Lithium-rich brine from an evaporation pond in the Atacama Desert, Chile
John Moore/Getty Images
The extraction of lithium for batteries, essential for the electric vehicle movement and renewable energy utilization, poses significant environmental risks. Nonetheless, innovative solar-powered techniques for generating fresh water and lithium might improve sustainability.
Currently, most lithium is sourced from subterranean salt lakes in the Andes. The brine undergoes a concentration process through evaporation in outdoor ponds for several months, followed by the extraction of lithium carbonate, which consumes a substantial amount of freshwater. Additionally, when salty water is removed from the reservoir, freshwater from the surrounding rock can trickle down to fill the gap, leading to a decline in the water table, highlighting the negative impact of mining on water availability.
Numerous research initiatives are exploring Direct lithium extraction methods that bypass field evaporation. A notable approach, developed by Yu Tang and her team at Lanzhou University in China, has successfully generated usable freshwater and allowed for recovery back into the underground aquifers.
The team utilizes the unique structure of manganese oxides, which exhibit two crucial characteristics: they can convert a significant amount of sunlight into heat and selectively bond with lithium ions.
In their method, a thin stream of salt or seawater flows over a layer of manganese oxide exposed to sunlight. As the sun heats the material, water evaporates and lithium ions adhere to the oxide. Once these layers are saturated, acidic solutions can extract the ions, enabling the reuse of the material.
This process operates within a sealed environment that captures and condenses evaporated water for collection. The research team has tested small prototypes that successfully completed five cycles of lithium adsorption and release, with the collected water meeting the World Health Organization’s drinking water standards.
According to Ugo Bardi from the University of Florence, Italy, the approach is “very clever.” He suggests it could potentially offer a more sustainable lithium source.
“The paper appears credible,” Bardi notes. “One possible concern could be the material’s stability. How many cycles can it endure under real-world conditions?”
Russian ambush drone with solar panels uncovered in Ukraine
Serhii Beskrestnov
The small racing quadcopter, known as first-person view drones or FPVs, has emerged as the primary weapon in the ongoing conflicts in Ukraine. Some of these drones are equipped with solar cells, enabling them to lie in wait for extended periods to ambush targets and act as a new kind of land mine.
“Drones can position themselves near roads and chokepoints, and when a target appears, they can rapidly accelerate toward it,” says Robert Bunker, a consultant with the US firm C/O Futures.
Drone ambush tactics have already become standard strategy for both Russian and Ukrainian forces, with devices hidden alongside roads and buildings waiting for targets. However, even if the engine is off, the camera and radio communications drain the drone’s battery, reducing their wait time to just a few hours.
Currently, Russian FPV ambush drones have been spotted utilizing solar panels for charging. While these panels can’t power the drones during flight, they can recharge other devices. Ukrainian drone warfare expert Serhii “Flash” Beskrestnov has shared images of this solar setup on his Telegram channel, highlighting these advancements.
Sold as camping equipment for approximately $50, these panels efficiently charge phones and other portable devices. Enthusiasts online have already posted guides on modifying drones to include solar cells.
“The initial generation of solar technology may be bulky, but it serves as a useful proof of concept,” Bunker remarks.
A 5-watt solar charger weighs several hundred grams and provides power to the drone while on the ground. Future models are expected to be sleeker and more efficient.
“The drone could feature a solar roll that unfolds after landing, creating a charging surface. You could then disconnect it when entering combat mode,” Bunker notes. “Future iterations will likely include improvements we haven’t yet considered.”
With solar assistance, drones can lie in wait for their targets as long as the sun is shining, recharging their systems at dawn for continuous operation. The solar cells can also gradually recharge the drone’s batteries for over a day, enabling a cycle of flying, landing, recharging, and flying again.
Both Russia and Ukraine have developed drones with artificial intelligence that can identify and engage targets autonomously. When combined with solar energy, these drones can saturate the battlefield with lethal units, autonomously navigating to find and track targets.
“It’s an evolution of the point land mine,” says Bunker.
Unlike traditional minefields, the network of solar-powered drones can self-repair, filling gaps where drones have been used or destroyed. Alternatively, this field might slowly advance towards enemy positions over several days through successive charging cycles.
Today’s solar drones are often experimental prototypes, with only a limited number currently deployed. However, the widespread availability of components suggests that these designs could proliferate rapidly, much like other small drones. With their affordability and ease of assembly, ambush drones may soon become commonplace.
A solar-powered surveillance drone boasting a wingspan larger than that of the Boeing 747 is capable of flying continuously for weeks or even months, as claimed by its operators. A test flight is currently underway off the US Gulf Coast this month.
Run by the US-Spanish venture Skydweller Aero, the Skydweller drone features a 72-meter wingspan, surpassing the width of most commercial jets. Weighing approximately 2,500 kilograms—similar to a Ford F-150 truck—this drone aims to achieve the first solar-powered flight globally, which was targeted for 2016, with a mission to carry out “pure targeted flights” over 13 kilometers during daylight, while aspiring towards building a “comparable solar-powered carbon fiber drone.”
The Skydweller drone executed the world’s inaugural autonomous solar-powered flight in April 2024, with several subsequent test flights conducted throughout the year. Military funding evaluations are focusing on the viability of marine drone patrols. Military funding is assessing the feasibility of marine drone patrols.
Most recently, the solar-powered drone accomplished its longest flight after departing from Stennis International Airport in Mississippi on July 20. According to the Flightradar24 Flight Tracking Service, it remained aloft over the Gulf Coast for more than three days, landing on July 23. The service also indicated that, on July 14, the drone had flown for over 18 hours.
