Sunscreen for lakes and dams: Could a thin floating layer of nanomaterial shield water from evaporation?
Water stored in dams and reservoirs for humans to use often evaporates, especially in hot regions like southern Africa. Rising temperatures speed up evaporation, leaving less water for people, farming and industry. Daniel Kwasi Kpeglo has just completed a Ph.D. in physics. He explains his laboratory research into a new design—a thin nanomaterial floating cover that could be placed over lakes and…
Dams and reservoirs store water for human use, but this water often evaporates, particularly in hot areas like southern Africa. As temperatures rise, evaporation accelerates, reducing the available water for people, agriculture, and industries. Daniel Kwasi Kpeglo, a recent Ph.D. graduate in physics, has developed a thin nanomaterial floating cover that could be placed over lakes and dams, similar to a blanket, to diminish evaporation by blocking infrared heat from the sun from reaching the water.
Kpeglo's research centers on a nanotechnology-based floating cover, akin to a strategically designed shade over the water surface. The aim was to discover if a specific nanomaterial could prevent water evaporation by permitting most visible light to pass through while obstructing most heat-carrying infrared radiation. The nanomaterial comprises a minuscule layer of transparent conducting oxide on a lightweight, flexible plastic sheet.
This cover maintains the water surface cooler by allowing useful light to pass while reflecting over 80% of infrared light back to the sun. Consequently, the water underneath the cover stays roughly 10°C cooler during peak sunlight hours, which minimizes evaporation. One significant benefit is that the cover is lightweight and water-repellent, enabling it to float rather than needing heavy support.
In tests, the water level remained stable under the coated cover throughout the experiment, indicating minimal evaporation, as opposed to uncovered or only lightly covered reservoirs where water levels dropped. While other methods, such as chemicals or natural barriers, have been used to prevent water evaporation, they often block all sunlight, unlike the new design.
Kpeglo's nanomaterial, applied as a thin coating a few hundred nanometers thick, is lighter and allows a substantial amount of visible light through, reducing evaporation without completely blocking sunlight necessary for aquatic life. The water-repellent surface also makes it less susceptible to algae growth, potentially reducing maintenance needs.
Though there are concerns about potential water contamination by the nanomaterial, this research avoids directly placing it in the water, instead using it as a coating on a plastic sheet. Laboratory tests in a controlled environment using an artificial sunlight source showed that the coated cover reduced water loss compared to uncovered or only lightly covered reservoirs.
The next critical step is transitioning from laboratory testing to real-world application. This includes conducting large-scale field trials to evaluate the cover's cost, durability, maintenance, and environmental impact compared to existing solutions. Additionally, the cover must be adapted for use in natural dams and reservoirs, with a floating system to keep the sheets in place amidst wind and water movement.
Finally, the cover's materials must withstand long-term exposure to sunlight, UV light, and other environmental factors while maintaining their floating performance.
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