Wind energy is one of the fastest growing sources of electricity in the world. A high-quality site wind speed measurement campaign is crucial for reducing the uncertainty in the predicted energy production of a proposed project. The goal for a wind measurement campaign is to provide information to allow the best possible estimate of the energy on the site to be provided.
Remote sensing techniques are now being used to measure the wind speeds at wind farm sites. Remote sensing is winning broader acceptance in the wind industry as wind farm developers use it to measure wind characteristics such as in-flow angle and turbulence and investors gain confidence in remote sensing data. The technology available for this is being developed rapidly and it is expected to become more widely used in the near future. Lidar devices have made an entry into the wind market over the last few years and a few main commercial products (ZEPHyIR, WindCube, Halo, WindTracer etc..) are currently available with additional models now entering the market.
Three-Dimensional (3D) coherent Doppler lidars have been extensively used in meteorological studies for the past few decades. Modern 3‑D scanning coherent Doppler lidars are well suited for characterizing wind farm airsheds, and may eventually form a new basis for real‑time adaptive control of wind turbines. Lidars can measure the velocity deficit downstream of an individual wind turbine, as well as the accumulated wakes from an array of turbines. ERSG owns a WindTracer coherent Doppler lidar, from Lockheed Martin Coherent Technologies, Inc.. Typical range of these instruments are 10 ~ 20 km, depending on the atmospheric conditions.
The flexibility of lidar to perform conical (Plan Position Indicator [PPI]), vertical-slice (Range Height Indicator [RHI]) or fixed-beam measurements, allows investigation of a variety of boundary layer characteristics. The wind-field structure from different points of view can be visualized, for example, mean wind and turbulent profiles, time series, or as images of individual scans – to reveal flow features at hub height and above the range of tower measurements. 3D scanning coherent Doppler lidar is capable of producing wind speed distribution of the wind field as a function of space. This can be used to obtain a spatial power density distribution over the entire region. The main advantages of deploying a 3D scanning Doppler lidar for wind farm assessment are:
i. To characterize the spatial wind field at the hub height over the entire region.
ii. To calculate (spatially varying) wind speed distribution, and spatial power density distribution over the region of interest,
iii. To estimate power density using multiple vertical layers within the rotor swept area,
iv. To demonstrate a simple algorithm for wind farm layout design based on spatial power density distribution and distance limitation,
v. Apply advanced optimal interpolation retrieval algorithms to lidar data and many more.