Project

The goal of the project is to significantly strengthen the scientific basis for the wind power industry in general and specifically the Danish wind power industry’s position in offshore applications.

To meet the goal the proposed research must have a significant potential for reduction of cost of energy from large offshore wind farms, and for contributing to reduction of the economic risks arising from inadequately founded design.

The key design driver for most offshore structures is safety. For offshore wind turbines/farms, however, the main design driver is economy and therefore there is a strong requirement for enhancing design tools and avoiding conservatism. Consequently, focus is on the following issues:

1. Mutual shadow effect between large blocks of wind turbines – ignorance of the effect may have disastrous consequences for the economy.
2. Extreme structural loading of offshore wind turbines – detailed understanding and description of extreme winds and gusts and resulting loads is crucial for the safety and economics of the wind turbines.
3. Interaction of large wind farms with waves and current – understanding and modeling may lead to reduced design loads on wind turbine units placed in the downwind end of the wind farms.
4. Grid connection and reliability – An unreliable grid caused by high wind energy penetration is an obvious barrier for the dissemination of the technology.
5. Optimized operation and maintenance for offshore wind farms – presently more than a third of the cost of energy from offshore wind farms relates to O&M and the potential for reductions is therefore large.

The project is sponsored by The strategic Research council and have participant from Risø National Laboratory, Elsam Engineering, Insitut for Mekanik, Energi og Konstruktion DTU, DHI, Svend Ole Hansen and Institute of Energy Technology AAU.

The institute of Energy Technology is especially involved in issue 4 in this project, by Birgitte Bak-Jensen, and also a Ph.D project is set up together with Risø and Elsam Engineering, with the title: Offshore Wind Power – Grid Connection and Reliability, see this project.

This Ph.D. project is carried out at Dong Energy in cooperation with Risø National Laboratory and Aalborg University.

The aim of the PhD project is to investigate the influence of wind generation on the reliability of power systems. This task is particularly important for large offshore wind installations, because failure of a large wind farm will have significant influence on the balance in the power system, and because offshore sites are normally more difficult to access than onshore installations. The reliability of power production from a wind farm depends on wind speed conditions, the wind turbines themselves, the system layout and the grid connection; besides, the offshore environment poses new challenges to face for the installers.

The project has been divided into three parts. Firstly, a model for yearly generation assessment of offshore wind farms has been developed: this model includes wind speed randomness and variability, components (e.g. wind turbines, internal cables and connectors to shore) failures, influence of site environment and some minor aspects of relevance. Secondly, this model has been used for evaluating the so-called HLI analysis (Hierarchical Level I), where the system adequacy to supply the load is assessed. The power system under study includes conventional power plants, an aggregated load and distributed generation together with offshore wind generation, whereas transmission facilities are neglected in this type of simulation. These two assessments are performed considering a sequential Monte Carlo simulation: this approach has shown more flexibility and completeness in the analysis of wind generation than analytical techniques.

With these two models, that are currently available, some sensitivity analyses will be carried out in the next months. Besides, some of the models will be used for performing an HLII analysis: in this type of study, the transmission facilities are included in the power system model and the adequacy of the system generation is evaluated including the availability of transmission lines and cables.

All analyses in the project are carried out by the use of the software Matlab and the power system analysis tool Power Factory from DigSILENT: simulations will include steady-state conditions as well as dedicated reliability analyses.