Solar-powered water harvesting and purification

Quick bibliography: reviews/recent articles on solar-powered water harvesting and purification.

Solar still

**updated July 2021**

Classic review:

*Sampathkumar, K., Arjunan, T.V., Pritchandi, P., & Senthilkumar, P. (2010). Active solar distillation—A detailed review. Renewable and Sustainable Energy Reviews, 14 (6), 1503-1526 . [PDF] [Cited by]

“All over the world, access to potable water to the people are narrowing down day by day. Most of the human diseases are due to polluted or non-purified water resources. Even today, under-developed countries and developing countries face a huge water scarcity because of unplanned mechanisms and pollution created by man-made activities. Water purification without affecting the ecosystem is the need of the hour. In this context, many conventional and non-conventional techniques have been developed for purification of saline water. Among these, solar distillation proves to be both an economical and eco-friendly technique particularly in rural areas. Many active distillation systems have been developed to overcome the problem of lower distillate output in passive solar stills. This article provides a detailed review of different studies on active solar distillation systems over the years.”

Recent reviews/articles:

*Dongare, P.D, Alabastri, A., Neumann, O., Nordlander, P., & Halas, N.J. (2019).  Solar thermal desalination as a nonlinear optical process. Proceedings of the National Academy of Sciences of the United States of America, 116 (27), 13182. [PDF]

One critical challenge of solar thermal distillation is the need to collect and focus sunlight, since purified water output increases with increasing solar intensity. Here we show substantial increases in the efficiency of solar thermal distillation by redistributing direct sunlight intensity with small focusing elements rather than by increasing overall intensity with large solar concentrators. This is because solar thermal distillation depends upon the saturation vapor pressure of water, which has an exponential temperature dependence, making purified water output exponentially dependent upon light intensity. This observation should redirect design efforts to focus on exploiting this nonlinearity, rather than increasing solar collector size, for higher-performance solar water purification systems within a small footprint, suitable for portability and use in remote locations.

*Fillet, R., Nicolas, V., Fierro, V., & Celzard, A. (2021). A review of natural materials for solar evaporation. Solar Energy Materials and Solar Cells, 219, 110814. [Cited by]   **new**
 
One way to harvest solar energy is to produce steam from liquid water. Steam can be used to provide freshwater even in a harsh environment, with extreme temperature and low groundwater supplies. It can also be extracted from polluted soil or water, purifying the water in the process at the same time. Water evaporation systems are energy effective, with efficiencies ranging from 60% to over 90%. Furthermore, they can be cost-effective and have a low environmental impact, using the right materials. In this article, we will review natural materials, mainly of biological origin, proposed for solar evaporation, from wood and plants to algae and other atypical biomass such as fungi or wastes such as pomelo peels, through gels and foams, raw or charred. Their evaporation effectiveness will be presented and discussed, as well as their energy efficiency. This timely review suggests the suitability of natural materials for this application and reports on the progress that has already been achieved, as well as on the advances that remain to be made to improve the performance of these low cost, low environmental impact but high performance systems.”
 
*Gong, F., Wang, W., Li, H., Xia, D., Dai, Q., Wu, X., . . . Xiao, R. (2020). Solid waste and graphite derived solar steam generator for highly-efficient and cost-effective water purification.  Applied Energy, 261. [Cited by] **new**
 
Utilizing the clean and renewable solar energy to generate steam for wastewater purification or seawater desalination is a promising solution to the worldwide scarcity of fresh water. Herein, we report a highly-efficient, eco-friendly and cost-effective solar steam generator based on ball-milling graphite and cellulose fiber from waste paper. Ball-milling graphite/cellulose fiber composite aerogels are facilely developed via a freeze casting-drying method, endowing a featured vertically aligned porous structure. The fabrication of composite aerogels and the construction of evaporation systems take full advantages of recycled materials, contributing to the low cost and solid waste reclamation. High porosity, strong solar absorption, hydrophilicity and low thermal conductivity of the composite aerogels collectively contribute to a splendid solar evaporation rate of water as high as 1.61 kg m−2 h−1, with photothermal efficiency of ~90% under one sun illumination (1 kW m−2). Quantitative studies reveal the effects of ball-milling graphite/cellulose fiber ratio, ball-milling graphite concentration and thickness of composite aerogels on the solar evaporation rates, suggesting the optimal design of composite aerogels. Furthermore, the cycling stability and the capability for seawater desalination as well as polluted water purification manifest the potential of the composite aerogels to purify diverse water. Outdoor tests show 8–13 L of fresh water could be produced daily by 1 m2 of composite aerogel.”
 

