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Engineers increase production of solar desalination system by 50%



Concentrating sunlight on small spots on the heat-generating membrane uses an inherent and unrecognized non-linear relationship between photothermal heating and vapor pressure. Regards: Pratiksha Dongare / Rice University
Rice University's solar approach to the treatment of salt water with sunlight and nanoparticles is even more effective than its creators have believed.


Researchers from Rice Laboratory of Nanophotonics (LANP) this week have shown that they can increase the efficiency of their solar desalination system by more than 50% simply by adding cheap plastic lenses to concentrate sunlight on " hotspots ". The results are available online at Proceedings of the National Academy of Sciences .

"The typical way to increase productivity in solar systems is to add solar concentrators and bring more light," said Prataksha. Donager, a graduate of Applied Physics student in Brown's Rice Engineer's career, and co-author of the article. "The big difference here is that we use the same amount of light, and we have shown that it is possible to redistribute this power and drastically increase the rate of production of purified water."

In conventional membrane distillation, hot, salt water passes through one side of a leaf membrane, while the cool, filtered water flows through the other. The difference in temperature creates a difference in vapor pressure which causes the water vapor from the heated side through the membrane to the cooler to lower the pressure. Increasing technology is difficult because the difference in membrane temperature ̵

1; and resulting clean water – decreases with increasing membrane size. Rice's Nano-Photonic Solar Membrane Recycling (NESMD) technology addresses this by using nanoparticles that absorb light to transform the membrane itself into a solar powered heating element. "Rice University researchers (from left) Pratiksha Dongare, Alessandro Alabastri and Oara Neumann showed that Rice's nanophotonics-enabled solar membrane distillation (NESMD) system was more efficient when the size of the device was scaled up and light was concentrated in 'hot spots.' Credit: Jeff Fitlow / Rice University "/>
                 Rice University Researchers (left) Prataksa Donager, Alessandro Alabastri and Oara Neumann have shown that Rice's NESMD is more effective when the size of the device is increased and the light is concentrated in the hot spots. "Regards: Jeff Fitlow / Rice University

Donagare and colleagues, including lead author Alessandro Alabastri, cover the top layer of their low-cost nanoparticle nanoparticle membranes that are designed to convert more than 80% of solar energy into heat. Sun nanoparticle reduces production costs, and Rice engineers are working to increase the technology for applications in remote areas that have no access to electricity.

The concept and particles used in NESMD were first demonstrated in 2012 by LANP Director Naomi Hallas and researcher Oara Neumann who co-authored the new study. Physicist Hallas, Donagh, Alabastri, Neumann, and LANP Peter Nordlander found that they could take advantage of the inherent and unknown link between the intensity of falling light and the pressure of the money

Texas Instruments Alabastres, Physicist and Researcher at the Department of Electrical and Computer Engineering Rice's computer engineering has used a simple mathematical example to describe the difference between a linear and a non-linear relationship. "If you get two numbers that are equal to 10, seven, three, five, five, six and four, you will always get 10 if you add them together, but if the process is nonlinear, you can compare or even cube them before So if we have nine and one, it will be nine in a square, or 81, plus one square, which is equal to 82. This is far better than 10, which is the best you can do with a linear connection. "

In the case of NESMD, nonlinear improvement comes from concentrating sunlight in small spots, similar to a child with a magnifying glass on a sunny day. Concentrating the light on a small space on the membrane leads to a linear increase in heat, but heating in turn leads to a nonlinear increase in vapor pressure. And the increased pressure forces more purified steam through the membrane in less time. more than 50% by adding cheap plastic lenses to concentrate sunlight on "hot spots". Regards: Pratiksha Dongare / Rice University

"We have shown that it is always better to have more photons in a smaller area than to have a homogeneous distribution of photons across the membrane," Alabastri said.

Hallas, a chemist and engineer who has spent more than 25 years pioneering the use of light-activated nanomaterials, said: "The effectiveness provided by this non-linear optical process is important because water scarcity is a daily reality for about half of people in the world, and effective solar distillation can change this. "

Water purification, this nonlinear optical effect can also improve technologies that use solar heating to drive chemical processes such as photocatalysis, Halas said. LANP develops a copper-based nanoparticle to convert ammonia into hydrogen fuel at ambient pressure

Hallas is Professor of Electrical Engineering and Computer Engineering Stanley K. Moore, Director of the Rice Institute Resin-Curl and Professor of Chemistry, Bioeng Engineering, Physics and Astronomy, Materials Science and Nanoengineering

NESMD is under development at the Rice-Based Nano-Technology Center (NEWT) and has won research and development funding from the Solar Desalination program The ministry of Energy in 2018


Freshwater saltwater using only solar power: Modular desalination technology outside the grid


More Information:
Pratiksha D. Dongare et al., Solar Thermal Desalination as Non-Linear Optical Process Studies of the National Academy of Sciences (2019). DOI: 10.1073 / pnas.1905311116

Provided by
Rice University

References :
Engineers increase production of solar desalination system by 50% (2019, June 18)
drawn up on 18 June 2019
by https://phys.org/news/2019-06-hot-efficiency-solar-desalination.html

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