Dec 2015 | Technology | Less than a year until amortisation
How to make ships fuel-efficient
The special, energy-saving propeller is lowered onto the RICKMERS DALIAN
The shipping industry’s eternal dilemma: Technological standards relevant at the time of order are outdated by the time of delivery of new built ships, due to long investment cycles and considerable construction periods. So how to keep up?
Even vessels that were built only a few years ago do not meet today’s requirements. Over the last years we have seen priorities shift from fastest possible transit times to highest possible energy efficiency. But how do shipping companies reduce their ships’ fuel oil consumption when they were built to meet contrary objectives? How does Rickmers do it?
“Energy efficiency and the lowest possible fuel consumption are key factors in ensuring the competitiveness of our ships,” says Dr Georg Eljardt, Senior Vice President Maritime Technology at Rickmers Shipmanagement. But since the biggest part of existing fleets was designed to be as fast as possible rather than energy efficient for a wider range of operating conditions, shipping companies look for ways to adapt their existing fleet to the new market environment that demands fuel efficiency. “We are therefore focusing our attention on retrofitting vessels in service,” explains Dr Eljardt.
“Energy efficiency and the lowest possible fuel consumption are key factors in ensuring the competitiveness of our ships.”
He and his team are now working on an extensive retrofit programme for a series of eight 13,600 TEU container vessels owned by Rickmers Group and chartered out to Maersk Line. The first vessel, SCORPIO RICKMERS, was modified at the end of the second quarter, the last one will be finished by the end of March 2016. “Once the vessels are retrofitted, we will have new state-of-the-art ships that provide a competitive advantage to Rickmers Group and its customers over operators of even recently-built ships,” Dr Eljardt confirms.
The goal: to optimise the operational profile through various adjustments
The aim of the retrofit programme is not only to optimise vessels with respect to fuel oil consumption, but also to find the biggest gain in overall technical and commercial efficiency, of course taking into account the actual conversion costs. To accomplish this, the operation and cargo profile of the fleet has been studied in detail based on the latest voyage data in operation and making a calculated estimate of future operations. This has helped optimise a realistic future-thinking operational profile rather than focus on a single design point.
Thorough data collection and an in-depth evaluation have led to a number of feasible measures specifically tailored to the eight 13,600TEU vessels and the needs of their long term operators.
Creating a new design for propeller and bulbous bow
Studies revealed that the key factors for improving a ship’s energy efficiency within a retrofit campaign are the bulbous bow and the propeller. So, on a spring day in April 2015 some Rickmers employees are standing aboard the RICKMERS DALIAN, waiting for the new cargo of the Rickmers-Linie vessel to arrive. Then there it comes: a new propeller with five blades instead of the usual six. Hovering in the air above the RICKMERS DALIAN it is not hard to believe that this propeller is larger in diameter than a standard one.
Mecklenburger Metallguss (MMG), one of the world’s market leaders in design and fabrication of large ship propellers, designed a complete make-over of the old standard propeller in conjunction with a so-called energy saving cap (ESCAP), both best suitable for the forecast operating profile. In order to unlock the full potential for improvement, the new propeller was designed for a limited main engine power. Reflecting the vessel’s future operation, owners and charterers thus get a sufficient speed margin.
Measures of the retrofit include:
- New propeller with energy saving cap
- New bulbous bow that allows for larger propeller
- New antifouling paint
- Variable frequency drive for main seawater cooling pumps and engine room fans
- Flexible turbocharger cut-out system (TCCO)
- Upgrading the efficiency and flexibility of the cargo securing system
- Draught increase
- Hatch cover & lashing bridge upgrade
- Reefer Upgrade
- Loading computer upgrade
The bulbous bow design that is also part of the retrofit has been executed by Flensburger Ship Design, a subsidiary of Flensburger Shipyard which is renowned for its innovative and highly energy-efficient ship designs. Both, the new bulbous bow and the reduced speed requirements, allow for an increased diameter of the propeller, a decrease in blade thickness and the reduction in the number of blades from six to five.
The new propeller alone reduces fuel oil consumption by almost ten per cent
While it is slowly lowered onto the ship Dr Eljardt explains to his colleagues the light, efficient, energy-saving design which cuts fuel consumption by a good eight per cent. The additional energy saving cap further minimises energy losses and raises performance by another two per cent. Both retrofit measures have recently been tested by experts at Schiffbau-Versuchsanstalt Potsdam SVA (Potsdam Model Basin). The results both in numerical simulations and the model tests were highly encouraging.
The RICKMERS DALIAN since carried the securely stowed new propeller to Shanghai from where it continued to its final destination COSCO Zhoushan shipyard on the Chinese Liuheng Island. The exchange of the new propeller for SCORPIO RICKMERS was completed within the yard stay for the whole retrofit programme of the particular vessel. Just like all the other steps of the retrofit for all the ships, the aim is to reduce the downtime to a minimum.
Material costs, labour costs at yards and the downtime of the vessel are only a few of the costs expected for such a conversion. But: “Just looking at the measures that target fuel oil consumption, return of investment will be achieved within less than a year“, says Dr Eljardt. “After the retrofit each vessel will decrease its average fuel consumption by about 15 per cent per year, depending on the operating profile.“