Mechanically Tunable Transmittance Convection Shield for Dynamic Radiative Cooling

Area of Science:

• Thermal Engineering
• Materials Science
• Sustainable Energy

Background:

• Radiative cooling dissipates heat to space via the 8-13 μm atmospheric window, offering building energy savings.
• Static radiative cooling materials can cause overcooling in colder conditions, limiting their year-round effectiveness.
• Dynamic spectral control is needed to optimize radiative cooling performance across different seasons and times.

Purpose of the Study:

• To demonstrate a dynamic radiative cooling system using a tunable transmittance convection shield (TTCS).
• To investigate the modulation capabilities of the TTCS in solar and atmospheric window spectral ranges.
• To evaluate the energy-saving potential by mitigating the overcooling issue.

Main Methods:

• Fabrication and integration of a tunable transmittance convection shield (TTCS).
• Dynamic adjustment of TTCS transmittance in solar (28.8-72.9%) and atmospheric window (27.0-80.5%) spectra.
• Field measurements comparing TTCS architecture with traditional radiative cooling under real-world conditions.

Main Results:

• The TTCS achieved significant modulation capabilities: ΔTsolar = 44.1% and ΔT8-13μm = 53.5%.
• Field tests showed the TTCS architecture was 0.3 °C cooler during the day and 3.3 °C warmer at night compared to static systems.
• The dynamic modulation effectively addressed the overcooling problem associated with traditional radiative cooling.

Conclusions:

• The developed TTCS enables dynamic radiative cooling, overcoming limitations of static materials.
• This technology offers enhanced energy savings by optimizing thermal management through spectral modulation.
• Dynamic radiative cooling presents a promising solution for efficient, year-round building climate control.