As the Jan. 1 deadline for implementing IMO 2020 regulations moves closer, most discussion has centered on three paths by which shippers might reach the new global 0.5% sulfur limits on maritime fuels: burning the cleaner fuel, installing exhaust scrubbers to continue to burn higher-sulfur fuel, or switching to LNG as fuel. Focus on these options is warranted, as they provide the only timely implementable solutions other than willful noncompliance.
It is likely, however, that concern over cleaner ways of shipping goods is going to continue for some time, and a wide gamut of alternative energy sources are being developed with an eye toward making maritime transportation not just cleaner but also more efficient.
Sun and wind
Norway’s Foundation for Scientific and Industrial Research (SINTEF) has been working on solar-fueled electric maritime mobility (SoFEM) for more than 2 years, seeking to demonstrate the feasibility and benefits of solar-fueled electric ferries in Tunisia and the wider Middle East and North Africa region.
Japan’s Eco Marine Power is studying rigid solar panel sails for use on larger sea-faring vessels. The sails would substitute both solar and wind energy for a portion of a ship’s combustion power, lowering the vessel’s emissions by as much as 10%, according to the company.
Rotor sail
Perhaps furthest along, however, is Norsepower Oy Ltd., with its rotor sail auxiliary wind propulsion system. The Finnish company’s solution in February received the first-ever type approval design certificate granted to an auxiliary wind propulsion system onboard a commercial ship.
DNV GL issued the type approval after a design assessment of Norsepower’s 30-m tall × 5-m diameter rotor sail, two of which were installed onboard the Maersk Pelican LR2 tanker in August 2018. The certification means that vessels operating the rotor sail are technically capable of safely navigating “all operational and environmental situations.” The Energy Technologies Institute and Shell Shipping & Maritime partnered with Maersk Tankers on the project.
Norsepower has now installed rotor sail systems on three vessels, logging more than 35,000 hr in operation and saving upwards of 4,500 tonnes of CO2 emissions in the process. Potential fuels savings realized have been as high as 20%.
The rotor sail technology is based on the Magnus effect. When wind meets the spinning rotor sail, air flow accelerates on one side and decelerates on the opposite side. The change in air-flow speed results in a pressure difference which creates lift force perpendicular to the wind direction.
Thrust induced by the Magnus effect can be used in ship propulsion by placing a rotor sail cylinder on the open deck of a vessel and rotating it around its vertical axis. A variable electric drive system, powered by the ship’s low-voltage network, rotates the cylinder.
Rotor sail is about 10 times more efficient than a conventional sail because more lift is produced with a much smaller sail area. It also requires no reefing or other crew attention while operating. Throttling back the main engines saves fuel and reduces emissions while the rotor sail provides the power needed to maintain speed and heading.
The optimal number and size of rotor sails for a given vessel depend on the ship’s size, speed, and operating profile. Norsepower holds 46 active patents on the rotor sail technology, which is available in heights of 18 and 24 m as well as the 30-m sails operating on the Pelican.
Data collection and analysis of the two sails’ operation will continue through end-2019, with the expectation that average fuel consumption on a typical global route will be reduced by 7-10%.
Maersk Pelican is a 245-m long, 42-m beam crude oil tanker, built in 2008 and operating between the Middle East and Southeast Asia. It has a deadweight tonnage of 109,647 tons and an average speed of 9.5 knots.