Yves here. I confess to having Luddite tendencies—let’s call it being risk-averse. The notion of geoengineering often unsettles me. Yet, as humanity continues to push the climate beyond its limits, we observe detrimental effects on ecosystems and human populations alike. The reluctance to adopt more responsible practices—exemplified by the immense energy demands of artificial intelligence—means that remediation strategies are likely to become essential in our defense against environmental degradation. Consequently, it’s crucial to assess both the advantages and risks of innovative solutions, such as the one discussed below, aimed at reducing water loss.
In this context, developing robust criteria for evaluating these solutions will be invaluable. While there may be existing papers or checklists, I have yet to encounter any comprehensive resources. This might indicate that upper-level discussions about policy parameters are not gaining the attention they deserve.
By Daniel Kwasi Kpeglo, PhD in Physics | Materials Science & Computational Physics | Scientific Computing, University of South Africa. Originally published at The Conversation
The water stored in dams and reservoirs often suffers from evaporation, particularly in hot regions such as southern Africa. The problem is exacerbated by increasing temperatures, which lead to reduced water availability for humans, agriculture, and industry. Daniel Kwasi Kpeglo has recently completed his PhD in Physics and explains his groundbreaking laboratory research involving a novel design: a thin nanomaterial floating cover that could be placed on lakes and dams like a protective blanket, significantly decreasing evaporation by limiting the infrared heat that reaches the water’s surface. He also discusses the challenges that must be overcome for this design to be tested in real-world conditions.
Why is reducing water evaporation so crucial?
Reducing evaporation translates to wasting less of our existing water resources. The rationale behind my research is straightforward: by retaining more of the water we already have stored, we can alleviate the pressure to seek new water sources.
This issue is particularly pertinent in Africa, where water stored in dams and lakes plays a critical role in ensuring water security, boosting food production, and enhancing resilience against drought.
How does the nanomaterial cover prevent evaporation while allowing sunlight to penetrate?
My research centered on a novel, nanotechnology-based floating cover designed to reduce evaporation. The concept is akin to installing a specially designed shade or cover over the water surface. I sought to investigate whether a prevailing nanomaterial could be deployed over water to function as a selective sunlight filter. The aim was to determine if this nanomaterial could address the evaporation challenge by allowing much of the visible light to penetrate while blocking a significant portion of the heat-carrying infrared radiation.
This nanomaterial consists of an extremely thin layer of a transparent conducting oxide deposited on a flexible, lightweight plastic sheet.
The cover serves to cool the water surface while permitting essential sunlight to pass through; otherwise, aquatic life would perish. My design allows beneficial light to reach the water while shielding it from excess heat.
In laboratory tests, the cover facilitated the passage of more than 60% of visible light on average while reflecting over 80% of infrared radiation back into the atmosphere. Consequently, water beneath the cover was kept significantly cooler than the surface. During peak sunlight, the water was recorded as being 10°C cooler, effectively minimizing evaporation.
Additonally, this lightweight and water-repellent cover can float on the water’s surface without requiring a heavy support structure.
In our trials, the water level beneath the coated cover remained virtually unchanged, indicating minimal evaporation. In contrast, water levels dropped significantly when left uncovered or simply covered with traditional plastic.
What other methods exist to reduce water evaporation, and why is this approach superior?
Various methods such as floating or suspended covers, shade cloths, wind barriers, and natural materials like palm fronds have been utilized to curb evaporation. Some researchers have even explored chemical solutions to create a water ‘sunscreen’. However, these tend to block all sunlight, while our research aims specifically to block infrared radiation.
We believe our innovative design outperforms others due to the lightweight nature of nanomaterials. The transparent conducting oxide is applied as a thin layer measuring only a few hundred nanometers in thickness over a flexible plastic sheet. To put this in perspective, one nanometer is a billionth of a meter. This characteristic makes our cover easier to manage compared to cumbersome permanent structures.
Moreover, because it allows substantial visible light to penetrate, it provides a means to reduce evaporation without entirely depriving the water below of sunlight. This feature is crucial for maintaining the health of the aquatic plants and organisms that depend on sunlight for survival.
Additionally, the coated surface is water-repellent, and our tests revealed it was less prone to accumulating algae or other natural growths. This could translate into reduced cleaning and maintenance efforts over time.
While concerns about the potential contamination of water by nanomaterials exist, our design focuses on utilizing the nanomaterial as a thin coating affixed to a plastic sheet, which does not come into contact with the water itself.
What are the next steps?
To date, our tests have only been conducted in a laboratory-scale reservoir using an artificial light source designed to simulate sunlight. We have assessed various lighting conditions and distances from the water surface, comparing an uncovered reservoir, one covered with regular plastic, and one with the nanomaterial-coated cover. The results consistently showed that the coated cover led to significantly less water loss.
The next critical phase is transitioning from laboratory tests to real-world applications.
The following steps are essential:
- Large-scale field trials are necessary to evaluate how the design compares to existing solutions concerning costs, durability, maintenance, and overall environmental impact.
- A field test will help address inquiries that laboratory experiments cannot answer, including how the material performs under actual sunlight, wind, and varying weather conditions. Essential questions include its longevity and cost of production, as well as its behavior on bodies of moving water.
- In practical applications, the cover would need to be secured to a floating framework to ensure that water and wind do not displace the sheets.
- A thorough scientific investigation into durable, UV-resistant materials, such as polycarbonate, is crucial. Prolonged UV exposure can degrade certain plastics, leading to brittleness and eventual breakdown. Before launching this cover, we must ensure that the selected materials will endure years of sunlight exposure while retaining their functional integrity.
