Virginia Tech researchers use new technology to simplify desalination processes

By Jama Green

virginia tech logoOne of the biggest global challenges facing future generations will be providing access to clean water for daily use. For some populations, the issue is lack of access, drought, or water shortages, while others struggle when contamination or lack of basic sanitation pollutes the supply.

Globally, water is abundantly available, but most of the world’s water is in the oceans. Ocean water is salty and unsuitable for drinking or for use in agricultural and industrial settings without desalination.

Researchers at Virginia Tech are working on a new kind of technology for use in desalination: a simpler, sustainable alternative to a traditional hydraulic pump, typically used in conventional wave-to-water devices. By swapping out the heavyweight mechanical pump with a pumping device made of fluidic flexible matrix composite material, there is potential to dramatically reduce energy consumption and maintenance costs, and eliminate the need for heavy, easily corrosive metal to be submerged in the ocean.

To Associate Professor Michael Philen of the Kevin T. Crofton Department of Aerospace and Ocean Engineering, the use of fluidic flexible matrix composites, which are frequently used in his Aerospace Structures and Materials Laboratory, represents an opportunity to simplify one step in the complicated desalination process. These composite materials have previously been used in aerospace structures, robotics, prosthetics, and wave energy conversion systems.

“This minimalistic tube pump, which harnesses wave energy, simplifies the pumping process while delivering the same functionality as a complex pump made of metal or composite materials,” said Philen. “Mechanical pumps often require complex mechanical linkages to convert ocean wave energy into hydraulic energy and can pose environmental risks to the ocean, while a flexible composite pump of this kind is a low maintenance, energy efficient, and nontoxic alternative.”

Fluidic flexible matrix composite pumps are long, cylindrical tubes constructed from multiple layers of helically wound, stiff fibers embedded within a soft flexible matrix. By attaching a floating object to the top of the pump, the pumps become stretched when a wave passes. This causes the stiff fibers to rotate, resulting in a volume reduction of the tube, thereby forcing fluid out of the pump. With check valves on both ends, the pumps can produce seawater flows suitable for cost-effective yields of desalinated water.

Philen’s team is collaborating with PCCI Inc., in Alexandria, Virginia, a firm that specializes in engineering and environmental projects at coastal, open ocean, and inland facilities. PCCI was awarded a Small Business Innovation Research grant from the U.S. Department of Energy to develop a pumping and compression device using marine and hydrokinetic energy.

For Phase I of the project, the research team has been developing and testing the flexible composite pumps to furnish high-pressure water for desalination using reverse osmosis. The team has already shown using small-scale experimental results that achieving the high pressures (600 psi) and desired flows at full-scale is attainable with the technology.

During this phase, the team has also shown that the pumps can indeed remove salt from ocean water using a reverse osmosis filter as proof of concept. Mathematical models are being validated by laboratory test results and will then be applied to numerical simulations of a heaving-body wave energy converter in various wave climates.

Phase II will include the design, build, and deployment of a complete wave-to-water prototype system at 1:16 scale in a sheltered wave environment near the Chesapeake Bay entrance.

“Our role as researchers is to apply affordable and innovative technologies to simplify complex processes,” said Philen. “In this case, this tube pump is a simple, smart solution that improves efficiency and reduces energy consumption and environmental hazards, and ultimately could make a difference in providing clean water for people all around the world.”

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