MIT

THIS $4 DESALINATION DEVICE PROVIDES DRINKING WATER FOR THE WHOLE FAMILY- China

So far, the prototype system has worked in the lab for at least a week without accumulating salt. The next challenge is to scale it to something more practical, but…

Researchers at MIT and in China have improved the old-fashioned solar still with a new inexpensive device that harnesses the sun to remove salt from water.

The key to this new technique is black paint and polyurethane with 2.5-millimeter holes drilled in it. The idea is that warmer water above the insulating medium causes the salt to concentrate in the cooler water beneath the insulator allowing efficient vaporization of the water.  As the water evaporates, it causes the salt concentration at the top to rise, which then sinks due to the higher density and lower-concentration salt water rises to the top to evaporate.

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System achieves new level of efficiency in harnessing sunlight to make fresh potable water from seawater – Cambridge

A completely passive solar-powered desalination system developed by researchers at MIT and in China could provide more than 1.5 gallons of fresh drinking water per hour for every square meter of solar collecting area.

Such systems could potentially serve off-grid arid coastal areas to provide an efficient, low-cost water source.

The system uses multiple layers of flat solar evaporators and condensers, lined up in a vertical array and topped with transparent aerogel insulation. It is described in a paper appearing today in the journal Energy and Environmental Science, authored by MIT doctoral students Lenan Zhang and Lin Zhao, postdoc Zhenyuan Xu, professor of mechanical engineering and department head Evelyn Wang, and eight others at MIT and at Shanghai Jiao Tong University in China.

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Scientists create simple, solar-powered water desalination – China

A completely passive solar-powered desalination system could provide more than 1.5 gallons of fresh drinking water per hour for every square meter of solar collecting area.

Such systems could potentially serve off-grid arid coastal areas to provide an efficient, low-cost water source.

The system uses multiple layers of flat solar evaporators and condensers, lined up in a vertical array and topped with transparent aerogel insulation.

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MIT suggests a different approach to reducing the rate of fouling – USA

The prevailing idea in the industry has been that the high pressure required by RO is responsible for the relatively high rate of fouling, compared to other systems such as forward osmosis. But the MIT study shows that this is not the case, a finding that opens up new approaches to reducing fouling in RO. The research, by Emily Tow ’12, SM ’14, PhD ’17 and MIT Professor John H. Lienhard V, was recently published in the Journal of Membrane Science and presented at the 2017 AMTA/AWWA Membrane Technology Conference, where it received the Student Best Paper Award.

Many experts believe that the high pressure in an RO system compresses the microbial mats that grow on the membranes, and that this “compaction” makes the growth much harder to remove. In contrast, in low-pressure forward osmosis (FO) systems, which are less energy-efficient but more fouling-resistant, the supposedly looser mat is thought to be easier to clean off.

However, these microbial mats are generally full of water, which does not compress under RO pressures, so “there is no good reason why high pressure should worsen fouling,” Tow says. She compares the microbes to a scuba diver: “There’s a lot of pressure at the bottom of the ocean, but it doesn’t make you stick to the seafloor.” But if pressure doesn’t matter, and the flow rates through FO and RO systems are similar, what could account for the disparity in fouling resistance?

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