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Surreal tap coming out of a solar panel
One of the toughest off-grid problems – water in the desert

The lineup for a Solar Desalination Prize has been announced by the US Energy Dept. Our pick is the Solar Aqua Flex: Off-Grid Solar Still from Vanderbilt University, Tennessee.

Its a multistage membrane distillation system made of floating, flexible, layered mats to desalinate water. The mat has a nonporous, heat-absorbing top layer; a water layer that evaporates; a distillate layer where the vapor ends up after moving through a membrane to condense; a feedwater layer; and a conductive layer that heats the feedwater.

There are 16 quarterfinalists  in the $9 million prize competition, providing an additional $1 million in support, designed to accelerate the development of low-cost desalination systems that use solar-thermal power to produce clean water from salt water.

Competitors will receive cash prizes as they advance through each stage of the competition, culminating in a $1 million grand prize for the successful testing and demonstration of a promising solar-thermal desalination system prototype.

Competitors include private companies, nonprofit organizations, academic institutions, students, and researchers at National Laboratories.

To enter the competition, participants had to submit their ideas for a solar-thermal desalination component or system prototype, along with a pathway to commercialization. When their ideas were selected, competitors received $50,000 in cash, advanced to the second phase to form a team, and refine plans for a fully operating solar-thermal desalination system.

The teams selected to advance to the third phase will receive $250,000 in cash and a $100,000 voucher that can be redeemed at a National Laboratory and/or qualified partner facilities to design their systems. While they’re completing detailed designs of their systems in the third phase, teams must also obtain the permitting and approval documentation necessary to build them.

Teams selected to advance to the fourth and final phase of the competition will be awarded a cash prize of $750,000 and another $100,000 voucher. These teams will then build their systems, demonstrate their operation, and validate key performance metrics. The U.S. Department of Energy will determine the winner, who will receive a $1 million cash prize.

Competitors can leverage industry expertise, access private capital, and obtain mentorship and support through the American-Made Network, a group of National Laboratories, incubators, investors, and industry experts. The Network also provides access to local capabilities that will help accelerate the development of their desalination system prototypes.

Competitors

Out of 162 applicants, 19 quarterfinalists from 12 states were selected to advance to the second phase of the competition. They were announced on October 19, 2020. They are:

Heat Storage for 24-Hour Solar Desalination

Location: Arcadia, CA

Project Summary: Element 16 is a small company developing a sulfur-based thermal energy storage (TES) technology to generate low-pressure steam for desalination. Sulfur has a low melting point (105 Celsius) and low cost ($80/ton). By using lower-cost containment materials, this project aims to reduce sulfur TES cost to below $15/per kilowatt-thermal and reduce heat-exchanger costs, to attain a levelized cost of water below $0.50 per cubic meter (m3).

Solar Thermal Enhanced Evaporation

Location: Minneapolis, MN

Project Summary: Researchers from the University of Minnesota propose a humidification-dehumidification desalination system that will handle small-volume brine from industrial facilities that do work such as electroplating, which coats metal onto surfaces, dyeing, and mining. This project will use large fans, evaporators, and heat-pump-driven condensation systems to manage brine mixed with industrial metals. The team plans to industrially source forced-flow evaporators and fans to attain a levelized cost of water no higher than $1/m3.

NoAir: Super-Vacuum Gap NanoMembrane Distillation

Location: Gainesville, FL

Project Summary: This team, led by the small company Focused Sun, proposes a linear Fresnel solar-collector system that will generate steam for a process called thermal vapor compression (TVC) to provide pumping power for the system. The brine will be preheated by a membrane desalination (MD) system, which is then fed with brine from the TVC system to further desalt and recover water. This MD-TVC system could attain high energy efficiency at low pressure and be used to treat water produced from oil and gas extraction, with no electricity input.

