Offshore Wind 2004 From Vindeby to Nysted A Manufacturer’s Experience Henrik Stiesdal Bonus Energy A/S

Bonus’ Offshore Wind Farms 6 Offshore Projects, Turbines, total 245 MW

Long-Term Strategy The long-term strategy behind offshore activities: Get one of the first, moderate-size demonstration projects to acquire longest possible experience Base offshore projects on proven turbine technology to avoid combination of new technology risks with offshore risks Accept early offshore projects only in shallow and/or less exposed waters and refuse projects in deep and/or exposed waters until complete offshore technology (turbine modifications, installation, service) proven

Vindeby

Vindeby, Main Project Data World’s first offshore wind farm: 11 x 450 kW, 1991 Built by ELKRAFT, owned by SEAS for demonstration of potential in offshore wind power Bonus scope of supply: Turbines, SCADA, installation, 2 years WOM Total project cost 7.0 M£ (1991) = 9.1 M£ (2003) Total project cost per MW installed 1.8 M£ (2003) Cost of Bonus supply 47% of total project cost

Vindeby, Turbine Details Offshore modifications implemented at Vindeby: Built-in nacelle crane for service works, can install larger crane for main component replacement Totally enclosed nacelle and tower Cooling with heat exchanges for gearbox and generator Climate control with dehumidifiers in nacelle and tower Transformer in bottom of tower

Vindeby, Infrastructure Details Essentially an onshore wind farm moved offshore: Water depths 2-5 m Moderate fetch (10-15 km) in prevailing wind direction Turbines in two rows, 8.5 D spacing in rows, 8.5 D spacing between rows Concrete caisson foundations, conical top to act as ice- breaker 10 kV wind farm grid voltage 10 kV land connection

Vindeby, Installation Installation by onshore methods moved offshore: Foundations and electrical infrastructure installed separately by others Turbines installed with normal onshore mobile crane placed on standard offshore barge Turbines shipped two at a time, completely assembled with rotors 11 turbines installed in 12 days

Vindeby, Experiences 12½ years of operation with no major problems: High turbine availability Climate control very efficient - turbines as new inside Higher incidence of lightning strikes than onshore Moveable crane for main components not used Conical foundations cause access problems due to standing waves Useful weather windows sometimes significantly shorter than predicted by statistics 10 kV voltage level for internal grid and land connection causes substantial grid losses (7%)

Vindeby, Landing Arrangements

Vindeby, Energy Production

Middelgrunden

Samsø

Nysted

Nysted, Main Project Data World’s largest offshore wind farm: 72 x 2.3 MW, 2003 Built by E2, owned jointly by E2, DONG and Sydkraft Bonus scope of supply: Turbines, SCADA, installation, 5 years WOM Total project cost app. 140 M£ (2003) Total project cost per MW installed app M£ (2003) Cost of Bonus supply app. 60% of total project cost

Nysted, Turbine Details Updated offshore modifications based on Vindeby: Built-in nacelle crane for service works, can install two versions of larger cranes Totally enclosed nacelle and tower Cooling with heat exchanges for gearbox and generator, temperature control in narrow range Climate control with dehumidifiers in nacelle and tower Transformer in bottom of tower Automatic lubrication systems with 12+ months capacity Permanent on-line machine condition monitoring Dynamic power factor correction system and fault-ride- through capability

Nysted, Infrastructure Details A true offshore wind power plant: Water depths 5-10 m Substantial fetch ( km) in prevailing wind direction Turbines in grid pattern, 5.8 D spacing in rows, 10.3 D spacing between rows Ballasted concrete pedestal foundations, inverted cone at top to act as ice-breaker 33 kV wind farm grid voltage 132 kV land connection

Nysted, Installation A true offshore installation setup: Foundations and electrical infrastructure installed separately by others Turbines installed with A2SEA vessel Turbines shipped four at a time, loaded on vessel as towers in two sections, nacelles, and completely assembled rotors 72 turbines installed in 81 days

Nysted, Installation

Nysted, Experiences Project still at early operational stage: Installation and commissioning according to schedule Taking-Over achieved one month ahead of schedule Minor teething troubles, mainly electrical and aerial warning lights Availability since Taking-Over 97%, not corrected for periods with no access 29 Nysted turbines each produced over 1 M kWh in December 2003, first and only time this level reached in Denmark

And then... So much for past and present - What about the future?

A Historical Trend...

…For a Reason

Where Does This Lead Us?

The Next Generation... A next generation offshore is: Large (because large turbines make cheaper electricity than small turbines) But not too large (because organic growth provides more safety than big leaps) Fitted with further developments of the offshore modifications proven in previous projects, including Vindeby and Nysted Compliant with all grid requirements, providing fault ride-through and fully flexible regulation

… Could Look Like This

Bonus 3.6 MW Main Data: 107 m rotor diameter m hub height Rotor weight 80 t Nacelle weight excl. rotor 120 t 100 m tower weight 250 t Variable speed with full converter to provide maximum flexibility and grid compliance

Bonus 3.6 MW Peculiar Data: At 10 m/s wind speed the amount of air passing through the rotor every second has a weight of 100 t The B52 blade root design bending moment in flatwise direction is kNm The maximum tip deflection of the B52 blade is 7 m

Bonus 3.6 MW Schedule: Prototype installed Summer series installed late 2004 / early 2005 First significant commercial projects second half 2005 Unlimited production early 2006

Relative Sizes