Coral-inspired and Colored Daytime Passive Radiative Coolers using Photoluminescent Carbon Dots for Cooling Power Recovery in Building Applications

Project: Research

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Description

Majority of electricity consumption in buildings is for air-conditioning. Daytime passive radiative cooling (DPRC) is an attractive cooling strategy that consumes zero-electricity without refrigerants. By reflecting sunlight and emitting mid-infrared thermal radiation to thecold universe, cooling is achieved. Unfortunately, current DPRCs suffer several problems, including UV degradation and poor aesthetics. To resolve these, scientists add UV absorbing materials and/or colored-pigments. However, this reduces solar reflectivity due to UV and visible light absorption, leading to low/no cooling. Herein, inspired by fluorescent pigments of corals, UV-resistant and colored daytime passive radiative cooling ceramic tiles (DPRCCTs) in a nano/micro-porous-structure adopting photoluminescent carbon dots (CDs), which are nontoxic, stable, low-cost and environmental-friendly, for cooling power recovery (CPR) (highcooling power with vivid color) are proposed. The CDs have two functions; 1) selectively absorbing visible light to reveal color, 2) converting the absorbed excitation light into emission light to reduce solar heat gain for CPR (called “Photoluminescent Cooling”). This project aims to develop colored-DPRCCTs with CDs (C-DPRCCTs-CDs) by combining radiative cooling and photoluminescent cooling, and to fundamentally study their optical properties to understand light scattering with photoluminescence in nano/micro-porous-structured materials. Preliminary results show the cooling power of a yellow-DPRCCT-CD is ~30W/m2, while thereis no cooling power obtained of an ordinary yellow-DPRCCT-pigment, successfully demonstrating the CPR capability.Despite these promising results, several academic challenges remain since the fundamental understanding of light scattering and heat transfer towards nano/micro-porous structures with photoluminescent CDs is lacking. Notably, a UV-resistant and colored DPRC with CPR remains unexplored. This work will focus on the development of a comprehensive mathematical model, starting from a fundamental light scattering study in nano/micro-porous structures of C-DPRCCTs-CDs to the final heat transfer and energy conversion together with CDs’ photoluminescent effects to estimate the cooling power/CPR. Parameters, such asconcentration, absorption, particle size and distribution, photoluminescence, photoluminescence excitation, and photoluminescence quantum yield of CDs, and porosity, pore size and distribution, and thickness of DPRCCTs will be included in the model that willbe experimentally verified. Utilizing the model, the optimized C-DPRCCT-CD will be fabricated and characterized. Field tests will be conducted to examine its cooling power/CPR in different climates. Finally, model houses will be built to study the feasibility and to evaluate the energy-saving performance of the optimized C-DPRCCT-CD. Overall, this study will promote and enhance fundamental understanding of the photonics and heat transfer of nano/micro-porous structures adopting photoluminescent particles, and realize the CPR of DPRCs, opening a new avenue for colored-DPRCs.

Detail(s)

Project number9043506
Grant typeGRF
StatusActive
Effective start/end date1/07/23 → …