Tunable daytime passive radiative cooling based on a broadband angle selective low-pass filter.

Area of Science:

• Materials Science
• Thermodynamics
• Optics

Background:

• Passive daytime cooling offers a promising avenue for reducing global energy consumption by achieving sub-ambient temperatures without external energy input.
• Current passive cooling technologies lack the crucial ability to be switched on and off, limiting their practical application.
• The need for dynamic control in passive cooling systems is critical for widespread adoption and energy efficiency.

Purpose of the Study:

• To introduce and investigate a novel method for achieving dynamic control of passive radiative cooling during daytime.
• To demonstrate the feasibility of a switchable passive cooling device by integrating an angle-selective solar filter with a passive radiator.
• To explore the potential of optically engineered photonic crystals for tunable thermal management solutions.

Main Methods:

• Development of an angle-selective solar filter utilizing one-dimensional photonic crystal structures.
• Integration of the angle-selective filter with a nocturnal passive radiator.
• Numerical simulations to analyze the performance and tunability of the filter/emitter device by varying the filter's angle.

Main Results:

• Demonstrated that tilting the angle-selective filter from normal incidence up to approximately 23° allows for a wide range of surface temperature tuning.
• Confirmed the feasibility of a switchable low-pass filter/emitter device through numerical simulations.
• Showcased the potential for dynamic control over passive radiative cooling performance.

Conclusions:

• The proposed angle-selective filter integrated with a passive radiator enables dynamic control of daytime passive cooling.
• This technology offers a pathway to switchable cooling, overcoming limitations of current passive systems.
• The findings pave the way for energy-efficient thermal management solutions with tunable cooling properties.