TSSE Desalination of Hypersaline Brines

Location: Santa Barbara, CA

Project Summary: A Columbia Universityled team proposes a desalination technique using a solvent that, when heated, attracts brine in high-salinity water, separating it from fresh water. Increasing the temperature of the feedwater will cause the clean water to float above the solvent, enabling reuse of the solvent in subsequent cycles. This method has the potential to be highly thermally efficient because it does not require evaporation and condensation, unlike in conventional desalination systems

Sorption-Based ZLD Technology

Location: Houghton, MI

Project Summary: A team of researchers from Oak Ridge National LaboratoryMichigan Technological University, and the company Artic Solar proposes to add an adsorption-desorption system to a multiple-effect desalination system (MED) to achieve zero liquid discharge (ZLD). They have identified a liquid that could extract all the water-vapor volume from the brine slurry of a MED system, thus enabling an energy-efficient, modular ZLD treatment

Portable Treatment of Oil/Gas Wastewater with ZLD

Location: Corvallis, OR

Project Summary: A team of researchers from Oregon State University and Michigan State University plans to advance a humidification-dehumidification process that can recover clean water from water produced by oil and gas extraction. A novel cyclone separator, which can be easily designed at small scale for portability, separates salt from humid air and enables the process. By separating humid air from solid salt particles, this technology could be a cost-effective method to achieve zero-liquid discharge (ZLD). The team intends to demonstrate their system with real produced-water brines integrated with solar-thermal energy and scaled up to 250 kilograms per hour.

Forward Osmosis Biomimicry at Work

Location: Rohnert Park, CA

Project Summary: This team of researchers from the Natural Energy Laboratory of Hawaii and Trevi Systems, a small company developing novel forward osmosis (FO) desalination technology, proposes to build a 500 m3/day FO system with solar collectors as a heat source. The team will advance its FO draw solution by significantly increasing throughput and lowering the systems energy requirements.

STREED Resonant Energy Exchange Desalination

Location: Houston, TX

Project Summary: A team led by researchers from Rice University has developed prototypes of a nanoparticle-based high-efficiency, low-maintenance solar-heated membrane distillation technology. The team plans to develop a commercializable system design that uses spiral-wound architecture to minimize the plants physical footprint.

Zero Discharge Multi-effect Adsorption Distiller

Location: Trenton, NJ

Project Summary: GreenBlu will develop a full-plant prototype of a zero-liquid discharge solar-thermal desalination system with mineral recovery using its multi-effect adsorption distillation technology. The concept has the potential to be much more thermally efficient, and require simpler operation and maintenance, relative to conventional distillation technology.

Modular Inexpensive Solar-Thermal Evaporative Desal

Location: Andover, MA

Project Summary: Physical Sciences, Inc. proposes to integrate a low-concentration solar receiver with a multistage flash evaporator in one device to reduce capital cost. The evaporator efficiently distills water by combining numerous distillation stages so that each one uses the heat output from the previous stage. The evaporator operates at low temperature, which allows the use of low-cost cylindrical optics. The team intends to build a 20-stage multistage flash device inside a cylindrical tube receiver to produce 100 m3/day of desalinated water.

Solar Aqua Flex: Off-Grid Solar Still

Location: Nashville, TN

Project Summary: This team, led by researchers from Vanderbilt University, will develop a multistage membrane distillation system made of floating, flexible, layered mats to desalinate water. The mat has a nonporous, heat-absorbing top layer; a water layer that evaporates; a distillate layer where the vapor ends up after moving through a membrane to condense; a feedwater layer; and a conductive layer that heats the feedwater. This concept has the potential to be modular and portable, with higher production than similar existing systems.

Brine Concentration with Managed Salt Precipitates

Location: Hopewell, NJ

Project Summary: This team, led by AIL Research, has proposed a membrane desalination system capable of handling very-high-salinity water and using recovered heat to preheat the brine feed. The membrane will not have to be corrosion-resistant because readily precipitating ions, such as magnesium and calcium, can supersaturate and crystallize in a brine tank above the membrane. Managing the precipitation of salt and using recovered heat allows more water recovery from high-salinity brines.

Urban Solar-Desal Building

Location: College Park, MD

Project Summary: A team led by the University of Marylands Center for Energy Environmental Engineering will develop a vertical, building-integrated desalination system for urban areas. Solar-thermal collectors will be the energy source to heat multistage vacuum membranes in the system. This concept has the potential to decentralize desalination at the point of use.

Membrane Distillation with Ceramic Membranes

Location: Storrs, CT

Project Summary: This team, led by researchers from the University of Connecticut, will integrate a SETO-funded, newly developed ceramic membrane technology with a solar collector system to treat high-salinity or chemically complex brines. The ceramic membrane

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