*Pichel, N., Vivar, M., & Fuentes, M. (2019). The problem of drinking water access: A review of disinfection technologies with an emphasis on solar treatment methods. Chemosphere, 218, 1014-1030.  [Cited by]

The lack of access to safe drinking water is one of the biggest challenges facing humanity in the 21st century. Despite the collective global effort that has been made, the drinking water sources of at least 2 billion people are faecally contaminated, resulting in more than half a million diarrhoeal deaths each year, with the majority occurring in developing countries. Technologies for the inactivation of pathogenic microorganisms in water are therefore of great significance for human health and well-being. However, conventional technologies to provide drinking water, although effective, present limitations that impede their global application. These treatment methods often have high energy and chemical demands, which limits their application for the prevention of waterborne diseases in the most vulnerable regions. These shortcomings have led to rapid research and development of advanced alternative technologies. One of these alternative methods is solar disinfection, which is recognized by the World Health Organization as one of the most appropriate methods for producing drinkable water in developing countries. This study reviews conventional technologies that are being applied at medium to large scales to purify water and emerging technologies currently in development. In addition, this paper describes the merits, demerits, and limitations of these technologies. Finally, the review focuses on solar disinfection, including a novel technology recently developed in this field.”

*Sharshir, S.W., Ellakany, Y.M., Algazzar, A.M., et al. (2019). A mini review of techniques used to improve the tubular solar still performance for solar water desalination. Process Safety and Environmental Protection, 124, 204-212.  [Cited by]

“Today, clean water availability is quite hard especially for people living in remote areas and coastal ones. Even for those who find underground water, they need to treat it before using. Solar still is a very useful method to be used in desalination and purifying water as it uses solar energy which is available around the globe with no cost and is eco-friendly. Many types of solar stills are invented to increase its daily productivity (stepped solar stills, inclined solar stills, pyramid solar still, wick, etc.). In this regard, this paper represents a mini-review of a new type of solar still named tubular solar still (TSS), its working method, thermal analysis, performance and method of enhancement. The remarkable improvement is attributed to the use of nanotechnology (ZnO nano-rod shape) by which the productivity and efficiency are increased by 30% and 38% respectively. Moreover, some futuristic developments on TSS are included in this review.”

*Wang, X., He, Y., & Liu, X. (2018). Synchronous steam generation and photodegradation for clean water generation based on localized solar energy harvesting. Energy Conversion and Management, 173, 158-166. [Cited by]

“Solving the problems of water shortage and water pollution is a vital challenge for sustainable development. Different strategies, such as photodegradation, solar distillation, and filtration, have been proposed to purify contaminated water and generate clean water. Energy-efficient clean water generation technologies play a critical role in augmenting freshwater resources. Solar energy has the potential to increase sustainable clean water production, which is a key facet of the water-energy nexus. In this study, a novel strategy to generate clean water was realized via a synchronous solar distillation and photodegradation technology based on localized solar energy harvesting using a trifunctional solar energy absorbing membrane. The membrane is composited of mixed cellulose ester (MCE) membrane, hedgehog-like hierarchical ZnO particles (HP) and gold nanoparticles (Au NPs). By floating the MCE/HP/Au membrane on rhodamine B contaminated water, the steam generation rate could reach up to ∼8.70 kg/(m2·h) and the concentration of organic pollutant in the residual water could be reduced to ∼30% within two hours’ solar light irradiation. It was found that the coupling between the hierarchical HPs and plasmonic Au NPs could enhance the solar light absorption and energy conversion for photodegradation and thermal generation. This work provides a new strategy for the high efficient utilization of solar energy for clean water generation.”

For additional research about solar-powered harvesting and purification of water, please see the Science Primary Literature Database.

Questions?  Please let me know (engelk@grinnell.edu).

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