A research team from McGill University has made significant strides in developing a sustainable method for desalinating seawater. The innovative approach, known as thermally driven reverse osmosis (TDRO), utilizes low-grade heat sourced from renewable energy, including solar thermal and geothermal, to produce fresh water. This breakthrough represents a crucial step toward enhancing global water access and promoting sustainable infrastructure.
The study, published in the journal Desalination on October 15, 2025, is the first to thoroughly investigate the thermodynamic limits of TDRO. Previous studies hinted at its potential, but this research provides a comprehensive analysis that could pave the way for practical applications.
Jonathan Maisonneuve, an Associate Professor of Bioresource Engineering and co-author of the study, explained the challenges of traditional desalination methods. “Most desalination is done by reverse osmosis, which uses electricity to drive water through a membrane,” he stated. The conventional process demands between one to four kilowatt hours (kWh) to produce one cubic meter of fresh water, making it less viable in remote areas where electricity is scarce.
In contrast, the analysis conducted by the McGill team suggests that TDRO could operate efficiently at around 20 kWh per cubic meter. While this number is still higher than the electricity-based methods, Maisonneuve highlighted the advantage of using heat, which is generally less expensive than electricity. “We don’t have to totally close that gap,” he noted, emphasizing the potential for cost-effective solutions.
The mechanics of TDRO involve heating and cooling a small working fluid within a sealed chamber. This temperature fluctuation causes the working fluid to expand, driving a piston that pushes seawater through a reverse osmosis membrane. This innovative combination of thermodynamic cycles and water purification has shown promising performance metrics, exceeding earlier expectations.
The researchers optimized various design elements based on a framework proposed by Peter Godart, a researcher at the Massachusetts Institute of Technology (MIT). Their findings indicate that TDRO may perform competitively against other existing thermal desalination technologies. However, further research is essential to refine the method.
Looking ahead, Maisonneuve stated, “Next, we need to model it in detail, see how quickly the system can operate, and introduce a number of non-ideal effects, such as heat loss through the environment.” This detailed modeling will be crucial in addressing any remaining challenges and advancing the technology toward practical implementation.
The implications of this research are substantial, particularly in regions facing water scarcity. By leveraging abundant renewable heat sources, TDRO could offer a more sustainable and accessible solution for freshwater production. As the global demand for water continues to grow, innovative approaches like this one will play a vital role in addressing the intersecting crises of water and energy.
