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Researchers at Northwestern University have introduced a fuel cell that uses soil microorganisms. It significantly outperforms similar technologies, provides a sustainable solution for powering low-energy equipment, and allows full public access to its design for widespread use. His 3D printed cap of the fuel cell peeks out from the ground. The cap prevents debris from entering your device while allowing airflow.Credit: Bill Yen/Northwestern University
A research team led by Northwestern University has developed a new fuel cell that harvests energy from microorganisms living in the soil.
About the size of a standard paperback book, this completely earth-powered technology could fuel underground sensors used in precision agriculture and green infrastructure. This could potentially provide a sustainable alternative to batteries, which leach toxic and flammable chemicals into the ground, have conflict-ridden supply chains, and contribute to the growing e-waste problem. may offer a renewable alternative.
To test the new fuel cell, researchers used it to measure soil moisture and power sensors that detect contact. This feature could be useful for tracking passing animals. To enable wireless communication, the researchers also equipped the soil power sensor with a small antenna that reflects existing radio frequency signals and transmits data to neighboring base stations.
Not only does the fuel cell operate in both wet and dry conditions, but its power output exceeds similar technologies by 120%.
The research will be published today (January 12) in the Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable, and Ubiquitous Technologies. The study authors have also made all designs, tutorials, and simulation tools publicly available so others can use and build on their research.
“The number of Internet of Things (IoT) devices continues to grow,” said Bill Yen, a Northwestern University graduate who led the work. “If we imagine a future with trillions of these devices, they cannot all be made from environmentally dangerous lithium, heavy metals, and toxins. We need to find alternatives that can provide us with soil microbial fuel, which uses specialized microorganisms to break down soil and use that small amount of energy to power sensors. We focused on batteries. As long as there is organic carbon in the soil that microorganisms can break down, fuel cells could last forever.”
Bill Yen, lead author of the study, buried the fuel cell during testing in his lab at Northwestern University.Credit: Northwestern University
“These microbes are everywhere. They already live in the soil everywhere,” said Northwestern’s George Wells, senior author of the study. “We can capture their electricity using a very simply designed system. We’re not going to power an entire city with this energy. But we can capture a small amount of energy. can drive practical low-power applications.”
Wells is an associate professor of civil and environmental engineering at Northwestern University’s McCormick School of Engineering. He is currently completing his Ph.D. Yen, a student at Stanford University, began the project when he was an undergraduate researcher in Wells’ lab.
dirty work solution
In recent years, farmers around the world have increasingly adopted precision farming as a strategy to improve crop yields. Technology-driven approaches rely on measuring precise levels of moisture, nutrients, and pollutants in the soil to make decisions that enhance crop health. This requires a widely distributed network of electronic devices to continuously collect environmental data.
“If you want to place the sensor in the field, on a farm or in a wetland, you need to install a battery or collect solar energy,” Yen said. “Solar panels don’t work well in dirty environments because they get covered in dirt, they don’t work unless the sun is out, and they take up a lot of space. Batteries are also difficult because they run out of power. Farmer I’m not going to walk around a 100-acre farm to change batteries or dust my solar panels on a regular basis.”
To overcome these challenges, Wells, Yen, and their collaborators wondered if they could instead harvest energy from the existing environment. “Either way, farmers will be able to harvest energy from the soil they monitor,” Yen said.
“Thwarted efforts”
First introduced in 1911, soil-based microbial fuel cells (MFCs) operate like batteries with an anode, a cathode, and an electrolyte. But rather than using chemicals to generate electricity, MFCs harvest electricity from bacteria that naturally donate electrons to nearby conductors. When these electrons flow from the anode to the cathode, an electrical circuit is formed.
A fuel cell covered in dirt after being removed from the ground for research.Credit: Bill Yen/Northwestern University
However, for microbial fuel cells to operate without interruption, they must maintain a supply of moisture and oxygen. This is difficult when buried in dry soil.
“MFC has existed as a concept for more than a century, but its unreliable performance and low output power have hindered efforts to bring it to practical use, especially under low-humidity conditions,” Yen said. .
victory geometry
With these challenges in mind, Yen and his team embarked on a two-year journey to develop a practical and reliable soil-based MFC. His research involved creating and comparing four different versions. First, the researchers collected a combined nine months of data on the performance of each design. The final version was then tested outside in the garden.
The best performing prototypes performed well in both dry and submerged environments. The secret of success: its shape. Instead of using a traditional design in which the anode and cathode are parallel to each other, the winning fuel cell adopted a vertical design.
The anode, made of carbon felt (a cheap and plentiful conductor for capturing microbial electrons), is horizontal to the ground. A cathode made of an inert conductive metal is placed vertically above the anode.
Although the entire device is buried, the vertical design keeps the top level with the ground. A 3D printed cap sits on top of the device to prevent debris from falling inside. Also, the hole at the top and the empty air chamber next to the cathode allow for stable airflow.
The lower end of the cathode is located deep below the surface of the earth, ensuring that it can receive water from the moist surrounding soil even when the surface soil is dried by sunlight. The researchers also coated part of the cathode with a waterproof material to allow it to breathe during floods. Also, after a potential flood, the vertical design allows the cathode to dry gradually instead of all at once.
The resulting fuel cell produced an average of 68 times more power than needed to operate the sensor. It was also robust enough to withstand large changes in soil moisture, from semi-dry conditions (41% water by volume) to fully submerged.
Make computing more accessible
The researchers say all components of the soil-based MFC can be purchased at local hardware stores. Next, we plan to develop a soil-based MFC made of completely biodegradable materials. Both designs avoid complex supply chains and avoid the use of conflict minerals.
“with” COVID-19 (new coronavirus infection) “In the wake of the pandemic, we have all become more aware of how crises can disrupt the global supply chain for electronics,” said study co-author and former Northwestern University faculty member. said Josiah Hester, now at Georgia Tech. “We want to use local supply chains and low-cost materials to build devices that make computing accessible to all communities.”
References: Bill Yen, Laura Jarif, Luis Gutierrez, Filotei Sahinidis, Sadie Bernstein, John Madden, Steven Taylor, Colleen Josephson, Pat Panuto, Wei Tao Shuai, George Wells, Nivedita Arora, and Josiah Hester, “Soil-Powered Computing,” January 11, 2024. Proceedings of the ACM on Interactive, Mobile, Wearable, and Ubiquitous Technologies..
DOI: 10.1145/3631410
This research was supported by the National Science Foundation (Award Number CNS-2038853), the Agriculture and Food Research Initiative of the USDA National Institute of Food and Agriculture (Award Number 2023-67021-40628), the Alfred P. Sloan Foundation, and VMware . Research and 3M.
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