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Highlights 2023: Massive ECO upgrades during dry-dockings

11 vessels were dry-docked due to scheduled classing and certification during 2023. All vessels achieved EEXI certification after installing EPL (engine power limitation), sandblasting and hull anti-fouling treatment, Mewis Ducts installed (9 vessels), as well as full drivetrain optimization on four of the vessels.

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All new regulations target fuel consumption, imposing stricter demands on vessel performance. This affects the commercial value of the vessel, posing a challenge to the shipowner to optimize operations and vessels. Solvang’s vessels built before 2013 don’t have accurate sea trial data available for engine power limitation calculations. Hence, derating formulas are based on default values, which tend to be conservative.

An overarching target for Solvang’s performance efforts is to reduce power and energy consumption without reducing the speed and commercial value. The engine setup plus vessel performance follow an iterative simulation strategy. Much like the yard during shipbuilding and first-time engine installation. The result has been even better than we expected.

Propulsion drive train optimization

MAN Enery Solutions has delivered Solvang’s propulsion drivetrain optimization programme for some vessels. This substantial procedure includes propeller blades, a propeller-hub fairing cone and rudder-bulb integration, all together meeting EEXI and CII regulations via mainengine power optimization and increase of propulsive efficiency. According to Michael Muff Jensen with MAN Energy Solutions, the Solvang collaboration project “is spot on in terms of performance, efficiency and reduced CO2 emissions. This is just Solvang’s latest investment in its current fleet, confirming its position in the market as a committed front-runner in the efficient and environmentally-friendly transport of LPG and petrochemical gasses.”

Part load optimization

The project “WPLO” (Wärtsilä 2-stroke Part Load Optimization) combines modifications of turbocharger components and tuning of the engine to shift the optimal load to a lower range. The test project was carried out onboard one of Solvang’s H-class, jointly by turbocharger specialist Accelleron and engine tuner Wärtsilä. WPLO is a straightforward solution, easily adaptable to standard overhaul procedures with no need for drydocking. The project took six working days to complete. Immediately thereafter the vessel was able to maintain market speeds while staying EEXI compliant. Fuel savings reached 3-4 % on the engine, while combined fuel savings were 25 %. As a result, the vessel’s CII rating improved from D to A.

“It is an almost unbelievable result”, Mr. Tor Øyvind Ask, Fleet Director at Solvang, says.

Mewis Ducts

In 2023, Solvang made new investments in the Mewis duct programme, in collaboration with Becker Marine Systems. In 2013, Clipper Posh and Quito became the first VLGCs in the world to feature Mewis Ducts, which consist of a duct positioned in front of the propeller along with an integrated fin system. By straightening and accelerating the hull wake into the propeller and also producing a net forward thrust, the Mewis Ducts save up to 7 % of fuel in the tank segment. In the case of Solvang’s fleet, annual savings will reach 10,000 tonnes of fuel or 30,000 tonnes of CO2 when all vessels have Mewis Ducts.

Operational improvement

Deep sea shipping is the world’s most energy-efficient transport. Still, the standard two-stroke direct driven lowspeed engine has an efficiency ratio at just 50 % at the propeller. When converted into thrust, axial, rotational and frictional losses account for 10-15 % further energy losses, leaving only 35-40 % of the original fuel energy to drive the vessel through the water. Again being deprived of effect by hull friction and wavemaking.

To mitigate such losses, Solvang instituted the ECO LPG Carrier programme in 2015, covering an extensive set of improvement and innovation measures to minimize losses and save energy for propulsion.