Environmentally friendly and versatile
Quantum is the name of a new container ship concept introduced by DNV that is based on both technical and[ds_preview] market research and innovation. The ship is designed to transport more cargo while using less fuel and having less of an environmental impact.
The containership market has recently announced recovering freight and charter rates, so the time has come to ensure that long-term opportunities and innovation are once more in focus. In late 2009, DNV started an extraordinary project called »Quantum«. While still in the middle of the crisis, the project was initiated to think about the Needs and Solutions of the future, especially for container ships.
However, with the change in the global economy and increased global environmental concerns, shipping is facing a new reality. Vessels ordered today will be in operation for the next 25–30 years. To match prospective market demands and be competitive, shipping companies will most probably have to go different and individual ways in the future.
So what are the challenges in this new reality? What will the design speed be? Should we design for the current super-slow steaming speed? What will be the impact of the increasing public awareness of the carbon footprint of consumer goods? Should we risk opting for untraditional solutions that may come at a higher investment cost? Is LNG a viable energy source for container ships? These and others were questions DNV asked itself and the market when introducing the Quantum project.
The price of oil is expected to remain high and to increase in the long term. A carbon tax will most likely be introduced. Will low-speed container ships with higher capacity and reduced engine output be the norm in the future? Or will the speed return to normal when the market recovers? What about the size? Will the trend towards ever increasing ship sizes continue?
DNV put together a team of its own experts from various disciplines to look at technology and solutions that are expected to be available in a 2–3 year perspective. As a basis for the project, separate market studies were carried out by AXS Alphaliner and Dynamar B. V., looking at the outlook and future developments in the container trades.
A loop from Europe to East Coast South America was chosen for this project. However, the technology and solutions chosen for Quantum will be applicable to ships in other trades as well. Further, a survey was conducted among industry professionals world wide asking for their views on »alternative« solutions for new container ship designs.
Definition of the design case
A fundamental basis for the study was the needs of the industry and the market, which had to be found out. So DNV has asked partners in the worldwide industry: »How would you rank the following items when considering building a new container ship?« (see also Fig. 2.) They were also asked about novel »alternative solutions«, such as the use of LNG for auxiliary engines and propulsion, see fig. 3. Technical and management staff, selected among ship owners, liner operators, ship yards and others (universities etc.) located world wide, participated in the survey.
The results show that »Schedule integrity« remains a top priority in the container industry, only superseded by fuel efficiency, perhaps not unexpectedly during an era of super slow steaming and increasing fuel prices. The high ranking of the »environmental footprint« was a slight surprise. The response to other typical »green« questions supports this impression, indicating that the industry is preparing for the future challenges. The demand for the same design speed as existing designs was only ranked in 25th place.
The answers to the second question are in line with the attitudes revealed in the first one. »Energy saving devices, such as heat recovery systems« and »Friction reducing coatings«, are on top. The use of »LNG for auxiliary power in port in (S)ECA« was ranked third, and »dual fuel propulsion diesel / LNG« came fifth.
Properties like high fuel efficiency, flexibility for speed variation and schedule integrity are difficult to combine in one design using proven and well established technology. DNV has therefore considered alternative solutions in the case study in order to better achieve this goal.
The market analysis which has been carried out is based on various items of information, the majority provided by Alphaliner and Dynamar, both of which are recognised and respected providers of shipping market intelligence. Based on assumptions regarding the development and recovery of the economic situation in different parts of the world and taking geographical aspects into consideration, a market potential was anticipated in the 5,000–7,500 TEU segment. »Ships in the 5,500 TEU region may become the new ›workhorse‹ of the industry«, says Alphaliner.
There are a number of growing economies and emerging trade lanes that will require relatively smaller, more compact ships with features such as shallow draft and high reefer capacity. One example of this is the trade to and from the east coast of South America. This trade is assumed to have a strong future growth potential and is likely to require shallow draft vessels in many of the ports along the coast. Furthermore, this trade is expected to require vessels with a high intake of reefer containers, as there are substantial exports of fruit, meat and other perishable goods.
