Graphic of mirrors and a water tap with an ocean in the background and text reading "Solar Desalination Prize"

The American-Made Challenges: Solar Desalination Prize is a four-stage  competition designed to accelerate the development of low-cost desalination systems that use solar-thermal power to produce clean water from salt water. Competitors receive cash prizes as they advance through each stage, culminating in a $1 million grand prize for the successful testing and demonstration of a promising solar-thermal desalination system prototype.

The second round of the prize was launched on April 12, 2020. Participants from private companies, nonprofit organizations, academic institutions, students, and National Laboratories submitted their ideas for a solar-thermal desalination component or system prototype, along with a pathway to commercialization.

On September 28, 2021, 12 quarterfinalists from 7 states were selected to advance to the second competition phase. These competitors received $50,000 in cash and will 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. DOE will determine the winner, who will receive a $1 million cash prize.

Quarterfinalists

Artic Solar: Engineered Solar-Thermal Osmosis  
Location: Jacksonville, FL 
This concept is an integrated solar-thermal desalination system that combines a non-tracking collector with a forward-osmosis desalination module. The technology uses a thermally responsive solvent, which draws water from a brine stream across a membrane. The solvent is then heated to separate it from the generated fresh water using Artic Solar’s external compound parabolic concentrator. 

AeroShield: Transparent Aerogels to Improve Solar Thermal  
Location: Cambridge, MA 
AeroShield is developing super-insulating, transparent silica aerogels to improve the performance of solar-thermal receivers by up to 40%. These aerogels could maximize solar transmittance while minimizing heat loss, improving the performance of concentrating and non-concentrating (flat-plate) solar collectors that can deliver heat to solar-thermal desalination systems. 

Sunvapor: Solar Cascading Evaporation Process 
Location: Pasadena, CA 
This technology takes in and treats brine using thermal energy from low-cost solar steam. Brine sources may be reverse-osmosis waste, power plant cooling towers, or other waste streams with high salt content. A steam accumulator discharges steam to provide thermal energy storage to support low- and high-temperature desalination processes. In the high-temperature stage, the accumulator uses a thermocompressor, which uses thermal energy to compress the steam, and in the low-temperature stage it uses a membrane distillation process.  

Team Trident: TSSE-ZLD Treatment of Produced Water  
Location: Santa Barbara, CA 
This concept aims to reduce the cost of treating high-salinity brines produced from oil and gas extraction by using a multi-stage temperature-swing solvent extraction technology for zero liquid discharge (TSSE-ZLD). This technology swings from high to low temperatures to extract water from brine. By using low-grade thermal heat to drive TSSE’s separation and solvent regeneration processes, the technology advances a non-evaporative, non-membrane solar-thermal desalination concept, which can be implemented at low cost.  

Physical Sciences: Modular Inexpensive Solar Thermal Evaporative Desal  
Location: Andover, MA 
Physical Sciences has developed an integrated solar-thermal collector and desalination system to produce low-cost fresh water for small- to medium-scale systems (that produce 100 cubic meters daily or less). This concept has individual concentrating solar-thermal modules with glass receiver tubes in which salt water is distilled by multi-stage flash—a process that boils water to make steam, which is condensed and collected as fresh water. The goal is to combine the low-cost simplicity of a solar still with the thermal efficiency of multi-stage flash to reduce complexity and materials costs compared to traditional, high-temperature concentrating solar-thermal power equipment.  

ORNL Solar Desalination: Modular Intensified Solar-Desal Technology  
Location: Oak Ridge, TN 
Researchers from Oak Ridge National Laboratory will produce fresh water from high-salinity water, with zero liquid discharge so that easily disposable salt is the only waste product, using a black graphite foam as a solar energy absorber and heat conductor. The graphite directly heats up salt water to produce fresh-water vapor, and by using a superhydrophobic coating on the surface of internal channels to repel water, this can be efficiently coupled to high-efficiency membrane distillation process, without requiring a heat-transfer fluid or electrical-to–thermal energy conversion.  

