Alcogel-Based Interfacial Evaporation for Vertical Thermal Diode-Structured Smart Walls with Radiant Cooling

Area of Science:

• Building Science
• Materials Science
• Thermodynamics

Background:

• Traditional building envelopes have fixed thermophysical properties, limiting their effectiveness in passive temperature regulation.
• The need for climate-adaptive building envelopes that can enhance heating in winter and cooling in summer is critical for energy efficiency.

Purpose of the Study:

• To investigate the feasibility of achieving single-direction heat transfer in building envelopes with climate-adaptive thermophysical properties.
• To develop and demonstrate a novel building envelope capable of passive temperature regulation.

Main Methods:

• Utilizing the capillary effect in interfacial evaporation and a thermal diode structure for single-direction heat transfer.
• Manufacturing an evaporation-condensation-based smart wall (ECSW) for spontaneous and continuous cooling/heating.
• Integrating radiant cooling and photothermal capabilities into the ECSW design.

Main Results:

• The ECSW demonstrated climate-adaptive heat transfer coefficients ranging from 3.33 to approximately 30 W m⁻² K⁻¹.
• Achieved heat transfer of 5.44 W m⁻² via radiant cooling (5 °C cooler surface) and 387.68 W m⁻² under solar illumination (1000 W m⁻²).
• Simulations indicated potential building energy savings of 66.47% in Kunming.

Conclusions:

• Successfully demonstrated vertical thermal diode building envelopes using natural heating/cooling sources via interfacial evaporation.
• The developed ECSW offers passive temperature regulation with low cost, stable performance, and significant energy-saving potential.
• This technology paves the way for smarter and more sustainable buildings.