For their senior design project, a group of Stevens naval engineering students have devised the Sail-Assisted Bulk Carrier, which seeks to make merchant shipping more sustainable by synthesizing masts and sails with more conventional approaches to propulsion.
When most of us think about grand sailing vessels, we imagine the old-time, 15th Century tall ships that carried Christopher Columbus across the Atlantic Ocean in his expedition to explore the Americas.
However, in the 1970s and 80s, Japanese shipbuilders experimented with use of massive sails to power cargo vessels, but were unsuccessful because they could not control the ships’ routing. Sailing vessels typically maneuver on a time- and distance-consuming zig-zag trajectory, operating at the whim of the wind’s strength and direction, which was not efficient for commercial bulk carriers that must adhere to rigid delivery schedules and operate on a frugal budget. The experiments were forsaken.
Between the late 19th and early 20th century, commercial sailing vessels fell out of favor due to the advent of steam and diesel power, along with the paddle-wheel and propeller.
Greener, cleaner and 'back in style'
Today, ships are still an essential form of transport in international trade, as they account for 90 percent of commercial transport. Bulk carriers are the workhorses of the global shipping fleet, transporting approximately 40 percent of goods, mainly iron, grain, coal and liquids.
More recently, the maritime transportation industry has suffered tremendous pressures from growing environmental regulations and the increasingly erratic price of oil, desperately seeking a new alternative for powering the gigantic vessels.
Marcia Lee, Colin Phillips, Austin Shaeffer and Nilsu Uyguner explored a variety of alternatives, including solar power and fuel cells, none of which could endure the ocean’s rigor and generate sufficient energy to cost-effectively power these ships.
“Isn’t it time we brought the sail back in style?” asked Lee. “We’re using old, simple technology in an innovative way.”
Simple as the sail seems, the group had to perform their due diligence in solving complicated problems that previously deterred shipbuilders from implementing the large-scale sails. They used Computational Fluid Dynamics (CFD) to determine the flow of air around the sails, and to calculate the lift and drag. They also used modeling software to analyze and design the hull, optimizing its performance. The final analysis suggests that the added thrust produced by the sails will lead to a fuel cost savings of 3 percent, annually.
A novel approach to combining existing systems
“From an educational standpoint, it was a compelling project that required significant independent research and analysis that covered the various interests of the student team,” says faculty advisor Michael DeLorme, a research associate in the Davidson Laboratory.
The students also took a novel approach to combining the sails with existing fuel systems in order to maximize efficiencies, running the ship with wind and diesel-electric propulsion, which is more effective for variable speeds and for power. The conventional power will augment the wind energy while navigating through areas of calm, and while steering the ship in and out of port.
“Running at a constant speed, the load on engines can vary,” says Phillips. “Our method only uses as much engine load as needed, and still maintains the timeline.”
Since more than 14,000 bulk carriers transit the Panama Canal each year, the group also had to plan for the narrow locks, which can only accommodate a beam of around 100 feet.
“The sails won’t interfere with operations of the ship,” said Shaeffer. “We had to accommodate bridges and other obstacles, and plan for the narrow straits and traffic.”
Uyguner explains, “The sails do not cause obstruction with loading or unloading; we used cameras to facilitate vision from the pilot house.”
Previous efforts to add, operate and maintain sails on a merchant vessel were too costly and labor-intensive, but the Sail-Assisted Bulk Carrier offers a viable alternative, reducing the overall expense of operating a merchant vessel throughout its 25-year lifespan.
“With an increased focus on global climate change, we are far more likely to see sail-assisted merchant vessels than ever before,” says DeLorme. “As they begin their careers, these students will take with them the advanced knowledge, benefits and complexities of such a design.”
The students will present their project at the Innovation Expo, on April 27, 2016.