As container ships get bigger, less becomes more in propulsion systems as operators seek solutions that offer lower running costs and meet stringent environmental standards while remaining equal to the task of powering today’s mega vessels.
In the pursuit of lower costs and lower levels of pollution, the byword in the industry is energy saving devices. These come in many forms, from real-time monitoring of all the elements that make up a complex propulsion system to the design of the appendages that have been part of a vessel since time immemorial. For example, operators everywhere are adopting scientifically proven and tank-tested rudders that exert the minimum possible drag.
Perhaps the most popular are the so-called twisted fin and twisted bulb rudders developed by Germany’s Becker Marine Systems. Scores of tank tests by Becker on Panamax and ultra large container vessels (ULCVs) have revealed energy savings of 2 to 5 per cent, depending on the speed of the ship. Well worth having, these efficiencies come about mainly because of improvements to the way the water is inducted to flow around the propeller.
A convert to the technology, United Arab Shipping Co (UASC), has just taken delivery of the last of ten container ships, varying between 14,500 and 18,800 teu, that were equipped from the outset with Becker’s twisted rudders and fins. Manufactured by Hyundai Heavy Industries Co (HHI), the technology promises big energy savings in an industry for which fuel is the single biggest expense, accounting for 50-60 per cent of costs on most merchant ships.
According to calculations by global power giant ABB, a reduction of just 1 per cent in fuel consumption can add up to an annual saving of US$30,000 for a large container ship. That is why fuel efficiency is the focus of most current research and technology. “Everything that is going on in the marine area has a huge focus on cost,” GE’s Marine Solutions president and chief executive Tim Schweikert said earlier this year. “Anything that can save fuel is going to save cost.”
The installation of energy saving devices such as rudders is one thing. Their efficient use is another. To ensure that crews extract the most benefit, manufacturers of these technologies increasingly provide digital monitoring systems to which signals are transmitted from sensors. In the case of Becker’s products, these sensors are placed on the rudder stock. Becker’s system relays the forces on the rudder to the bridge so that the rudder can be set at the optimum angle for efficiency and, in more critical situations, manoeuvrability.
Jörg Haase, managing director of Becker Marine Systems China which is headquartered in the shipbuilding hub of Shanghai, Nanjing and Zhenjiang, explains that the challenge is to get the greatest possible lift, or manoeuvrability, with the least possible drag. “Today’s rudders need to be more than just efficient or of a high-lift type. The market demands a combination of both – a high-lift rudder, which in general produces higher drag, with energy-efficient performance.”
Commensurate with developments on the outside of the hull, there is a concerted push to waste nothing of the energy that is generated inboard. In its first-ever contract for the container ship industry, signed in May, GE Marine Solutions will deliver its new power take off (PTO)/power take in (PTI) technology to 11 second generation Triple-E container vessels for Maersk Line.
The manufacturer says that the system will produce significant fuel savings. It is built around a shaft generator motor installed between the main engine and the propeller and is designed to convert the mechanical power of the generator into electrical energy. When not required to help run the engine, the surplus energy is used to boost power for onboard systems and equipment, thus taking a major load off the engine.
Although other manufacturers have unveiled similar fuel saving technology that taps the power of the generator, GE says that the induction motors it uses, rather than synchronous motors, make the system cheaper, simpler and more reliable. And, responding to the main preoccupation of operators, the technology can collect energy when the vessel is in slow steaming mode or at its design speed. Maersk Lines does not release details of the economies achieved by PTO/PTI, which has been years in development. GE Marine says however that the technology can be installed on engines other than those of its own manufacture.
A whole range of factors go into the efficiency of propulsion systems, including the optimal use of space. A spokesman for ABB points out: “Increasingly larger vessels demand megawatt-class motors, but space is a valuable resource on board which calls for compact, water-cooled motor technology.” Thus in April ABB released a new engine – a frame-size 500 low voltage, water-cooled unit that the company describes as robust, compact, economical and simple in design.
But the biggest space saver may come from liquefied natural gas (LNG)-fuelled vessels. As the high level PERFECt ship exercise is showing, on a Europe–Asia–Europe voyage by an LNG-fuelled ULCV equipped with LNG membrane tanks, almost the entire space normally occupied by the engineroom and the funnel structure could be used for cargo. PERFECt – the Piston Engine Room Free Efficient Containership – is a joint project between Gaztransport et Technigaz (GTT), CMA CGM and class society DNV GL. It concluded that the combination of gas turbine power, a clean fuel and electric propulsion could be a winner. “It is expected that this approach can lead to new maintenance strategies as found in the airline industry, which may make it possible to reduce the ship’s engine crew, leading to further cost savings.”
Thus, in a decade or so the next big breakthrough will probably be fully gas powered container ships. Because of the pressure on the industry to cut emissions, there is a considerable amount of research to investigate the potential of LNG as the fuel of choice among other solutions that may permanently banish fossil fuels. Biofuels cannot be produced in sufficient scale to power the merchant fleet, according to the latest research. “We are working with CMA CGM and other partners on the PERFECt ship design,” explains Nikos Späth, DNV GL’s head of media and public relations. “And we have just entered the second phase of the feasibility study, with ABB as a new partner.”
