Hierarchical Cellulose Aerogel Reinforced with In Situ-Assembled Cellulose Nanofibers for Building Cooling

Abstract

The development of new structural materials for passive daytime radiative cooling (PDRC) of buildings will significantly reduce global building energy consumption. Cellulose aerogels are potential PDRC materials for building cooling, but the cooling performance and mechanical strength of cellulose aerogels are considered as challenges for their practical applications. Herein, a bio-inspired hierarchically structured cellulose aerogel (HSCA) was fabricated through an assembly strategy assisted by a high-voltage electrostatic field. The HSCA possesses outstanding PDRC performance and moderate mechanical strength owing to aligned hierarchical porous network microstructures reinforced with in situ-assembled crystalline cellulose nanofibers. Promisingly, the HSCA achieves a max cooling temperature of 7.2 °C and exhibits 1.9 MPa axial compressive strength. There was no significant cooling performance degradation after the hydrophobically modified HSCA was placed outdoors for 3 months. A simulation of potential cooling energy savings shows that by using HSCA as the building envelopes (side wall and roof), it can save 52.7% of cooling energy compared to the building baseline consumption. This new strategy opens up the possibility of developing advanced functionally regenerated cellulose aerogel, which is expected to provide a revolutionary improvement in aerogel materials for building cooling.

Hydrophilic Asymmetrical Boron Nitride Nanoparticle/Glutaraldehyde–Poly(vinyl alcohol) Aerogels for Dual-Mode Passive Cooling

“…As shown in Figure b, it can be demonstrated that GP and PS foam have similar thermal insulation properties, while the thermal insulation properties of BN/GP are slightly lower than those of GP and PS foams, due to the doping of BN, which improves the thermal conductivity of the composite aerogel . However, the BN nanoparticles are mainly concentrated on the surface because of the gravity effect during the preparation process, which limits the further improvement of the thermal conductivity of BN/GP; meanwhile, the obvious temperature difference from the top and the bottom of the asymmetric BN/GP aerogel cooler also confirmed that it still has outstanding thermal insulation properties and can inhibit heat-transfer effect as shown in Figure S6, which is expected to expand applications as building energy-saving materials …”

All-in-One Cast-Molded Hydrophobic Silicon Dioxide-Phase Change Microcapsule/Gelatin-Hydroxyethyl Cellulose Composite Aerogel for Building Cooling

“…32 Therefore, it is crucial to develop and adopt environmentally friendly, biobased PDRC materials with efficient cooling properties. 33−35 For example, renewable materials such as gelatin 36,37 and cellulose 38 are expected to be promising PDRC candidates due to their diversity, accessibility, biocompatibility, and biodegradability. 39 During the day, the radiative cooler provides effective subambient cooling that meets the real needs of the population.…”

“…These include nanocomposite films, − metamaterials, − multilayer photonic structures, − and coatings. − Although significant progress has been made in improving solar reflectance and increasing the emissivity of atmospheric transparent windows to optimize cooling efficiency, the overuse of nonrenewable materials remains a pressing issue . Therefore, it is crucial to develop and adopt environmentally friendly, biobased PDRC materials with efficient cooling properties. − For example, renewable materials such as gelatin , and cellulose are expected to be promising PDRC candidates due to their diversity, accessibility, biocompatibility, and biodegradability …”

Investigation of Gelation Techniques for the Fabrication of Cellulose Aerogels

“…In construction, cellulose-based aerogels can serve as structural materials for passive daytime building radiation cooling. In [17], the authors scrutinized the fabrication of such a material. The results indicated that the synthesized aerogels enable the attainment of a maximum cooling temperature of 7.2 • C and exhibit an axial compression strength of 1.9 MPa.…”