LIDAR II

For future multi-megawatt wind energy converters (WEC) in large-scale offshore wind farms new and advanced control strategies are required. Dynamic wind loads have to be reduced efficiently and with minimal controller operation, in order to deliver electricity to the grid in an optimized way. Already small deviations from normal operation have to be detected using new instruments - lidar - and adapted control strategies.

Up to now the implementation of these visions suffers from fundamental obstacles, despite the progress in many fields of wind energy technology. Large uncertainties due to the complex inflow within the rotor area influence the control and operation of wind energy converters. This problem becomes even more serious with growing rotor diameters beyond 120 m. Current control concepts can only react to wind field fluctuations which have already caused changes in rotational speed or loads. When evaluating the averaged or instantaneous power production, it is unclear from which exact wind conditions they have been obtained. Thus, a precise performance analysis is impossible.

The emphasis of the completed RAVE project LIDAR (development of lidar wind measurement for the offshore test field) and its extension LIDAR+ was the application of existing lidar technology and the development of methods and measurement procedures using largely available technology. The current project LIDAR II focuses on the following topics, which are considered crucial for the vision of a future “intelligent offshore wind turbine”:

1. Prototype of a robust and cost-efficient lidar for nacelle-mounted application on WEC, which is suitable for industrialisation.

2. Methods to determine the power performance of a WEC using a nacelle-based lidar for inhomogeneous inflow in wind farms, which are common operating conditions in contrast to the idealized conditions according to IEC 61400-12-1.

3. Procedures for monitoring the Langevin power characteristic using the robust lidar.

4. Control strategies for optimization of power performance and reduction of loads, using nacelle-based lidar measurements.

These components shall be developed and tested with the help of diagnostic equipment which is already installed in the offshore test field alpha ventus.

Furthermore, the results concerning nacelle-based lidar technology and power performance evaluation shall be standardized and distributed to the wind energy sector through the FGW committee “power curve”. In addition to nacelle-based measurements, uncertainties in standardized power curve measurements due to the blockage effect shall be investigated.

The project RAVE-LIDAR II thus continues the successful work of the completed LIDAR project and aims at results which can directly be utilised for the development of cost-efficient large-scale wind energy converters. The offshore test field alpha ventus serves as an ideal testing opportunity for lidar development as well as for new control and monitoring strategies. The co-operation with turbine manufacturers ensures the relevance for future industrial utilisation.