28-10-2021 | By Sam Brown
Recently, researchers demonstrated a new undersea energy generator that looks like seaweed and can be used to power marine devices. What challenges do ocean-based devices present, what did the researchers develop, and could it be expanded to large scales?
Man has climbed the highest mountains, crossed the largest deserts, and has even sent robots to other planets. Despite all of these incredible feats of achievement, the ocean floor is the one place that man has struggled to conquer. The main reason for this is the extreme pressures faced underwater; every metre of water is equivalent to 1 atmosphere of pressure. Anything built at the surface that goes to the seafloor either needs to be designed to increase in pressure as it sinks or be encased in a sphere.
However, the oceans also present other challenges almost unseen in different environments. For one, any kind of electrical technology needs to resist the salt in both the air and water as salt accelerates the rusting process. Secondly, underwater communication is extremely difficult without cables as water is an excellent absorber of radio waves. Thirdly, power sources are virtually non-existent. Unless a device that floats have access to either solar or wind power, the only viable alternative is a battery that will eventually run out.
Overall, installing sensors and other forms of technology in the ocean is an extreme challenge that pushes material science to the limit while simultaneously creating a logistical nightmare.
As solar and wind energy is virtually non-existent under the surface, the ocean energy sources are far and few between. However, one abundant form of energy is the fluid motion of water in the form of waves, tides, and natural currents, which can be thought of as an underwater version of wind.
Recognising that such motion carries energy (albeit small), researchers recently developed sea-weed-like triboelectric generators that generate power as they sway in ocean currents. To create these generators, the researchers took two different polymers measuring approximately 1.5 x 3 inches and then coated these polymers with conductive ink. From there, a small sponge is sandwiched between the two layers creating an air gap, and then the unit is sealed to trap the air.
The generator's results showed that it can function down to depths of 30 feet where there is little movement in ocean water. Then, it demonstrated that multiple devices could be used to power a range of different devices, including LEDs, thermometers, and a model lighthouse.
One of the significant advantages of such a generator is that it does not need to generate much power to be a practical device in the ocean. Marine-based sensors that cannot access a cable for power and communication will be required to either float at the ocean's surface for energy or contain a battery.
As there is plenty of space in the ocean that is entirely unused, small marine sensors could easily attach multiple generators to their underside with a design similar to jellyfish, where movement in the ocean generates energy that is stored over time. When data transmission is needed, the stored energy can be released in bursts to transmit data either to satellites or other marine devices in the form of a mesh network that eventually arrives at a coastal receiver.
Furthermore, a device using these generators does not need to be located at the water's surface and could very easily be installed at reasonable depth. For example, ocean floor sensors would have their generators floating above them to generate power. In contrast, depth-specific sensors could be similarly mounted to chains to sea mines.
These new generators may still be in their research phase, but the use of triboelectric generators in marine applications is clearly the right move.