- Engineered wood stores solar heat and releases it to produce electricity
- Nanoscale modifications turn balsa into heat-powered energy material
- Phosphorene coating provides broad spectrum absorption of sunlight and efficient heat conversion
Ordinary balsa wood can now absorb sunlight, store heat and produce electricity even in the dark after a team of Chinese scientists redesigned its cellular architecture.
A team from Kunming University of Science and Technology and Guangdong University of Technology claims that the internal structure of wood was transformed to 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.
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How the wood-based system actually works
The scientists first removed lignin, the component that gives wood its color and stiffness, increasing the material’s porosity above 93 percent.
They then covered the channel walls with ultrathin sheets of black phosphorene, a material that absorbs sunlight in ultraviolet, visible, and infrared wavelengths and converts it directly into heat.
Each phosphorene nanosheet was given a protective layer composed of tannic acid and iron ions, creating a molecular shield that prevents oxidation.
Even after 150 days of solar exposure, the coated material remains stable.
Silver nanoparticles were added to improve 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 would simply flow off.
The channels were filled with stearic acid, a biologically derived 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 incoming sunlight into usable heat.
It conducts heat approximately 3.9 times more efficiently in the direction of the wood grain. When paired with a thermoelectric generator, it produces up to 0.65V 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 continue producing electricity even after the light source disappears.
After 100 heating and cooling cycles, the performance of the material has barely changed. It also resisted combustion by self-extinguishing within two minutes.
The scientists note that their design is flame-retardant, superhydrophobic and antimicrobial, preventing dust and microbes from degrading outdoor performance.
Similar designs could help manage heat in electronic devices, improve the energy efficiency of building materials, or support small, off-grid electrical systems.
The research is published in Advanced Energy Materials, but the gap between a laboratory-tested prototype and a commercially viable product remains large.
The team avoided high-temperature carbonization to preserve the chemical characteristics of the wood, which is promising for scalability.
However, producing this material on a large scale while retaining its complex layered structure will not be easy.
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