An artist's rendition of the new Equinox Class vessels. Photo: Algoma Central Corp.

Algoma Central Corp., the largest Canadian shipowner and operator of Canadian-flagged Great Lakes vessels, has announced plans to install fresh water exhaust gas scrubbers on six new vessels that the company says will remove 97% of sulphur oxides emissions generated by vessel engines.

The St. Catharines, Ontario-based company has signed a contract with Wärtsilä Ship Power for the supply of the systems for its Equinox Class vessels, which are currently being built by Chinese shipbuilder Nantong Mingde Heavy Industry Co. Ltd, for a total supply and installation cost of the six scrubber systems is US$12 million.

The two gearless bulk carriers and four self-unloading bulk carriers are designed specifically for Great Lakes service with high efficiency hulls that will require less horsepower to achieve higher speeds than any previous Great Lakes design and thus achieve the lowest fuel consumption and emissions per tonne/kilometre of cargo carried.  The first Equinox Class vessel will arrive in Canada in the first half of 2013.

The Algoma order is the first for Wärtsilä’s new, integrated, fresh water, exhaust gas scrubber design. The scrubbers are designed to clean the exhaust gases of the vessels’ main and auxiliary engines as well as the oil-fired boiler and will meet more stringent environmental regulations taking effect over the next three years.

These scrubber systems will allow shipowners to use lower cost, heavy fuel oils while, at the same time, meet the new Emission Control Area sulphur limits established by the International Maritime Organization (IMO) and adopted by Canada and the United States for the Great Lakes and coastal waters.  Without scrubber technology, shipowners will be forced to convert vessels to burn more expensive low sulfur diesel.

The Wärtsilä scrubber concept works with fresh water recirculating in a closed-loop system. Sulphur oxides that are washed out of the exhaust are neutralized with caustic soda. A small amount of scrubbing water is continuously extracted and an on board water treatment unit removes other captured contaminants such as particulate matter.

A major advantage of fresh water scrubbers is the possibility to operate in a zero discharge mode which means that there is no effluent (waste product) from the scrubber discharged into the lake water. The treated, clean effluents would be held in a holding tank for discharge at an appropriate location while solid contaminants are disposed of at reception facilities in port.

“These are truly important vessels as they will set new standards for environmentally sustainable shipping on the Great Lakes and for cargo vessels in general. The Wärtsilä integrated scrubber solution removes more than 97 percent of sulphur oxides emissions,” says Juhani Hupli, Vice President, Ship Power Technology at Wärtsilä Ship Power.

“In addition to the environmental initiatives another key focus for Algoma’s fleet renewal process has been to reduce maintenance costs. Wärtsilä’s capability in providing both an integrated marine solution and global service support was a major reason Wärtsilä was selected to provide this comprehensive equipment package.” says Al Vanagas, Senior Vice President Technical, Algoma Central Corporation.

This process meets all the quality and monitoring requirements stipulated by the IMO. Wärtsilä is the first manufacturer to have been awarded a marine scrubber certificate by the classification societies Det Norske Veritas, Germanischer Lloyd, and Bureau Veritas.

More about Wärtsilä’s Fresh Water Scrubbers

Click here to view the embedded video.

Currently under construction at the STX Finland yard in Turku, the NB 1376 represents a completely new generation of ferries with it’s revolutionary Liquified Natural Gas (LNG) fuel system built by Wärtsilä, interior design by the award-winning dSign Vertti Kivi & co, and a host of other innovations providing the passengers with a totally new and fresh cruise experience.

Wärtsilä 8L50DF

Wärtsilä’s scope of supply for this contract includes four Wärtsilä 8L50DF main engines, the transverse bow and stern tunnel thrusters, and two stainless steel fixed pitch, built-up main propellers with complete propeller shaft lines and environmentally sound shaft line seal systems. The propellers are designed with the lowest possible pressure impulses for superb vibration control.

The vessel will be fueled by LNG, meaning that sulphur oxide emissions will be almost zero, and nitrogen oxide emissions will be at least 80 percent below the International Maritime Organization’s (IMO) current stipulated level. Furthermore, there is a reduction of particulate emissions of more than 90 percent compared to the emissions from conventional diesel engines, while carbon dioxide emissions are also 20-30 percent lower. The use of Wärtsilä’s duel-fuel engine technology will enable this ferry to sail without restrictions in Sulphur Emission Control Areas (SECAs) and Nitrogen Emission Control Areas (NECAs). LNG offers the most economical and environmentally sound solution for the future.

