LIDAR

The LIght Detection And Ranging (LIDAR) system is designed to measure atmospheric characteristics including wind speed and direction at a number of heights from ground level. This instrument emits a stream of photons that interact with a variety of particulates in the air, some of which is scattered back toward the LIDAR where the signal is analyzed and wind data is reported based on the Doppler shift phenomenon. This technology uses the same

basic principle that radar uses.The most common scientific uses for LIDAR technology are in aerial surveying and bathymetry (water depth measurement) but it is now being extended to include wind resource assessment. The small size of the LIDAR allows much greater freedom of deployment when compared to traditional meteorological tower data collection that is commonly used today. Another important benefit of the LIDAR is its capability to provide a description of the vertical wind shear profile at a given site location.

Typical meteorological towers measure wind speed and direction at heights of 30 to 50 meters. The industry standard for calculating the wind speed at the hub height of a modern wind turbine (60 to 80 meters) utilizes mathematic equations to extend the height resolution of data that is collected from meteorological towers.This data extrapolation technique is subject to errors of up to 15% depending on site terrain and length of measurement data. The consequences associated with this source of measurement error can carry significant implications to areas from turbine component life to actual power production.Since the characteristics of the local wind shear are often only partially understood, the higher elevation wind speed and direction data that the LIDAR provides can play a key role in making wind energy projects more effective and, in consequence, more profitable.

The concept of measuring wind speed and direction from a ground-based instrument has already been established with SODAR technology, but the LIDAR is unique in that it is not subject to echo interactions with surrounding topography and structures. Also, the LIDAR operates silently which can help avoid possible disturbance conflicts and it does not require a special building permit, which has previously caused problems with the erection of meteorological towers.

Currently, the Renewable Energy Research Laboratory owns one LIDAR unit, manufactured by Qinetiq. RERL ran a validation process of the LIDAR at Hull in 2006 - 2007 and the report is available.