Presentations

Abstract

In WindCal2, we have developed and demonstrated a new method to calibrate nacelle lidars with considerably lower uncertainty and much faster than present methods. This concept could be used, potentially, to calibrate any type of wind speed sensor. This work achieves a goal long-sought by the wind industry: obtaining lidar measurement uncertainty substantially lower than conventional cup anemometers. This contributes to improving the economic performance of wind power assets by lowering the wind resource uncertainty and increasing investor trust. This work also solves a problem introduced by some modern nacelle-mounted lidars, that their increasing number of laser beams was taking longer time to calibrate. Thus, it will also improve the time efficiency of wind measurement projects, by dramatically reducing the pre- and/or post-campaign time allocated to calibrations. WindCal2 has two main innovations: 1. We built a highly accurate, lidar-based wind speed sensor ("2D-lidic"). It consists of two very short range continuous wave lidars (lidics); each measures the wind component in a single line of sight, so the 2D-lidic measures wind speed and wind direction. The 2D-lidic replaces the cup anemometer as the reference in the nacelle-lidar calibration. Our uncertainty analysis showed a 2D-lidic standard uncertainty of 0.5% of the measured speed or lower (depending on the selected 2D-lidic geometry). This is a substantial reduction compared to the standard uncertainty of a cup anemometer, which is typically about 1%-1.5% at best. The key to this uncertainty reduction is the calibration of each lidic against a flywheel. 2. The calibration process was automated by mounting the nacelle lidar on a pan and tilt unit (motion device). This innovation allows both an automatic measurement of the angles between the lidar laser beams and also alternating quickly (every two minutes) between the beams during the wind speed calibration process, leading to an outstanding reduction in the total calibration time for multi-beam nacelle lidars. Additionally, making this an automated process increases the repeatability and robustness of nacelle lidar calibrations. We will share with Wind Europe Technology Workshop 2024 participants the main achievements of this project. These include the results of the extensive demonstration campaigns carried out over more than a year, where several nacelle lidars were calibrated using the innovative WindCal2 method and test setup. This work demonstrates that it is possible to calibrate nacelle-mounted wind lidars without the need for wind tunnels or cup anemometers and with a substantial measurement uncertainty reduction. WindCal2 is the beginning of the second generation of wind speed calibrations: cup-less, more accurate, faster and automated. WindCal2 is a project sponsored by the Danish Energy Technology Development and Demonstration Programme (EUDP) and project partners DTU, Ørsted, Siemens Gamesa Renewable Energy and Vaisala. The project started in 2021 and it will end in 2024.