SCIENCEscience.org 17 DECEMBER 2021¥VOL 374 ISSUE 6574 1503
Fig. 2. Optical and thermal performance of
the RCRT window.(AandB) Spectra of the
sample with (A) and without (B) RC regulation
in the visible-NIR and LWIR range at 20°C
(blue line) and 90°C (red line) against a
normalized AM1.5 global solar spectrum
(yellow shadow) and LWIR atmospheric
transmittance window (blue shadow),
respectively. The schematics on the left
illustrate the structure of the samples with
and without RC regulation, respectively. Both
samples give solar modulation, but the RCRT
window shows a loweLWIRat 20°C and a
higheLWIRat 90°C, whereas theeLWIRchange
for the sample without RC regulation is small.
(C) IR camera image of the RCRT window
(top) and the VO 2 sample without RC regu-
lation (bottom) with temperature increasing
from 30° to 100°C. TheeLWIRfor background
is 0.5. The darker color of the sample with RC
regulation compared with background from
30 to 60°C indicates that itseLWIRis <0.5,
whereas a brighter color from 70° to 100°C
indicates thateLWIRswitches >0.5. By con-
trast, from 30° to 100°C, the sample without
RC regulation is brighter than the background.
Fig. 3.eLWIRemissivity regulation and energy consumption simulation for the
RCRT window.(A)eLWIR-L(solid line) andeLWIR-H(dotted line) spectra for maxe
(red line), maxDe(yellow line), and mine(blue line) VO 2 RCRT samples, respectively.
The samples with differenteLWIRregulation abilities were fabricated by varying the
thickness of PMMA spacer while fixing the thickness of VO 2 -PMMA layer and the
VO 2 weight ratio. (B) Mapping result on the effects ofTsolandeLWIRto the cooling
(left) and heating (right) energy usage in climate zone 4. The minimum energy
consumption for cooling happens ateLWIR= 0.9 andTsol=10%,andtheminimum
energy consumption for heating happens at the point witheLWIR= 0.1 and
Tsol= 90%. This observation agrees well with the proposed ideal window in
Fig.1A.(C) Heating and cooling energy saving (blue columns) of simulated
optimized dynamic samples against optimized static samples (red square) from zones
1 to 7. In this simulation,Tsolwas fixed to 30%. The optimized staticesample is
derived from the point of minimum total energy consumption by adding heating and
cooling in seven climate zones by fixinge. The optimized dynamicewindow has a
eLWIRof 0.9 for cooling and 0.1 for heating. The optimized dynamicewindow has lower
energy consumption than optimized staticewindow from zones 2 to 7. (D) Estimated
world heating and cooling energy-saving of a W-doped maxDesample against a
commercial low-E glass as the baseline. RCRT windows outperform the commercial
low-E across different climate zones. Unit for the energy-saving is MJ m−^2.RESEARCH | REPORTS