The yield and performance technical working group is one of five technical working groups of the Offshore Wind Accelerator (OWA), consisting of experts from each of the OWA’s partner organisations and the Carbon Trust.
It focuses on investigating the energy yield analysis process to increase understanding, improve the industry standard, and to reduce costs. In former stages of the OWA it was known as the wakes and wind resource technical working group.
The group seeks to develop a better understanding the behaviour of wind flow across an offshore wind farm and improving modelling techniques within energy yield analysis. At the centre of the research is the goal to reduce the uncertainty around energy losses, improving the bankability of projects.
Research to date has accelerated the move to LiDAR technologies from meteorological masts, validated new wake models and assessed the impact of blockage. Of particular note has been the pioneering floating LiDAR roadmap, which is now recognised as the industry standard definition for floating LiDAR devices. The OWA has also funded and managed several ground breaking campaigns offshore, including deployment of floating LiDAR and new scanning LiDAR devices.
Below are examples of key pieces of work from the yield and performance technical working group.
Global blockage effect
In 2018, the yield and performance working group launched an exciting new project to investigate the ‘Global blockage effect’. The project has set out to increase understanding of the underlying physics behind the blockage effect, the scale of the effect and how it can be incorporated in to future modelling practices. Ultimately, the project will develop methods for more realistic predictions of energy yield.
OWA wake modelling challenge
In 2019 the yield and performance working group invited offshore wind wake modellers to participate in a series of benchmarks to test wake models under a wide range of wind climates and layout characteristics, based on operational wind farm data provided by OWA partners. This exciting multistage process saw wind farm benchmarks being introduced periodically throughout the year.
The aim of the project was to improve confidence in offshore wind wake models and in the prediction of array efficiency which is important to reduce uncertainty in energy yields for offshore wind farms. The work has been an important demonstration of the accuracy of state-of-the-art models in predicting array efficiency; and has helped tool vendors, research institutions and wind farm developers to improve the accuracy of their models based on real wind farm data.
Guidelines for Scanning LiDARs for Power Curve Testing
Wind turbine power curve verification (PCV) is a crucial measurement task in wind energy since it provides the means for performance monitoring and the basis of energy production guarantees. Offshore, nacelle lidars quickly replaced the traditional (and financially inviable, in this environment) meteorological masts for this purpose. As turbine rotor sizes increases, the need to measure the wind further away from the turbine in PCV (to reduce the blockage effect) increases as well, rapidly approaching the measurement distance range of state-of-the-art nacelle lidars. For this reason long-range scanning lidars, due to their greater measurement range and versatility, can be considered a suitable alternative to nacelle lidars for PCV. One disadvantage, in comparison to nacelle lidars, is that they lack tailor-made standards or guidelines.
This OWA project has developed best practice guidelines which highlight items that need to be modified or completed for the use of transition-piece scanning lidars for wind measurement.
The OWA has been at the forefront of the development and commercialisation of floating LiDAR for wind resource assessment purposes. Unlike traditional meteorological masts (met masts), which can cost around £10-£12m, a significant outlay during the development stages of a project, a floating LiDAR system not only costs significantly less (~£1-£2m ), and also offers added flexibility in siting.
Floating LiDAR: Roadmap
LiDAR systems have been used for decades to measure wind speeds, for example in aviation, but had previously not been used for wind resource assessment purposes. Therefore, there were limited to no guidelines as to what criteria a floating LiDAR system would be required to follow and demonstrate in order for the data collected in this manner to be deemed acceptable and reliable by funders.
In response to this, the OWA developed the Roadmap for the commercial acceptance of floating LIDAR in collaboration with industry, which sets out in detail the steps and criteria that floating LiDAR systems must meet in order to be deemed bankable.
The Roadmap was quickly adopted as the go-to industry standard for LiDAR demonstration and development for wind resource assessment and the demand and interest in floating LiDAR systems quickly grew from a new and emerging technology to one being widely accepted and adopted by the industry. In 2018 we published an updated version of the Roadmap.
Floating LiDAR: Demonstration trials
A key part of the validation criteria as set out in the OWA Roadmap were long-term demonstrations against an IEC-compliant met mast in relevant offshore conditions. The OWA therefore also supported the offshore demonstration trials for five systems at six different sites across Europe:
- Babcock at Gwynt y Mor;
- FLiDAR at Gwynt y Mor, Narec (now ORE Catapult Blyth), and Neart na Gaoithe;
- EOLOS FLS200 at IJmuiden Met Mast;
- Fugro Oceanor Seawatch Floating LiDAR at East Anglia ONE; and
- Fraunhofer IWES Wind LiDAR Buoy at FINO1 Met Mast.
Following the trials, many of the devices tested are now being deployed by offshore wind farm developers in commercial campaigns. In addition to direct cost reduction, the validation trials also provided valuable hands-on operational experience of the devices for developers and floating LiDAR suppliers to streamline operations and maintenance activities, including improved HSE. Read more here.
Floating LiDAR: Recommended practice
As a result of the significant number of floating LiDAR deployments, more details and guidance were required on the deployment and management of such systems to ensure clarity and consistency across the industry, and provide comfort to developers carrying out data campaigns that data collected would be of high quality and bankable. The OWA worked closely with IEA Task 32 for several years developing and refining the recommended practices. The first version was published by the OWA in 2016, and the IEA built upon this work to publish a further version in 2017.
"The development of the 'OWA Recommended Practices for Floating LiDAR systems' was a fundamental milestone for the total acceptance of this technology to measure bankable wind conditions in the offshore environment."
Javier Rodriguez Ruiz, ScottishPower Renewables
Floating LiDAR: Repository
In 2018 we published a repository of floating LiDAR deployments to give clarity to the market which systems had been deployed and where. This document includes trials completed through the OWA and other trials, as well as commercial deployments.
The repository is now updated on an annual basis to reflect the growth in the use of floating LiDAR. If a contractor wishes to submit information to be included in the annual update of the repository, please email firstname.lastname@example.org for details.
OWA measurement campaign at Rødsand II
In 2013, the OWA launched a measurement campaign at the Rødsand II wind farm. The £2m wake effects measurement project provided detailed measurement data to the wind industry to help better understand how the wind behaves in complex situations offshore. This data is used to help industry improve prediction accuracy, reduce financing costs and optimise windfarm layouts.
Remote wind measurements using scanning LiDAR in Dublin Bay
Understanding the detailed behaviour of wind at a wind farm site can help lower the uncertainty around wind resource and hence further reduce financing costs. A level of uncertainty and risk is applied to assessments to account for potential variation in wind speed across a site, given that resource is generally only measured at one or two points. Scanning LiDAR systems offer a solution as they have the ability to measure wind speeds across a larger range than met masts or floating LiDAR systems.
To investigate the applications that scanning LiDAR systems in offshore wind, we deployed four scanning LiDAR systems across Dublin Bay, and cross-referenced the measurements taken with three vertical profiling LiDAR systems we installed onshore and offshore. The measurement campaign ran for several months and demonstrated the use of scanning LiDAR systems operating in single and dual Doppler at ranges up to 15km.
For any questions relating to the yield and performance workgroup please contact email@example.com.