Noise pollution in the oceans is indirectly affecting not only marine life, but also the climate. This is why engineers are now creating new propellers with looped blades. Engineered in a way to reduce noise pollution and help protect marine life, these loop-based models are also increasing energy efficiency.
The boats’ propellers generate high and low pressure regions, and these changes create cavities of air that form bubbles. This process, called cavitation, contributes to most of a boat propeller’s noise. Tommy Sebastian, a senior staffer at MIT Lincoln Laboratory, and Greg Sharrow, who is trying to make quieter drones, believe that their loop-based propellers reduce both tip vortices and cavitation. As a result, their propellers are about 20 decibels softer than traditional ones, and tests done by BoatTEST found that their propellers were up to 30% more efficient.
Sharrow Marine, the company founded by Greg Sharrow, started selling loop-based propellers for recreational boaters in 2020. They are also running tests to assess the noise reduction for marine life and to better understand the extent of their move efficient propellers. They plan to publish the results in the next year.
In order to reduce emissions and conserve energy, cargo ships must also switch to alternative fuel sources. This means redesigning ships and retrofitting old ones, as well as building coastal infrastructure to refuel them. Implementing strategies such as reshaping bows and hulls, maintaining a clean hull and undamaged propellers, and extra structures to decrease cavitation around the propeller, can help save energy, reduce noise, and make the shipping industry greener.
Tommy Sebastian is a senior staffer at MIT Lincoln Laboratory and is currently an engineer who is tinkering with unconventional propeller shapes. He has been actively designing propellers of 10 meters in diameter for many years and working collaboratively with many shipping-container companies to apply his technology for container ships. Sebastian views loop propellers not just as a way to reduce noise pollution and protect marine life, but also as a way to increase energy efficiency.
Greg Sharrow founded the company Sharrow Marine to make quieter drones to film live classical music. Sharrow Marine started selling loop-based propellers for recreational boaters in 2020, and they also hope to expand into the shipping industry. Sharrow’s propellers are not widely used for commercial shipping vessels right now, but they may one day replace those ships’ noisy screw propellers or traditional blade propellers.
