Dynamic ice load model in overall simulation of offshore wind turbines

Offshore wind energy is one of the most promising technologies in the field of renewable energy, especially in cold climate regions. This paper introduces a new way to get a better understanding of ice induced vibrations at offshore wind turbines. Therefore a well established empirical ice model was implemented in the aero-hydro-servo-elastic simulation tool OnWind utilizing the modeling language Modelica. To retain a realistic dynamic behavior, an overall wind turbine model including relevant environmental conditions like soil and wind is used. For the investigations representative ice conditions from the Gulf of Bothnia were chosen

Introduction of Ice Loads in Overall Simulation of Offshore Wind Turbines

Due to the global aim of reducing the CO2 emissions, renewable energy production comes more and more into focus. Offshore wind energy is one of the most promising technologies especially in northern regions because of the high and constant wind velocities. The challenges among the others are ice loads and especially ice induced vibrations, which are one of the most significant uncertainties in offshore wind turbine design. Recent investigations in the field of ice mechanics lead to the conclusion that the ice failure has a strong dependency on the dynamic ice-structure interaction. Therefore, a self excited ice structure interaction model by Määttänen-Blenkarn was implemented in a aero-hydro-servo-elastic simulation tool utilizing the state-of-the-art modelling language Modelica. The simulation platform OnWind with a simplified wind turbine model was utilized for simulations. The structural model of an offshore wind turbine consisted of a single wind turbine support str ucture (tower and vertical monopile substructure) with a representing dead mass on tower top. The implemented ice models were validated by comparing results with existing simulation tools. The influence of ice velocity on the displacement response in ice-structure interaction was studied by two configurations representing different structural stiffness due to various water depths: 30m ("soft") and 10m ("stiff"). Both configurations were sensitive on frequency lock-in vibration superposed by 1st natural frequency and other frequencies depending on the ice velocity. Vibration of stiffer structure indicated that multiple eigenmodes contributed to lock-in vibration. It was observed that Määttänen-Blenkarn model was not able to simulate either continuous brittle crushing or intermittent ice crushing. Further investigation should be concentrated to improve the ice load model to describe various ice failure phenomena. Simulations with OnWind software were carried out successfully creating a promising basi

State-of-the-art comparison of standards in terms of dominant sea ice loads for offshore wind turbine support structures in the Baltic sea

The paper is focused on a comparison of different design guidelines and standards, with emphasize on the dominant sea ice loads for offshore support structures for wind turbines in the subarctic. The documents published by Germanischer Lloyd (GL), The International Electrotechnical Commission (IEC), Det Norske Veritas (DNV) and The International Organization for Standardization (ISO) are accounted for in the comparison as the key standards and guidelines. The comparison is conducted on several layers of complexity. First, a general applicability of the examined documents to offshore wind turbines (OWT) is briefly studied. Then, an examination of the standards upon their coverage on the sea ice topic and interaction with various OWT support structures is presented. And finally, a proposal for an integrated set of design load cases, where a interaction between various environmental conditions and an OWT, is given

A review of the effects of ice accretion on the structural behavior of wind turbines

Icing of wind turbines happens occasionally at different latitudes and locations in the world and consequently affects the wind turbine fatigue loads. Large ice accretion may cause wind turbine vibration due to uneven ice shedding, which could lead to structural failures in addition to hazardous issues accompanied with ice being shed off wind turbine blades. In this paper, a review study of the effects of ice accretion on the structural behavior of the wind turbines is presented.Peer reviewe