Scientists get inspired by sunblock mechanism to curb water loss in hot regions

Water stored in dams and reservoirs for human use is often lost through evaporation, particularly in hot regions. Rising temperatures accelerate the process, leaving less water available for households, agriculture and industry.

Reducing evaporation could therefore help preserve valuable supplies, especially in regions already struggling with water shortages. A new study is investigating an unconventional approach to slowing the process by covering water surfaces with a “shield” designed to protect them from infrared heat, in a concept somewhat similar to the principle behind sun blocking curtains.

The approach could be particularly relevant for Africa, where water stored in dams and lakes plays an important role in water security, food production and resilience to drought. The study, conducted by University of South Africa PhD alumnus Daniel Kwasi Kpeglo and highlighted by The Conversation platform, examines a new nanotechnology-based floating cover designed to reduce evaporation from water surfaces,

The idea is similar to placing a carefully engineered shade or protective layer over the water. Kpeglo, a physics scholar, investigated whether an existing nanomaterial could be placed on the surface of water and act as a selective filter for sunlight.

His research sought to establish whether the nanomaterial could address evaporation while still allowing much of the visible portion of sunlight to pass through, while blocking much of the infrared radiation that carries heat.

The material is produced by applying an extremely thin layer of a substance known as a transparent conducting oxide to a lightweight and flexible plastic sheet. The resulting cover is designed to keep the water beneath it cooler. Allowing some sunlight through is essential because completely blocking solar radiation could harm aquatic plants and animals. The design therefore seeks to let useful visible light reach the water while shielding it from heat.

Experiments conducted in partnership with the university found that the cover allowed more than 60% of visible light to pass through on average, while reflecting more than 80% of infrared radiation away from the water. As a result, the water beneath the cover remained noticeably cooler than the upper surface of the material. During the sunniest part of the day, the water was around 10°C cooler, significantly reducing the conditions that drive evaporation.

The research highlights another potential advantage of the design. Because the material is lightweight and water-repellent, meaning water does not readily cling to its surface, it can float directly on the water rather than requiring a heavy supporting structure to keep it suspended above the reservoir.

In laboratory experiments, the water level beneath the coated cover remained essentially unchanged during the testing period, indicating that very little water was being lost through evaporation. By comparison, water levels declined when the reservoir was left uncovered or protected only with an ordinary plastic sheet.

Scientists have previously explored a variety of methods for reducing evaporation, including floating or suspended covers, shade cloths, wind barriers, plants and natural materials such as palm fronds. Some researchers have also investigated using chemicals to create a kind of sunscreen for water. Such approaches, however, can block sunlight altogether, while the South African design specifically aims to filter out infrared radiation while allowing visible light to reach the water.

According to the outlet, the next major step will be to determine whether the concept can work outside controlled laboratory conditions. Large-scale field trials will be needed to assess how effectively the floating nanomaterial cover performs on actual dams and reservoirs, as well as its durability, environmental impact and practicality for long-term use.

By Nazrin Sadigova