Unlike traditional desalination systems that rely on fragile filtration membranes and centralized infrastructure, the Rice team's Solar Thermal Resonant Energy Exchange Desalination (STREED) system uses a streamlined, membrane-free design. This innovative approach captures and reuses thermal energy in a self-sustaining cycle, enabling continuous freshwater production even when sunlight is intermittent.
The STREED system operates by tuning the flow rates of heated saline water and air to create a resonant thermal exchange, similar to how energy oscillates between magnetic and electric fields in an electrical circuit. This method allows the system to efficiently recover and transfer heat, significantly reducing energy loss and maintenance demands.
"Our key innovation is using insights from electrical engineering and the physics of oscillators to inform the adjustment of the system's internal flow rates to match the sun's shifting power throughout the day," said William Schmid, a doctoral student in electrical and computer engineering at Rice and National Science Foundation Fellow. "This light-dependent flow control hasn't been done before."
Aleida Machorro-Ortiz, a graduate student in Rice's Applied Physics Graduate Program and a co-lead author on the study, highlighted the system's durability. "The system operates robustly and with minimal maintenance around the clock," she said.
The prototype, tested in San Marcos, Texas, produced up to 0.75 liters of drinking water per hour and demonstrated a 77% higher water-recovery efficiency over conventional systems when tested using various solar intensity profiles from regions across the United States. This performance indicates that the system can achieve high energy-to-water efficiency without relying on peak solar conditions, making it suitable for a wide range of climates.
The design's simplicity is another advantage. Instead of using membranes, the STREED system employs a single heated channel of saline water paired with an adjacent air channel that captures evaporated water vapor. This vapor then condenses in a heat exchanger, separating pure water from contaminants without the risk of membrane fouling.
"We were intentional in using durable, low-maintenance materials to make the system easily scalable and accessible," said Alessandro Alabastri, assistant professor of electrical and computer engineering at Rice and a corresponding author on the study.
The study's other co-authors include Naomi Halas, University Professor and the Stanley C. Moore Professor of Electrical and Computer Engineering; Qian Ye, a Rice graduate student; Pratiksha Dongare, former Rice faculty and senior physicist at SLB; and Peter Nordlander, Wiess Chair in Physics and Astronomy at Rice.
Research Report:Resonant energy transfer for membrane-free, off-grid solar thermal humidification-dehumidification desalination
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