Scientists from Pacific Northwest National Laboratory in the United States jointly with researchers from the University of Washington and the British engineering company WITT Energy have developed and tested a unique drifting buoy that can independently generate electricity from sea waves. This design could solve one of the biggest problems faced by Arctic oceanographers: shortages of electricity for scientific instruments amid the polar night, low temperatures and limited battery capacity.
Conventional power sources show instability at high latitudes: batteries quickly lose capacity in the cold, and solar panels are practically useless in winter due to ice accumulation and the lack of sunlight. As a result, buoys are forced to reduce the number of measurements and often go out of order long before the end of their service life. The researchers have proposed a fundamentally different approach: turning the measuring buoy into a miniature wave power plant.
This concept is based on harnessing the buoy’s natural motion on the waves. Its tilts and vertical movements cause pendulums inside the hull to swing. Their motion is converted into generator rotation through a gearbox; the generated current is used to recharge the internal battery. A streamlined buoy that had been used in Arctic expeditions was chosen as the basis. Before assembling the prototype, the scientists conducted computer modeling to compare the behavior of differently-shaped buoys (spherical, cylindrical and elongated spherical ones) in real wave conditions of the Bering Sea. Calculations showed that it is the elongated spherical shape that gets subjected to the strongest wave motion, which means that it is best suited to drive the pendulum mechanism.
The heart of the system is a WITT pendulum energy converter. The hull houses two pendulums that can rotate along multiple axes. Their motion through the gearing system drives the electric generator, after which the current is rectified and used to charge the battery. To ensure reliable operation at low temperatures, all moving parts were treated with a special frost-resistant lubricant. Additionally, a so-called keel plate, a large aluminum disk that increases water resistance and amplifies the buoy’s vertical oscillations to improve the efficiency of the pendulums’ swing, was attached to the bottom of the buoy on a long cable.
Prototype testing took place in Sequim Bay in northwestern Washington. A control buoy with wave sensors drifted nearby, making it possible to precisely compare its power output with real water conditions. In waves about 0.4 meters high, the system demonstrated short-term power peaks of up to 5 watts. Much more illustrative was the average power calculated over every ten minutes of operation: it stood at about 37 milliwatts. While this is lower than the typical power consumption of an Arctic measuring buoy, which averages 60 milliwatts, even this power makes it possible to significantly extend the battery life. Analysis showed that power generation increases with wave height and period, and the pendulums are activated by both the tilt of the hull and its vertical jerks relative to the keel plate.
The scientists stress that this is only the first stage of their work. In order to improve efficiency, they will have to conduct additional testing in more powerful wave conditions characteristic of Arctic storms and further optimize the hull shape and internal dynamics of the pendulum system.
