ENERGY SAVING IN SHIPS

Markku KanervaDeltamarin Ltd

Meriliikenne ja Ympäristö8.-9.12.2005 Hanasaari, Espoo

ENERGY SAVING IN SHIPS

Fuel & energy consumption can be divided in three main categories:

HYDRODYNAMICS AND PROPULSIONENERGY PRODUCTIONSHIP SYSTEMS

This presentation concentrates mainly on hydrodynamics and propulsion.Other areas will be covered briefly.

ENERGY SAVING – KEY WORDS

The following principles should be followed:Clarification of state of the art.Set objectives for required propulsion power and energy consumption.Use organisations with known, good references.Ask for third party reviews.Utilise references and modern tools.Avoid sub-optimisation.Study alternative solutions.

OPTIMISE BUT REMEMBER: OPTIMUM IS NOT YET REACHED!

IMPROVED PERFORMANCE -HYDRODYNAMICS

Typical rate for improvements 5% per 5 years.However, sometimes quantum leaps are taken, 10-15%.How is this possible?

Growing interest in hull form development.Extended model test series, not just trial speed.Use of CFD, potential and most recently viscous (RANSE code).Better understanding of actual flow and wave making.Better specifications.

POTENTIAL SAVINGS

ENERGY SAVING - FERRIESFast full displacement ferries

Mega Express 1, delivered 2000LWL 160 mB 24.8 mT 6.25 mDisplacement 14,910 m3

27 knots with 28,300 kWFerry delivered in 1996

LWL 165,2 mB 24 mT 6.25 mDisplacement 14,860 m3

27 knots with 32,000 kW

DIFFERENCE OF 13%

ENERGY SAVING – CRUISE SHIPS

Speed-power curves of two cruise ships1. Panamax cruise ship designed 7 years ago, 81,000 grt.2. Postpanamax cruise ship of today, 118,000 grt.13,800 tons of additional displacement but same performance.

ENERGY SAVING – STATE OF THE ART

Easily comparable coefficients, first checkSuch as Power Coefficient, Admiralty Coefficient,Heickel Coefficient

∇ displacement in m3

PB engine power in kWVs ship trail speed in m/s

sB

xVP

K 3/1)( ∇=

’Mega Express’ is the third curve from the right.

ENERGY SAVING – STATE OF THE ART

Froude number

g = 9.81 m/s2

L = waterline length

Curves on left for conventional ferries, speed 20-22 knots.Curves on right for fast full displacement ferries, speed 25-30 knots.

ENERGY SAVING – STATE OF THE ART

gLV

Fn s=

ENERGY SAVING – MAIN CHARACTERISTICS

Example – Ferries

Fast full displacement ferries, Fn above 0.30Length over beam not less than 6.Block coefficient 0.57-0.63.Midship section coefficient 0.950-0.99, the shorter the vessel, the lower the figure.Longitudinal centre of buoyancy, LCB, between –2.6% to –3.6% of Lpp aft of midships.

Froude number pushed towards Fn 0.40.

ENERGY SAVING – HULL FORM

Possible features and characteristics to improve performance of newbuildings and existing ships in all prevailing service conditions.Trial speedService speed in moderate and high seasShallow waterOperatational modes

MAIN FEATURESDucktail; typical potential 5…10%Interceptor configuration/trim wedge; typical potential 5…10%Ducktail & interceptor configuration/trim wedge together; typical outcome 10…15%Bulb & stem modification, so-called surface piercing bulb with soft stem; typical gain 3…7%Stabilizer fin box modification; typical potential 3…10%Rudder head-box & rudder design modification; typical gain 2…5% plus improved manoeuvrability & course stability (better course stability means smaller fuel consumption)Shaft line modifications (long water lubricated shaft & modern brackets); typical gain 2…4% plus reduced vibrationsNew propeller blades; typical gain 1…3% plus reduced noise & vibrations

Above modifications may have an interaction and combined improvement may not be sum of above figures.

Added Ducktail, Saving 8.5%Original aft body (Costa Classica) Modified aft body

5m

No interceptor

ADDED DUCKTAIL, SAVING 13%Original stern (Ferry) modified stern (wedge 4 deg.)

Interceptor Plate with fairingin Ducktail

Interceptor Development

Optimisation of interceptor configuration with viscous CFD toolFluent prior to model testing

Interceptor Plate with fairing

Interceptor plate’s influence on calm water performance

7%

10%

Modern Stem and Bulbous Bow

Surface piercing bulbous bow with soft stem.

