Balsa wood engineered at the nanoscale now absorbs sunlight, stores the resulting heat, and generates electricity after the light source is removed, reaching a photothermal conversion efficiency of 91.27 per cent and a sustained output voltage of 0.65 volts.
That is according to Yang Meng, Feng Wu, Yuchan Li, Zhe Xiang, Mengyuan Luo, Xinxin Sheng, and Delong Xie, whose study published in Wiley’s Advanced Energy Materials describes a carbonisation-free wood composite as “a scalable and environmentally friendly wood-based platform for advanced solar thermal energy harvesting.”
The team chose balsa for its internal architecture rather than its mechanical properties. Under a microscope, the wood’s cross-section shows a dense network of aligned microchannels, each 20-50 micrometres wide, that act as a natural scaffold and give balsa a directional geometry that synthetic solar materials require energy-intensive fabrication to match.
Stripping the wood of lignin raised its internal porosity above 93 per cent, exposing a reactive surface whilst preserving the channel structure that drives thermal performance. The process bypassed high-temperature carbonisation entirely, removing the step that has made most competing designs difficult to manufacture sustainably.
The channel walls were coated with black phosphorene, a semiconductor that absorbs sunlight across ultraviolet, visible, and infrared wavelengths, before a protective layer of tannin and iron ions was applied around each nanosheet. Phosphorene degrades rapidly in open air, and the tannin-iron coating solves that problem, with the treated material maintaining its performance across 150 days of simulated outdoor exposure without measurable loss.
Silver nanoparticles were then added to the surface to enhance solar absorption, after which a water-repellent coating produced a contact angle of 153 degrees. The result is a self-cleaning, antimicrobial composite that self-extinguishes within two minutes of ignition and resists the biological growth that degrades competing outdoor systems.
Stearic acid, a bio-based phase change material, was then loaded into the microchannels to complete the system. In sunlight, it melts and stores latent heat at approximately 175.03 kilojoules per kilogram, and as it cools, it releases that energy through an attached thermoelectric generator, sustaining 0.65 volts of output after dark whilst thermal conductivity increases 3.9-fold along the grain.
The 175 kJ/kg result is what the field of wood nanotechnology will examine most closely. Professor Lars Berglund, Research Director of the Wallenberg Wood Science Center at KTH Royal Institute of Technology in Stockholm, achieved wood-based phase change energy storage in 2019 using a delignified substrate with a latent heat of approximately 76 kJ/kg.
The Meng team’s composite more than doubles that figure. It also adds the solar-to-electricity conversion step that Berglund’s earlier design did not include, taking wood-based energy storage from passive heat management into active power generation.
Berglund has previously identified scalability as the central challenge for the field, asking how researchers move “from lab processing… to something that can be done on an industrial scale.” The carbonisation-free method produced by Meng and colleagues addresses that question directly, using a process compatible with existing wood manufacturing infrastructure in a way that carbon-based designs are not.
Wood Central understands that the species choice carries its own commercial implications. Balsa, grown primarily as a wind turbine blade core, has been absent from the energy materials literature, and the Meng team’s findings suggest its value may be seriously underpriced, given that cellular anatomy rather than mechanical strength is what qualifies it as a viable plantation feedstock for solar-thermal applications at scale.
Meng and colleagues deliver a photothermal conversion efficiency of 91.27 per cent and post-dark electricity generation of 0.65 volts from a carbonisation-free wood composite, a result that places plantation balsa, for the first time, at the frontier of bio-based solar energy materials.
- For further information: Meng, Y., Wu, F., Li., Xiang, Z., Luo, M., Sheng, X., & Xie, D. (2026). Interface-Engineered Wood-Based Composite Phase Change Materials Integrating Superhydrophobic, Flame-Retardant, and Antimicrobial Properties for Sustainable Solar–Electric Energy Conversion. Advanced Energy Materials. https://doi.org/10.1002/aenm.70872