 

Production begins on the NB1376…

Click here to view the embedded video.

Wärtsilä and Kongsberg Maritime have been contracted to supply the power, positioning, and automation systems for two new drilling rigs ordered by Songa Offshore AS, the Norwegian arm of the Cyprus-based offshore drilling company. These so called cat D semi-submersible rigs are tailor designed for use by Statoil in mid-water segments, and are being built at the Daewoo Shipbuilding and Marine Engineering Co.Ltd (DSME) shipyard in South Korea.

“The proven reliability and superior efficiency of the Wärtsilä propulsion solutions were the major factors in the award of this contract. Calculating the average load profile for deepwater drilling rigs, the efficiency is approximately three per cent better than those offered by competitors. The high efficiency enables fuel cost savings and has also clear benefits in terms of reducing carbon dioxide emissions (CO2). Furthermore, the local Wärtsilä service network in Norway will provide full support for the equipment,” says Magnus Miemois, Vice President at Wärtsilä Ship Power, Offshore.

Kawasaki Heavy Industries LNG-powered containership concept design

Wartsila’s John Hatley and Det Norske Veritas‘ Tony Teo gave an extraordinary presentation at this year’s SNAME conference in Houston last year titled, LNG as a Fuel, one that really helped to define the key characteristics of LNG, the current state of the LNG shipping industry, and why using LNG as a fuel source is unquestionably the future of the global shipping industry.

Tony Teo, DNV’s North American Business Development Director, began his presentation with an overview of his LNG and some insight from his experiences while working in Qatar.

“Qatar is one of the richest countries in the world and the largest exporter of LNG.  It’s a clean natural resource and everyone wants to use it because it is environmentally friendly.”

Properties of LNG:

• 96% methane (CH4)
• Flammable 5 to 15% conc. in air
• Liquefied at -259 deg F (-162 deg C)
• Stored in Cryogenic materials 
• Density 42% of water
• Expands 600 times 
• Cleanest burning fuel

There are a hazards associated with LNG because it is very cold.  If it spills on steel it will crack the steel right away and you can sink a ship, or a rig if you are not careful with it.  So, the handling of LNG, this special material, has to be done with safety and utmost care.

Look at the scenario today from Europe where the Baltic and the North Sea are an ECA [Emissions Control Areas], they are getting a shortage of low-sulfur fuel.  Next year, we will see the same issue and as you know, everything is on a demand and supply basis.  When the demand is high, the price will go up.

At $100 per barrel oil, the price of low sulfur oil is around $1000 per ton, and the price will definitely go up.

This is THE attraction to LNG.  If you are burning a large amount of fuel, you get cost savings by switching to LNG.

The Market for Natural Gas

John Hatley, VP Ship’s Power at Wärtsila, gives a macro perspective…

“Oil and gas companies widely recognize the US natural gas market demand as mature and overwhelming at 23 trillion cubic feet (TCF) per year, which is the largest in the world.  What comes as a surprise is illustrating that the next greatest potential gas market is the world’s commercial shipping fleet, which today consumes nearly 370 million tons of heavy fuel oil annually.

That much fuel oil is equivalent in gas terms to 15 TCF, which is two-thirds the size of the ENTIRE US gas market.  It looms out there on the horizon, but off the radar of many companies and governments due to the difficulties inherent in maritime shipping, whereas they possess a much greater awareness with other transportation modes encountered in daily life, such as cars, trucks, trains, and planes.

The reaction is telling when we provide US stakeholders with a global top down view:

Considering 8 percent of the world trade comes to the United States, the potential natural gas market is roughly 1.2 TCF.

Looking at this issue from a marketing standpoint, would your business prefer sales to a large number of small consumers, or a small number of large consumers?  Obviously the latter is easier to target as it exhibits a lower cost basis to effectively pursue, particularly when a new market such as the natural gas market is developing.

The typical gas company business plan of today takes this idea forward by seeking to target truck fleets as a key to achieving bulk sales.  It’s an easy to understand fact as many highway trucks each consume about 20,000 gallons of diesel per year, or 34,000 diesel gallon equivalents LNG.

Alternatively, let’s consider the fuel consumption numbers for a marine player.

Take a common ocean tug that burns 30 tons of diesel fuel daily, or about 200,000 gallons monthly.  This represents a couple million gallons per year, or 3.4 million diesel gallons equivalent of LNG.    Scaling this up, let’s now consider a large container ship that consumes 200 tons fuel per day.  Suddenly, your potential market for LNG has now exceeded  20 million gallons of LNG per year, per ship!

