MIT engineers have successfully developed a new solar-powered desalination system that runs with the rhythms of the sun as a much more affordable way to produce clean water, compared to other solar-driven designs. The new system builds on a previous design, which aimed to desalinate water through a process of flexible batch electrodialysis.
Electrodialysis and reverse osmosis are the two main ways to desalinate brackish groundwater. As salty water is pumped through a membrane and is filtered salts out using pressure, an electric draws salt ions through a stack of ion-exchange membranes.
The electrodialysis system consists of water pumps, an ion-exchange membrane stack, and a solar panel array. It removes salt from water by closely following changes in solar energy. It is designed with a control system using sensor readings from every part of the system, allowing it to predict the optimal rate at which to pump water through the stack and how much voltage should be applied. Therefore, it can maximize the amount of salt drawn from the water.
Unlike other solar-driven desalination designs, the MIT system does not require extra batteries for energy storage or a supplemental power supply. The team looked to eliminate the need for batteries by updating the system’s desalination rate, three to five times per second, allowing it to adjust to changes in sunlight throughout the day, without making up any lag in power with additional power supplies.
The engineers operated the system on groundwater wells over six months at the Brackish Groundwater National Research Facility in Alamogordo, New Mexico. Throughout the trial, the system harnessed on average over 94 percent of the electrical energy generated from the system’s solar panels to produce up to 5,000 liters of water per day in variable weather conditions and water types.
Because brackish groundwater is more prevalent than fresh groundwater resources, researchers see it as a huge untapped source of potential drinking water, particularly as reserves of freshwater are stressed in parts of the world. The new renewable, battery-free system is expected to provide much-needed drinking water at low costs, especially for inland communities where access to seawater and grid power is limited.
Article & Image Source: Massachusetts Institute of Technology
