Radiative Cooling Paints

Radiative cooling is a passive cooling technology to promise significant cooling power saving and alleviate climate change, by reflecting sunlight and emitting radiation in the sky window. We focus on developing the paint format to enable wide range of residential and commercial applications, with full daytime sub-ambient cooling and low-cost scalable fabrication.

• Guinness World Record of “World’s Whitest Paint”.

• Finalist for 2021 R&D 100 Awards.

• More than 1000 worldwide media appearances, including BBC, CNN, USA TODAY, Wall Street Journal, Washington Post, Guardian, Science Magazine.

Publication and Patent:

[1] Peoples, J., Li, X., Lv, Y., Qiu, J., Huang, Z., & Ruan, X. (2019). A strategy of hierarchical particle sizes in nanoparticle composite for enhancing solar reflection. International Journal of Heat and Mass Transfer, 131, 487-494.

[2] Li, X., Peoples, J., Huang, Z., Zhao, Z., Qiu, J., & Ruan, X. (2020). Full daytime sub-ambient radiative cooling in commercial-like paints with high figure of merit. Cell Reports Physical Science, 1(10), 100221.

[3] Li, X., Peoples, J., Yao, P., & Ruan, X. (2021). Ultrawhite BaSO4 paints and films for remarkable daytime subambient radiative cooling. ACS Applied Materials & Interfaces, 13(18), 21733-21739.

[4] Ruan, X., Li, X., Huang, Z., & Peoples, J. A. (2021). U.S. Patent Application No. 17/282,958.

[5] Peoples, J., Hung, Y. W., Li, X., Gallagher, D., Fruehe, N., Pottschmidt, M., ... & Ruan, X. (2022). Concentrated radiative cooling. Applied Energy, 310, 118368.

[6] Tong, Z., Peoples, J., Li, X., Yang, X., Bao, H., & Ruan, X. (2022). Electronic and phononic origins of BaSO4 as an ultra-efficient radiative cooling paint pigment. Materials Today Physics, 24, 100658.

Solar Desalination

Recent advances in solar evaporation hold significant promise for vapor generation, seawater desalination, wastewater treatment, and medical sterilization. However, salt accumulation is one of the key bottlenecks for reliable adoption, especially for wicking materials commonly used. By leveraging natural convection enabled by the density gradient, highly efficient and salt rejecting solar evaporation can be simultaneously achieved by engineering the fluidic flow in a wick-free confined water layer.

• Featured in MIT News, Nature Communications Editors’ highlights of “Materials science and chemistry” and “Devices".

Publication and Patent:

[1] Zhang, L.,† Li, X.,† (co-first author) Zhong, Y., Leroy, A., Xu, Z., Zhao, L., & Wang, E. N. (2022). Highly efficient and salt rejecting solar evaporation via a wick-free confined water layer. Nature communications, 13(1), 1-12.

High Temperature Heat Exchanger Design

The efficiency of a heat engine can be significantly improved by operating in a high-temperature and high-pressure environment, which is crucial for a wide range of applications such as aviation as well as power generation. A key challenge is the heat exchanger under such extreme operating conditions. Despite materials development such as super alloys and ceramics, using these materials in a traditional heat exchanger design requires high cost and yields low power density. We propose an ultrahigh power density ceramic heat exchanger enabled by a multiscale porous design, offering significant improvement to both heat transfer and structural strength with a negligible pressure drop penalty.

Publication and Patent:

[1] Li, X.,† Wilson, C. T.,† (co-first author) Zhang, L., Bhatia, B., Zhao, L., Leroy, A., ... & Wang, E. N. (2022). Design and modeling of a multiscale porous ceramic heat exchanger for high temperature applications with ultrahigh power density. International Journal of Heat and Mass Transfer, 194, 122996.

[2] Wang, E.N., Zhao, L. Bhatia, B., Li, X., Leroy, A., Wilke, K., Zhang, L., Youngblood, J., Trice, R., Wilson, C., Brandt, O., and Guerra, R. Devices and Methods for Fabrication of Components of A Multiscale Porous High-Temperature Heat Exchanger. U.S. Patent: 63/166,973, filed March 27, 2021.