The procedure provides the basis for performance verification with nacelle Lidars. It has been submitted to the expert and standardisation groups Measnet and IEA Task 32 in order to be upgraded to an internationally recognised standard. “It opens new possibilities for cheaper and more frequent power performance measurements,” said Avent.
The project has been conducted by a consortium made of DTU Wind Energy (formerly Risø Wind Energy Department), DONG Energy, Siemens Wind Power and Avent Lidar Technology, funded by the Danish Energy Technology Development and Demonstration Program (EUDP).
“Measurements of wind turbine power curves are a key issue for the wind industry. But conducting power performance verifications with met-masts is often difficult and extremely expensive, particularly offshore or in onshore complex terrains, which means that verifications and measurements are sometimes skipped all together,” said Avent CEO Thomas Velociter. “Nacelle-mounted Lidars present a cost effective solution to this problem. They allow for accurate and affordable measurements, resulting in reduced cost of energy and increased competitiveness.”
The project started from the basis of a ground-based Windcube Lidar from Leosphere, which was adapted to be placed on the turbine nacelle for forward looking horizontal measurements. Over the course of the project, several prototypes were developed and tested, and have evolved into a new product called Wind Iris, which integrates all the elements of the procedure. The Wind Iris, manufactured and commercialised by Avent, has been specifically designed for turbine-mounted measurements, which require a product that can deal with adverse factors such as nacelle vibrations.
“One of the main challenges was to obtain an equivalent procedure to the IEC 61400-12-1 power performance measurement standard,” said Velociter. “To achieve the required level of accuracy and repeatability, the developed procedure accounts for each one of the measurement requirements. For example, it specifies how to measure at hub-height +/- 2.5% at 2.5 rotor diameter in front of the turbine and account for the deviation inherent to the flexibility of the turbine. With a 400m range Lidar, we can work even on the largest wind turbines.”
The Wind Iris is already in operation on a number of projects including DONG Energy’s 367 MW Walney offshore wind farm located in the Irish sea.