Brave New World

Change is coming to ship design, and coming fast. Commercial pressures are mounting as multiple sectors face an environment of overcapacity and depressed freight rates and operators look for reductions in bunkering costs and overhead. In addition, new IMO requirements for emissions reductions are on the horizon: after 2025, the Energy Efficiency Design Index (EEDI) standard will require most internationally trading newbuilds to achieve reductions of 30 percent. In the wake of the recent Paris Agreement on climate change, some groups are calling for even more.

Paradigm Shift

The new era of commercial and regulatory pressure means a paradigm shift for shipowners and ship design. “For years it was all about extracting as much deadweight tonnage as you could,” says Professor Steven Ceccio, Department Chair and ABS Professor of Marine & Offshore Design Performance at the University of Michigan, “and you could burn what you wanted. Those days are gone. Because owners have these pressures, they're willing to look at new technologies which a more conservative approach would have precluded.”

Many observers suggest that the new levels of efficiency are within reach. DNV GL predicts that shipowners could improve fuel economy by 60 percent over current levels by mid-century. The EU, in justifying its upcoming CO₂ reporting regulations, suggests that a combination of design measures and operational changes could yield gains on the order of 75 percent over the same period.

Only time will tell if these ambitious claims are realized, but progress toward existing standards is moving swiftly. In an interim report on EEDI, an IMO committee found that over half of the 180 recently built ships it surveyed already exceed its requirements for vessels built after 2020. Excluding bulkers from the sample, that number rises to 94 percent.

Ceccio confirms that the technology for 2020 requirements is already here, but “when you get to 2025, you're beginning to push the envelope.” Getting there is going to take a little of everything, he says, and a lot of careful design to make sure it all works together: “There's no magic bullet – you're going to have to use lots of different components. That's what makes it so interesting to be in marine engineering and naval architecture today. These are challenging problems. It's not just a matter of putting more grease on the bearings.”

Design Intervention

What are some of the changes designers are looking at? There is the time-tested strategy of going bigger with ever larger ships powered by ever-larger main engines, recently popular in container shipping. Over 100 container vessels of more than 18,000 TEUs are on order or trading, and as of last year the designs were still growing. Samsung Heavy Industries already holds a contract for six 21,100-TEU vessels for OOCL with first delivery scheduled for 2017. But the practical limits may be in sight, says DNV GL. Designs of more than 26,000 TEUs could be too big to transit the Suez Canal, and efficiency gains from going bigger are diminishing. DNV GL calculates that further improvements in fuel efficiency per ton-mile from the next generation of ultra-large container vessels will only be in the range of five percent.

Beyond going bigger, there may be opportunities in hull form. Last year, environmental consultancy CE Delft published an analysis suggesting gains could be had from fine-lined hulls. With that intervention alone, ships “can improve their design efficiency by about five to 15 percent on average,” CE Delft wrote. “If one takes into account improvements in engine technology and hull, rudder and propeller designs over the past 25 years, larger efficiency improvements are probably within reach. Lower design speeds could improve design efficiencies even more.” The researchers noted that as with many other efficiency interventions, finer lines could mean a more costly ship.

In addition to large-scale, capital-intensive changes, there are multiple off-the-shelf products or services offering smaller fuel efficiency gains – like the Becker Mewis Duct, which has over 1,000 installations on vessels of all types and yields improvements in the range of five percent. Propeller Boss Cap Fins can yield as much as another five percent, and MOL Techno-Trade has sold 3,000 of the devices over the years. Coatings manufacturer Hempel offers a silicone hydrogel/biocide antifouling paint with a claimed six percent fuel savings, and many of its competitors also market drag-reducing products.

Many novel interventions are just beginning to gain acceptance, like the air lubrication systems offered by Silverstream Technologies and Mitsubishi. Both firms recently announced commercial installations on cruise ships: The Mitsubishi-built AIDAprima, delivered in March, has the firm's proprietary MALS system, and Silverstream's technology will be installed on the Norwegian Bliss, due next year. Silverstream predicts fuel consumption savings on the order of ten percent depending on hull type – a value in line with Mitsubishi's claims for installed units.

