Electrochromic Adaptive Solar Heater and Sub-Ambient Passive Daytime Radiative Cooler

Area of Science:

• Materials Science
• Sustainable Energy
• Building Physics

Background:

• Heating, ventilation, and air-conditioning (HVAC) systems are significant energy consumers.
• Energy-efficient building envelope technologies are crucial for reducing global energy consumption.
• Leveraging solar and radiative resources offers a sustainable approach to thermal management.

Purpose of the Study:

• To demonstrate a dual-mode electrochromic device for dynamic thermal regulation.
• To achieve reversible switching between solar heating and sub-ambient radiative cooling.
• To evaluate the potential for annual energy and CO2 emission savings in buildings.

Main Methods:

• Fabrication of a dual-mode electrochromic device using electrodeposited Cu-Bi nanoclusters on graphene.
• Characterization of optical properties (solar absorptance and thermal emittance) in cooling and heating modes.
• Evaluation of device performance under simulated daytime conditions for thermal regulation.

Main Results:

• The device achieves sub-ambient passive daytime radiative cooling by 1°C and heating by 33°C above ambient.
• High optical contrast was achieved: cooling mode (α=7.99%, ε=93.58%) and heating mode (α=47.7%, ε=20.14%).
• Demonstrated annual energy savings of 73.7 MBtu and CO2 emission reduction of 4063 kg in U.S. climate zones.

Conclusions:

• The developed electrochromic device offers a promising solution for dynamic thermal regulation in buildings.
• The technology enables significant energy savings and reduced carbon footprint through sustainable resource utilization.
• The device exhibits excellent durability, paving the way for scalable sustainable building technologies.