A New Type of Foam Made from Nano Fibers in Wood Promises to Significantly Reduce Indoor Temperatures and Save Energy Consumption by Cooling Devices.
In a report published in the journal Nano Letters on May 5, researchers designed a super-lightweight foam made from cellulose nano crystals derived from wood, which can reflect sunlight, emit absorbed heat, and provide insulation. According to them, this material can reduce energy demand for cooling buildings by more than one-third.
Cooling foam material derived from wood. (Photo: Nano Letters)
Although scientists have developed many cooling materials, they still have several drawbacks. Some materials release a lot of heat absorbed through the building under direct sunlight during midday in the summer months. Other materials are ineffective in hot, humid, or cloudy weather. Therefore, the research team from Nanning Forestry University aimed to develop a material that could reflect sunlight, passively release heat, and prevent heat transfer through the building.
To produce the cooling material, researchers bonded cellulose nano crystals together using a silane compound bridge before freezing and freeze-drying the material in a vacuum chamber. This process causes the nano crystals to align vertically, creating a super-lightweight foam that reflects 96% of visible light and emits 92% of the infrared radiation it absorbs.
When covered on top of a foil-lined box placed outdoors at noon, the material helps keep the temperature inside the box 9.2 degrees Celsius lower than the outside temperature. Furthermore, the material also maintains an internal temperature that is 7.4 degrees Celsius cooler than the outside in humid conditions. When the cellulose foam is tightly compressed, its cooling ability decreases, revealing many adjustable properties.
The research team calculated that if the cooling foam is applied to the roofs and exterior walls of a building, the energy demand for cooling would decrease by an average of 36.4%. The performance of the cellulose foam from wood can be adjusted according to weather conditions. Researchers noted that the technology could be applied in various environments.