Surface Wave Comparison Between Two Versions of Panamax Size Cruiser

(Calculated with the old program, waves strongly amplified)

Modified Bulb and Stem, Saving 8%Original Bow (Costa Classica) Modified Bow

~3m

~5m

Combined improvement of Added Ducktail with Modified Bulband Soft Stem 16,5%!

MODIFIED BULB, SAVING 5%Original Bow (Ferry, no bow ramp) Modified Bow

SMALLER FEATURES

Sea chest modifications; scallops & properly oriented gridsThruster tunnels; scallops & properly oriented gridsZinc anodes; removal from high flow speed areas (like rudders), aligning with local flow directionBilge keels; removal, resizing & better aligningAll hull openings in general; proper grids & scallopsPotential saving with all the a/m together is up to several percentages

Tunnel Thruster Location & Grid Alignment

Bow Thruster Tunnel Optimisation

Pressure distribution and turbulence around thruster tunnels

Shows area for improvement

Bow thruster tunnels

Alignment of tunnel positions to streamlines

Scallop design

Grid alignment/design

Look for evidence of stagnation pressuresSigns of turbulence generators

FERRY REFERENCE

Bow thrusters & AST, front view

FERRY REFERENCE

Grid on the foremost tunnel and scallop fairing behind the backmost tunnel

Stabfin recess (including stabfin)Depth of scallop

Design of stabfin for minimised drag (while not in-use)

Other stagnation pressures and turbulence generators

Control of swirling eddy

Most recent study shows drag coefficient variation of 15% for different designs

FERRY REFERENCE

Fin stabilizer on port side looking aft.

FERRY REFERENCE

Proposed modification for the fin stabilizers

FERRY REFERENCE

Use of fin stabilizers

Sea Chest grills

A single sea-chest opening has a small contribution to total drag (circ 0.02%) -but numerous!

Alignment of opening positions

Alignment of opening grillages

Grillage density

Large variations (circa 50%) in drag coefficient with grill alignments

Sea Chest OptimisationTypical, without scallop

Optimised, with scallop

HULL & PROPELLER SURFACEBetter anti-fouling & better hull surface smoothness; potential up to 6…7%Regular underwater hull cleaning; typical potential 1…3%Regular underwater propeller polishing; typical gain 1…2%Propeller coating; not tried yet, but very promising product available today (with guarantees?); potential 2…4%, plus reduced noise & vibrationsGrinding off the welding seams; potential 3…4%

RUDDER MODIFICATIONS

Improved low and high speed manoeuvrabilityImproved, better balanced profile, e.g. NACA 600 profilesImproved, non-cavitating performanceTwisted profile as neededEnd plates, simple, easy to installMost efficient combinations depending on required performance

ROUTE PLANNING & OPERATIONAL POLICIES

Route optimisation (scenario simulations & weather statistics) for current, water depth, waves, wind direction etc.Speed management, minimize the speed variation, together with route optimisation minimize the required average speed, minimize the time spent in harbours etc.Better autopilot control (better adaptation for prevailing conditions); big potential on podded shipsBetter fin stabilizer control & proper instructions (no idle use)Trim optimisation as a function of draft & speed

Comparison of Different Trims for a Cruiser

At speeds higher than 20 knots the trim of 0.5m by stern seems to be the optimum at that draughtAt all speeds the bow trims should be avoided

T=8.1m98.00

99.00

100.00

101.00

102.00

103.00

104.00

105.00

19.5 20 20.5 21 21.5 22 22.5 23 23.5 24

V (kn)

Ct (%

of e

ven

keel

)

Trim -1mTrim -0.5mEven keelTrim 0.5mTrim 1m

Auto-Pilot OptimisationContainer Vessel Auto-Pilot Optimisation (Part of large project addressing rudder fatigue for container vessel)

Average yearly fuel-losses due to course-deviations and rudder drag calculated for typical vessel voyage

Full range of auto-pilot settings considered.

Most efficient auto-pilot settings for wave direction and sea state recommended to owner.

OPERATION IN SHALLOW WATERIn shallow water the hull resistance and required propulsion power increases rapidly as the water depth decreases (at constant speed). Three essential phenomena happen:

relative water flow under the vessel bottom increasesvessel sinks and trims moreaft ship wave pattern is magnified!

SHALLOW WATER

OPERATION IN SHALLOW WATERShallow water has big increasing influence on propulsion power.At critical speed and water depth any increase of propulsion power only increases dynamic sinkage, trim and wave height. No speed increase is gained.Hull form and propeller configuration has an influence on shallow water performance.

SHALLOW WATER

SHALLOW WATER

Model test results of two ferries in deep and shallow water.

