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1250kW speed assisted stall wind turbine



-To demonstrate a highly innovative drive system for stall regulated variable speed turbines.
-To design and manufacture a 1250 kW variable speed stall regulated wind turbine capable of maintaining precisely rated power at all above rated wind speeds to cut out, and therefore satisfy present and emerging utility power quality requirements.
-To quantify the performance, loading and cost implications of both pitch and stall regulation of variable speed applied to MW scale wind turbines; "speed assisted stall" (SAS) through measurements and variable speed pitch (VSP) through calibrated predictions.
The research aim of this project is to reduce the installed cost of large scale wind turbines and at the same time to improve their grid connection qualities. Achievement of this second objective will allow an increased penetration of the large scale machines. It will also improve the understanding of the differences between pitch and stall regulation, operating with variable speed at very large scale. There is a general move towards variable speed and every manufacturer is faced with the choice between stall and pitch control. Various manufacturers have already made the choice of pitch control with variable speed but the present partners suggest that this choice has not been made on an entirely informed basis.


The objectives of the project will be achieved through a series of technical goals:
To construct a validated set of load predictions for an existing 1250 kW fixed speed stall "reference" wind turbine.
To build load prediction models of candidate 1250kW SAS and 1250kW VSP wind turbines.
To design, build and implement a variable speed drive optimised for SAS control of a 1250 kW wind turbine and able to satisfy all power train heat dissipation requirements with a single, simple and efficient nacelle ducted liquid cooling system.
To design, build and install a set of rotor blades that have been tailored to the requirements of SAS operation.
To erect a 1250kW wind turbine with the SAS drive train, electrical system and rotor. The wind turbine will be fitted with a WEGA-II compliant monitoring system to enable refinement and validation of the load prediction models. To provide an appraisal of the electrical performance of the turbine by a public network operator.
To define the advantages and disadvantages of speed assisted stall and variable speed pitch control in terms of electrical power regulation. To extrapolate the speed assisted stall control concept to a 2.5 MW wind turbine design.


-The turbine developed will have access to a larger number of sites, especially in areas with weak public utility networks.
-It will have been demonstrated that the level of power quality and energy capture which can be realised with variable speed stall regulation is equal to that with pitch regulation.
-The maximum level of network penetration without the complexity of pitchable blades will have been determined.
-As a result of this project it will be possible to provide the appropriate mix of machine capabilities and costs for different applications - simultaneously to minimise cost of energy and to meet local utility requirements.
The direct benefit will be the possible use of large scale simple machines to obtain much greater penetration on weak grids and also on strong grids which are operated by critical utilities. It will thus increase the acceptability of these machines to the European utilities as a whole. It is widely recognised that the utilities will play an important part in the determination of the level to which the wind energy potential can be exploited.
It is considered that the SAS optimised variable speed drive which will be used to increase the energy capture over existing variable speed stall regulated wind turbines and maintain variable speed pitch standard power quality is patentable and initial patent work has already been undertaken. It is considered that the successful conclusion of this project will realise an increased market share in the large scale machines by approximately 50 machines per year, for the years 1999-2002. The sites available for exploitation have, however, been constrained by the grid connection characteristics of some of the large machines. A successful conclusion to this project will relieve that constraint.

Funding Scheme

CSC - Cost-sharing contracts


Nordex Balcke-Dürr GmbH
Meschendorfer Weg
18230 Ostseebad Rerik

Participants (2)

United Kingdom
Saint Vincent Works, Silverthorne Lane
BS2 0QD Bristol