The wingspan of the Skydweller drone is nearly double that of major surveillance drones, such as the Northrop Grumman RQ-4 Global Hawk used by the US Air Force. Its payload capacity of 400 kilograms significantly surpasses the lifting capabilities of most solar drones. Recently, the French aerospace company Thales contributed to the development of the Skydweller drone by equipping it with air surveillance radar. Equipment was provided for enhancing its capabilities.
However, experts suggest that the decades-long pursuit of commercializing solar drones has largely been marked by unmet promises and monumental failures. Arthur Holland Michele, a research partner at the Oslo Peace Institute, points out that both Google and Facebook attempted to create solar-powered drones for internet services but eventually discontinuing their initiatives. Aerospace manufacturer Airbus, too, has heavily invested in smaller Zephyr solar-electric drones, yet “we haven’t observed significant returns thus far,” states Michele.
“The military has funded solar drone demonstration flights for over ten years, and no one has yet acquired the technology,” Michele explains. “While solar drones are impressive and theoretically meaningful, their practical sustainability as a business case remains unclear.”
Cambridge researchers have developed a solar power device that converts contaminated water into clean hydrogen fuel and potable water, providing a sustainable solution to the global energy and water crisis. Credit: Chanon Pornrungroj/Ariffin Mohamad Annuar
A research team from the University of Cambridge has developed an innovative floating device that uses solar energy to convert contaminated or seawater into clean hydrogen fuel and purified water.
The device can operate on any open water source and does not rely on external power sources, making it particularly beneficial for regions with limited resources or without access to the electrical grid.
Innovation inspired by nature
Inspired by photosynthesis, the process by which plants convert sunlight into food. But unlike previous versions of “artificial leaves” that could produce green hydrogen fuel from clean water sources, this new device can work from polluted or seawater sources and produce clean drinking water at the same time.
Tests of the device have shown that it can produce clean water from highly polluted water, seawater and even the River Cam in central Cambridge.of result reported in a magazine natural water.
Technical challenges and breakthroughs
“It’s difficult to combine solar fuel production and water purification into a single device,” said study co-lead author Dr Chanon Pornunglozi from the Yusuf Hameed Department of Chemistry at the University of Cambridge. “Solar-powered water splitting, where water molecules are split into hydrogen and oxygen, requires starting with completely pure water, as contaminants can poison the catalyst or cause unwanted chemical side reactions. .”
“Water splitting is extremely difficult in remote and developing regions, where clean water is relatively scarce and the infrastructure needed to purify water is not readily available,” said co-lead author Arifin. Mohammad Annua said. “If we have a device that works with contaminated water, we could potentially solve two problems at once: we could split water to make clean fuel and we could make clean drinking water.”
Researchers have developed a solar-powered floating device that can turn contaminated or seawater into clean hydrogen fuel or purified water anywhere in the world. Credit: Chanon Pornrungroj/Ariffin Mohamad Annuar
Pornunglozi and Mohammad Annua, members of Professor Irwin Reisner’s research group, have devised a design that does just that. They deposited a photocatalyst on a nanostructured carbon mesh that easily absorbs both light and heat, producing water vapor that the photocatalyst uses to produce hydrogen. The porous carbon mesh treated to repel water facilitated the levitation of the photocatalyst and served to keep it away from the water below so that pollutants would not interfere with the photocatalyst’s function.
Additionally, new devices use more solar energy. “The process of using light to produce solar fuels uses only a small portion of the solar spectrum; much of the spectrum remains unused,” said Mohammad Anuar.
The research team used a white UV-absorbing layer on top of the floating device for hydrogen production through water splitting. The rest of the solar spectrum travels to the bottom of the device, where the water evaporates.
“This way, we are making better use of light. We get steam for hydrogen production, and the rest is water vapor,” Pornunglozi said. “This way we can now incorporate the process of transpiration, so we can really mimic real leaves.”
Potential global impact
A device that can create clean fuel and clean water all at once using only solar power could help address the energy and water crisis facing many parts of the world. For example, according to the World Health Organization, indoor air pollution caused by cooking with “dirty” fuels such as kerosene is responsible for more than 3 million deaths a year. Cooking with green hydrogen instead could potentially reduce that number significantly. And around the world, he said, 1.8 billion people still don’t have safe drinking water at home.
“The design is also very simple. In just a few steps, you can build a device that works well with water from a variety of sources,” said Mohammad Anuar.
“It is very resistant to contaminants, and the floating design allows the substrate to work in very murky or muddy water,” Pornungloj said. “It’s a very versatile system.”
“While our device is still a proof of principle, these solutions will be needed to develop a truly circular economy and sustainable future,” said Reisner, who led the research. Stated. “The climate crisis and issues around pollution and health are closely linked, and developing approaches that help address both could be a game-changer for many people.”
References: “Hybrid photothermal-photocatalytic sheets for solar-powered whole water splitting coupled with water purification” by Chanon Pornrungroj, Ariffin Bin Mohamad Annuar, Qian Wang, Motiar Rahaman, Subhajit Bhattacharjee, Virgil Andrei, Erwin Reisner; November 13, 2023 natural water. DOI: 10.1038/s44221-023-00139-9
This research was partially supported by the European Commission’s Horizon 2020 programme, the European Research Council, the Cambridge Trust, the Petronas Educational Sponsorship Program and the Winton Program for the Physics of Sustainability. Erwin Reisner is a fellow at St. John’s College. Chanon Pornrungroj is a member of the University of Darwin and Ariffin Mohamad Annuar is a member of Clare University.
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