Ocean observation is critical for the understanding of oceanic ecosystems and climate change. Sensors and other devices on platforms in the ocean are used to monitor tsunamis, hurricanes, and maritime weather to help keep coastal communities safe. Ocean observation systems are mainly powered by batteries with limited lifetime, which makes it necessary to develop a sustainable blue-energy harvesting solution.
Now, researchers at the Pacific Northwest National Laboratory (PNNL) have developed a new cylindrical triboelectric nanogenerator (TENG) – a small powerhouse that converts wave energy of all kinds into electrical energy to power sensors and devices at sea. This eliminates the need for expensive battery replacements.
The larger versions of this generator could be used to power ocean observation and communications systems, including acoustic and satellite telemetry.
“TENGs are low cost, lightweight, and can efficiently convert slow, uniform or random waves into power – making them particularly well-suited to powering devices in the open ocean where monitoring and access are challenging and costly,” explained Daniel Deng, a PNNL laboratory fellow and co-developer of the new TENG device.
The patent-pending frequency-multiplied cylindrical triboelectric nanogenerator (FMC-TENG), developed by Deng and his team, uses carefully placed magnets to convert energy more efficiently than other cylindrical TENGs and better transform slow, uniform waves into electricity. The prototype FMC-TENG has so far been able to produce enough electricity to power an acoustic transmitter on ocean observing platforms that can be used for communications.
The cylindrical TENG is made up of two nested cylinders, with the inner cylinder rotating freely. Between the two cylinders are strips of faux fur, aluminum electrodes, and a Teflon-like material called fluorinated ethylene propylene (FEP).
When the TENG is rolled by an ocean wave, the artificial fur and aluminum electrodes on one cylinder rub against the FEP material on the inside of the other cylinder. In doing so, they generate static electricity, which is converted into power. The more a cylindrical TENG moves, the more energy it generates.
To increase the amount of wave energy converted into electricity in the FMC-TENG, the team positioned magnets inside the device that prevent the inner cylinder from rotating until it reaches the crest of a wave. This allows the device to build up more and more potential energy. Nearing the crest of the wave, the magnets release, and the internal cylinder starts rolling down the wave very quickly. The faster movement generates electricity more efficiently, generating more energy from a slower wave.
Currently, the FMC-TENG prototype can produce enough power to run small electronics, like temperature sensors and acoustic transmitters. The team plans to improve its design for commercial use, which is expected to produce enough power to run an entire open ocean monitoring platform comprised of multiple sensors and satellite communications. Additionally, the FMC-TENG is lightweight and can be used in both free-floating devices and moored platforms.
“The FMC-TENG is unique because there are very few wave energy converters that are efficient and able to generate significant power from low-frequency ocean waves,” said Deng. “This type of generator could potentially power integrated buoys with sensor arrays to track open ocean water, wind, and climate data entirely using renewable ocean energy.”
- Hyunjun Jung, Habilou Ouro-Koura, Aljon Salalila, Marsobyn Salalila, Zhiqun Daniel Deng. Frequency-multiplied cylindrical triboelectric nanogenerator for harvesting low-frequency wave energy to power ocean observation system. Nano Energy, 2022; DOI: 10.1016/j.nanoen.2022.107365