HEAVY SEAS PERFORMANCE

Extreme deck area requirementExtreme bow flareHigh wave induced impactsHigh accelerationsNoise and whipping vibrationsInvoluntary speed lossVoluntary speed loss, delaysStructural damages

BOW FLARE

Good rule of thumb

Minimum bow flare angle towards waterline50 degrees for unlimited service45 degrees for limited serviceNo large flat shapesOutwards bent section shape

Bow flare estimator - BFE

Simple tool for bow shape design verification.BFE = X / Lpp / tan αX = distance from midshipsLpp = perpendicular lengthα = smallest angle at station x against waterplane

Bow flare estimator

Bow flare - sustained speed

Two cruise ships compared: Oriana and Victoria.Flare angle difference at maximum 4-6 degrees.Both vessels sailing from Southampton to Madeira and to MediterraneanBig difference in operability.

Figures 8 & 9

Bow flare - sustained speed

Bow flare - sustained speedCruise liner comparisonin bow quartering seas

Downtime analysis bow flare impacts with 100 kN criterion

Version I Version II

Flare angle (minimum) 38.2º 43.6º

Downtime

20 knots 80 5

16 knots 68 4

12 knots 49 2

8 knots 39 0

Figures of average downtime exceeding the criterion 1/1000 of time.

Difference between the two versions being 94-96%!

Version II practically has no problem with this criterion.

Bow flare - sustained speedCRUISE LINER COMPARISONIn bow quartering seasDowntime analysisCombined criteria sustained speed and bow flare impacts, criterion 100 kN (noise and vibration)

Version I Bow flare impacts are limiting=> Voluntary speed loss

Version II Sustained speed is limiting=> Sea margin can be fully used

OPERATION

How to combine all above into a simple straight forward every day use, to take into account:

WindCurrentShallow waterEngine modesTrim Other possible operational features

Reliable, simple to use system on bridge required helping in all required calculations on line!

NAPA POWER

Software for:1. Planning routes, voyages and schedules

Voyage planningImmediate cost estimate of the planPlanning routes and itineraries

2. Optimizing the operation of the ship taking into account weather, currents, loading condition etc.

Finds the theoretical optimum operation of the ship in the givenconditionsFollows the optimal plan using speed pilot interfaceImmediate comparison of the plan with the minimum cost plan

3. Keeping the schedule by speed / ETA pilot

NAPA POWER includes

Accurate hydrostaticsAccurate calm water resistanceInfluence of wind forces and momentsInfluence of added resistance in wavesShallow water effects

Influence of drag due to drift and turningCalculation of steering forcesAccurate propulsion system modelMain engine specific fuel consumption envelopesOffice analysis tools

Examples from the ship installations

(Average Speed 22.6 knots)Average saving with NAPA Power 7.3% (13.8ton)

150

160

170

180

190

200

210

Weeks

Ton(

HFO)

2004 206,45 195,05 184,85 183,45 180,55 178,752005 184,65 182,75 180,25 179,15 160,65 158,95

1 2 3 4 5 6

6 weeks comparison excluding hotel load, saving 7.3%

SPONSON-DUCKTAIL MODIFICATIONS FOR IMPROVED STABILITY AND DEADWEIGHT

Sponson-ducktail is the most efficient external method to improve stability of a vesselBuoyancy – weight ratio is positive, additional deadweight can be gained Aft ship sponson is very sensitive for proper hydrodynamic designWorst case design can lead to 30% increase in required propulsion power meaning loss of two (2) knots in speedGood sponson design is a compromise between stability, deadweight and speed, and takes into account structural integrity, construction and installation

SPONSON-DUCKTAIL / BULBOUS BOW

Typical good design has the following main features:

Stability improvement in both stability lever and rangeAdditional deadweight gained from 150 tons up to 450 tons.No reduction in speed, best references with speed improvement up to 1 knotImproved behaviour in rough seasImproved performance in shallow waterReduced propeller induced noise and vibrations

Stockholm Agreement and Solas-90 conversion

Owner:Color Line AS

Main dimensions:LPP 181.60 mB 26.60 mT 6.10 m

Passengers 1875Trailers 43Cars 700

‘PRINSESSE RAGNHILD’

‘PRINSESSE RAGNHILD’Commission:

Stockholm Agreement & Solas 90Internal and external modificationsCFD calculationsModel tests at Marin and Marintek (seakeeping)Cooperation of numerical simulations and model tests at SSRC, Strathclyde UniversityNew bulbous bow

‘PRINSESSE RAGNHILD’

Benefits:Increased displacement and improved deadweightReduced ballast in fore shipBetter trimming capabilitiesOptimised performance on the route in deep and shallow waterCheck of performance in heavy sea states, no slamming risksReduced noise in aft ship

Performance comparison in model tests

‘PRINSESSE RAGNHILD’

New bulbous bow and open sea ducktailSpeed Original ship Deep water Shallow water (20m)

18 100 95,6 96,519 100 95,5 93,820 100 95,4 93,221 100 95,7 94,722 100 96,1 97,0

Figures in percentage of propulsion power, 100 % original ship.