So now let’s ask the same question again, does it make more business sense to sell to a large number of small consumers, or a small number of large consumers?”

In ExxonMobil’s “Outlook for Energy” they write:

Natural gas will be the fastest-growing major fuel to 2040, with demand rising by more than 60 percent. Much of this growth will come from electric utilities and other consumers shifting away from coal in order to reduce CO₂ emissions. By 2025, natural gas—which emits up to 60 percent less CO₂ emissions than coal when used for electricity generation—will have overtaken coal as the second most popular fuel, after oil.

Demand is expected to grow in every part of the world, but especially in the Non OECD countries in the Asia Pacific region, where demand for natural gas is expected to triple over the next 30 years. The Middle East also will see significant growth, while Russia/Caspian demand flattens.

Current Operations in the Maritime LNG Sector

GLUTRA, The prototype for short sea shipping (c) DNV Builder: Aker Langsten, NorwaySystem: Gas / ElectricEngines: 4 Mitsubishi Engines (lean burn with gas pre chambers @ 2 bars & spark ignited) Speed: 12 knots

Glutra, the prototype for short sea, LNG-powered shipping.  Tony Teo remarks:

“The vessel needs to be refueled once every 6 days, with a bunkering time of approximately 2-hours.  Ever since she was delivered 10 years ago, she has been trading without any problem for 19 hours per day, every day.

Because of the potential explosive area of the engine room, we need the room as simple as possible so that there is no corners, or spaces that could trap any escaped gas, and the ventilators and gas detectors are all EX-certified.  Anything that is not necessary is outside the engineroom, like incinerators and gas generators etc.  We developed this technology with the Norwegian Maritime Directorate, and this is their advice to us:

‘Do a formal safety assessment, and consider a worst case scenario… an explosion.’

Therefore, we make the room as small as possible so anything that is not necessary is outside, and limit the equipment inside to the bare minimum.”

Mr. Teo continues,

“There are 23 LNG-powered vessels in operation throughout the world.  It varies from ferries, coasters, OSVs, and even the Norwegian Coast Guard.  When they need high speed, they switch to diesel, but when on normal steaming speed, they switch to LNG.”

DNV announced on 19 January that they had approved in principle, a design by Kawasaki Heavy Industries (KHI) for a 9000 TEU containership powered by LNG following DNV’s innovation concept “Quantum 9000” announced last year.  This ship is designed with a prismatic Type B LNG fuel tank that allows for more space for container cargo.  There have been no requests yet to build this ship, however the formal safety assessments for the gas supply and storage are underway between KHI and DNV.

A few challenges associated with LNG…

The bunkering process presents new and perhaps unfamiliar challenges to the operator.

Transferring cryogenic and flammable fluid is detailed process, one typically operated by engineers at the helm of  computer-controlled valves inside the ship.  From the initial hookup, throughout the transfer, and the final inert gas flushing of the lines, the engineers must be skilled in using computer technology, use proper safety equipment, and be highly process and safety-driven.

Where do you store it, and for how long?

Mr. Teo notes,

“You can store LNG for a long time.  On small ferries, you can actually store the LNG for up to 4 weeks.  The pressure will increase by only 2 or 3 bar, and the tanks are built to 10 bar pressure.  After a few weeks, or when the pressure gets up to say around 7 bar, for safety reasons it’s important to start a piece of equipment just to burn the excess pressure off.”

One of the biggest challenges facing the wide-scale adoption of LNG-powered ships is infrastructure.

LNG terminal under construction in Rotterdam, Photo: PR / Arndt

Bunkering (a.k.a refueling)…

The primary means of bunkering the short sea shipping industry in Norway and Finland is currently via trucks from a liquefaction plant to the vessels, or to a storage location with bunkering facility.  In a discussion with Dr. Pierre Sames, SVP of Strategic Research and Development at Germanischer Lloyd (GL), he commented that current studies were being conducted with the Hamburg Port Authority (HPA) in an effort to develop LNG bunkering capability.

Their initial plan is to identify possible locations for a 10,000 – 20,000 cubic meter LNG terminal in Hamburg, while also looking at potential hazards such as navigational risks associated to small gas tankers operating in a relatively busy port, and the hazards associated with LNG bunkering and the simultaneous loading and unloading of containers.   Current LNG bunkering options include loading LNG on to small carriers from export terminals in Rotterdam or Belgium, and refueling container feeder vessels in Hamburg.  Dr. Sames also discussed an option for the Baltic region’s short sea ferries where instead of going through the time consuming process of refueling the fuel tanks when the ship returns to the pier, empty, or depleted LNG fuel tanks could be swapped out with newly recharged ones.  It would be a bit like swapping out the canister on an outdoor grill.

