Introduction of the Sway Turbine ST10

IQPC 3rd International Conference

Drivetrain Concepts for Wind Turbines

22-24 October 2012

Swissôtel Bremen, Germany

Introduction of the

Sway Turbine ST10

Eystein Borgen

CTO Sway Turbine AS

1

Sway Turbine AS proprietary

Reproduction without written permission strictly forbidden

2

To be presented:

• Sway Turbine’s new large

diameter generator technology

with ironless stator core

• Generator and blade rotor

integration

• Weight and cost advantages

• Cost of energy prospects

compared to state of the art DD

turbines



Who are we?

– Sway AS founded in Norway 2000 (floating foundations for wind turbines)

– De-merged into two independent companies in 2010:

– Sway AS (development of floating foundations for wind turbines)

– Sway Turbine AS (10MW wind turbine development, for fixed and floating foundations)

– Sway Turbine AS is a technology company

– Commercialization of the technology with preferred industrial partner(s)



The challenge

• High Balance of Plant cost per unit related to:

– Installation

– In-field transmission (connection by submerged cable)

– Operation & Maintenance (O&M)

• Less units, i.e. larger turbines, may reduce the above costs

BUT: The cost per MW of the wind turbine itself increases by size (cube-square law)

• 10MW turbine development with ironless generator stator initiated by Sway Turbine in 2005 to overcome this challenge

• Approximately 70 engineers have been involved

• € 20 million spent on the development and design phase



Top Head Mass comparison

Mass conventional DD turbine (te)

Sway Turbine scaled to 5MW (te)

Comment

280 201/ 185*

*Blade supports in composite (-34%)

Mass conventional DD turbine (te) Sway Turbine ST10 (te)

Comment

770 625 Prototype mass (-19%)

570 Expected mass after optimalisation (-26%)

530 Blade supports in composite (-31%)

Top Head Mass of 5MW-115m diameter rotor

Top Head Mass of 10MW-164m diameter rotor



ST10 specification • Power regulation: Pitch regulated with variable speed

• Rated power: 10MW

• Cut-in wind speed: 4 m/s

• Cut-out wind speed 28 m/s

• Nominal rotor speed 12 rpm (tip speed 103m/s)

• Operational temperature range : -10- +30 deg C (North sea)

• Extreme temperature range: -20- +40 degC

• Wind class IEC: IEC S

• Annual average wind speed: 10,0 m/s

• Turbulence intensity: IEC B

• Structural design lifetime: 20 years

• Main bearings design life time: 40 years +

• Rotor diameter: 164 m

• Blade length: 67 m

• Generator type: PM synchronous axial flux with ironless stator windings

• Nominal generator voltage: 3.5kV

• Converter type: Full 4Q converter



Why ironless stator core?

Ironless stator core

• No attracting forces. No cogging, ”forgiving” to large air gap variations, flexible generator structure possible

• More usage of magnets on same dimensions, stator is a part of the air gap

• Large generator diameter reduces the magnet usage.

• No laminated iron in either the stator or rotor

• Generator structure lighter

Iron core

• Large forces between rotor and stator in case off centered, High stiffness and production tolerances needed.

• Less magnet usage on same dimensions, due to small air gap

• Air gap integrety brings on a lot of mass for larger diameters (T ~ k*D^2*L). Large diameter difficult to realize



Permanent Magnets in Generator

• Low cost magnets can be used (35-40% lower price)

• The total cost of PM is equivalent to a conventional PM machine.

• There is no laminated iron in either the stator or rotor, saving considerable cost relative to conventional direct drive generators

• The generator structure in the ST10 is 55-60% lighter than in an equivalent size conventional DD PM generator

• Total cost saving of generator of approx. 20%



• Parametrizized model

• OD, L, f,ag, and current loading varied

• 65 000 machines investigated

• Sensitivity curves used as design

input for the overall design

• Electro magnetic calc’s calibrated with 50kW . scaled prototype

Optimizing the generator



Main Features, Generator

-

• Segmented 25m diameter generator

• Passive air cooling through open air gap

• Both stator segments and rotor magnets totally

encapsulated to resist the offshore environment



Generator stator

De-moulding of full scale stator segments



Generator and blade rotor integration

10MW -164m rotor diameter:

Generator mass:

Conv. PM DD:373te

ST10: 162te

6% less turbine costs

Blade mass (3 off)

Conv. :133te

ST10: 71te

10%-4%= 6% less turbine costs

2 ”small” main bearings on fixed

shaft

Several suppliers identified for

each of the large components

Main bearing masses:

Conventional PM DD:18te

ST10: 2x4te

6% less turbine costs



Sway Turbine 10MW.wmv


-

• Special direct coupling

between blade rotor

and generator short

torque loop saves

weight +air-gap in

generator not affected

by the rotor blade loads

• Generator rotor

yoke has double

function; carries

both magnetic flux

and edgewise

gravity loads

between the

blades




-

• Generator rotor and stator

included in global dynamic

analysis (air gap

clearances and forces)

