Wind profiling using LIDAR at a coastal location on the Mediterranean island of Malta

Abstract

Wind measurement campaigns usually involve the installation of a wind monitoring mast equipped with multiple-level sensors in order to measure wind and other climatological parameters that reflect prospective wind turbine installation site conditions. With the advent of larger multi-megawatt wind turbines, monitoring masts must be taller and are hence more expensive. As such developments unfold; measurements in an offshore environment are becoming even more challenging. Consequently, remote sensing tools such as Light Detection and Ranging (LIDAR) are gaining popularity since they are able to provide accurate information on wind flow at heights which surpass those of conventional wind monitoring masts. In June 2014, a LIDAR wind measurement system was deployed on a coastal watch tower at Baħar iċ-Ċagħaq on the Mediterranean Island of Malta. One year of data, starting from July 2015 to June 2016, was collected from the LIDAR unit for 10 heights extending up to 200 m above the unit’s window. This data allows for a detailed analysis of the wind speed, wind speed shear, wind direction shear and turbulence behaviour. This project is divided into four phases. In the first phase, a literature review is conducted on remote sensing systems, the advantages and limitations are presented and their reliability compared to that of conventional monitoring masts. The second phase presents a detailed review of the theory behind the effects of atmospheric stability, wind speed shear, wind direction shear and wind turbulence. The third phase gives an overview of the measurement site and validates the data collected. The fourth phase analyses the wind data collected by the LIDAR unit from three perspectives; the first one studies the results of every height recorded by the LIDAR unit, the second one analyses the flow conditions at a typical offshore wind turbine hub height and the third one presents a sectorwise analysis, which analyses flow conditions coming from over the sea surface and from a more disturbed sector, where the flow approaches from over the land.