GE Marine Solutions’ Mr Schweikert is another believer in LNG. “Damage to the environment is a serious issue that has to be addressed and there are a number of approaches people are trying to take, with solutions such as scrubbers,” he said in a recent interview. “We do not think that is a sustainable approach to the problem. We are very interested in leveraging our expertise with LNG.”
And so is Wärtsilä, whose subsidiary Winterthur Gas & Diesel (WinGD) is testing a dual-fuel propulsion unit with South Korea’s Doosan Engine. The engine, which is Wärtsilä’s first low speed, low pressure six cylinder system, is designed to work at between 5 and 100 per cent of capacity. This is what customers want at a time when pricing pressure continues to make slow steaming a necessity for many operators.
“Low speed diesel or dual-fuel engines for the direct drive of fixed pitch propellers will remain the number one solution for large container vessels,” predicts WinGD’s general manager for marketing and application Rudolf Wettstein. “They ensure the lowest capital and operating expenditures for line operators who continue to utilise slow steaming for fuel savings. Freight rates are under pressure and there is an overcapacity of vessels in the market.”
WinGD is certainly a believer in dual fuel. Its current portfolio covers the full range of engines suitable for container vessels ranging from 500 to 22,000 teu.
If slow steaming becomes the norm in the foreseeable future, it may necessitate adjustments to engines that are designed to run – and often perform better – at higher speeds. Thus, in common with other engine manufacturers, Wärtsilä offers a package for partially-loaded propulsion systems. Known as the Low-Load Tuning system, it can be retrofitted to existing engines that ensure smooth running at less than 90 per cent of engine capacity.
As well as more sophisticated engineering, big data is coming into play. In May, Japan’s Fujitsu Laboratories and Tokyo University’s department of marine science and technology unveiled a technology that claims to make the most accurate estimates yet of fuel efficiency, speed and other performance parameters in actual sea conditions. The sensor-gathered data that is analysed includes meteorological and hydrographic conditions such as wind, waves and ocean currents. When that is combined with data from the ship’s engine log, the vessel’s speed and position and other information, the operator is in a better position to maximise the technology that is working in the engineroom. “The margin of error is low,” claim the researchers.
According to Fujitsu Laboratories, the program was tested on a route across the Pacific from Tokyo to Los Angeles, USA with results that should make shipowners sit up and take notice. “Taking an optimal route based on the ship’s performance can reduce fuel consumption by 5 per cent.” Predictably, there were also measurable savings in fuel costs and CO2 emissions.
Following similar lines, GE’s Marine Solutions has launched its own big data based programs originally developed for the aviation and rail industries. Its SeaStream Insight product claims a remarkable 20 per cent reduction in fuel consumption simply by better managing the power of a vessel when holding position. To follow this, GE’s Marine Solutions expects to develop a second generation route optimisation product that might take navigation duties out of the captain’s hands.
This is not mere theory. Line operators are already seeing the gains that can be made from applying big data – or advanced analytics – to performance. In May, German shipping company Leonhardt & Blumberg began the installation of DNV GL’s ECO Insight system across its 40-strong fleet of container vessels, after trialling it through 2015. Chairman Frank Leonhardt says: “Improving fuel efficiency is high on our agenda, so that we remain attractive to our customers.”
As well as feeding data to the operator about the performance of the propulsion systems, ECO Insight provides information about the degradation of the hull such as the degree to which it is fouled. And, as environmental regulations become tougher and more global, the system enables operators to measure their fleets’ performance against standards such as the Environmental Ship Index, Clean Shipping Index and the imminent European Union monitoring, reporting and verification regulations.
Green is good
Under pressure from regulators, ships are becoming greener. Currently plying the Asia–Europe trade route, UASC’s Al Nefud, an 18,800 teu vessel whose maiden voyage was in February, boasts an energy efficiency design index (EEDI) that is 50 per cent lower than the IMO limit. Classed by DNV GL and built by HHI, the vessel is one of the most ecologically responsible container ships afloat. The ship owes its impeccable credentials, as would be expected, to its LNG powered propulsion system, but also to its highly developed hullform and superstructure, both of which are crucial elements in economical steaming.
In keeping with the growing reliance on big data, the performance of Al Nefud’s entire propulsion system will be monitored and optimised on a real-time basis.
In the future
In the not-too-distant future we should see hybrid battery–fuel powered container ships. A start has already been made with tugs and shortsea ferries, with small feeder and cargo vessels to come. And in the near future, DNV GL’s Mr Späth predicts: “For larger seagoing vessels, battery technology could also play a role as an auxiliary power source for manoeuvring, port operations and cranes.”
A 2016 study by DNV GL notes: “Battery powered propulsion systems are already being engineered for smaller ships while the current focus of engine manufacturers is on hybrid electric solutions for larger vessels. The expectation is that by 2025, a larger share of new commercial ships will probably include some degree of hybridisation.”
According to a variety of experts, the main problem to overcome is the energy density of batteries, which limits an electrically powered vessel’s cruising range. But when the latest research is converted into commercially available and financially viable technology, the industry is likely to embrace it fully.
The advantages of hybrid powered propulsion systems seem unarguable. Besides lower costs, they include power redundancy, a reduction in noise and vibration, and cleaner air in ports and populated coastal areas, say researchers.
But in the meantime, the best solution appears to be slow steaming and related technology, space saving engines, real-time monitoring and sea-kindly hulls and appendages.