Influence of modifications

Deep water Shallow waterBulbous bow Power reduction Power reductionSponson-ducktail Small power increase Small power reductionTOTAL Power reduction Power reduction

Investment in model test well paid. Both bulbous bow and sponson-ducktail installed.

‘PRINSESSE RAGNHILD’

All energy is in fuelReviewing overall power balance

Both mechanical and heat power originates from fuel. Thus fuel saving means:• Focusing on both energy production and consumption • Avoiding system or device operation at low efficiency modes• Running devices only when needed• Active overhauling • Improving existing systems to meet ships actual operation modes

CRUISE SHIP; MEASURED AT SEA

5217

0 65

18617

1790

12552

0 0 0 810

4994

310 20 860

21291

0

5000

10000

15000

20000

25000

PASSENGERCOMFORT

ELECTRICPRODUCTION

SAFETYSYSTEMS

PROPULSIONPRODUCTION

ENERGYPRODUCTION

POW

ER D

EMA

ND

IN

kW

MECHANICAL HEAT COOL

To prepare a proper energy balance we have to look all energy flows including not only mechanical, but also heating and cooling energy.We have also to approach the topic from two sides; How the energy is produced and how it is consumed.On a cruise vessel the major power consumption is concentrated on three main groups as seen on the graph which is based on actual measurements on one vessel:Passenger comfort includes items like air conditioning and fresh water production. There we need considerable amount of heat for fresh water production and mechanical and cooling power on cooling process with compressor cycle.Energy production includes mainly power plant engines and here the cooling power is clear single topic.Already this graph gives an idea that cooling power from energy production group should be used with maximum efficiency on heating purposes on passenger comfort group, and that there should be possibilities to avoid burning oil fired boilers.

All energy is in fuelReviewing overall power balance

Power analysis is only half of the truthand weak basis for energy evaluations

Calculation shows power, but not energy

When rated propulsion power is also included, it tends to overrule decision making process

Definition of energy efficiency calls for real operation profile

ELECTRIC POWER DEM AND ON ROPAX

18 %

4 %

44 %

4 %

13 %

15 %2 %Auxiliary machinery for

propulsionAuxiliary machinery for ship

HVAC

Galley, laundry andworkshops Cargo, deck, hull

Lighting

Navigation, radio,automation

ELECTRIC POWER DEMAND ON CRUISE SHIP

8 %4 %

53 %

14 %

5 %

15 %1 %Auxiliary machinery for

propulsionAuxiliary machinery for ship

HVAC

Galley, laundry andworkshops Cargo, deck, hull

Lighting

Navigation, radio,automation

Power analysis is only half of the truthand weak basis for energy evaluations

Electric load analysis, as carried out for each project, gives a good hint for energy flows. However the weakness is that this calculation considers only power, not energy. Electric load analysis shows how the power demand matches with power production, but nothing about energy efficiency. The missing parameter is actual operation profile which affects heavily on propulsion side but much less on other groups on electric load analysis.But if we remember all this, the analysis can be used when searching for most potential consumer groups for energy saving.These graphs are average values based on 15 cruise vessels and 15 ro-paxferries.We can see two groups which proportional share is very similar on both vessel types; Lighting and air conditioning, whereof air conditioning is clearly dominating.So it is worthwhile to dig this group deeper by basing the survey on actual measurements.

Energy is Power x TimeMeasured fuel consumption on Caribbean cruise ship

Regarding energy consumption,HVAC is as important topic as propulsion.

MEASURED FOR WHOLE CRUISE

33 %

67 %

propulsion other

MEASURED FOR WHOLE CRUISE

33 %

34 %

33 %

propulsion HVAC other

Energy is Power x TimeMeasured fuel consumption on Caribbean cruise ship

It is the port time which changes the whole picture since all the other consumption is pretty constant, but propulsion is missing.These measurements were done for two complete cruises and covering totally 12 days with measuring interval of two hours.When whole cruise is considered, including also port operations, we can see that there are two consumption groups which are equally important; Propulsion and air conditioning.The graph shows that air conditioning consumes equal amount of fuel than propulsion.One could assume that considerable fuel saving can be achieved by putting similar focus on air conditioning power consumption than what is put on propulsion and model testing

Optimising chiller operation

Optimum operation sequence of turbo and screw compressor is not similar.

