Abstract
With rapid urbanization, population growth, and rising global temperatures, cooling-related energy consumption has surged, placing significant pressure on environmental and energy systems. Conventional cooling technologies, such as air conditioning, heavily depend on fossil fuels, leading to substantial greenhouse gas emissions and environmental degradation. In contrast, passive radiative cooling (PRC) offers a sustainable, energy-efficient solution by utilizing the atmospheric transparency window (8-13 μm) to radiate heat into outer space without external energy input. Despite advances in material design and performance optimization, PRC technology still faces challenges in ensuring performance stability and adaptability across diverse applications. Additionally, the environmental sustainability of current materials is insufficient, with a critical need for high-performance, biodegradable, or recyclable alternatives. This thesis systematically investigates the development and application of PRC technology in buildings, industrial systems, and Personal Thermal Management (PTM), while proposing innovative adaptive cooling solutions to expand its functionality and address key thermal management challenges.In the context of building applications, a porous polymeric radiative cooling coating (PRCC) was developed using an immersion precipitation method. PRCC exhibited outstanding optical properties, with a solar reflectivity of 96.2% and mid-infrared emissivity of 95%, achieving sub-ambient cooling effects of up to 4°C during the day. Field experiments and EnergyPlus simulations demonstrated that PRCC reduces annual cooling energy consumption by 11.3% in humid subtropical climates, with even greater energy savings in hot and dry climates, highlighting its scalability and effectiveness.
The same PRCC was also applied in industrial applications, particularly for chemical storage tanks, to mitigate evaporative losses and improve thermal regulation. Small-scale experiments showed an 81.4% reduction in ethanol evaporation over five days compared to uncoated containers, while large-scale numerical modeling revealed annual chemical savings of 50% in humid climates and up to 52% in hot regions. PRCC provides a cost-effective, passive alternative to conventional solutions, significantly reducing operational costs and environmental pollution from volatile organic compounds (VOCs).
Beyond applications in buildings and industry, PRC technologies were also explored for PTM. A bioinspired and biodegradable composite material (Bio-PREC) was developed, integrating radiative and evaporative cooling mechanisms. Bio-PREC achieved a 9°C cooling effect in dry conditions and an additional 8°C under simulated perspiration scenarios, outperforming commercial fabrics. Its sustainable design and dual-gradient structure make it an effective solution for wearable cooling in diverse environments, with potential applications in sportswear, medical textiles, and industrial uniforms.
Finally, recognizing that the aforementioned applications offer only fixed cooling effects, a thermally adaptive film radiator (TAFR) system was developed to enable self-adaptive thermal regulation for buildings. Inspired by the temperature-regulating mechanisms of butterfly wings, the system incorporates a thermochromic layer for temperature-responsive reflectivity and color changes. TAFR demonstrated cooling effects of 3.6-4.2°C below ambient temperature and heating effects up to 5.1°C above ambient temperature, with annual energy savings ranging from 13.8 to 62.8 GJ depending on climate conditions.
This work showcases the potential of PRC technologies as scalable, energy-efficient, and sustainable solutions for diverse thermal management challenges, paving the way for advancements in cooling technologies across multiple domains.
| Date of Award | 9 Apr 2025 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Chi Yan TSO (Supervisor) |