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Carbon TrustOffshore Wind AcceleratorOWA floating LiDAR campaign: Babcock trial at Gwynt Y MôrCopenhagen, 11 March 2015Megan Smith

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Trial Overview

Using RWE’s Gwynt y Mor mast in the Irish Sea

MeasNet-calibrated cup anemometers at 90m and 50m above LAT, wind vane at 70m

Fixed LiDAR (ZephIR 300) on met mast platform

Waverider buoy

Reasonably benign wave climate but large tidal range (8m)

Validation mapped against OWA Floating LiDAR Roadmap1. Three assessment criteria:

– Availability

– Accuracy

– Sensitivity to metocean conditions

1http://www.carbontrust.com/resources/reports/technology/owa-roadmap-for-commercial-acceptance-of-floating-lidar-technologies

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FORECAST Device OverviewPlatform

3.2m x 3.2m platform housing all systems

Wind turbines mounted on outriggers

Main lifting points for whole buoy

Access from ladder below

Handrails all around

Low Motion Buoy

Inherently stable, shallow draft spar buoy

Low pitch, roll and heave

Modular design

Three-point mooring design

Three main sections

Main Tube – 812mm OD Pipe

Buoyancy Tank – 3800mm Ø tank with internal stiffeners

Ballast Tank – 2600mm Ø tank filled with high density concrete

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Wind Speed Accuracy

Reference: Cup anemometer

Height above LAT

Regression Slope

Regression r2

90m 0.993 0.987

50m 0.997 0.987

Roadmap best practice 0.98 – 1.02 >0.98

Reference: Fixed LiDAR

Height above LAT

Regression Slope Regression r2

50m 0.998 0.900

90m 0.997 0.976

Correlation between wind speed measurements from the floating

LIDAR and the cup anemometer at 90m above LATLAT = Lowest astronomical tide

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Wind Direction Accuracy

Scatter at +/- 108deg due to the flow reversal at the ZephIR met station

Additional scatter thought to be due to magnetic interference with the compass. Babcock are now working on using a GPS compass to improve the accuracy

Correlation between wind direction measurements from the floating

LIDAR and the wind vane at 30m above LAT

Note: data at 70m height is not presented due to a suspected offset in the 70m wind vane

Reference: Wind Vane

Height above LAT

Regression Slope

Regression r2

30m 0.989 0.972

Roadmap best practice

0.97 – 1.03 > 0.97

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Turbulence Accuracy

Correlation between turbulence intensity measurements from the

floating LIDAR and the cup anemometer at 90m above LAT

Correlation between turbulence intensity

measurements from the fixed LIDAR and

the cup anemometer at 90m above LAT

Comparison

Regression at 90m

Slope r2

Floating LIDAR vs Cup Anemometer

1.106 0.520

Fixed LIDAR vs Cup Anemometer

1.158 0.455

Comparison between fixed and floating LiDAR data sets shows that the floating LiDAR (right) gives no worse correlation to the cup anemometer than the fixed LiDAR (below)

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Gust Accuracy

Gust speeds are captured well

Correlation between maximum gust speed measurements from

the floating LIDAR and the cup anemometer at 90m above LAT

Reference: Cup Anemometer

Height above LAT

Regression Slope

Regression r2

90m 0.988 0.978

50m 0.998 0.978

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Sensitivity of Wind Speed Accuracy to Metocean Conditions

Overall the device showed good performance to the various metocean conditions experienced during the trial

No sensitivity to wave height, wave steepness, or wave period are evident

Sensitivity to error in wind speed to wave

steepness

Sensitivity to error in wind speed to

significant wave height

Sensitivity to error in wind speed to peak

wave period

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Sensitivity of Wind Speed and Direction Accuracy to Metocean Conditions

Negligible sensitivity to tide height

Some sensitivity in wind direction to buoy orientation, addition of a DGPS compass for future deployments should remedy this error

Sensitivity to error in wind speed to tide height Sensitivity to error in wind direction to buoy bearing

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Availability

Overall system availability for the 6 month trial was 99.86%

– Roadmap criteria: >95%

Every month of the trial had (post-processed) data availability of over 95%

– Roadmap criteria: >90%

Processing of data consists of removal of 9999 and NAN values only

As the graph shows, consistent and good data availability for all measurement heights

Summary of overall availability for the trial by height above LAT

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How does this trial fit in with the OWA programme?