Winston Cone Optics: Portable Optics for Solar Heat  
Location: Merced, CA 
Winston Cone Optics has developed a low-cost, compact solar concentrator designed to minimize system capital costs, complexity, and operations and maintenance costs of a solar desalination collector system. It is designed to be quickly deployable and portable, allowing solar-thermal water-treatment systems to enter niche markets that need seasonal or multi-site applications. Unlike traditional solar-thermal collectors, this concept does not require tracking and tilting to perform well. It also allows modules to be installed next to each other, without casting shade, so they can fit in limited areas. 

Winston Cone Optics: Integrated Compound Parabolic Concentrator  
Location: Merced, CA 
Winston Cone Optics has developed a non-tracking solar-thermal collector called the integrated compound parabolic concentrator (ICPC) for process-heat applications up to 150°C. The ICPC is designed to maximize solar-to-thermal efficiency, with limited or no tracking, through a silver coating that reflects light toward an aluminum mini-channel absorber. The absorber has a selective coating that maximizes solar absorption and minimizes thermal emissions. As a result, the ICPC has the potential to heat fluids at more than 50% solar-to-thermal efficiency. 

Planet A Energy: Solar Heat Collector with Built-in Storage  
Location: Pasadena, CA 
This system couples a low-cost solar collector with a directly heated low-cost thermal energy storage material. The collector, absorber, and energy storage are integrated into one module, eliminating many system complexities associated with traditional concentrating solar-thermal power. The design uses an inert solid material as both an absorber and a storage medium. It provides integrated long-duration storage for around-the-clock operation for solar-thermal desalination and other process-heat applications. 

SolMem: Solar NZLD  
Location: Houston, TX 
This concept combines a solar-thermal-driven multi-effect membrane distillation (MD) process with electricity-powered reverse osmosis (RO) to desalinate various wastewater streams and produce drinking-quality water. The MD technology uses a nanophotonics-enabled photothermal membrane that converts light to heat to simultaneously collect solar energy and desalinate water. This improves thermal efficiency and water recovery compared with conventional MD. The conceptual hybrid system combines the low energy consumption of RO with the high salt tolerance of MD while mitigating the disadvantages with near-zero liquid discharge (NZLD) so salt is just about the only waste product. 

D&D Manufacturing: Concentrated Solar Multi Effect Distillation  
Location: Fletcher, NC 
D&D Manufacturing and Low Impact Technologies USA Inc. are working together to develop a solar-thermal multi-effect distillation (MED) process that can handle a wide range of input brine salinities. The team developed a low-cost, thermoplastic parabolic trough that provides heat to a solar-thermal desalination process. Thermoplastic allows for a more precise trough design because it can be melted, then molded. The trough acts as both the solar collector and a horizontal distillation column. The system is designed to recapture the heat of vaporization of the produced water vapor to maximize thermal efficiency. This technology is modular, scalable, and can potentially support zero-liquid discharge requirements for various applications. 

Frontier Research Group: Clouds & Rain: Optimum Solar Thermal Desalination 
Location: San Marcos, TX 
Frontier Research Group is developing a humidification-dehumidification (HDH) approach to desalination with a combination of technologies designed to optimize solar-thermal desalination over a range of salt concentrations. This concept significantly enhances the HDH process by creating sub-millimeter microbubbles with hot air, called sparging. Solar energy directly heats air and salt water through a compound parabolic concentrator. Then the air and salt water are mixed to improve heat transfer and evaporation. To collect fresh water, condensation is enhanced with advanced materials that form superhydrophobic structures, which repel water. This combination of technologies is a novel design that could be used in various solar-thermal desalination markets. 

Timeline

Graphic of water running down a pipe outlining the timeline for Round 2 of the Solar Desalination Prize
  • Innovation: The first phase opened on April 12, 2021, and will close July 15, 2021. Quarterfinalists were announced on September 28, 2021.
  • Teaming: The second phase opened on September 28, 2021, and close February 9, 2022. Semifinalists will be announced April 12, 2022. 
  • Design: The third phase will open April 12, 2022, and close when competitors have completed their designs and obtained the required documents, no later than April 10, 2025.
  • Test: The fourth phase also opens April 12, 2022. Submissions will be evaluated every second Monday in April, starting in 2023. Winners will be determined approximately one month after visits to their newly built system sites.

Learn More

The Solar Desalination Prize is administered by the National Renewable Energy Laboratory and is part of the American-Made Challenges.