THESIS
2021
1 online resource (xv, 50 pages) : illustrations (chiefly color)
Abstract
With the global temperature rise by global warming, population growth, and urbanization,
space cooling and air-conditioning are developing into a major challenge in building comfort
and liveable habitation. The traditional air-conditioning system requires greenhouse gases such
as Hydrofluorocarbon (HFC) and consumes a vast amount of fossil fuel. Solar and thermal
radiation modulation by smart windows and adaptive radiative cooling devices are drawing
great interest as alternative cooling systems. Thermochromic hydrogel-based smart windows
are promising indoor temperature regulator which undergoes reversible solar transmittance
change at around the phase change temperature. Adaptive radiative cooling devices can
passively or actively change their thermal radiation emissivity, thereby man...[
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With the global temperature rise by global warming, population growth, and urbanization,
space cooling and air-conditioning are developing into a major challenge in building comfort
and liveable habitation. The traditional air-conditioning system requires greenhouse gases such
as Hydrofluorocarbon (HFC) and consumes a vast amount of fossil fuel. Solar and thermal
radiation modulation by smart windows and adaptive radiative cooling devices are drawing
great interest as alternative cooling systems. Thermochromic hydrogel-based smart windows
are promising indoor temperature regulator which undergoes reversible solar transmittance
change at around the phase change temperature. Adaptive radiative cooling devices can
passively or actively change their thermal radiation emissivity, thereby manages indoor
temperature. At present, these technologies can only change from neutral to cooling mode, and
thus, their energy-saving potential is revealed only in hot and sunny weather. In this work, all-weather
energy-saving windows were realized. This thesis introduces two novel solutions to
achieve all-weather energy saving by smart windows. The first work presents the solar and
thermal regulating (STR) window made of poly(N-isopropylacrylamide) (pNIPAm) hydrogel
and silver nanowire (AgNWs) composite which reversibly switches between transparent heat
preservation mode and opaque heat dissipation mode via solar and thermal modulation. The
solar ( Δ?
??? = 53.8% ) and thermal radiation ( Δ?
?ℎ? = 57.1% ) modulation successfully
regulated indoor temperature. The performance of the STR window was tested under simulated
summer and winter conditions. The STR window maintained the indoor temperature ~15℃
and ~6℃ cooler than Low-e glass and bare hydrogel smart window, respectively, in summer.
In winter, ~1℃ higher indoor temperature was determined in the STR window equipped house.
The second work introduces ethyl cellulose (EC) based radiative cooling and transparent
photothermal heating dual-mode window. The porous EC film with high hemispherical solar
reflectance (?
??? = 97%) induced ~1.7 ℃ daytime cooling during at noon, from 12:30 to 13:30. When the window was turned to the heating mode, the transparent photothermal coating
raised the temperature by ~16.8 ℃ at most. The accelerated durability test ensures sustainable
material stability of the STR and dual-mode windows under repeated operation cycles and UV
light exposure. It guarantees the feasibility of the two presented works in practical uses. At last,
the potential improvement was discussed with the possible cutting-edge technologies applicable
to the windows.
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