Abstract
This paper discusses whether profiling LiDARs can replace meteorological tower-based wind speed measurement for wind energy applications without severely compromising accuracy. To this end, the accuracy of LiDAR is evaluated in a moderately complex terrain by comparing long-term wind data measured by a profiling LiDAR against those obtained from tower-mounted cup and sonic anemometers. The LiDAR-measured wind speeds show good agreement with those measured using the sonic anemometer, with the slope of regression line being 1.0 and R 2 > 0.99 . Furthermore, the turbulence intensity obtained from the LiDAR has better agreement with that from the sonic anemometer compared to the cup anemometer which showed the lowest turbulence intensities among the three devices. A comparison of the turbulence intensity obtained from the 90th percentile of the standard deviation distribution shows that the LiDAR-measured turbulence intensities are mostly larger (by 2% or less) than those measured by the sonic anemometer. The gust factors obtained from both devices roughly converged to 1.9, showing that LiDAR is able to measure peak wind speed with acceptable accuracy. The accuracy of the wind speed and power distributions measured using the profiling LiDAR are then evaluated by comparing them against the corresponding distributions obtained from the sonic anemometer. Furthermore, the annual capacity factor—for the NREL 5-MW wind turbine—from the LiDAR-measured wind speed is 2% higher than that obtained from the sonic anemometer-measured wind speed. Numerical simulations are performed using OpenFAST in order to compute fatigue loads for the wind speed and turbulence distributions for the LiDAR and the sonic anemometer measurements. It is found that the 20 years lifetime Damage Equivalent Loads (DELs) computed for the LiDAR wind speed were higher than those for the sonic anemometer wind speeds, by 2%–6% for the blade root bending moments and by 11%–13% for the tower base bending moments. This study shows that even with some shortcomings, profiling LiDARs can measure wind speeds and turbulence intensities with acceptable accuracy. Therefore, they can be used to analyze wind resource and wind power potential of prospective sites, and to evaluate whether those sites are suitable for wind energy development.
Highlights
LiDAR-based wind speed measurements have received significant attention in recent years in a wide range of wind energy applications including initial wind resource assessment, optimization of wind turbine sitting in prospective farms and operation and control of wind farms [1,2,3,4]
We focus on profiling LiDARs to investigate whether they can be used as a reliable alternative to meteorological masts for the measurement of wind data and resource characterization
In addition to validating the wind data collected using LiDAR against those measured with sonic and cup anemometers mounted on a neighbouring met-mast, the wind power potential of the site and the fatigue load for the NREL-5MW reference wind turbine estimated using wind speeds measured by the LiDAR and the sonic anemometer are compared
Summary
LiDAR-based wind speed measurements have received significant attention in recent years in a wide range of wind energy applications including initial wind resource assessment, optimization of wind turbine sitting in prospective farms and operation and control of wind farms [1,2,3,4]. The objective of this study is to answer the question of whether a single profiling LiDAR can replace the meteorological mast in a moderately complex terrain, without having to make major compromises in terms of accuracy or data availability To this end, a LiDAR-based measurement campaign is conducted for a period of approximately one year. In addition to validating the wind data collected using LiDAR against those measured with sonic and cup anemometers mounted on a neighbouring met-mast, the wind power potential of the site and the fatigue load for the NREL-5MW reference wind turbine estimated using wind speeds measured by the LiDAR and the sonic anemometer are compared.
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