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Wind propulsion

Björn Allenström ,

SSPA Sweden AB

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Content:

• Introduction

• Auxiliary energy sources

• Wind propulsion

– Kites

– Flettner rotors

– Sails (EffSail)

• Comparison kites, rotors and sails

• Conclusions

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Introduction

We have been sailing for a 1000 years, why did it end?

• Difficult to be ’on time’?

• Large crews?

• Inexpensive fuel?

• No environmental concerns?

• Better engines?

East Indiaman Götheborg III Vidfamne Bark Viking

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Auxiliary energy sources

• Wave energy Theoretically possible and demonstrated at

small scale but yet not practical for large ships.

• Solar energy Demonstrated at large scale.

Very limited savings in propulsive power ( about 2 %).

Expensive installation cost.

Produces electricity instead of wind thrust.

M/V Auriga Leader

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Auxiliary energy sources

• Wind energy Several alternatives available producing thrust:

Textile: Kites (SkySails) and textile sails (DynaRig)

Non textile sails: Suction sails (Turbosail), flap sails,

fixed sails (EffSail)

Rotors

Wind turbines

give electricity

or both thrust

and electricity.

Maltese Falcon (DynaRig)

ORACLE

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Kites

MS Beluga using a 160 m2 SkySail kite

Artist’s impression. In EffShip the panamax Stena Companion was used as a reference ship with a 640 m2 kite.

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Kite mathematical model I

Assumptions:

• Traction line is always straight. It is not elastic and has no extension.

• The flying track is predefined in a butterfly shape by given coordinates of nineteen points along the track.

• The kite mass is negligible in the simulation.

• The built-in kite angle of attack is set to 4 degrees. This has been verified against full scale data.

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Kite simulations

• Aerodynamic forces were calculated based on the effective relative wind velocity and the optimum angle of attack.

• The radial component of the aerodynamic forces provided a traction force in the connection line. The traction force contributed to forces and moments acting on the simulated ship.

• Throughout the simulations, forces, moments, and motions of the tanker were recorded, as well as rudder angle and propeller efficiency. These output variables were plotted and analyzed to describe the influence of the auxiliary kite propulsion on ship performance.

• The result shows that auxiliary kite propulsion can play a significant role in reducing engine power in beam and following sea conditions. The course keeping ability of the simulated Panamax tanker was under control while using the kite.

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Flettner rotor Magnus effect

Anton Flettner racing

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SSPA tests in the 80s

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Flettner rotors

Enercon E-Ship

Green Waves test rig

Anton Flettner’s ’Buckau’ with two rotors instead of sails

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Rotor mathematical model

0

2

4

6

8

10

12

0 1 2 3 4 5

Cl,

Cd

spin ratio alfa

Rotor lift and drag coefficients

Cl

Cdhigh

Cdlow

α = πnD/V n= rotor revs Cl=FL/(½ ρ D H V2) Cd=FD/(½ ρ D H V2) FL is the lift force (N) FD is the drag force (N) Ρ is the density of air (kg/m3) D is the rotor diameter (m) H is the rotor height (m) V is the resulting wind velocity (m/s) Cm = 0,0057α2 - 0,0021α + 0,0089 M=½ ρ H D2 V2 Cm P= 2 M V α / ( η D)

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Rotor thrust

V

T

FL

FD

F

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Rotor vortices

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EffSail

From CFD calculations using FLUENT a symmetric profile with camber has been developed giving a lift coefficient Cl= 1 with a drag coefficient Cd=0.1

0,000

1,000

2,000

3,000

4,000

0 2 4 6 8 10 12 14 16 18 20

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EffShip panamax with rotors and sails Rotor projected area 530 m2

Sail projected area 3 550 m2

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EffShip Delivered power for panamax from SEAMAN simulations

0

2000

4000

6000

8000

10000

12000

14000

0 30 60 90 120 150 180

de

live

red

po

we

r P

d (

kW)

True wind dir. (degr.)

12 kn, 6 m/s

12kn, 9 m/s

12 kn, 12 m/s

12 kn, 15 m/s

14 kn, 6 m/s

14kn, 9 m/s

14 kn, 12 m/s

14 kn, 15 m/s

16 kn, 6 m/s

16kn, 9 m/s

16 kn, 12 m/s

16 kn, 15 m/s

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Results from simulations using kite

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

90 120 150 180

red

uct

ion

(-)

true wind dir. (degr.)

