increase 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 the water simply rolls off.
The channels were filled with stearic acid, a bio-based phase change material that stores heat when it melts and releases it when it solidifies.
The material stored approximately 175 kJ of heat per kilogram and converted 91.27% of the 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 gradually released after dark to maintain a temperature differential across the generator.
This allows the system to continue producing electricity even after the light source is gone.
After 100 heating and cooling cycles, the performance of the material hardly changed. It also resisted burning by self-extinguishing within two minutes.
The researchers note that their design is flame retardant, superhydrophobic and antimicrobial, preventing dust and microbes from degrading outdoor performance.
Similar designs can 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 significant.
The team avoided charring at high temperatures to preserve the wood’s chemical properties, which is promising for scalability.
However, it will not be easy to produce this material at scale while maintaining its complex layered structure.
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