Target & Benefit


The Performance Transparency Project (PTP) aims for demonstrating that the iSpin Spinner Transfer Function (STF), once being obtained for a turbine in one terrain, can be transferred to other wind turbines as long as these turbines are of the same type and running with the same general settings.

An important part of the demonstration is the evaluation of the robustness of the iSpin measurement characteristic not only for free inflow sectors of individual turbines but also under consideration of 360° inflow conditions. By achieving this ROMO Wind’s patented iSpin technology can function as a cost-effective, universal tool for verifying and monitoring power curves of all wind turbine generators in a wind farm and in all wind farm terrains (including offshore).


The advantages of a wind measurement system that is robust in terms of measurement characteristics and that can be used on all wind turbines would be considerable. The comparability of the performance curves produced by this method allows the reduction in output of individual turbines to be identified, and measures for optimisation to be initiated. These range from correcting nacelle misalignments to throttling turbines to eliminate excess loads.
Another important application is the verification of the effects of modifications or manufacturer upgrades. The transparent processing of the data gives all parties the assurance that the measures introduced were the right ones and that the successes they had hoped for will actually materialise.

The benefits for the entire wind energy industry will be far-reaching in the medium term: the ability to quickly and reliably evaluate modifications of wind turbine technology will shorten innovation cycles, and technological innovations, e. g. to increase efficiency, will be established more quickly.


What did we reach and what is planned


PTP participation agreement

Agreements about PTP participation in place with operators and OEMs for 7 sites and 3 turbine types.



Selection of 3rd party consultants via tendering process

Cooperation agreements and contracts signed with 3rd party wind expert companies covering the scope of supply, schedule, data validation procedure.



Measurement data for all sites available to 3rd party experts for validation

Measurement data for turbine type a, b, c) for normal, semi-complex resp. complex sites and offhsore sites available to 3rd party experts for validation.

REACHED for turbine type a, b and c


Conclusive robustness proof report

Summary report for evaluated turbine types containing the proof of robustness results for normal, semi-complex/complex and offshore site.



Conclusive uncertainty evaluation report

Final uncertainty components report and recommendation for re-working IEC 61400-12-2.



Conclusive report concerning best practice iSpin PC verification method

Final best practise report.


PTP Work Packages

PTP Work Packages



The preparation phase of the PTP contains of following tasks:

Site and turbine identification

In cooperation with participating operators and OEMs and by using information from 3rd parties, which are involved in power curve measurements, adequate turbine types and sites will be identified and agreed. For this purpose, specifications describing the requirements towards the turbine types and sites shall be issued. It is planned to identify 3 different turbine types, which are installed in at least 3 sites of different complexity.

Validation method and criteria definition

The standard IEC 61200-12-2 provides the general procedure and criteria to perform the power curve measurements using nacelle-mounted anemometry (including iSpin spinner anemometry). Additional requirements or deviations to this standard reflecting the iSpin technology will be defined and agreed between RW and DTU  to perform the data validation process. As a result of this task, validation specifications including a description of necessary data content will be created.

3rd party wind expert selection for data validation

The group of 3rd party wind expert companies  to evaluate the PTP data will be selected through a tender process. Depending on the sites and turbine types, data validation contracts with up to three 3rd wind expert companies will be established. During the tendering preparations, detailed requirement specifications will be elaborated and reviewed together with DTU.

Database and Data access definition

For each PTP-site data from individual iSpin measurements, SCADA data and IEC compliant wind measurements as well as configuration information will be stored.  The amount and type of information (raw data, normalised data, intermediate and final reports etc.) and the access to this information will be defined and agreed between RW, DTU and the involved participants.

Drafting of installation instructions

Based on the finally identified and agreed turbine types detailed iSpin installation instructions reflecting the turbine specific dimensions and interfaces will be created. To make the installation at the turbines as smooth as possible and to reflect manufacturer requirements especially concerning Health & Safety, visits to existing turbines are foreseen before installation at the identified turbine sites.

Execution & Analysis

Execution & Analysis

All selected PTP turbines will be equipped with MEASNET wind tunnel calibrated iSpin systems. The installations will be performed and documented according to the respective turbine type specific instructions to achieve minimal installation deviation, high tracebility and therefore optimal comparison possibility for each turbine type.

For each site the Spinner Transfer Function (STF) is determined at a reference turbine by means of the met mast or a nacelle lidar system. In order to evaluate the STF stability over time, at least 12 months of combined met mast/nacelle lidar and iSpin data will be evaluated. Identified turbine type specific STFs will be compared for flat, semi-complex, complex terain or offshore PTP sites. iSpin based power curves using the STFs will be compared with met mast based power curves according to IEC 61400-12-2 for the reference turbine and for all PTP turbines per site.

Independent Validation

Independent Validation

The validation of the PTP data will be performed by the selected 3rd party wind experts. Each 3rd party wind expert is responsible for one turbine type, i.e. for the individual and combined evaluation of PTP sites in flat, semi-complex/complex terrains or offshore. Following tasks are foreseen:

Perform power curve verification for the reference turbine following IEC 61400-12-1

Perform power curve verification for the reference turbine following IEC 61400-12-2:

  • Generation of the iSpin Spinner Transfer Function (STF) for the specific turbine type for the free inflow sector(s) between met-mast/nacelle lidar and turbine
  • Generation of the uncertainties calculation (combination of category A and B) of the free wind speed measured with the iSpin system
  • Generation of the iSpin based power curve (NPC) with information about the uncertainty per wind speed bin (category A and B as well as combined)
  • Compare PC verification results acc. IEC 61400-12-1 with results acc. IEC 61400-12-2
  • Self consistency check of the STF
  • Generation of the AEP analysis with information about uncertainty per wind speed bin
  • Comparison of the free inflow sector power curve (NPC) with the 360° power curve

Transfer the iSpin STF to the other wind farm turbines equipped with iSpin

  • Generation of the iSpin based power curve (NPC) according IEC 61400-12-2 with information about the uncertainty per wind speed bin (category A and B as well as combined)
  • If applicable, comparison of the iSpin STF and the NPC generated for a second turbine which can be assessed with the met-mast according IEC 61400-12-2
  • Comparison of the free inflow sector power curves with the 360° power curve
  • Comparison/Discussion of the results from 3rd party consultant and ROMO Wind analysis
  • Evaluation of effects of environmental conditions on iSpin STF (e.g. full wake, partial wake, shear, temperature gradient, turbulence, etc.)

Validation reports (intermediate and final) for the site specific as well as the overall turbine specific evaluation