Design Concept for a Zero-Emission Container Feeder Vessel – courtesy Germanischer Lloyd

In December, Lloyd’s Register announced the delivery of MT Argonon, a 6,100-DWT dual-fueled chemical tanker to a Deen Shipping subsidiary, Argonon Shipping B.V.  We asked Lloyd’s Register’s Inland Waterway Product Manager, Bas Joormann, how the LNG distribution and storage issues had been mitigated.  His reply:

An LNG infrastructure is not yet available as this is the first inland waterway vessel using LNG as fuel.   The fact is, this is a chicken and egg situation.  As long as there are no more vessels, no real infrastructure will be provided.  The first bunkering with LNG is done in Zwijndrecht (20 km south of Rotterdam) from a truck.  At the moment, LNG bunkering stations in Rotterdam, Zwijndrecht, and Harlingen are planned.  In addition, a bunkering facility in Brunsbuttel in North Germany  is planned, however this will be for the bunkering of seagoing vessels.

Until they are operational, the bunkering will be done by trucks which bring the LNG from Zeebrugge in Belgium.  The LNG is stored on board the Argonon in a 35 m3 tank, which is situated on deck in the cargo zone.

MT Argonon, image courtesy Deen Shipping

This ship represents the first-ever LNG-fueled tanker.

“This has been a great project and it is a significant first,” said Piet Mast, Lloyd’s Register’s Marine Business Manager for Western Europe. “The nature of inland waterways traffic, which passes through or close to major population centres, makes LNG an attractive way to reduce harmful local emissions. We had to look carefully at the risks and worked closely with the owner and the regulators to ensure that they understood, and were comfortable with, the technical solutions that were developed.”

The dual-fuel system on board the Argonon is designed to burn an 80/20 mixture of natural gas and diesel, greatly reducing SOx, NOx and particulate-matter emissions compared to conventionally-powered vessels of similar size.  Some technologies being implemented by some marine engine manufacturers raise that ratio closer to 95/5, and still others use Ott0-cycle engines that burn 100% LNG.  There are trade-offs of course and the technology continues to evolve.

What are our options for meeting future emissions requirements?

We could continue to use Low Sulfur Diesel…

• Higher fuel Cost
• Loss of Lubricity, more wear
• Fuel injectors pressure loss
• Supply shortage = EXPENSIVE

We could use Heavy Fuel Oil (HFO) with SOx Scrubbers…

• Confined Space
• Discharge prohibition
• Rapid corrosion
• Increased maintenance
• NOx is not removed

Or we could switch to LNG- fueled ships…

• Clean burning engines
• No fuel heating
• No Separators
• Less filtration
• Less oil pollution risk

Considering the massive Marcellus Shale gas finds in the Appalacian mountains and companies such as BG and Cheniere committing to significant US-LNG export plans, as well as multi-billion dollar gas developments off Northwestern Australia, it’s highly evident we’re in a global transformation toward a new fuel source.

A fuel source that is not only clean-burning, but an abundant natural resource.

A faster port turnaround time makes it possible to decrease the vessel speed at sea. This is mainly a benefit for ships with scheduled operations, such as ferries and container vessels. The turnaround time can be reduced for example by improving maneuvering performance or enhancing cargo flows with innovative ship designs, ramp arrangements or lifting arrangements.

Regular in-service polishing is required to reduce surface roughness on propellers caused by organic growth and fouling. This can be done without disrupting service operation by using divers.

Up to 10% improvement in service propeller efficiency compared to a fouled propeller.

Modern hull coatings have a smoother and harder surface finish, resulting in reduced friction. Since typically some 50-80% of resistance is friction, better coatings can result in lower total resistance.

A modern coating also results in less fouling, so with a hard surface the benefit is even greater when compared to some older paints towards the end of the docking period.

Saving in fuel consumption after 48 months compared to a conventional hull coating:

• Tanker: ~ 9%
• Container: ~ 9%
• PCTC: ~ 5%
• Ferry: ~ 3% 
• OSV: ~ 0.6%

Engines are usually optimized at high loads. In real life most of them are used on part loads. New matching that takes into account real operation profiles can significantly improve overall operational efficiency.