OWA: customer-drivenoffshore wind R&D

Babcock

EOLOS Axys

TBC

FLiDAR

OWA Roadmap

TBC

Upcoming trials

Completed projects

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Conclusions

Availability is very good

– 99.86% Overall System Availability, with monthly availabilities all over 95%

Wind speed accuracy is very good

– 0.993 slope

– 0.991 r2

Wind direction accuracy is good

– 0.984 slope

– 0.976 r2

Gust prediction is good

– 0.988 slope

– 0.978 r2

Turbulence intensity prediction is no worse than fixed LiDAR measurements

Wind speed measurements are largely insensitive to metocean conditions over the range experiences (Hs = 3m)

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Assessment against the Roadmap

The Babcock device has reached Stage 2, as validated by Frazer-Nash and DNV GL.

Babcock intend to implement modifications to the compass as recommended by DNV GL and will validate the updated system

In summary:

– Results of the GyM trial are extremely encouraging

– Causes of wind direction offset have been identified and resolved

– Technology is definitely on the right track

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Questions?

Megan.Smith@carbontrust.com

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KPIs / Acceptance Criteria – Data Quality

KPI Definition / Rationale Acceptance Criteria

Best Practice Minimum

Xmws Mean Wind Speed – Slope

single variant regression with

the regression constrained

through origin.

0.98 – 1.02 0.97 – 1.03

R2mws Mean Wind Speed –

Coefficient of Determination

>0.98 >0.97

Mmwd Mean Wind Direction – Slope

two-variant regression

0.97 – 1.03 0.95 – 1.05

OFFmwd Mean Wind Direction – Offset < |5°| < |10°|

R2mwd Mean Wind Direction –

Coefficient of Determination

> 0.97 > 0.95

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KPIs / Acceptance Criteria – Availability

KPI Definition / Rationale

Acceptance

Criteria across

total of six (6)

months data

MSA1M Monthly System Availability – 1 Month

Average, for every month

≥90%

OSACA Overall System Availability – Campaign

Average

≥95%

MPDA1M Monthly Post-processed Data Availability – 1

Month Average for every month

≥80%

OPDACA Overall Post-processed Data Availability ≥85%

In the above table, during periods of maintenance; the system is deemed unavailable.

≥90%

≥95%

≥80%

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OWA Floating LiDAR programme objectives

Define criteria required of a floating LiDAR system to achieve various stages commercial acceptance

– Stage at which measurement data recorded using a particular floating LIDAR technology is accepted by funders of commercial scale offshore wind projects

Support trials to validate floating LiDAR technology

– Gwynt Y Môr

– Irish Sea site

– Narec / Neart na Gaoithe

– East Anglia

– IJmuiden

Formulate and promote best practice by sharing lessons learned

– OWA Floating LiDAR Workshop

– OWA Roadmap

– IEA Annex 32

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Babcock datasets

The data sets shown are from 6 months of continuous operation from May to November 2014

This data includes ~2 months of data which has been corrected for a 37° direction offset identified early in the deployment

– This offset was caused by magnetic interference with the compass. The correction was performed in-situ

– DGPS compass will be used on future projects

– Babcock have now developed a compass commissioning procedure to address the direction offset, which have been reviewed and supported by DNV-GL for future trials

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Roadmap describes KPIs required of a successful trial

Key areas for assessment are accuracy and availability and sensitivity to metocean conditions

KPIs are defined for each areas as well as acceptance criteria, when relevant, for example

– Monthly system availability ≥90%

– Wind Speed R2 ≥97% (minimum) ≥98% (best practice)

Data coverage requirements and guidance on the analysis needed are also provided in the Roadmap document

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Roadmap Assessment Criteria

3 key areas for assessment– Accuracy

– Wind speed and direction

– Turbulence intensity & gust speeds

– Sensitivity to metocean conditions

– Wave height, period, steepness

– Tide height

– Availability

– Applied to ten-minute-averaged data

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Examples of commercial uses of floating LiDAR at various stages

Increased bankability

Increasing # trials

Maturity Level 1:Baseline

Scenario A Fixed met mast supplemented by ≥1 floating LiDARs

Maturity Level 2:Pre-commercial

Scenario C • ≥1 floating

LiDAR(s) deployed

Maturity Level 3:Commercial

Scenario D• Fixed met mast

supplemented by ≥1 floating LiDARs

Scenario F• ≥1 floating

LiDAR(s) deployed

Scenario G• Fixed met mast

supplemented by ≥1 floating LiDARs