Renewable Energy Global Innovations features: Recycled waste black polyurethane sponges for solar vapor generation and distillation

Significance Statement

Owing to the rising global concerns of energy problems, renewable energy resources are being pursued in high demand. Solar power is the most promising and yet naturally unlimited energy source in the foreseeable future. Recently, solar vapor generation has attracted extensive attention owing to the fact that water pollution, water shortages and energy shortages are alarmingly becoming global issues that ought to be addressed. The use of solar energy to enhance evaporation is currently emerging as an attractive strategy for sustainable and practical system such as in desalination, ethanol distillation and sterilization. Plasmonic metallic nanoparticles of noble metals have been widely investigated as solar absorbers due to their unique photo-thermal conversion property despite their limited applicability due to their costly nature. The quest for a high solar-thermal efficiency solar absorbers has led researchers right into the dumpsites, where waste black polyurethane sponge has been observed to possess the desired qualities upon treatment.

Researchers led by professor Yuen Hong Tsang at The Hong Kong Polytechnic University proposed a study to demonstrate that the recycled black polyurethane sponge with porous structure, low thermal conductivity and low mass density to be self-floating, could behave as an ideal absorber for solar vapor generation despite its weak hydrophilicity. Their aim was to present a recycled self-floating black polyurethane sponge which could efficiently generate water vapor after a simple treatment procedure. Their research work is now published in Applied Energy.

The research team begun by modifying the chemical properties by using a facile dopamine solution stirring treatment, so as to achieve the fast dynamic wettability of the black polyurethane sponge, for fluent water supply on the top surface of the absorber. They then used the porous floatable black polyurethane sponge with low thermal conductivity and high durability to generate localized heat at the air-water surface so as to effectively enhance the water evaporation efficiency. Afterwards, they examined the sponge for application in ethanol distillation.

The authors observed that the surface modified black polyurethane sponge showed that the evaporation rate increased by more than 3.5 times compared to the existing natural evaporation processes. They also observed that the black polyurethane sponge for the solar energy distillation application, showed that the sponge could yield up to 25 wt% concentration promotion under each distillation cycle.

The fact that the black polyurethane sponge is a major waste of the packaging industry supports its application for solar energy conversion as an alternative way for disposing it without polluting the environment. It is more advantageous as opposed to other alternative methods since it does not consume any fossil fuel which generate greenhouse gases during combustion.  Based on environmental sustainability and energy costs, the work presented is promising to be an exciting prospect and competitive for applications in practical solar-thermal technologies.

About The Author

Dr. Yuen Hong Tsang has completed his undergraduate and PhD study in the School of Physics and Astronomy, The University of Manchester, UK in 2004. He came back to Hong Kong in 2009 and he is now Assistant Professor in Applied Physics Department, The Hong Kong Polytechnic University. He has published >100 SCI international peer reviewed journals with H-index >20 and total citation >1400.

His current research interests include development of novel materials, e.g. graphene, MoS₂, WS₂ etc. for laser photonics, photo-catalysis, solar energy conversion applications, e.g. photo-catalyst, solar heat absorber, saturable absorber, optical limiter, photo detection, fiber laser, Q-switched and mode locked lasers, etc.

He has involved and successfully completed several research projects funded by some well-known international companies. These projects include 1.  Laser range funder for military applications (funded by Thales.) 2. Imaging system for dental applications (funded by Colgate Palmolive) 3. Narrow linewidth tunable lasers (funded by Huawei) 4. Carbon based mode locking laser system (funded by Fianium Asian Ltd.)

Reference

Sainan Ma, Chun Pang Chiu, Yujiao Zhu, Chun Yin Tang, Hui Long, Wayesh Qarony, Xinhua Zhao, Xuming Zhang, Wai Hung Lo, Yuen Hong Tsang. Recycled waste black polyurethane sponges for solar vapor generation and distillation. Applied Energy volume 206 (2017) pages 63–69.

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