The Europe-East Coast of South America trade was chosen as an example of a trade which is assumed to have a strong future growth potential. In light of this, it was chosen to focus in our Quantum study on a baby post-Panamax container vessel with a capacity of about 6,000 TEU, increased reefer capacity and a high degree of flexibility which can carry as many containers as possible using as little fuel as possible, and also to take into consideration the environmental demands expected in the future.
Quantum – the solution proposed by DNV
Novel hull shape
The idea of this concept is that more containers can be carried above the waterline without increasing the resistance and fuel consumption, since the under-water part of the hull is unchanged. After juggling with structures, container rows, power curves and stability, the breadth at the waterline was ultimately optimised at 42.5 m for maximum fuel efficiency and DNV decided on 16 containers across at amidships and a novel narrow side structure. Retaining the NPX beam (<49 m) topside, the ship’s length ended up at 272.3 m.
After giving our hydrodynamic experts a free hand to shape the best possible lines within these constraints, the final block coefficient is a very low 0.57, with very low resistance and thus high fuel efficiency, see Figures 2 and 3. With the wider deck, the design could still carry 6,100 TEU, 600 more than the benchmark ship, thus offering added economy of scale.
Hull – outline
• increased beam (42.5 m), providing improved stability and minimising the need for ballast water
• increased deck container capacity due to a novel WidedecK™ design (B = 48.8 m)
• a novel robust narrow wing tank design (b = 1.0 m) that minimises steel weight while providing sufficient damage stability
• An optimised hull form and bulb with a super low block coefficient (Cb = 0.57)
• Significantly reduced weight using sandwich composite materials
• A novel wave breaker with aerodynamic design reducing wind resistance
Operational flexibility due to uncommon machinery system
Container ships are known for utilising the largest engines available, justified by one single reason: the need for speed. However, in today’s uncertain market, more variations in operational speed are seen. A large portion of the container fleet is now slow steaming, with engine loads down as low as to 10 % MCR. Although the ships are reducing their total fuel bill by slow steaming, the specific fuel consumption is increasing. This is because these engines often have their maximum fuel efficiency at around 80–85 % MCR, while the amount of fuel needed per kW is larger at lower loads.
With a conventional design, large variations in power consumption can lead to operational challenges. Long periods of low engine load operation will result in problems with soot formation, due to the lower compression temperature and reduced exhaust gas velocity. As a result, a »blow out« with high engine loads at regular intervals may be needed. In addition to being an operational disturbance, this will also result in unnecessary increased fuel consumption compared to continuous RPM sailing. This opens up for diesel electric transmission, where the power management system will ensure a balance between the consumed and available power. Diesel electric systems are much better than traditional mechanical systems with respect to operational flexibility, engine location and the utilisation of space.
The Quantum concept focuses on flexibility at a time when the world economy and international regulations are changing. The final concept has electric propulsion powered by four dual fuel generator sets fuelled by HFO, MDO or MGO and LNG. When the ship needs to operate at a lower speed, one engine may be shut down, leading to optimised operation and fuel consumption for the remaining three engines that are still running.
The concept proposes using a diesel electric propulsion system, which is an imprecise term when using dual fuel engines. Today there are two makers of dual fuel engines; Wärtsilä (50DF) and MAN (51/60DF). Both these manufacturers’ engines have a rating of approx. 950–1,000 kW/cyl which may be increased to 1100–1200 kW/cyl within some five years. These engines are 4-stroke medium speed engines well suited for generator application operating at approx. 500 rpm depending on the electric frequency.
Do tomorrow’s container ships need a speed as high as 25 knots or could it be less? With the strong focus on the carbon footprint, this issue was thoroughly evaluated, since all other environmental initiatives are of less importance than the operating speed. It is estimated that Quantum would need nearly 50 MW of propulsion power for a service speed of 25 kn, while less than 24 MW is enough for a service speed of 21 kn, including the sea margin. To ensure some flexibility, a maximum propulsion power of 30 MW has been defined for Quantum, which gives a maximum service speed of 22.5 knots. This includes an 18 % sea margin, 4 % air resistance, 5 % appendices resistance and 70 % propeller efficiency.
Quantum has 36 MW installed engine power, which makes her able to keep the 21 kn design speed with all possible service loads taking into consideration the 1,200 reefer plugs.
