New Aerogel Technology Offers Hope for Scalable Solar Desalination
Despite Earth’s appearance as a “blue planet,” access to drinkable water is becoming increasingly scarce, and a breakthrough in materials science may offer a solution. Researchers have developed a new photothermal aerogel that dramatically improves the efficiency of solar desalination, potentially providing a sustainable source of freshwater for billions.
Earth is covered by approximately 71 percent water, yet a staggering 97 percent of that is saltwater found in oceans. Only 3 percent is freshwater, and much of that is locked away in glaciers and ice caps. This leaves a mere 0.3 percent of the world’s freshwater readily accessible in surface-level sources like lakes, rivers, and streams.
The situation is further complicated by a confluence of factors—climate change, rapid urbanization, widespread pollution, and a growing global population—all of which threaten existing freshwater supplies. Currently, over 2 billion people rely on contaminated water sources, exposing them to dangerous pathogenic microbes that can cause life-threatening illnesses like cholera, diarrhea, dysentery, polio, and typhoid, particularly in regions lacking adequate healthcare.
Desalination, the process of removing salt from seawater, has long been considered a viable solution. One promising approach involves using porous materials to absorb water, which is then evaporated using solar energy. However, scaling up these solar-powered evaporators to meet the needs of large populations has proven challenging. Existing systems often experience decreased performance as their size increases, as water vapor struggles to escape through tiny pores and thick material boundaries.
That’s where the work of researcher Xi Shen of the Hong Kong Polytechnic University comes in. Shen and his team have engineered an aerogel designed to overcome these limitations. “The key factors determining the evaporation performance of porous evaporators include heat localization, water transport, and vapor transport,” Shen explained in a study recently published in ACS Energy Letters. “Significant advancements have been made in the structural design of evaporators to realize highly efficient thermal localization and water transport.”
The team’s innovation centers around photothermal materials, which absorb sunlight and convert it into heat energy to accelerate evaporation. While various materials—including polymers, metals, alloys, ceramics, and cements—can be used to create these materials, Shen’s team opted for an aerogel over traditional hydrogels. Hydrogels, while capable of desalination, are designed to retain water, hindering both efficiency and stability. Aerogels, conversely, are composed of polymers that hold air, offering a more effective structure for evaporation.
The result is a system that leverages the power of the sun to efficiently produce freshwater, offering a beacon of hope in a world facing increasing water scarcity. This new aerogel technology represents a significant step toward ensuring access to clean, sustainable water for communities around the globe.
