Abstract:
like heat treatment, dehydration, cooling, and fermentation have been developed.
Cooling is generally the most adopted method by using refrigerators or freezers.
However, it consumes more energy and emits environmental pollutants. Radiative
cooling is a sustainable, alternative method using thermal radiation, which removes heat
without releasing pollutants. Also, radiative cooling is the process of cooling objects on
the earth's surface through the emission of thermal infrared radiation into space via the
atmosphere infrared window (IR window). Radiative cooler mostly uses long-wave
infrared (LWIR) as its IR window because the maximum infrared radiation transmission
through the atmosphere is provided by the LWIR window. The radiative cooler requires
high thermal emission in the infrared spectrum (LWIR approximately within 1200 cm-1
to 800 cm-1) without visible light absorption. Radiative coolers can designed in several
groups of materials such as dielectric multilayer, organic-inorganic composite, porous
polymer, and metamaterials. This research aims to design a sustainable and energy
efficient radiative cooling material for food preservation applications. For that, this
research used organic-inorganic composite material for fabricating radiative cooling
material. As well cellulose was used as an organic matrix and was extracted from water
hyacinth aquatic plants. Cellulose has potential as a radiative cooling material due to its
ability to absorb infrared light through molecular vibration. However, due to its low
solar reflectance, it is not suitable for direct use. For that SiO2 was used as an inorganic
filler to increase the efficiency of the radiative cooler. Initially, 10 g of water hyacinth
biomass was taken and treated with 5% NaOH and 5% NaOCl 64% H2SO4 solutions to
obtain cellulose. 5 g of cellulose was dissolved with 7% NaOH and 12% urea solution
and was treated with 2% sodium silicate solution to fabricate cellulose-silica composite
material. After Alkali & bleaching treatments, both hemicellulose and lignin were
removed from the biomass and a bleached cellulose yield of 57.52% was obtained.
42.48% of the weight was lost from water hyacinth biomass. Stretching of the Si-O and
Si-O-Si bonds in the composite material is shown by detectable peaks at 923 cm-1 and
1041cm-1. Therefore, the FTIR spectrum corresponds to the material's emissive
properties within the LWIR range. These peaks indicate vibrational modes associated
with bonds that contribute to the thermal radiation emission. According to this study,
the cellulose-silica composite material can be used for fabricating radiative coolers for
zero-energy food preservation