Missing this feature can generate annual fuel cost penalty of about $90000 on a cruise vessel.

But is this considered in automation and control system design ?

COMPRESSOR RELATIVE EFFICIENCY

50

60

70

80

90

100

40 50 60 70 80 90 100ELELCTRICAL LOADING (%)

REL

ATI

VE E

FFIC

IEN

CY

(%

TURBO SCREW

Optimising chiller operationRunning a device far from optimum point is typical area where energy is easily lost. Good example is ac-compressor. There are two dominating compressor types, screw and centrifugal. Both have about equal efficiency but the shape of efficiency curve is totally different. So load sharing with these two compressor types must be different in order to avoid energy loss in parallel operation. However, if designer does not know this difference, he might select similar load control logics for both compressor types. Or if operator has experience from ship having one type of compressor and he runs other type in similar way it is easy to cause remarkable increase in fuel bill.Same applies in general in many systems onboard; Full load operation is not problematic, but real losses occurs when the system has to be operated at part load. Shape of the graph gives also a hint to consider one additional small compressor or sw heat exchanger for operation in cold waters.

Auditing – Evaluating - Improving

No heat is waste heat on cruise vessel.

Even small improvements on existing systems can generate considerable fuel savings due to reduced use of oil fired boilers.

$ 50 000 at annual basis on this case

Steam Consumption versus Engine Power for production of 2x400 t/d of Distillate

(Engine Load Distribution acc. to DELTAMARIN Recommendations)

0

1

2

3

4

5

6

7

8

9

10

11

12

5 10 15 20 25 30 35

Electrical Power (MW)

Stea

m C

onsu

mpt

ion

(t/h)

Old System 2x400 t/d

New System 2x400 t/d

Auditing – Evaluating - Improving

Waste heat is wrong wording on cruise ship. All heat is valuable and should be recovered effectively.However, since systems are typically designed for full power operation they seldom work effectively at part load. Same applies on heat recovery.If too high power demand and engine loading is assumed at design phase, the heat recovery installation is often too small at actual operation.Here is good real example, where an energy audit indicated, that oil fired boilers were needed almost continuously to cover the heat demand ofevaportors.On the other hand engines delivered excess heat which was dumped on central coolers. On this example small improvements in diesel heat recovery circuit reduced boiler running hours considerably and allowed annual fuel savings worth 50 000 $.

Some examples on HVAC systemsCruise vessel and todays fuel price

COP reduction from 4.5 to 4.4 cost 30 000 $/a

1 degC increase in condencer temperature cost 30 000 $/a

15 % reduced SW flow through condencer cost 30 000 $/a

100 kW lighting bulbs on air conditioned area cost 50 000 $/a

However, there is always a risk to draw false conclusions in energy saving evaluations if right ”control area” is missed.

Some examples on HVAC systemsCruise vessel and todays fuel price

There are numerous examples where clear savings can be achieved easily just by focusing on right areasOne decimal change in chiller efficiency happens very easily but the cost implication is seldom realised. Condensing temperature is easily increased due to dirty tubes. Already one degree increase cost 30 000 $ annually due to reduced COP. 4-5 degrees is typical for dirty condenser.Worn-out impeller on sea water pump reduces condenser capacity. Already 15% reduction cost again same 30 000 $ at annual basis.Efficient way to save energy is to reduce heat load. 100 kw incandescent lamp load cost 50 000 $ annually both in direct electric cost and indirectly in cooling cost. Attention should be paid on bulb ratings and shutting down lights on unoccupied areas. The clue is to reduce heat sources, design systems for flexible loading and let them work at optimum areas and well maintained.Most important issue on energy saving evaluations is to consider right control area. It is not saving if temperature on one area is rised in order to save cooling energy but simultaneously heat is transferred to adjacent area and to be treated from there.

Training is the clue to see the big pictureFuel saving needs a continuous process:

1. Auditing of actual energy consumption flows and main consumers

2. Evaluation of operation modes of these key consumers

3. Improving running and operation practises and system design

4. Training to understand how the single devices affect on whole system performance

IMPROVEMENT

EVALUATION

AUDITING

TRAINING

Training is the clue to see the big picture

Understanding the big picture is crucial when evaluating energy flows and fuel saving potential.

When the crew, and all other involved, are trained for this, it is easier for them to carry out energy audits, evaluate continuously system operation performance, understand the importance to keep the sensitive systems in good condition, improve the onboard solutions and bring general energy thinking into all activities onboard.