Reduction in power using kite

12 knots, 9 m/s

12 knots, 12 m/s

12 knots, 15 m/s

14 knots, 9 m/s

14 knots, 12 m/s

14 knots, 15 m/s

16 knots, 9 m/s

16 knots, 12 m/s

16 knots, 15 m/s

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Results from simulations using rotors

0

0,2

0,4

0,6

0,8

1

1,2

0 30 60 90 120 150 180

red

uct

ion

fac

tor

(-)

true wind dir. (degr.)

Reduction in power for panamax using rotors 150 rpm

12 kn, 6 m/s

12kn, 9 m/s

12 kn, 12 m/s

12 kn, 15 m/s

14 kn, 6 m/s

14kn, 9 m/s

14 kn, 12 m/s

14 kn, 15 m/s

16 kn, 6 m/s

16kn, 9 m/s

16 kn, 12 m/s

16 kn, 15 m/s

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Results from simulations using EffSail

0

0,2

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0,8

1

1,2

0 30 60 90 120 150 180

red

uct

ion

fac

tor

(-)

true wind dir. (degr.)

Reduction in power for panamax using EffSails

12 kn, 6 m/s

12kn, 9 m/s

12 kn, 12 m/s

12 kn, 15 m/s

14 kn, 6 m/s

14kn, 9 m/s

14 kn, 12 m/s

14 kn, 15 m/s

16 kn, 6 m/s

16kn, 9 m/s

16 kn, 12 m/s

16 kn, 15 m/s

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0

2000

4000

6000

8000

10000

12000

14000

0 30 60 90 120 150 180

Po

we

r (k

W)

true wind direction (degr.)

Power at 14 knots for panamax

As built 6 m/s wind

With sail, 6 m/s wind

With rotor 6 m/s wind

As built 15 m/s wind

With sail 15 m/s wind

With rotor 15 m/s wind

With kite 15 m/s wind

Comparison kite, rotors and EffSails

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Journey Caracas-Rotterdam

Mean wind speed and direction over year mid

Atlantic

Wave direction

Wave

height Wind speed Frequency

[m] [m/s] [%]

Head sea 1,24 7,9 17,1

Bow sea (SB) 1,12 7,6 7,8

Bow sea (P) 1,49 8,6 19,8

Beam sea (SB) 1,09 7,5 7

Beam sea (P) 1,71 9,3 13,2

Quartering sea (SB) 1,17 7,7 10,7

Quartering sea (P) 1,71 9,3 12,7

Following sea 1,31 8,1 10,7

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saving

all year/winter %

ship speed (kn) sail rotor kite

12 21/24 15/17 9/10

14 17/20 13/15 6/7

16 12/14 9/10

Round trip Rotterdam-Caracas

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Assumptions:

Costs (kEUR) EffSail Rotor Kite

Investment 1 500 2 000 1 500

Maintanence/

year 50 50 100

0

5

10

15

20

25

12 14 16

pay-b

ack t

ime (

year)

ship speed (kn)

500 EUR/ton

0

5

10

15

20

25

12 14 16

pay-b

ack t

ime (

year)

ship speed (kn)

1000 EUR/ton

sail

rotor

kite

Does it pay off?

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Fuel Oil Price Scenario

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

2020

2021

2022

2023

2024

2025

2026

2027

2028

2029

2030

CO2 surcharge

MGO premium

IFO 380

Source GL

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0

2

4

6

8

10

12

14

16

18

20

6 8 10 12 14 16 18

PD

T (

MW

)

Ship speed (knots)

Delivered power for a panamax tanker

80%

reduction

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Conclusions

• Fixed sails (e.g. EffSail) is probably the most efficient and cost effective way to use wind energy

• The drawback of fixed sails is the sight from the bridge

• Rotors are much more effective than sails per area, but probably more expensive and more complicated

• Rotors might cause vibrations

• Kites are very effective in following winds and are a proven design but can show a high payback time.

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Conclusions, cont.

• All wind propulsors need a relatively high wind speed to be attractive for fuel cost reduction

• Today’s fuel prices give a payback time that is not satisfactory except if costs can be kept low and efficiency high (EffSail)

• For a large ship such as a panamax neither sails, rotors nor kites affect the ship’s overall behaviour significantly as long as the propeller gives thrust

• For future ship designs one must consider the actual wind conditions on the expected route to evaluate if and how wind energy can be used

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Thank you!