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ECN publication
Current developments in wind - 2009
Published by: Publication date:
ECN Wind Energy 6-1-2010
ECN report number: Document type:
ECN-E--09-096 ECN publication
Number of pages: Full text:
85 Download PDF  

The purpose of this report is to give the reader an understanding of current wind turbine designs,the differences between them and how changes in the main design parameters can affect the final cost of energy. For this purpose, we gathered data on more than 130 different wind turbines, 80 different offshore windfarms and from other cost studies. This data was analysed to see whether technological trends can be distinguished and what impact research and design changes may have on the cost, either on parts specifically or the total cost of energy.

The report consists of 3 parts. The first part examines the major parts of the wind turbines (drive train, rotor and support structure). The second examines the cost and the third examines current research.

An analysis of drive trains of turbines with a rated capacity of 3 MW or more did not show convergence to any particular drive train layout. Variable speed and pitch-to-feather control is universal in this class of turbines.

The mass of a tower can be approximated fairly easily, but the spread in the data is very large. For offshore foundations, trends in design are not very clear yet. Most farms have been installed with monopiles though.

Data on the blade designs of wind turbines blades shows a different trend than what would be expected on the basis of scaling functions published in literature, though both could be considered a valid approximation. This shows that one must be very careful when using such scaling functions. Onshore, the rotors of IEC class II and III turbines with higher power ratings are relatively larger in comparison to their rating than their smaller class II and III turbines. I.e. they have a much lower power density. Within each class, the difference in power density varied up to a factor 1.5.

Cost break-downs of existing turbines vary significantly in their cost-estimates of the main parts,even for similar wind turbines. On direct drive wind turbines too little data is available for comparison. Therefore, the costs of different drive-train layouts can not be compared across multiple studies. For onshore wind turbines an estimate of the cost price (excluding delivery, service, works, profit margin and warranties) was established on the basis of average cost distribution and turnover data from gearbox and blades manufacturers. This estimate amounts to 570-666 €/kW. Turnover data from the manufacturers indicate that onshore turbines are sold at a price of about 1000 €/kW (including, delivery and warranty). Contracts for offshore turbines show that these are significantly (200-750 €/kW) more expensive.

In terms of cost, prices for both onshore and offshore windfarms rose sharply in recent years. Onshore it can be shown that increases in raw materials can only have contributed a small part in this increase. High demand relative to supply chain capacity will certainly have played an important part. Offshore, the location of the wind farm in terms of depth and distance to shore plays a big role. The data had such high variability that it was unclear whether supply and demand mismatch played an important role here.

Given current designs and turnkey costs, it should be possible for onshore wind turbines to achieve a cost of energy as low as 0.04 to 0.05 €/kWh. Capital cost (7% interest) and maintenance have been taken into account in these figures. Offshore, current cost of energy ought to be between 0.08-0.10 €/kWh. These values with yields that were obtainable at 8.0 and 9.5 m/s respectively.

Current research focusses on reducing the uncertainties in calculating the loading of components, reducing maintenance cost, improving the use and the properties of materials and on reducing the overall loads using control.

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