Big Experience with Small Wind Turbines235 SWT and 15 Years of Operational Results

Paul Kühn

ISETInstitut für Solare Energieversorgungstechnik Kassel/ Hanau, Germany

EWEC 2007- Milan, Italy, 9 May 2007, Technical Track:Small wind turbines, distributed generation and autonomous systems

Paul Kühn

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ISET has been monitoring the development of wind energy use in Germany since 1989, in the framework of the “250 MW Wind” programme.

Operational results gathered by questionnaire (more than 1 500 WT) and measurements (200 sites) about:

• effects by external conditions

• fluctuation of fed in wind power

• economy of wind energy

• energy yields

• reliability of WT

This contribution:Operational results of 235 SWT

Evaluation Programme Wind Energy in Germany, WMEP

Paul Kühn

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40 m2 < swept area < 200 m2 swept area ≤ 40 m2

Big Experience - SWT models in the WMEP

Krogmann 15/50 Südwind N715 AEE Peters PG 10

LMW 2500Wenuns

Inventus 6Lagerwey

15/75

Paul Kühn

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0 %

50 %

100 %

1988 1990 1992 1994 1996 1998 2000 2002 2004

1 - 75 kW 76 - 499 kW 500 - 999 kW1000 - 1999 kW 2000 kW ...

data source: IWET

1. DevelopmentShare of Newly Installed WT

Big Experience - Evaluations

3. Energy YieldsSpecific Power Output

0

30

60

90

W / m2

Large WT

SWT

40 m2 < A < 200 m2

SWT

A ≤ 40 m2

2. EconomicsOperational Costs

0

5

10

15

20

ct / kWh

0

1

2

3

1 2 3 4 5 6 7 8 9 10

4. ReliabilityAnnual Failure Rate

operational year

Paul Kühn

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More than 62 000 reports concerning maintenanceand repairs:

4 200 reports from SWT

repairdowntime

cause of failure

costs

reason for report

consequenses

WMEP - Data Acquisition Maintenance and Repair Reports

Paul Kühn

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control system malfunction: 22 %

ice: 2 %

lightning: 8 %

grid failure: 4 %

storm: 10 %

unknown: 9 %

others: 10 %

loose parts: 4 %

defective parts: 31 %

Small wind turbines: both size categories

Reliability - Causes of Failure

Paul Kühn

- 7 -Reliability - Repairs

Small wind turbines: 40 m2 < swept area < 200 m2

supporting structure: 3 %

yaw mechanism: 5 %

hydraulic system: 5 %

drive train: 3 %

mechanical brake: 7 %

gear box: 5 %

control unit: 17 %

sensors: 11 %

electrical system: 26 %

generator: 5 %

rotor blades: 5 %

rotor hub: 8 %

Paul Kühn

- 8 -Reliability - Repairs

Small wind turbines: swept area ≤ 40 m2

supporting structure: 5 %

mechanical brake: 11 %

gear box: 5 %

control unit: 14 %

sensors: 6 %

electrical system: 13 %

generator: 7 %

rotor blades: 9 %

rotor hub: 23 %

yaw mechanism: 3 %drive train: 3 %

hydraulic system: 2 %

Paul Kühn

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supporting structure/ housing

drive train

gearbox

generator

hydraulic system

rotor blades

yaw system

rotor hub

mechanical brake

sensors

electronic control

electrical system

annual failure frequency downtime per failure in days

1 0,75 0,5 0,25 0 4 8 12 16 20 24

Reliability - Frequency of Failure & Related Downtime

Small wind turbines: both size categories

Paul Kühn

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technical availability 8

286

1

21

18

0

18

3

12

0

16

6

19

9

20

6 20

7

19

8

19

9

18

9

18

6

4

19

22

22

252

7

29

30

30

30

28

17

80 %

85 %

90 %

95 %

100 %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

operational year

number of SWT reported about

40 m2 < SWT swept area < 200 m2

SWT swept area ≤ 40 m2

Small wind turbines in the WMEP

Reliability - Age Dependent Technical Availability

Large WT: 97 %

Paul Kühn

- 11 -Conclusions & Outlook

Main Barriers: Costs and Reliability

SWT @ ISET: Further Development and Optimization

Approach: Most Simple Turbine Design

Paul Kühn

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contact: pkuehn@iset.uni-kassel.de

www.iset.uni-kassel.dehttp://reisi.iset.uni-kassel.de

Electrical systems technology for the use of renewable energies and for the decentral power supply

ISET advancing energy systems

Applications-oriented R&D

• Wind Energy• Photovoltaics• Bio Energy• Hydro Power and Marine Energies• Energy Conversion and Storage• Hybrid Systems• Energy Economy

Thank you for your attention!