New engine matching means different TC tuning, fuel injection advance, cam profiles, etc.

Reducing the ship speed an effective way to cut energy consumption. Propulsion power vs. ship speed is a third power curve (according to the theory) so significant reductions can be achieved. It should be noted that for lower speeds the amount of transported cargo / time period is also lower. The energy saving calculated here is for an equal distance travelled.

Reduction in ship speed vs. saving in total energy consumption:

•  0.5 kn –> – 7% energy
•  1.0 kn  –> – 11% energy
•  2.0 kn  –> – 17% energy
•  3.0 kn  –> – 23% energy

The purpose of weather routing is to find the optimum route for long distance voyages, where the shortest route is not always the fastest. The basic idea is to use updated weather forecast data and choose the optimal route through calm areas or areas that have the most downwind tracks. The best systems also take into account the currents, and try to take maximum advantage of these. This track information can be imported to the navigation system.

Shorter passages, less fuel.

The optimum trim can often be as much as 15-20% lower than the worst trim condition at the same draught and speed. As the optimum trim is hull form dependent and for each hull form it depends on the speed and draught, no general conclusions can be made. However by logging the required power in various conditions over a long time period it is possible to find the optimum trim for each draught and speed.

Or this can be determined fairly quickly using CFD or model tests. However it should be noted that correcting the trim by taking ballast will result in higher consumption (increased displacement). If possible the optimum trim should be achieved either by repositioning the cargo or rearranging the bunkers.

Optimal vessel trim reduces the required power.

Poor directional stability causes yaw motion and thus increases fuel consumption. Autopilot has a big influence on the course keeping ability. The best autopilots today are self tuning, adaptive autopilots.

Finding the correct autopilot parameters suitable for the current route and operation area will significantly reduce the use of the rudder and therefore reduce the drag.

Finding the correct parameters or preventing unnecessary use of the rudder gives an anticipated benefit of  1-5%.

A shipping company, with its human resources department, could create a culture of fuel saving, with an incentive or bonus scheme based on fuel savings. One simple means would be competition between the company’s vessels. Training and a measuring system are required so that the crew can see the results and make an impact.

Historical data as reference. Experience shows that incentives can reduce energy usage by up to 10%.

In a CBM system all maintenance action is based on the latest, relevant information received through communication with the actual equipment and on evaluation of this information by experts.

The main benefits are: lower fuel consumption, lower emissions, longer interval between overhauls, and higher reliability.

Correctly timed service will ensure optimum engine performance and improve consumption by up to 5%.

Algae growing on the hull increases ship resistance. Frequent cleaning of the hull can reduce the drag and minimise total fuel consumption.

Reduced fuel consumption:

• Tanker: ~ 3%
• Container: ~ 2%
• PCTC: ~ 2%
• Ferry: ~ 2% 
• OSV: ~ 0.6%

Part 1: How to Design a More Efficient Ship

Part 2: How to Propel a More Efficient Ship

Part 3: Marine Engineering Technology for More Efficient Shipping

All information and images courtesy of Wärtsilä

Hybrid auxiliary power system consists of a fuel cell, diesel generating set and batteries. An intelligent control system balances the loading of  each component for maximum system efficiency. The system can also accept other energy sources such as wind and solar power.

Result:

• Reduction of NOX by 78%
• Reduction of CO2 by 30%
• Reduction of particles by 83%

Combined diesel-electric and diesel-mechanical machinery can improve the total efficiency in ships with an operational profile containing modes with varying loads. The electric power plant will bring benefits at part load, were the engine load is optimised by selecting the right number of engines in use. At higher loads, the mechanical part will offer lower transmission losses than a fully electric machinery.

Total energy consumption for a offshore support vessel with CODED machinery is reduced by 4% compared to a diesel-electric machinery.

Low Loss Concept (LLC) is a patented power distribution system that reduces the number of rectifier transformers from one for each power drive to one bus-bar transformer for each installation. This reduces the distribution losses, increases the energy availability and saves space and installation costs.

Result: Gets rid of bulky transformers.  Transmission losses reduced by 15-20%.

The system uses generating sets operating in a variable rpm mode. The rpm is always adjusted for maximum efficiency regardless of the system load.  The electrical system is based on DC distribution and frequency controlled consumers.

• Reduces number of generating sets by 25%
• Optimized fuel consumption, saving 5-10%

Switching to LNG fuel reduces energy consumption because of the lower demand for ship electricity and heating. The biggest savings come from not having to separate and heat HFO. LNG cold (-162 °C) can be utilised in cooling the ship’s HVAC to save AC-compressor power.

