Development and operating experience of the WEC Winwind WWD-1 G.Böhmeke, WINWIND OY

Concept origin Direct drives appeared on the market 1994-’95 Comparative study on direct drives, including slow- speed drives with single-stage gearing at aerodyn GmbH in 1996-’97 First publication EWEC ’97 Dublin

Study results, facts... Direct drive leads to very high generator mass and cost, the machine is not competitive if bought from ready-made components The situation becomes worse with increasing size This can only be partially neutralized by making the generator and inverter in large series in the own workshop A newcomer can not start on this basis

... Facts Large-scale gearbox failures from 1999 to 2002 Investigations partially confidential. Published results leave many questions open Damages seem to concentrate on high-speed parts A newcomer should not take the risk of using a conventional gearbox

Aim Reliable and competitive wind turbine, suitable also for arctic and remote locations Concept scaleable up to several MW Components bought from well-known component deliverers, but own test and assembly Avoiding all gearbox problems known today Avoiding the cost and mass problems of direct drives

Solution Low-speed drive train, planetary gearbox with comparatively slow generator Gearbox and generator risk analysis and measures against possible problems Further measures to increase overall reliability

Patents, co-operation, funding Slow-speed integrated drive train concept called MULTIBRID and patented by aerodyn GmbH WinWinD and its cooperation partner Pfleiderer Wind Energy GmbH hold the utilisation rights. Pfleiderers 5MW-MULTIBRID is in parallel under development TEKES subsidy to WINWIND for the development of the 1MW wind energy converter WWD-1

Founded in March 2000, share company Largest share holders Powest Oy, A subsidiary of biggest Finnish power company, Pohjolan Voima Oy Head Future Technologies Oy, Venture capital company, member of the Head Team Presently 20 employees, three locations WinWinD

Location Workshop, assembly and test Ii-Raasakka Machine design and development Helsinki Main office and administration Oulu

WWD-1 Main component deliverers Hub and mainframe casting METSO FOUNDRY Tower steel RAUTARUUKKI Inverter ABB Main bearing HRE Blades EUROS Gearbox METSO DRIVES Generator ABB

WWD-1 drive train

WWD-1 drive train (simplified)

WWD-1 Basic data Rated power kW Rotor diameter 56 (60) m ClassificationIEC 2-A (3-B) Tower height m Cut-in wind speed 3 m/s Cut-out wind speed 25 (20)m/s Rated wind speed12.5 m/s Top mass53 to Rated rotor speed25.6 rpm Rated gen. speed 146 rpm Gear ratio5.71 Temperature range First machine (Oulu)-30C to +25C Seriessite-specific

WWD-1 Basic data Diagram from aerodyn GmbH E112 ca. 500t

Design rules gearbox Bearings and gears Own crosscheck and neutral expert approval No high-speed parts FEM analysis of bearing influence on gearing Load peaks Variable speed and pitch concept, defined torque Slip clutch against short circuit torque peaks Brake dynamics torque peaks Brake acts with only rated torque Reaction forces and casing deformations Concentric structure and FEM analysis Spherical roller bearing problems Only cylindrical roller bearings Oil quality and temperature Ample cooling and fine filtering

Design rules generator Winding temperature level Inherently large surface per kW of loss Water jacket cooling Permanent excitation saves losses and heat Dielectric winding stress dU/dt Adequate filter Salt, water, erosion Preformed coil winding, no round-wire No ambient air through generator Air gap collision Conventional length/diameter ratio, stiff casing No direct influence of rotor loads on air gap Sensor and supervision Magnet degrading Quality control Thick glassfibre sleeve Current limiting

WWD-1 assembly

WWD-1 back-to-back test

WWD-1 test and running-in

WWD-1 site assembly

WWD-1 August 2001 First machine erected in Oulu April 2003 two units to Kokkola June 2003 three units To Oulunsalo September 2003 three units to Kristiinankaupunki 1Q 2004 two units to France

Operational experience... Power curve As predicted, pitch control needed parameter refinements Noise First results Lpa= 103 dBA No measured single tone content Gearbox silent Dominant machine noise is generator slot frequency No elastic suspension/insulation needed anywhere Grid interference As designed and predicted by inverter manufacturer EN-SFS limits are fulfilled Dynamics As designed

... operational experience Site Some days of downtime due to rime ice Blade heating system not justified Generator air cooling => water jacket for series machine Preheating procedure needed optimization Temperature level during operation Gearbox oil max. 60C so far, est. 80C with 25C ambient Generator winding max. 85C so far, est. 100 C Conclusion No problems related to the drive train concept Low temperature levels, no unexpected loads, high reliability and long lifetime can be expected.

From WWD-1 to WWD-3 Same drive train concept, but increased gear ratio to cancel the lower rotor speed Still more compact structure and special measures against structure-born noise Machine development is under work, prototype scheduled for spring 2004 First machine to be sited near Oulu

WWD-3 preliminary base data Rated power kW Rotor diameter 90 m Tower height m Cut-in wind speed 4 m/s Cut-out wind speed 25 m/s Rated rotor speed15.9 rpm

Aim: MULTIBRID 1, 3 and 5 MW product family