1. Big Experience with Small Wind Turbines 235 SWT and 15 Years of Operational Results Paul Kühn ISET Institut für Solare Energieversorgungstechnik Kassel/ Hanau, Germany EWEC 2007- Milan, Italy, 9 May 2007, Technical Track: Small wind turbines, distributed generation and autonomous systems

2. Paul Kühn - 2 - 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

3. Paul Kühn - 3 - 40 m 2 < swept area < 200 m 2 swept area ≤ 40 m 2 Big Experience - SWT models in the WMEP Krogmann 15/50Südwind N715AEE Peters PG 10 LMW 2500 Wenuns Inventus 6 Lagerwey 15/75

4. Paul Kühn - 4 - 1. Development Share of Newly Installed WT Big Experience - Evaluations 3. Energy Yields Specific Power Output W / m 2 Large WT SWT 40 m 2 < A < 200 m 2 SWT A ≤ 40 m 2 2. Economics Operational Costs ct / kWh 4. Reliability Annual Failure Rate operational year

5. Paul Kühn - 5 - More than 62 000 reports concerning maintenance and repairs: 4 200 reports from SWT repair downtime cause of failure costs reason for report consequenses WMEP - Data Acquisition Maintenance and Repair Reports

6. Paul Kühn - 6 - Small wind turbines: both size categories Reliability - Causes of Failure

7. Paul Kühn - 7 - Reliability - Repairs Small wind turbines: 40 m 2 < swept area < 200 m 2 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 %

8. Paul Kühn - 8 - Reliability - Repairs Small wind turbines: swept area ≤ 40 m 2 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 %

9. Paul Kühn - 9 - 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

10. Paul Kühn - 10 - technical availability number of SWT reported about 40 m 2 < SWT swept area < 200 m 2 SWT swept area ≤ 40 m 2 Small wind turbines in the WMEP Reliability - Age Dependent Technical Availability Large WT: 97 %

11. Paul Kühn - 11 - Conclusions & Outlook Main Barriers: Costs and Reliability SWT @ ISET: Further Development and Optimization Approach: Most Simple Turbine Design

12. Paul Kühn - 12 - contact: pkuehn@iset.uni-kassel.de www.iset.uni-kassel.de http://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!