Wind turbine wake visualization and characteristics analysis by Doppler lidar

Abstract

Wind power generation is growing fast as one of the most promising renewable energy sources that can serve as an alternative to fossil fuel-generated electricity. When the wind turbine generator (WTG) extracts power from the wind, the wake evolves and leads to a considerable reduction in the efficiency of the actual power generation. Furthermore, the wake effect can lead to the increase of turbulence induced fatigue loads that reduce the life time of WTGs. In this work, a pulsed coherent Doppler lidar (PCDL) has been developed and deployed to visualize wind turbine wakes and to characterize the geometry and dynamics of wakes. As compared with the commercial off-the-shelf coherent lidars, the PCDL in this work has higher updating rate of 4 Hz and variable physical spatial resolution from 15 to 60 m, which improves its capability to observation the instantaneous turbulent wind field. The wind speed estimation method from the arc scan technique was evaluated in comparison with wind mast measurements. Field experiments were performed to study the turbulent wind field in the vicinity of operating WTGs in the onshore and offshore wind parks from 2013 to 2015. Techniques based on a single and a dual Doppler lidar were employed for elucidating main features of turbine wakes, including wind velocity deficit, wake dimension, velocity profile, 2D wind vector with resolution of 10 m, turbulence dissipation rate and turbulence intensity under different conditions of surface roughness. The paper shows that the PCDL is a practical tool for wind energy research and will provide a significant basis for wind farm site selection, design and optimization.

Shipborne Wind Measurement and Motion-induced Error Correction of a Coherent Doppler Lidar over the Yellow Sea in 2014

“…It will be further validated and improved under different sea conditions using CFD model simulation in further field campaigns. More specific studies are being carried out or prepared, including atmospheric turbulence characteristic statistics and multi-scale wind field observations in MABL, wind turbine wake and atmospheric turbulence interaction over offshore wind power field (Wu et al, 2016a;Zhai et al, 2017), mass transport and flux analysis in MABL with combination of CDL, and multiwavelength polarization Raman lidar (Wu et al, 2016b).…”

“…Wu et al (2016a) and Zhai et al (2017) provide a comprehensive description of the CDL including a figure of the optical setup. The lidar has a semi-conductor single frequency seed laser that provides both the local oscillator reference beam for heterodyne detection as well as the transmitted beam.…”

Shipborne Wind Measurement and Motion-induced Error Correction by Coherent Doppler Lidar over Yellow Sea in 2014

“…Wu et al (2016) and Zhai et al (2017) have given a comprehensive description of CDL. The lidar has a semi-conductor single frequency seed laser that provides both the local oscillator reference beam for 25 heterodyne detection as well as the transmitted beam.…”

Performance validation on an all-fiber 1.54-μm pulsed coherent Doppler lidar for wind-profile measurement

“…Coherent Doppler lidar (CDL) has been developed as a powerful tool for atmospheric wind velocity measurement, [1][2][3][4] aircraft wake-vortex hazard detection, [5][6][7] and wind turbulence measurement 8,9 with high temporal space resolution and high measurement accuracy due to its high carrier-to-noise detecting characteristics. The enabling modules for high-performance CDL system include laser transmitter, [10][11][12] balanced detection, 13,14 and weak-regime wind estimation algorithm.…”

“…Performance validation on an all-fiber 1.54-µm pulsed coherent Doppler lidar for wind-profile measurement 1…”