Filter feeding basking shark inspires more efficient hydroelectric turbine
By Darren Quick
February 7, 2011
Studying the bumpy protrusions on the fins of humpback whales has already led to more efficient wind and tidal power turbines and now nature is once again the source of inspiration for a new and more efficient hydroelectric turbine. The latest source of biomimicry is the basking shark, which industrial design student Anthony Reale has borrowed from to create "strait power," a water-powered turbine generator that tests have shown is 40 percent more efficient than current designs.
Despite being the second largest shark in the ocean, the basking shark is generally considered harmless to humans as it is a filter feeder. It swims with its mouth open to sift zooplankton, small fish and invertebrates from the water before the water is expelled through extended gill slits that nearly encircle its whole head. Although this flow of water assists in the shark’s swimming, Reale recognized that the shape of the shark’s body also played an important role.
With the basking shark’s jaw able to stretch up to 1.2 meter (3.9 ft) in width, a pressure differential is created as the shark swims. As with the wings of an airplane, the water pressure is greater along the straight bottom, while the curved surface of the shark’s body increases the distance the water has to travel, resulting in lower pressure across the shark’s top.
This pressure differential helps draw the water out of the basking shark’s gills and allows the basking shark to be only filter feeder shark that relies solely on the passive flow of water through its pharynx to feed. Other filter feeder sharks, the whale shark and megamouth shark, assist the process by suction or actively pumping water into their pharynxes.
With this in mind, Reale designed his ‘Strait Power’ turbine with a double converging nozzle or an opening within an opening. The water enters the turbine through the first opening and the second nozzle – like the shark’s gills – compresses the water and creates a low-pressure zone to draw the water through and generate more energy.
Reale came up with the design for his senior project at the College for Creative Studies (CCS) in Detroit and recently had the opportunity to put it to the test at the University of Michigan’s (UM) Marine Hydrodynamics Laboratory. The UM researchers with whom Reale collaborated were interested as they had been working on something similar to provide power for remote research camps in Alaska.
Subjected to 200 hours of testing in UM’s 100-yard-long (91 m), 22-foot-wide (6.7 m), 10-foot-deep (3 m) tow tank, Reale’s 900-pound (408 kg) turbine model made mostly of wood, screwed together and sealed with marine paint came out looking battered and bruised. But the results were promising with the researchers saying the design improved the power output of a single blade by around 40 percent – a figure that Reale expects to improve upon with future versions.
Reale has filed a patent for the technology and has designed five potential commercial uses of the Strait Power system ranging from a portable and collapsible version for charging small electrical devices designed for outdoor and military use, up to industrial versions with 10-foot (3 m) diameter blades for powering high-power electrical generators of 40,000 watts and higher.