Pods for Propulsion
The propulsion arrangement chosen for Quantum is a concept involving two rotating pods as presented in Fig. 12. The main advantage of pods is the excellent manoeuvrability that is achieved. With pods there is also no need for stern thrusters and rudders. Quantum will call at 10 ports in a round trip voyage, 45 % of which will be in coastal waters. Good manoeuvrability increases the efficiency in harbour and reduces the need for tugs.
The estimated savings on tug assistance are in the range of € 400,000 per year, taking account of the fact that some ports have mandatory tug assistance. The main disadvantages of a pod solution are the higher investment costs, increased losses in the transmission of propulsion power and the need to have qualified electricians on board. Pods are also a relatively new concept compared to direct driven or geared mechanical systems; hence there have been some quality cases which are well known in the maritime business – leading to some scepticism. However, new design generations have now been presented and the initial problems are expected to have been solved.
The major makers of large pods (6–25 MW) are ABB (Azipod) and Rolls-Royce / Alstom (Mermaid), while smaller pods are made by Siemens Schotle (SSP) and ABB (Compactpod) There have also been uncertainties regarding the hydrodynamic loads acting on the pods. ABB and DNV have carried out continuous full-scale measurements of a pod in service over two years in order to investigate this issue.
The main advantages of pods are the lack of a need for stern thrusters and rudders, the low speed manoeuvrability and the fact that there is less damage to the hull from tugs. The main disadvantages are the higher investment and need for qualified electricians on board.
Machinery and propulsion – outline
• a re-designed power production plant facilitating the use of low carbon fuels such as LNG, yet based on proven technology
• propulsion provided by an electrically driven 5-bladed 8m diameter propeller providing optimal propeller efficiency
• improved manoeuvrability and reduced thruster capacity forward due to two manoeuvrable pods aft, eliminating the need for aft thrusters and a rudder
• Redundant propulsion and machinery
• designed for high efficiency under variable loading conditions
• improved performance in shallow draught conditions
• space saving arrangement, allowing room for large LNG tanks
LNG fuel mix – an environmentally friendly alternative
When choosing fuel for the Quantum concept, some assumptions and choices were made:
• electric propulsion
• increased prices of LSHFO due to lack of LS crude
• new areas with emission restrictions (ECAs) will be established, e.g. 200 nm from all coasts
• LNG will become available once there is a market
A dual fuel solution was chosen, using MDO for Atlantic crossings and LNG for the coastal legs and refuelling LNG in Europe and South America. A pure LNG solution was not realistic since LNG requires more space for tanks and gas handling, which is lost cargo space. The result has been to consider an appropriate dual fuel concept.
More or less all merchant ships today use fossil fuel as their energy source. Up to now, heavy fuel oil (HFO) has been the most common fuel for sea-going ships. This fuel consists of heavy products, named residuals, and is what is left of the crude after lighter products have been removed during the refinery process. Its properties vary widely with respect to viscosity, flash point and amount of contaminants such as sulphur.
The use of low sulphur heavy fuel (LSHFO), which means less than 0.1 % in 2015, is one option to reduce emissions, but removing the sulphur increases the fuel price. In the table below, the difference is only 20 USD/ton, probably because both may be based on an LS crude, but the difference will increase when the demand for LS fuel rises. It is not easy to compare fuels since the prices vary so much, e.g. IFO380 was down at 210 USD/ton in 2008. It should be noted that IFO is a blend of HFO and a small amount of MGO. The density of HFO is near or above 1,000 kg/m3, hence separation of water can be a challenge.
Marine gas oil (MGO) and marine diesel oil (MDO) are refined from crude and are so-called distillates. The main disadvantage of residuals / HFOs compared to distillates is the need for heating before use or pumping, which normally requires a steam system. Maintenance and operation are also easier when HFO can be avoided.
At the moment, the price of MDO is 26 % higher than LSHFO. This has to be balanced by other benefits.
LNG is different since it is based on natural gas and not on crude. LNG contains no sulphur and it emits 9 % less NOx and almost no particulates. The CO2 emissions can be reduced by approx. 25 % (but with an increase in methane this benefit is reduced to approx. 15 %).
