Green Energy at Night: Radiative Cooling Meets Thermoelectric Generation

Significance 

The use of fossil fuels for energy generation has led to severe environmental consequences, primarily in the form of increased carbon emissions and climate change. To address this critical challenge, there is an urgent need to explore alternative energy sources that are both sustainable and environmentally friendly. One promising avenue in this pursuit is the fusion of two innovative technologies: Radiative Sky Cooling (RSC) and Thermoelectric (TE) power generation. RSC is a groundbreaking technology that leverages the vast coldness of outer space to dissipate heat, effectively cooling objects on earth without consuming any energy. This innovative approach has found applications in reducing building energy consumption, decreasing global energy dependency, and improving personal thermal management. RSC’s potential for passive cooling and its environmentally friendly nature have attracted considerable attention from researchers and industries alike. On the other hand, TE technology enables the direct conversion of heat into electrical energy. TE systems are solid-state devices with no moving parts, offering several advantages, including zero emissions, precise temperature control, long service life, and portability. These attributes make TE technology an attractive candidate for green energy solutions in various applications, such as local power generation and refrigeration. The integration of RSC and TE technologies has given rise to a novel concept: Radiative Sky Cooling-Driven Thermoelectric Power Generation (RSC-TE). This hybrid system utilizes RSC’s cooling capabilities to maintain a temperature gradient across a TE module, thereby generating electrical power. Several recent studies have explored the feasibility of RSC-TE, demonstrating its potential for nighttime power generation. Notably, these investigations have yielded experimental results showing promising voltage outputs and power densities. While RSC-TE holds great promise, it is essential to acknowledge the current limitations and challenges associated with this technology. Existing devices have suffered from low power generation, complex manufacturing processes, and high costs. However, these issues should not discourage further exploration of RSC-TE’s potential. Rather, they should serve as catalysts for innovation and optimization.

In new study published in the peer-reviewed Journal Energy by Dr. Yishuang Ji and Professor Song Lv from the Wuhan University of Technology, developed a new RSC-TE system driven by a TiO2/PMMA radiative cooling coating. This innovative system is designed to achieve passive power generation at night while offering advantages such as simplicity, cost-effectiveness, and high efficiency. The researchers conducted a continuous nighttime experiment to assess the thermal and electrical performance of their RSC-TE system using a self-made device. To complement their experimental work, the researchers also developed a 3D simulation model using COMSOL Multiphysics software. This simulation model, validated against experimental data, provides a valuable tool for analyzing the impact of environmental parameters (wind velocity, ambient temperature, relative humidity) and component-related parameters (non-radiative heat transfer coefficient, area ratio, TEG leg structure, number of leg pairs, heat sink fin height) on the thermal and electrical performance of the RSC-TE system.

The authors’ experimental results confirmed that the RSC-TE system successfully maintained a temperature gradient between the cold and hot sides of the TE module, leading to electrical power generation. The study revealed that the temperature difference between the sides of the TE module, as well as the open circuit voltage, were within the expected range, demonstrating the feasibility of passive power generation at night. They used comprehensive sensitivity analyses to gain valuable insights into the influence of various parameters on the system’s performance. The researchers identified key strategies for enhancing RSC-TE performance, firstly, maintain a low non-radiative heat transfer coefficient for the radiative cooler. Secondly, optimize the area ratio between the radiative cooler and TEG. Thirdly, carefully design the structure of TEG legs to improve heat transfer and finally addressing issues related to uneven temperature distribution at the thermal interface.

In conclusion, the integration of Radiative Sky Cooling and Thermoelectric technology in the form of Radiative Sky Cooling-Driven Thermoelectric Power Generation developed by Dr. Yishuang Ji and Professor Song Lv holds significant promise as a sustainable and environmentally friendly energy solution.

About the author

Song Lv

Associate Professor, Ph.D. Supervisor, Assistant to the Dean, Department Secretary,  |[email protected]

Awarded a Ph.D. in Thermal Science and Energy Engineering from the University of Science and Technology of China in June 2019. Served as a visiting scholar at Carnegie Mellon University’s Department of Mechanical Engineering in 2018. Reviewed for numerous SCI-indexed journals, including “Applied Energy” “Energy” and “Energy Conversion and Management” Published 40 academic papers in Top journals in the field. Holds 10 patents and contributed to two professional books. Achieved 30/32 SCI/EI indexed publications and received 708 citations. Led five projects funded by the National Natural Science Foundation of China, Hubei Provincial Natural Science Foundation, and national key research and development sub-projects. Received one provincial and ministerial-level talent project. Participated in three national major projects and scientific support projects, accumulating a total funding of 10.7 million RMB. Awarded the 45th Geneva International Invention Gold Award as the first author and received the Hubei Provincial Science and Technology Progress First Prize. Honored with the title of “China’s Most Beautiful Person” by the Ministry of Education and the Central Committee of the Communist Party of China for contributions to technological innovation. Previously received honors such as “Chinese University Student of the Year,” ” Top Ten Outstanding University Students Nationwide,” “Guo Yonghuai Award” from the University of Science and Technology of China, “The Thirteenth Chinese University Student of the Year,” “China’s  Top Ten University Students,” “Hundred Talents Program” in the United States, “Outstanding Community Service and Academic Award” in New York State, and “Mozi Outstanding Youth” from the University of Science and Technology of China.

Reference

Yishuang Ji, Song Lv, Experimental and numerical investigation on a radiative cooling driving thermoelectric generator system, Energy, Volume 268, 2023, 126734,

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