• Inertial loads

• Short circuit

• Thermal expansion

Vibration sources:

• No gear box

• No generator cogging

• Bearings only vibration

source



Maintenance

All components except blades, main structural steel, main bearings and yaw bearing can be replaced by onboard crane and special tools



Weight and cost advantages

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800,00

1000,00

1200,00

0 2 4 6 8 10 12

we

igh

t (t

e))

Size (MW)

Top head Weight comparison, Large rotor size

Conventional PM DD Turbine weight (331W/m2)

Sway Turbine weight (331W/m2)

Issue to keep in mind:

• Extensive thrust clipping (latest

6-7MW conventional designs)

reduces weight of turbine but

also reduces annual energy

production

The ST10 uses only limited thrust

clipping

The overall Sway Turbine solution

should result into 20-30% lower

weight and 15-20% lower turbine

cost

0,00

100,00

200,00

300,00

400,00

500,00

600,00

700,00

800,00

0 2 4 6 8 10 12

we

igh

t (t

e))

Size (MW)

Top head Weight comparison, medium rotor size

Conventional PM DD Turbine weight (480W/m2)Sway Turbine weight (480W/m2)



Cost of Energy (CoE) input assumptions

• 490MW wind farm 40km from shore, 30m water depth (fixed) and 120m

water depth (floating).

• IRR of 10.9% on the total wind farm CAPEX

• Manufacturing costs are based on European costs levels

• 3 different generator to rotor area ratios; medium (480W/m2), medium to large (405W/m2) and large (331W/m2)

The Cost of Energy calculations includes: • Electrical grid connection to shore + onshore grid reinforcement • 33% additional costs of wind turbine due to offshore application (additional

corrosion protection, landing platforms, market factor, warranty risk etc) • 10% contingency on total farm Capex and 10% profit to the OEM.



CoE fixed foundations, 10m/s

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18

0 5 10 15 20 25

Co

st o

f En

erg

y (€

cen

t/kW

h)

Turbine size (MW)

COE - Conventional DD PM turbines versus Sway Turbine (ST), both on fixed foundations, 10m/s site, 10.9%IRR, Foundation and installation calibrated with wind farm operator’s cost model.

Conventional Turbine DD PM Medium rotor diam. 480W/m2 on fixed foundation

Conventional Turbine DD PM Medium to large rotor diam. 405W/m2 on fixed foundation

Conventional Turbine DD PM Large rotor diam. 331W/m2 on fixed foundation

Sway Turbine (ST) Medium rotor diam 480w/m2 on fixed foundation

Sway Turbine (ST) Medium to large rotor diam. 405W/m2 on fixed foundation

Sway Turbine (ST) Large rotor diam. 331W/m2 on fixed foundation

ST10-164



CoE fixed foundations, 9m/s

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15

16

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18

19

20

0 5 10 15 20 25

Co

st o

f E

ne

rgy

(€

cen

t/k

Wh

)

Turbine size (MW)

COE - Conventional DD PM turbines versus Sway Turbine (ST), both on fixed foundations, 9m/s site, 10.9%IRR, Foundation and installation calibrated with wind farm operator’s cost model.

Conventional Turbine DD PM Medium rotor diam. 480W/m2 on fixed foundation

Conventional Turbine DD PM Medium to large rotor diam. 405W/m2 on fixed foundation

Conventional Turbine DD PM Large rotor diam. 331W/m2 on fixed foundation

Sway Turbine (ST) Medium rotor diam 480w/m2 on fixed foundation

Sway Turbine (ST) Medium to large rotor diam. 405W/m2 on fixed foundation

Sway Turbine (ST) Large rotor diam. 331W/m2 on fixed foundation

ST10-164



CoE floating, 10m/s

12

13

14

15

16

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19

20

0 5 10 15 20 25

Co

st o

f En

erg

y (€

cen

t/kW

h)

Turbine size (MW)

COE - Conventional DD PM turbine versus Sway Turbine, both on Sway foundations, 10m/s site, 10.9%IRR

Conventional Turbine DD PM Medium rotor diam. 480W/m2- on Sway floating foundation

Conventional Turbine DD PM Medium to large rotor diam. 405W/m2- on Sway floating foundation

Conventional Turbine DD PM Large rotor diam. 331W/m2- on Sway floating foundation

Sway Turbine (ST) Medium rotor diam. 480W/m2- on Sway floating foundation

Sway Turbine (ST) Medium to large rotor diam. 405W/m2- on Sway floating foundation

Sway Turbine (ST) Large rotor diam. 331W/m2- on Sway floating foundation



Summary: (apple to apple 10MW-164m rotor diam.)

Generator -6% turbine cost

Blades -6% turbine cost

Main bearing -6% turbine cost

Misc. -4% turbine cost

Fewer units. Less balance of plant costs.



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Thank you! Sway Turbine AS proprietary


Documents

Introduction of the Sway Turbine ST10