Floating LiDAR for the remote measurement of wind data
EDF’s UK R&D Centre has provided the Group with a turnkey solution that reduces the high cost of conducting wind-based research offshore: the floating LiDAR. A (much) cheaper optical radar system that delivers better performance than traditional meteorological masts and can be reused for other wind farm projects. It uses a laser beam to measure the speed of airborne particles, and therefore, the speed of the wind itself. The acronym is derived from the word 'RADAR', and stands for Light Detection And Ranging.
How does floating LiDAR work?
The laser light beam 'bounces' off the airborne particles it comes into contact with. This reflected wave is then collected by the telescope, enabling the difference in frequency to be calculated by applying the Doppler effect to the particle speeds and thus determine the wind speed.
In practice, the floating LiDAR emits 5 or 6 laser beams to form a cone around 100 metres high with a spread of approximately 30° to measure wind vectors (speed and direction) at multiple altitudes. Measurements are taken at 1 hertz frequency, and the data gathered is transmitted every 10 minutes.
Before delivering this solution to EDF Group wind power developers, the R&D team selected THE best breakthrough technology for the future, and developed it through to industrial production readiness.
the height of wind measurement, compared with 100 metres for traditional masts
and more: the depth of water in which the floating LiDAR solution can be installed, compared with just 50 metres for traditional masts
the cost of offshore wind farm studies is now 5 times lower
Although the basic technology is backed by a decade of experience, adapting it to a floating application demands adaptation to the point of innovation. "The first difficulty is to obtain a valid measurement from any kind of mobile object, especially one that floats. So a number of strategies are used. The first is to limit the movement of the LiDAR by using stabilisation gyroscopes and a moving cradle, followed by extremely accurate measurement of the movements and travel of the entire assembly through the use of accelerometers that compensate for their effects on wind data measurement using a digital post-processing solution", explains research engineer Sami Barbouchi of the EDF Energy R&D UK Centre.
The installation also requires a very special type of expertise that combines anchoring and cabling to suit the depth and natural environment (seabed topography, waves, winds and storms). In order to validate and qualify the floating LiDAR solution, the R&D Centre teams made comparisons between its measurements and those made using a traditional mast as a benchmark.
Data availability of over 90%
In addition to measurement validity, R&D also worked on the issue of reliability: "It's essential to be able to gather data in a continuous stream. So you have to check the quality and robustness of the various onboard telecommunication devices (radio, satellite, etc.), as well as the entire onshore IT system (servers, cloud systems, security, etc.). Faultless integration of the power supply is also a major challenge in achieving a 90% data availability target. So we analysed the redundancy and complementarity of a range of devices, such as photovoltaic panels, small wind power generators, batteries and even fuel cells, in terms of their reliability/cost ratio", continues Sami Barbouchi. As a result, the cost of offshore wind farm studies is now 5 times lower. The investment is profitable because the ease with which floating LiDAR units can be relocated will make it possible to conduct more detailed studies on a single site and, of course, reuse them for future wind farm projects