NY_load_resp_fig2The LOAD RESPONSE module provides easy-to-use calculations of fatigue loads for IEC 61400-1 ed. 3 site suitability assessment. The module includes generic turbine models, which represent typical turbines on the market, and manufacturers can implement in-house turbine models.

LOAD RESPONSE rests on a solid scientific foundation and is developed as part of a research project between Aalborg University and EMD, funded by Innovation Fund Denmark.

For many sites one or more of the main IEC checks fail and a site assessment based directly on SITE COMPLIANCE is not conclusive (see figure below). LOAD RESPONSE can assess if failed IEC checks in SITE COMPLIANCE lead to exceeded load levels or if they are balanced by buffer in the other IEC checks.


NY_load_resp_fig1LOAD RESPONSE requires a separate license, but is fully integrated in SITE COMPLIANCE. The license to LOAD RESPONSE opens the easy-to-use functionality of load calculations directly inside SITE COMPLIANCE. The module is based on an advanced response surface methodology, which allows very fast and yet accurate fatigue load assessments. Typical calculation time for a full layout of e.g. 40 turbines is a few seconds.

The results of a LOAD RESPONSE calculation are fatigue loads on the main turbine components e.g. blade, tower, shaft and nacelle, for each turbine in the layout. Per default the presented loads are normalized to the design loads of the chosen IEC design class e.g. IIB, to show the so-called load index. This provides a clear indication if design loads for each main component of a turbine are exceeded or not. I.e. if the load index is larger than 100% or not.


FT16-Z_4c_EN 13155 - Wind_E_Type-testedThe response surface method to estimate fatigue loads implemented in LOAD RESPONSE has been certified by TÜV SÜD for compliance with the requirements in IEC 61400-1 ed. 3 (2010).

Generic turbine models

LOAD REPONSE comes with two generic turbine response models, one for rotors larger than 90m and one for rotors smaller than 90m. These generic models enable project developers and consultants to assess fatigue loads at very early project stages of a wind farm development. This will ensure better design of layouts, optimal use of the leased land and easier selection of appropriate turbine models for the site – and in general fewer iterations in the project development phase.

Load indexes predicted using the generic models have been validated against commercial turbines and were proven to be accurate for wind turbines with a standard design with three blades, a gearbox and standard controller.


Turbine manufacturers can speed-up the internal project turnaround time by implementing their own turbine response models for LOAD RESPONSE. The procedure to implement new models is easy and can be done fully in-house by the manufacturers using their own aero-elastic simulation tools and post-processing. Implemented turbine models are subject to a very strong multi-level security, including encryption, license control. In addition, the manufacturer decides with whom to share the response files.

Example from main report