MIT engineers have developed an innovative desalination system that operates in harmony with solar cycles. By eliminating the need for costly energy storage during non-sunny periods, this technology has the potential to deliver affordable drinking water to communities.
The solar-powered system efficiently extracts salt from water, adjusting its desalination rate in real-time as solar energy fluctuates. As sunlight intensifies throughout the day, the system increases its desalting activity and adapts seamlessly to sudden changes, such as minimizing operations when clouds pass or ramping up when the sun emerges.
This ability to swiftly respond to minor shifts in sunlight allows the system to optimize solar energy usage, generating substantial amounts of clean water despite daily sunlight variations. Unlike other solar desalination methods, this MIT design does not require additional batteries for energy storage or supplementary power from the grid.
Engineers tested a community-scale prototype in New Mexico, utilizing groundwater wells over a six-month period under varying weather conditions and water types. The system averaged over 94% efficiency in converting the electrical energy from its solar panels into up to 5,000 liters of water daily, even during significant weather fluctuations.
“Traditional desalination methods depend on consistent power and battery storage to stabilize variable energy sources like solar. Our technology continuously adjusts power consumption in sync with the sun, allowing for a direct and efficient use of solar energy to produce water,” stated Amos Winter, the Germeshausen Professor of Mechanical Engineering and Director of the K. Lisa Yang Global Engineering and Research (GEAR) Center at MIT.“Creating drinking water using renewable sources without the need for battery storage is a significant challenge we have successfully addressed.”
The system specifically targets brackish groundwater, a saline water source found in underground reservoirs, which is more abundant than fresh groundwater.
Researchers view brackish groundwater as an extensive, underutilized source of drinking water, particularly as global freshwater supplies become strained.
They anticipate that this new renewable, battery-free system can deliver essential drinking water at low costs, especially to inland communities lacking access to seawater and grid electricity.
“Most people live far from the coast, making seawater desalination impractical. They rely heavily on groundwater, especially in remote, low-income areas. Unfortunately, this groundwater is increasingly becoming saline due to climate change,” explained Jonathan Bessette, an MIT PhD student in mechanical engineering.“This technology could provide sustainable and affordable clean water to underserved regions globally.”
Pump and flow
Electrodialysis and reverse osmosis are the primary techniques for desalinating brackish groundwater. Reverse osmosis uses pressure to push salty water through a membrane that filters out salts, while electrodialysis employs an electric field to extract salt ions as water flows through a series of ion-exchange membranes.
Researchers have sought to power both methods with renewable energy, but this has proven particularly challenging for reverse osmosis systems, which typically require a steady power supply that conflicts with the variable nature of solar energy.
The team concentrated on enhancing electrodialysis, aiming to create a more adaptable, “time-variant” system that responds effectively to fluctuations in solar power.
In their earlier design, the team constructed an electrodialysis system that included water pumps, an ion exchange membrane stack, and a solar panel array. A key innovation was a model-based control system that utilized sensor data from all components to optimize water pumping rates and voltage application, maximizing salt extraction from the water.
When tested in the field, this system demonstrated a capacity for water production that aligned with natural sunlight variations. On average, it utilized 77% of the electrical energy generated by the solar panels, representing a 91% improvement compared to conventional solar-powered electrodialysis systems.
Source :MIT