Saving in total energy < 4 % for a typical ferry. In 22 kn cruise mode, the difference in electrical load is approx. 380 kW. This has a major impact on emissions.

Waste heat recovery (WHR) recovers the thermal energy from the exhaust gas and converts it into electrical energy. Residual heat can further be used for ship onboard services. The system can consist of a boiler, a power turbine and a steam turbine with alternator. Redesigning the ship layout can efficiently accommodate the boilers on the ship.

Exhaust waste heat recovery can provide up to 15% of the engine power. The potential with new designs is up to 20%.

Delta tuning is available on Wärtsilä 2-stroke RT-flex engines. It offers reduced fuel consumption in the load range that is most commonly used. The engine is tuned to give lower consumption at part load while still meeting NOx emission limits by allowing higher consumption at full load that is seldom used.

Result: Lower specific fuel consumption at part loads compared to standard tuning.

Common Rail (CR) is a tool for achieving low emissions and low SFOC. CR controls combustion so it can be optimised throughout the operation field, providing at every load the lowest possible fuel consumption.

Result:

• Smokeless operation at all loads
• Part load impact
• Full load impact

Using lighting that is more electricity and heat efficient where possible and optimizing the use of lighting reduces the demand for electricity and air conditioning. This results in a lower hotel load and hence reduced auxiliary power demand.

Fuel consumption saving: Ferry: ~1%

Power Management: Correct timing for changing the number of generating sets is critical factor in fuel consumption in diesel electric and auxiliary power installations. An efficient power management system is the best way to improve the system performance.

Result: Running extensively at low load can easily increase the SFOC by 5-10%. Low load increases the risk of turbine fouling with a further impact on fuel consumption.

Solar panels installed on a ship’s deck can generate electricity for use in an electric propulsion engine or auxiliary ship systems. Heat for various ship systems can also be generated with the solar panels.

Depending on the available deck space, solar panels can give the following reductions in total fuel consumption:

• Tanker: ~ 3.5%
• PCTC: ~ 2.5%
• Ferry: ~ 1%

Pumps are major energy consumers and the engine cooling water system contains a considerable number of pumps. In many installations a large amount of extra water is circulated in the cooling water circuit. Operating the pumps at variable speed would optimise the flow according to the actual need.

Pump energy saving (LT only) case studies:

• Cruise ships (DE) 20-84%
• Ferry 20-30%
• AHTS 8-95%

An Integrated Automation System (IAS) or Alarm and Monitoring System (AMS) includes functionality for advanced automatic monitoring and control of both efficiency and operational performance.

The system integrates all vessel monitoring parameters and controls all processes onboard, so as to operate the vessel at the lowest cost and with the best fuel performance.

Power drives distribute and regulate the optimum power needed for propeller thrust in any operational condition.

Engine optimization control, power generation & distribution optimisation, thrust control and ballast optimisation give 5-10% savings in fuel consumption.

Power management based on intelligent control principles to monitor and control the overall efficiency and availability of the power system onboard. In efficiency mode, the system will automatically run the system with the best energy cost.

Reduces operational fuel costs by 5% and minimizes maintenance.

Part 4 will focus on specific Operational and Maintenance factors and their impact on a vessel’s efficiency.

 The technologies are grouped under four main headings:

• Ship design
• Propulsion
• Machinery
• Operation & Maintenance

Combining these areas and treating them together as an integrated solution can result in truly efficient ship operations.

The following are design concepts and their associated contribution to a more efficient ship design.

A larger ship will in most cases offer greater transport efficiency  – “Efficiency of Scale” effect.  A larger ship can transport more cargo at the  same speed with less power per cargo unit.  Limitations may be met in port handling.

Regression analysis of recently built ships show that a 10% larger ship will give about 4-5% higher transport efficiency. 

Minimising the use of ballast (and other unnecessary weight) results in lighter displacement and thus lower resistance. The resistance is more or less directly proportional to the displacement of the vessel. However there must be enough ballast to immerse the propeller in the water, and provide sufficient stability (safety) and acceptable sea keeping behaviour (slamming).

Removing 3000 tons of permanent ballast from a PCTC and increasing the beam by 0.25 metres to achieve the same stability will reduce the propulsion power demand by 8.5%.

The use of lightweight structures can reduce the ship weight. In structures that do not contribute to ship global strength, the use of aluminium or some other lightweight material may be an attractive solution.

