Objective
Objectives of the project
The majority of wind turbines installed in Europe and of those produced at present, use aerodynamic stall as a method of power limitation in high wind speeds. A considerable number of these stall controlled wind turbines, with rotor blades produced by various manufacturers, installed at different locations, have shown a behaviour which is now commonly referred to as multiple stall behaviour. This phenomenon can be described as the occurrence of more then one stall power level under apparently equal conditions. Rotors displaying this behaviour can produce stall power at one level for longer periods of time (hours, or days) and then suddenly switch to a different (higher or lower) stall level at which they remain for some time. Up to four power levels have been identified for certain rotors; the difference between the highest and the lowest level can be 25 to 30% of nominal power. Usually, the high stall level coincides with the design level, or nominal generator power. This means that at the lower power levels, energy production will be below the guaranteed power curve level and rotor blade manufacturers are quite concerned. As stated above, the problem is not blade or industry specific, but of a generic nature.
The basic objective of this project is to identify ways to prevent or control the multiple stall behaviour. To achieve this, the underlying cause(s) must be known. Hence the collateral objective is to determine these cause(s). It is presently believed that the basic phenomenon is premature stall, but it is not clear what triggering mechanisms can be responsible for this, nor which parts of the blade(s) suffer changes in the 'regular' flow pattern. A solution to the problem is of high industrial relevance as it enables turbine manufacturers to produce the guaranteed power curve consistent with design calculations. Depending on the wind climate of a specific location, the multiple stall phenomena may account for an energy production loss between 2 and perhaps 7 %, the higher number being valid for high wind speed regions.
The fact that this problem is not yet solved, some four of five years after the first definitive observations, is mainly due to the lack of good diagnostic possibilities and of a dedicated measurement and analysis program The turbines in question usually have been non-instrumented production machines. Up to date, it has not been possible to equip commercial rotor blade showing multiple stall, with the necessary diagnostic tools at a reasonable cost.
Technical Approach
In the present project, a innovative technique will be used which adds a new diagnostic possibility. Use will be made of 'stall flags', which are thin detectors pasted onto the blades, indicating the main flow direction by either covering or uncovering reflectors. With the help of a lighting set and a video camera on the ground, the state of the stall flags can be determined during the operation of the turbine. This enables the analysis of the flow pattern on all the blades simultaneously.
Additional to the stall flag pattern observations, blade loads will be measured, and power will be recorded with a sampling frequency of about 1 Hz. The blade surface conditions, and details of the wind and yaw error, will be monitored also. Interpretation of these results will show under what circumstances power level shifts can occur. The interpretations will be supported by extensive calculation efforts, with BEM and Navier Stokes methods, in order to estimate the sensitivity of the flow field the external factors. In as far as possible, already existing measurements will also be analysed.
Expected achievements
The expected achievements of the project are:
- understanding of the causes of multiple stall phenomena;
- rotor blade design rules and/or turbine operational recommendations that prevent or control multiple stall behaviour.
Partners in the project are ECN (co-ordinator), CRES, NTUA (all three research and development establishments) and Aerpac (rotor blade manufacturer). Nordex (turbine manufacturer) will act as a subcontractor.
Fields of science (EuroSciVoc)
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
- engineering and technology electrical engineering, electronic engineering, information engineering electronic engineering sensors optical sensors
- engineering and technology environmental engineering energy and fuels renewable energy wind energy
You need to log in or register to use this function
Programme(s)
Multi-annual funding programmes that define the EU’s priorities for research and innovation.
Multi-annual funding programmes that define the EU’s priorities for research and innovation.
Topic(s)
Calls for proposals are divided into topics. A topic defines a specific subject or area for which applicants can submit proposals. The description of a topic comprises its specific scope and the expected impact of the funded project.
Calls for proposals are divided into topics. A topic defines a specific subject or area for which applicants can submit proposals. The description of a topic comprises its specific scope and the expected impact of the funded project.
Call for proposal
Procedure for inviting applicants to submit project proposals, with the aim of receiving EU funding.
Data not available
Procedure for inviting applicants to submit project proposals, with the aim of receiving EU funding.
Funding Scheme
Funding scheme (or “Type of Action”) inside a programme with common features. It specifies: the scope of what is funded; the reimbursement rate; specific evaluation criteria to qualify for funding; and the use of simplified forms of costs like lump sums.
Funding scheme (or “Type of Action”) inside a programme with common features. It specifies: the scope of what is funded; the reimbursement rate; specific evaluation criteria to qualify for funding; and the use of simplified forms of costs like lump sums.
Coordinator
1755 LE PETTEN
Netherlands
The total costs incurred by this organisation to participate in the project, including direct and indirect costs. This amount is a subset of the overall project budget.