New Device Use the Sun to Create Fresh Water From Salt Water

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A new desalination system has been created, utilizing sunlight alone to turn saltwater into drinkable fresh water.

The device was created through a federally funded research effort to transform water treatment, and it uses a mixture of membrane distillation technology and light harvesting nanophotonics.

The device of the first major invention from the Center for “Nanotechnology Enabled Water Treatment” (NEWT), which is an engineering research center formed via collaboration by multiple institutions, and based at Rice University.

The “nanophotonics-enabled solar membrane distillation” (NESMD) technology combines traditional water treatment techniques with advanced nanotechnology to convert sunlight to heat, which is then employed in the desalination process. Membrane desalination happens as the hot saltwater moves across one side of a porous membrane, with cold fresh water flowing across the other side. The water vapor is drawn across the membrane from the hot side to the cold side, and since the seawater does not need to boiled, the energy needed for distillation is far less than traditional distillation operations.

“Unlike traditional membrane distillation, NESMD benefits from increasing efficiency with scale,” said leader of NEWT’s nanophotonics research efforts, Naomi Halas from Rice University. “It requires minimal pumping energy for optimal distillate conversion, and there are a number of ways we can further optimize the technology to make it more productive and efficient.”

New Device Use the Sun to Create Fresh Water From Salt Water

NEWT’s technology improves upon research done at Halas’ lab to engineer nanoparticles which can harvest up to 80% of sunlight to generate steam. The low-cost nanoparticles are added to the porous membrane, turning the membrane into a one-sided heating device that sheets water to drive membrane distillation.

“The integration of photothermal heating capabilities within a water purification membrane for direct, solar-driven desalination opens new opportunities in water purification,” said Menachem Elimelech, lead researcher for membrane processes.

A proof of concept offered by the researchers successfully separated the salt out of a small chamber of water just a few millimeters thick, with a thin half millimeter thick layer of salt water on top of the membrane and freshwater below.

The NEWT research team wants to continue refining the technology and testing how it functions in much larger systems. They have already created a larger system which contains a panel about 70 cm x 25 cm in size. The goal is to produce a modular system which would allow users to order as many panels as they need based upon their daily water demands.

“Direct solar desalination could be a game changer for some of the estimated 1 billion people who lack access to clean drinking water,” said water treatment expert at Rice Univsersity, Qilin Li. “This off-grid technology is capable of providing sufficient clean water for family use in a compact footprint, and it can be scaled up to provide water for larger communities.”