Changing the Operating Profile

In addition to design interventions, operators have long known that changing the operational profile of a vessel offers significant gains. Reducing speed from 25 to 20 knots can cut fuel consumption in half for a 4,500-TEU ship, according to ABS estimates. But it’s not always that simple.

“If we thought that a ship was going to have one operational profile for its entire life,” says Ceccio, “and we could fix the economic conditions under which it operates, we could optimize the design. We could find the sweet spot. Always the challenge is that things change.”

Of course, with investment the ship's shape can be altered mid-life to match a specific operational profile. Maersk, Hapag-Lloyd, NYK and many others have “re-delivered” old vessels for a new economic reality, cutting the bulbous bows off selected ships, for example, and welding in sections designed for slower speeds. DNV GL estimates a savings potential of five to ten percent for a carefully designed bow refit.

To reach ever-loftier goals, ship designers and owners will have to work with the full portfolio of smaller interventions to create a complete package, Ceccio says. He likes to compare the opportunities for improved ship design to recent improvements in cars: “If you look at vehicles today, they're much more efficient than they were in the ?60s, and it's not just because the tires are a little better. Everything's a little better.” He adds that the task of making a better vessel is much more than efficiency alone: The designer must also consider seakeeping, maneuverability, crew comfort and more – all of the traditional factors in creating a useful ship for an economic purpose.

A Better Toolkit

New challenges require new tools, and with recent advances in 3D computer modeling designers are better equipped than ever to optimize vessel design. “With our more advanced tools come greater challenges,” says John Waterhouse, Chief Concept Engineer at Elliott Bay Design Group. “It used to be a four- minute mile was fast. Now we're able to run even faster.” Starting from a 3D model, engineers can evaluate a design holistically with computational fluid dynamics (CFD), even for unusual or complex underwater forms, and make ever-more-accurate predictions about hydrodynamic behavior.

However, with increased sophistication comes increased cost. “CFD and finite element analysis [for strength and vibration] do add cost to the design process rather than the old methods of just using standard formulas and adding margins to them for extra insurance,” Waterhouse adds. But owners are increasingly saying the investment is worth it. They can see the business case for added value over time from efficient, optimized and crew-friendly ships, and they are asking for precise results.

Bryan Nichols, Director of Business Development for Jensen Maritime, says that internal use helps support its sophisticated capabilities (Jensen is a subsidiary of U.S. operator Crowley Maritime): “We use advanced software and engineering expertise for more than just vessel design. For example, we can model rig tow arrangements for Crowley to determine the best towing setup. Having internal uses for CFD and other analytical tools distributes the cost and allows our clients to capitalize on our investment.” As an example, Jensen recently designed a tug suited for both escort and ocean towing applications, an unusual combination, and achieved it without the use of ballast tanks, thereby avoiding the requirement for ballast water management.

Without internal use or large volume demand, the added cost might not fit within the design budget. Jamie Benoit, a principal engineer at Murray & Associates, only sees CFD used for many commercial vessels through subcontracting or through an arrangement with a vendor – as when an inflow study is included in the price of an integrated engine and propulsion package.

Elizabeth Boyd, President of Nautican Research & Development, concurs: “The construction value of a workboat is only a fraction of a big ship, so the budget is small. You don't usually end up doing a lot of CFD.” Her firm offers high-efficiency propeller nozzles and triple rudders for tugs and workboats. Given the cost constraints in designing smaller vessels, Nautican has created standard propulsion packages to reduce the need for custom engineering. For the future, Boyd plans to create CFD-optimized standard hull forms and nozzle/rudder configurations. Once complete, they will allow her to give clients a stern section carefully designed to match Nautican’s equipment, bringing computer-aided hull optimization to the broader workboat market. – MarEx