Energy efficient and environmentally friendly technology is being applied to stabiliser solutions aimed at ferries and cruise ships
“Every time we discuss newbuild projects, we face green and environmentally friendly topics. This is the main focus for a ferry and cruise operator.” So said SKF director of fin stabiliser and steering gears Christopher Schnäckel, a man who knows a lot about the industry and how current trends are shaping future plans.
The company is applying fuel and environmental efficiency to its products. At the beginning of last year it launched its Dynamic Stabilizer Cover (DSC), designed to reduce drag and improve the efficiency of passenger vessels equipped with SKF retractable fin stabilisers type S and Z. When a vessel is in motion, the fin box opening in the side of the hull creates turbulence, increasing drag on the vessel.
“The fin box opening causes a lot of drag and therefore creates a lot of fuel consumption,” Mr Schnäckel explained. “We wanted to close these openings to support the operator in reducing propulsion power and so being more environmentally friendly and reducing the fuel consumption.”
The DSC uses two specially shaped air cushions, fitted to the top and bottom of the fin box with small steel rails. In normal operation, the cushions are inflated using compressed air from the vessel’s existing pneumatic systems. Inflated, the cushions form a cover over the fin box opening. When the stabiliser fin is to be extended or retracted, air is released from the cushions by opening the valve. The cushions are then deflated by the water pressure outside the hull, creating room for the fin’s movement. When deployment or housing is complete, the cushions can be re-inflated. Control of the cover is fully integrated into the stabiliser fin control systems, requiring no additional action by the crew.
SKF said that closing the hull openings reduces drag by up to 90%, leading to a 1% to 2% reduction in fuel consumption each time the cushions are inflated.
The product will be tested by a large cruise operator this year and Mr Schnäckel said that he hoped by the end of 2018 it would be ready to go to market.
The company also has another product in the pipeline: Eco Mode is being launched at SMM this year, with the aim of making stabilisers more intelligent and reducing fuel consumption. “Two big stabiliser fins in operation cause drag, but crew are not sure if they need one or two fins in operation. Our software detects when water is calm and sends a message to say only one fin is needed,” explained Mr Schnäckel.
The product also gives information on when the fin angle can be reduced, therefore saving energy consumption. Usually the fin angle is rotated to plus or minus 18 degrees. But the Eco Mode software indicates when the fins can be angled at lesser degrees, down to five degrees. The system is currently being trialled on a ferry. SKF is also using Eco Mode to reduce the electricity used by the stabilisers’ hydraulic power units (HPU).
“Using more intelligence, we can see when the stabiliser is not being used heavily, therefore one pump of each HPU can be shut down, reducing electricity consumption,” said Mr Schnäckel.
Elsewhere, GEPS Techno has also applied an energy efficient technology to its stabiliser solution: Green Stabiliser Integrated with Recovery of Energy (GSIRE) is a passive anti-rolling tank for hulls. It consists of a tank filled with water that is positioned on the beam of the vessel. Vortex chambers are placed on either side and the water follows the lead of the chambers, stabilising the vessel. The GSIRE produces electricity from the waterflow, of up to 250 kW capacity, via turbines in the vortex chambers that are turned by the water. The return on investment is estimated at five to seven years.
The GSIRE was retrofitted from an existing flume tank space below the bridge deck on research oceanographic vessel Thalassa in September 2016 in a pilot project. Its sea trial result is approximately 50% roll reduction and 90% at peak period. GEPS Techno installed two 15 kW capacity turbines.
GEPS Techno commercial director Audrie Jordan said “We are not yet producing enough electricity to reduce fuel consumption on Thalassa, but it is generating electricity to the main switchboard.” She added that there was the possibility to store the electricity produced on a battery, which could be used in case of a sudden loss of power. The company is working with Bureau Veritas (BV) to certify this. The switchboard electrical installation has already been certified by BV.
GEPS Techno used its oscillating bench to test at a representative scale of reality, to analyse the results and to then test the chosen solution at sea on Thalassa. Ms Jordan said that it revealed stabilisation performance was improved by the presence of the turbines used to generate electricity. She said that this was because the turbine keeps water in vortex chambers longer, allowing better control of the flow of the water.
She also explained that GEPS Techno’s technology is in competition with fins [that are outside the vessel] in the passenger ship stabilisation market. “These fins are deployed at sea and are efficient with high speeds. We have studied the case with one of our cruise line customers to combine smaller fins that would be less expensive [than larger ones], with our system, so that the vessel is stabilised at zero speed and high speeds and to limit the costs.”
She added: “It is the only stabiliser that is producing added value [through the creation of electricity].”
A solution on ice
Rolls-Royce launched a new type of stabilisation at rest solution this year that is particularly attractive to ice-class expedition cruise ships.
The company has been supplying stabilisation at rest solutions - providing roll damping when the vessel is at anchor or stationary - since 2006, mainly to the yacht market. Rolls-Royce Dunfermline head of sales Paul Crawford told Marine Propulsion “Part of the trailing edge is exposed when retracted and gives an added bilge keel effect. Then the fin is deployed and works actively both at rest and underway.”
Rolls-Royce’s new stabilisation at rest product consists of a swept fin that is totally housed when retracted, as opposed to having the trailing edge of the fin exposed. “This is more important for ice-class vessels, where they do not want the fin exposed in the ice when retracted,” Mr Crawford said. It is also the first five-sided fin and provides more performance with less rolling or pitching, according to the company.
Rolls-Royce has several contracts for the new style of fin, which include expedition ships, a retrofit for a vessel conversion, while Poseidon Expedition’s 114-passenger vessel Sea Spirit will be fitted with new retractable fin stabilisers for installation in 2019.
Rolls-Royce has also agreed a cruise contract for Hurtigruten’s newbuilds. It is supplying a package of equipment, including its Aquarius 100 stabilisers. Current ferry projects include vessels being built in Caspian, Finland, Poland, India and Scotland.
As stabiliser technology develops, Mr Crawford said he believed that instead of using the current hydraulic power units, electric motors would become a way of powering stabilisers. “There is less maintenance needed and less equipment and I see this used especially within ferries in the future, as many are becoming more electric.” He added that while Rolls-Royce did not offer such a product yet, the company had looked into this technology
Despite the maturity of the stabiliser product, innovations keep coming and energy efficiency will feature heavily in future releases.