How are LiDAR products driving wind farm development and supporting resource assessment?
From the numerous independent studies published on climate change over the last 6 months, it is clear that we need to accelerate the decarbonisation of the planet if we are to keep the global temperature rise this century well below the 2°C target set during the COP 21 Paris Agreement. According to DNV GL’s Energy Transition Outlook 2018, renewables are forecasted to represent a significant proportion of our electricity production by 2050, accounting for over 80% globally. Despite the rapid energy transition forecasted, more action is needed if we are to secure a sustainable future for generations to come, and wind energy plays an important role.
Accurate wind resource and energy yield assessments are the cornerstone of wind farm development. Both are important to get right from the start of any project to optimise the site and safeguard investment. For decades, conventional meteorological masts equipped with mechanical cup anemometry have been the stalwart ‘go-to’ for wind measurements. However, the last decade has seen a rapid rise in the development and application of LiDAR products which use laser technology to measure wind speed and direction at multiple heights by detecting the movement of particles within the atmosphere. They are typically quicker and easier to deploy, avoiding the drawn-out planning consent process to construct a tall meteorological mast.
As turbine hub heights and rotor diameters reach new heights, so must the equipment to measure wind speed and direction, making remote sensing vertical profilers, such as Lidars, very attractive for wind resource assessment. However, there are some challenges that the technology has had to overcome to be considered ‘proven’ and commercially accepted by the industry for wind resource applications.
This has been achieved by building a body of evidence to demonstrate that devices are meeting certain milestones relating to different development stages and thus ‘proven’ status. Firstly, to be considered proven, devices need to demonstrate they can record accurate wind measurements reliably and consistently across a wide range of sites with different meteorological conditions. Secondly, it has been important to maintain traceability of wind measurements to international standards which have historically been based on cup anemometry. These concerns have been addressed through extensive validation work against conventional meteorological masts, carried out by LiDAR device manufacturers, the wider wind industry and academic community, which have helped inform an understanding of the performance of these devices in a range of operational and environmental conditions. This evidence has been used by independent expert third parties to judge the maturity of a device and it is now accepted that leading LiDAR technologies offer comparable levels of accuracy to conventional mast measurements when deployed according to industry best practice and in appropriate locations.
A recent development has been the application of LiDAR technology in the offshore environment, specifically floating LiDAR systems, which represents a cost-effective way of measuring the resource at proposed offshore wind farm sites, particularly in deeper waters.
As with any maturing technology, floating LiDAR requires defined industry best practice validation procedures to improve industry confidence in the devices performance before commercial use. Originally published in 2013, the Carbon Trust Offshore Wind Accelerator (OWA) Floating LiDAR Systems Roadmap defines different stages of maturity and establishes the prerequisites for floating LiDAR systems to satisfy these defined stages of maturity. DNV GL led a consortium to update the OWA Roadmap in 2018 which reviewed floating LiDAR system deployments worldwide. This review demonstrated a significant rise in deployments of floating LiDAR systems globally since 2013. The updated roadmap therefore reflects the latest industry experience, providing a clear framework for floating LiDAR suppliers to align with and to help increase industry confidence in its use. The revised OWA Roadmap provides a clear definition related to Stage 3 maturity, providing detailed requirements for systems to progress to this final maturity stage (e.g. fully commercial).
LiDAR technology presents a great example of technology progressing faster than industry standards. This is highlighted by the OWA Roadmap update and by industry working groups, such as the IEA Task 32, who recently published recommended practices for floating LiDARs. The industry is also starting to see remote sensing technology, such as LiDAR, be recognised in international standards (Edition 2, IEC 61400-12-1 international standard, published in 2017).
LiDAR technology has made significant progress in the last decade in becoming a widely accepted source of accurate data to support resource assessments and thus, wind farm developments. Although LiDAR technology provides more flexibility and data insights than conventional meteorological masts, it is worthwhile being aware of its limitations and some work still needs to be done before this technology replaces standard meteorological masts. For instance, meteorological towers remain an important part of a well-executed resource assessment campaign for capturing turbulence and extreme wind speed information and for providing a reference for wind speed correlations for example. However, it’s clear that the industry has made great strides in updating recommended practices and standards to reflect the advancing technology. We at DNV GL are proud to be involved in the numerous industry working groups and projects seeking to progress LiDAR technology and are happy to provide you with independent, expert advice about the technology.
 “Deployments of Floating LiDAR Systems”, 2018