The weight of the steel structure can also be reduced. In a conventional ship, the steel weight can be lowered by 5-20%, depending on the amount of high tensile steel already in use.

A 20% reduction in steel weight will give a reduction of ~9% in propulsion power  requirements. However, a 5% saving is more realistic, since high tensile steel has already been used to some extent in many cases.

Finding the optimum length and hull fullness ratio (Cb) has a big impact on ship resistance.

A high L/B ratio means that the ship will have smooth lines and low wave making resistance. On the other hand, increasing the length means a larger wetted surface area, which can have a negative effect on total resistance.

A too high block coefficient (Cb) makes the hull lines too blunt and leads to increased resistance.

Adding 10-15% extra length to a typical product tanker can reduce the power demand by more than 10%.

The Interceptor is a metal plate that is fitted vertically to the transom of a ship, covering most of the breadth of the transom. This plate bends the flow over the aft-body of the ship downwards, creating a similar lift effect as a conventional trim wedge due to the high pressure area behind the propellers. The interceptor has proved to be more effective than a conventional trim wedge in some cases, but so far it has been used only in cruise vessels and RoRos. An interceptor is cheaper to retrofit  than a trim wedge.

1-5% lower propulsion power demand. Corresponding improvement of up to 4% in total energy demand for a typical ferry.

A ducktail is basically a lengthening of the aft ship. It is usually 3-6 meter long. The basic idea is to lengthen the effective waterline and make the wetted transom smaller. This has a positive effect on the resistance of the ship. In some cases the best results are achieved when a ducktail is used together with an interceptor.

4-10% lower propulsion power demand. Corresponding improvement of 3-7% in total energy consumption for a typical ferry.

The shaft lines should be streamlined. Brackets should have a streamlined shape. Otherwise this increases the resistance and disturbs the flow to the propeller.

Up to 3% difference in power demand between poor and good design. A corresponding improvement of up to 2% in total energy consumption for a typical ferry.

The skeg should be designed so that it directs the flow evenly to the propeller disk. At lower speeds it is usually beneficial to have more volume on the lower part of the skeg and as little as possible above the propeller shaftline. At the aft end of the skeg the flow should be attached to the skeg, but with as low flow speeds as possible.

1.5%-2% lower propulsion power demand with good design. A corresponding improvement of up to 2% in total energy consumption for a container vessel.

The water flow disturbance from openings to bow thruster tunnels and sea chests can be high. It is therefore beneficial to install a scallop behind each opening. Alternatively a grid that is perpendicular to the local flow direction can be installed. The location of the opening is also important.

Designing all openings properly and locating them correctly can give up to 5% lower power demand than with poor designs. For a container vessel, the corresponding improvement in total energy consumption is almost 5%.

Compressed air is pumped into a recess in the bottom of the ship’s hull. The air builds up a “carpet” that reduces the frictional resistance between the water and the hull surface. This reduces the propulsion power demand. The challenge is to ensure that the air stays below the hull and does not escape. Some pumping power is needed.

Saving in fuel consumption:

• Tanker: ~15 % 
• Container: ~7.5 % 
• PCTC: ~8.5 % 
• Ferry: ~3.5%

Part 2 of this series focuses on ship propulsion technology.  

Installing wing thrusters on twin screw vessels can achieve significant power savings, obtained mainly due to lower resistance from the hull appendages.

The propulsion concept compares a centre line propeller and two wing thrusters with a twin shaft line arrangement.

Result: Better ship performance in the range of 8% to 10%.  More flexibility in the engine arrangement and more competitive ship performance.

Counter rotating propellers consist of a pair of propellers behind each other that rotate in opposite directions. The aft propeller recovers some of the rotational energy in the slipstream from the forward propeller. The propeller couple also gives lower propeller loading than for a single propeller resulting in better efficiency.

CRP propellers can either be mounted on twin coaxial counter rotating shafts or the aft propeller can be located on a steerable propulsor aft of a conventional shaft line.

CRP has been documented as the propulsor with one of the highest efficiencies. The power reduction for a single screw vessel is 10% to 15%.

The propeller and the ship interact. The acceleration of water due to propeller action can have a negative effect on the resistance of the ship or appendages. This effect can today be predicted and analyzed more accurately using computational techniques.

Redesigning the hull, appendages and propeller together will at low cost improve performance by up to 4%.

The rudder has drag in the order of 5% of ship resistance. This can be reduced by 50% by changing the rudder profile and the propeller. Designing these together with a rudder bulb will give additional benefits.