Today several coastal ships like ferries and offshore vessels use LNG as ordinary fuel in dual fuel (MAN and Wärtsilä) or pure lean burn gas engines (Rolls-Royce and Mitsubishi). The main challenge for ocean-going vessels is the increased need for fuel tank volume, but stricter emission requirements may compensate for this. Today’s gas code is meant for passenger ships and gas carriers, but in general there are three tank alternatives (A, B and C – ref. the IMO’s IGC code). The most realistic alternative today is a C-tank, which is insulated and pressurised up to approx. 10 bars.
Fuel consumption and tank sizes
When following the operating profile with a service speed of 21 kn but with 1,200 reefers to Europe and 300 to South America, the total energy consumption will be 92,300 TJ. By using equal energy density (45 MJ/kg) and an equal estimated overall efficiency rate of 0.38, the estimated fuel consumption will be 5,700 t per journey, of which 56 % is required in the northbound leg due to the reefers.
All combinations are possible, but Quantum’s tank arrangement is based on case 4. Preferably, LNG should be refuelled in every port, but if this is limited to Rotterdam and Buenos Aires a net LNG tank volume of abt. 5,000 m3 is required. The space required for the LNG tank system is approx. 7,000 m3, compared to 2,300 m3 for MDO which it replaces. The increased need for space is approx. 110 TEU. A refuelling in Santos would reduce the required space by 30 %.
Availability of LNG
The production of LNG requires high-cost facilities and power. Today, most consumers of natural gas are connected to a distribution grid with gas pipes. It is considered most realistic to distribute LNG as fuel through the existing bunker sites. MAGALOG partners (EU project) have been in contact with several large LNG terminals in Europe and some may be technically suited for loading small LNG ships with no or small modifications (this has already been done from a terminal in Spain). Many existing bunker sites may include equipment for LNG bunkering without extensive investments.
Equipment for LNG bunkering is today normally arranged pursuant to an agreement between the operator and customer.
Europe:
• The availability of LNG (large scale) today is good
• Several LNG terminals (large scale) are under development/construction
• A few LNG bunkering sites exist, mainly located in western Norway
• Small LNG vessels for small-scale distribution of LNG already in place
• Vessels propelled by LNG already exist and new ones are under construction
South America:
• LNG is today available, but fewer terminals compared to Europe
• LNG production based on Brazilian gas is under development, increasing the amount of available LNG in the region
• No LNG bunkering sites yet
Venezuela, Bolivia and Peru have large reserves of natural gas, but there are some uncertainties regarding the political situation. The terminal in Bahia Blanca is 600 km south of Buenos Aires and Pecem also has a brand new terminal for LNG imports in order to produce electricity. At the moment, there is an overcapacity in the LNG tanker market, hence existing LNG tankers may be used as LNG bunkering facilities. In general, the increase in the availability of LNG is a world wide trend, e.g. Nippon Oil is planning to build LNG terminals in Japan.
LNG – outline
• flexible engine arrangement – 4-stroke engines, either dual fuel (LNG/diesel) or a selection of dedicated energy converters
• LNG fuel for auxiliary power in ECAs and partly for propulsion. LNG storage tanks provided above the engine room area, allowing maximum container capacity
• environmentally friendly and prepared for future regulations
• LNG is proven in service on 4-stroke engines, while 2-stroke engines for LNG may not yet have a track record
Summary
With Quantum, DNV has presented a concept consisting of various design features for a new generation of container vessels that are innovative but realisable in the near future. Flexibility and environmental friendliness can be the basis for the vessels to match the market’s future requirements using the individual advantages of the features shown in this project. Quantum provides some new aspects for strategic decisions which could determine the market position of shipping companies in future.
Although some main features have been presented in this article, many more innovative solutions have been considered, such as
• the minimisation of necessary water ballast
• the use of lightweight materials
• container handling etc.
Even though it would be possible to realise Quantum in the next 3–5 years, it is a concept study, developed to start a discussion about innovations in container ship design. We will most probably not see all the Quantum ideas in one single vessel but some features will be realised on a case-by-case basis.
DNV is pleased that Quantum has initiated a very fruitful debate about not only future needs but also our innovative proposals as possible solutions. Quantum has been created for our special assumed design case. The reality may look a bit different in detail. The first follow-up projects will go ahead based on thinking outside the box.
Frank Hensel
