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Title:
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InnoTIP end report rev 2
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Author(s):
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Kalken, van J.; Ceyhan, O.
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Published by:
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Publication date:
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ECN
Wind Energy
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23-5-2017
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ECN report number:
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Document type:
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ECN-O--17-011
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Other
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Number of pages:
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Full text:
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72
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Download PDF
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Abstract:
The InnoTIP project is a collaboration project between Energy research Centre of the Netherlands (ECN) and LM Wind Power (LM) aimed at reducing Offshore Wind Levelized Cost of Energy (LCoE) by improving turbine yield by blade tip geometry.
InnoTIP is aimed at developing 3 different tip shapes, which have been manufactured as retrofits to be tested in field on 2.5 MW turbines. During the conceptual phase a number of software tools have been utilized to find optimum for each of the 3 concepts (turbulators, winglet and conventional tip). The quick analysis done by blade element momentum theory (BEM) are initially used where a more refined Lifting Line Method (LLM) is used to have a more accurate understanding of conceptual changes. The final configurations are analysed using Computational Fluid Dynamics (CFD) which are far more accurate but also have a large computational cost.
A number of parameter variations for each concept have been done to investigate which shape has the most beneficial LCoE decrease (aimed at increase in yield) and the choice of final configuration has been based upon this together with practicalities. Some of the parameters that have been investigated are the twist angle, the sweep angle and the planform shape. Once the conventional tip has been fixed, the winglet has been chosen to be comparable to this. Some off design conditions have been evaluated prior to making the final decision on which tip shape is chosen. Finally, the chosen configurations for winglet and conventional tip have been analysed using CFD analyses. The turbulators geometry has been analysed using LLM as here the wake is of main interest.
The chosen concepts are afterwards taken into a detailed design phase where issues regarding e.g. lightning protection, structural strength, attachment, drainage have been solved. During this design period input from a large amount of stakeholders (including the LM Service team) has been used to optimize the methodology. Once the designs were in finalization state, prototypes of the tips were made on full scale and an installation test on a scrapped blade tip have been performed in a controlled environment. This has been done in order to take away any potential issues, as the original blade was not to get damaged. Following the installation test, a structural test for extreme loads have been done to verify the structural strength of the system. Finally the extension was removed and the original blade tip successfully restored.
Tests have been performed at the EWTW test site where 5 Nordex N80 2.5MW turbines were available for use. The turbines are assisted with a MetMast which has been used for verification of the weather conditions. The turbulators and conventional tips have been installed and tested mainly by noting the turbine performance change compared to other turbines. In preparation to the field test the turbines have been monitored several weeks to have comparison material to be used during the field test.
The test results for the conventional tip show an increase in power at higher wind speeds of more than 4% (the effect of having a longer blade). The actual increase due to geometry change is in the order of 2% to 9% for wind speeds above 8 m/s. Data for the wake influenced turbine did not show an actual increase in power mainly due to lack of measurement time where the turbine has been in the wake. The turbulators themselves do increase the power on the retrofitted turbine itself. Here the increase in power is in the order of 2% to 10% for wind speeds above 8 m/s.
A wind farm simulation performed for the Hyller project shows the effect of scaling the new tip shapes to a larger rotor diameter with its effect on wind farm yield. A simulated wind farm shows the effect of distance between turbines with respect to turbine diameter. Looking at a standalone machine the scaled up version (to 5 MW platform) of the conventional tip is calculated to have an AEP increase of about 3%. The results are presuming the solution is a retrofit, however the actual benefits will likely be higher when the solution is integrated in the design such that no interference effects are present as well as the possibility for a better optimization for the complete blade.
The LCoE is the fraction of the total cost over the lifetime versus the electricity produced over the lifetime. Looking at literature references, it can be found that turbine cost are counting for approximately 25% of the total cost and 22% of those cost are due to the blades. This results in a fraction of 5.5% of blade cost compared to the overall energy cost. The conventional tip is not expected to have a large increase in cost as it’s a relative small change to the current practice. However, even a 1% increase in blade cost, would be negligible compared to a yield increase of 3%. As such all three options are good for implementation and reducing LCoE.
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