Session: 02-02: Advances in Green Energy Modeling and Innovative Technologies

Paper Number: 138349

138349 - Luminescent Thermochromic Smart Windows for Solar Regulation and Power Generation in Green Buildings 

Abstract: 

Windows play a crucial role in the energy performance of buildings, as they are often responsible for a significant amount of heat gain or loss. Their limited ability to control solar irradiation contributes to this issue. However, researchers have been exploring innovative solutions to improve energy efficiency, and one such solution is thermochromic smart windows (TSWs). These windows passively adjust the amount of solar irradiation entering a building based on the ambient temperature, which helps reduce the need for excessive cooling or heating. While TSWs have shown promise in reducing energy consumption, they also present a challenge. Solar irradiation is a valuable resource that could potentially be harnessed to generate power, but conventional TSWs typically block this energy to fulfill their regulation function. This leads to a missed opportunity for energy capture and utilization. To address this limitation, our study introduces a groundbreaking dual-functional TSW known as TSW-HQD. This advanced window design incorporates a thermochromic hydrogel embedded with CdSe/ZnS quantum dots (QDs), which boast an impressive quantum yield of approximately 95%. The hydrogel in TSW-HQD is custom-designed to modulate both visible and near-infrared light, enhancing its energy-saving capabilities. Additionally, the QDs within the hydrogel have the ability to down-convert ultraviolet irradiation into visible light. When combined with the scattered visible and near-infrared light, these converted photons can be captured by photovoltaic cells attached to the edges of TSW-HQDs, enabling power generation. This concept is akin to the functioning principle of conventional luminescent solar concentrators (LSCs), which are widely utilized as power-generating windows. Furthermore, the hydrogel used in TSW-HQD exhibits high emissivity in the mid-infrared region, which enables effective radiative cooling. This additional feature helps reduce the cooling load on buildings, further enhancing their energy efficiency. The results of our study demonstrate the exceptional optical properties of TSW-HQD. In the cold state, the window exhibits a luminous transmittance of 91%, while in the hot state, it reduces to 30%. The window's solar modulation ability is measured at 41%, highlighting its effective regulation of solar irradiation. Importantly, TSW-HQD outperforms pure-hydrogel TSWs in terms of power conversion efficiency (PCE) by approximately 65%, enabling simultaneous energy-saving and power generation. Moreover, the hydrogel's high emissivity of over 90% contributes significantly to the effectiveness of radiative cooling. In conclusion, the development of TSW-HQD opens up new possibilities for next-generation smart windows that integrate solar modulation, power generation, and radiative cooling. This innovation has the potential to significantly enhance the energy efficiency of buildings, making them more sustainable and environmentally friendly.

Presenting Author: Sai Liu City University of Hong Kong

Presenting Author Biography: Sai Liu is currently a postdoc researcher in the City University of Hong Kong. He received his B.S. degree in building environment and energy application engineering from Hunan University, M.S. degree in intelligent building technology from The Hong Kong University of Science and Technology, and Ph.D. degree in energy and environment from City University of Hong Kong in 2017, 2018 and 2022, respectively. His research focuses on advanced building technologies and smart materials for energy saving, including the development of building smart windows with investigations on thermochromic materials and transparent woods for window applications.

Authors:

Sai Liu City University of Hong Kong
Yuwei Du City Univeristy of Hong Kong
Chi Yan Tso City University of Hong Kong