Improved fuel efficiency of 2% to 6%.

Advanced blade sections will improve the cavitation performance and frictional resistance of a propeller blade.   As a result the propeller is more efficient.

Improved propeller efficiency of up to 2%.

Winglets are known from the aircraft industry. The design of special tip shapes can now be based on computational fluid dynamic calculations which will improve propeller efficiency.

Improved propeller efficiency of up to 4%.

Installing nozzles shaped like a wing section around a propeller will save fuel for ship speeds of up to 20 knots.

Up to 5% power savings compared to a vessel with an open propeller.

For controllable pitch propellers, operation at a constant number of revolutions over a wide ship speed reduces efficiency. Reduction of the number of revolutions at reduced ship speed will give fuel savings.

Saves 5% fuel, depending on actual operating conditions.

Wing-shaped sails installed on the deck or a kite attached to the bow of the ship use wind energy for added forward thrust. Static sails made of composite material and fabric sails are possible.

Fuel consumption savings:

• Tanker ~ 21%
• PCTC ~20%
• Ferry ~8.5%

Spinning vertical (Flettner) rotors installed on the ship convert wind power into thrust in the perpendicular direction of the wind, utilising the Magnus effect. This means that in side wind conditions the ship will benefit from the added thrust.

Less propulsion power is required, resulting in lower fuel consumption.

The new VS 4146 PLV design

Wärtsilä announced today that it has won a key contract in Brazil to supply the design and propulsion and positioning systems for a series of two new flexible pipe laying vessels (PLVs).  The vessels will be built at DSME in Korea and were ordered by a joint venture between Technip and the Brazilian oil & gas company, Odebrecht Óleo & Gás (OOG). Once completed, the vessels will work on a long-term charter in Brazilian waters for Petrobras.

Wärtsilä says the contract represents a major breakthrough for Wärtsilä Ship Design in Brazil as well as their ongoing relationship with one of the world’s major shipyards, DSME.

“The selection of Wärtsilä Ship Design for this important and challenging project reflects our strong global track record in designing state-of-the-art pipe laying vessels,” says Riku-Pekka Hägg, Vice President Ship Design, Wärtsilä Ship Power. “These ships will be a high profile representation of our capabilities in this area for oil and gas companies operating in Brazilian waters.”

The new VS 4146 PLV design has been tailored to the stringent requirements of both the owners and Petrobras. The vessels, which have a high pipe lay tension capacity of 550 tonnes, are designed to achieve optimal fuel consumption in the design conditions, and to meet the need for efficient flexible pipe laying operations. They will be utilized mainly to install umbilical and flexible flow lines and risers to connect sub-sea wells to floating production units in waters more than 2,500 meters deep.

Harvey Gulf International has awarded a contract to Wärtsilä to supply liquified natural gas propulsion equipment for two of Harvey Gulf’s newbuild offshore support vessels for operation in the Gulf of Mexico.  Once completed, the supply vessels will be the first ever U.S.-flagged offshore supply vessels to be powered by LNG.

The OSV’s will be based on the STX Marine Inc SV310DF design and are to be powered by Wärtsilä 6-cylinder 34DF dual-fuel engines. The vessels, with LNG storage capacity of 290 cubic meters (m3), will have more than a week of vessel operational time. In addition, the vessels will have the capacity to carry 5520 tons of deadweight at load line and have a transit speed of 13 knots.

The Wärtsilä 34DF engine is capable of running on either gas or diesel fuel with full EPA emissions Tier 2compliance.  When running in gas mode, NOx emissions are reduced by some 85 percent compared to diesel operation.  Furthermore, Sulphur oxide emissions are completely eliminated and emissions of CO2 are also lowered.  The contract includes options for supplying propulsion equipment for additional follow-on vessels.

In addition to being powered by cleaner burning natural gas, the vessels will achieve “ENVIRO+, Green Passport” Certification by the American Bureau of Shipping.  The requirements for this certification include, among others, that the vessels be continuously manned with a certified Environmental Officer, be completely constructed with certified environmentally friendly materials, and have advanced alarms for fuel tanks and containment systems.  Along with Harvey Gulf’s other vessels under construction, they will be the first OSV’s to achieve this certification, making them the most environmental friendly OSV’s in Gulf of Mexico.

The OSV’s are reportedly being built by Trinity Offshore, a subsidiary of Trinity Yachts Corporation, at Trinity’s Gulfport, MS yard.  The vessels are scheduled for delivery in 2013 and will operate in the Gulf of Mexico.