Energy harvesting: Etching tellurite glass, self-powered sensors, limestone putty TENG.
Physicists from EPFL and Tokyo Tech propose a way to create photoconductive circuits, where the circuit is directly patterned onto a tellurite glass surface with femtosecond laser light. The exposure formed nanoscale tellurium and tellurium oxide crystals, both semiconducting materials.
“Tellurium being semiconducting, based on this finding we wondered if it would be possible to write durable patterns on the tellurite glass surface that could reliably induce electricity when exposed to light, and the answer is yes,” said Yves Bellouard who runs EPFL’s Galatea Laboratory, in a statement. “An interesting twist to the technique is that no additional materials are needed in the process. All you need is tellurite glass and a femtosecond laser to make an active photoconductive material.”
Turning tellurite glass into a ‘transparent’ light-energy harvester by etching semiconducting patterns using femtosecond laser light. (Credit: © 2024 EPFL / Lisa Ackermann / Creative Commons CC-BY-SA 4.0)
After exposing a simple line pattern on the surface of a tellurite glass 1 cm in diameter, the team found that it could generate a current when exposing it to UV light and the visible spectrum, which worked reliably for months. [1]
Researchers from MIT developed a battery-free, self-powered temperature sensor that harvests energy from the magnetic field generated in the open air around a wire. The sensor could be clipped around a wire that carries electricity, such as a wire that powers a motor, to automatically harvest and store energy used to monitor the motor’s temperature.
The team also created a framework for the key components of a device that can sense and control the flow of energy continually during operation. The framework is not limited to sensors that harvest magnetic field energy, so it could also be used for power sources such as vibration or sunlight.
Key aspects include the ability to cold start with no initial voltage; storage and conversion of the harvested energy without a battery using a series of capacitors; and a series of control algorithms that run on a microcontroller to dynamically measure and budget the energy collected, stored, and used by the device.
They envision the framework being used to build networks of sensors for factories, warehouses, and commercial spaces. [2]
Researchers at The University of Alabama in Huntsville created a new kind of triboelectric nanogenerator (TENG) that produces electricity through the use of limestone putty, which makes it more cost-effective and simpler to build compared to traditional TENGs.
The use of the limestone-based mounting putty, along with a metallized polyester sheet, also extends the operational frequency bandwidth for small energy-harvesting applications that collect energy from human motion.
“Typical contact-separation TENGs operate at a frequency below 10 Hz,” said Gang Wang, an associate professor of mechanical and aerospace engineering at UAH, in a release. “However, we are able to extend the bandwidth up to 80Hz by introducing these triboelectric layers in a vibration-based energy-harvester design. After the successful demonstration of the TENG design using double-sided tape, we started to explore less tacky materials for easier separation of the materials. This is how we came up with the idea of using limestone-based putty.”
Future investigation of putty-based generators will explore the effectiveness of different minerals such as marble, sandstone, and lunar soil. [3]
[1] Gözden Torun, Anastasia Romashkina, Tetsuo Kishi, Yves Bellouard. Femtosecond-laser direct-write photoconductive patterns on tellurite glass. Physical Review Applied, 2024; 21 (1) http://dx.doi.org/10.1103/PhysRevApplied.21.014008
[2] D. Monagle, E. A. Ponce and S. B. Leeb, “Rule the Joule: An Energy Management Design Guide for Self-Powered Sensors,” in IEEE Sensors Journal, vol. 24, no. 1, pp. 6-15, 1 Jan.1, 2024, http://dx.doi.org/10.1109/JSEN.2023.3336529
[3] Moon-Hyung Jang, Sean P. Rabbitte, Yu Lei, Simon Chung, and Gang Wang, Power Generation by a Limestone-Contained Putty. ACS Omega 2023 8 (10), 9326-9333 https://dx.doi.org/10.1021/acsomega.2c07688
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