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www.scottishpowerrenewables.com 1

Alberto Avila Armella

Weather Down Time in Offshore

Wind Installation Works:

Assessment and Potential R&D

Work Lines

Studi di Aggiornamento sull'Ingegneria Off-Shore e Marina AIOM

"Tecniche e tecnologie nelle costruzioni marittime e offshore"

https://www.iberdrola.es/


Content

1. Introduction

2. Operational limits

3. Potential work lines

a) WDT assessment

b) Monitoring

c) Improved operational limits

4. Conclusions

Weather Down Time in Offshore Wind Installation Works: Assessment and Potential R&D Work Lines




ScottishPower/Iberdrola Portfolio

West of Duddon Sands

(JV with Dong)

Operating

(108x3.6=389 MW)

Wikinger

Under construction

(70x5=350 MW)

East Anglia One

CfD secured

(102x7=714 MW) St. Brieuc

Development

East Anglia Three

Development



1. Introduction


Offshore Wind

Offshore O&G Onshore Wind

Key differences

Technology under development. More stable wind resource, and less turbulent.

Multiple elements: long periods, repetitive. More expensive components.

Complex O&M Logistics due to dispersion. Challenging O&M

Transmission



1. Introduction

Offshore Wind founding and financial decision

Process:

1. Development rights

2. Consent, feasibility studies

3. Basic engineering and tenders

4. Preferred suppliers and contractors selected

5. Final Investment Decision

6. Fabrication

7. Installation

8. Operations

9. Decommissioning




1. Introduction

Uncertainties

The final investment decision requires certainty (reduced margins)

Weather conditions ≠ Certainty

• Energy yield:

• Long term → mean regime

• Installation costs (due to WDT)

• Short term → risk management, statistical analysis




2. Operational Limits

Definition of offshore operations

Marine operations must be engineered to guarantee:

• Safety of people

• Environment protection

• Integrity of elements to install

• Integrity of installation means





Movements

• Movements are the ultimately factor that determines operability.

• But metocean agents are used to define limits (difficult standardization).






Offshore operations are

• planed

• contractually regulated

• executed

based on a breakdown of activities, with limits and durations

defined.






Critical path


ACTIVITIES Hs

(m) Tp (s)

u10

(m/s)

uhub

(m/s)

Current

(m/s)

Visibility

(m)

Duration

(hours)

7 Jack-up and preload x x x

8 Release sea fastening crane x x

9 Tower installation x x

10 Nacelle + hub installation x x

11 Blades set installation x x

12 Crane in safe position x x

13 Jack-down, move to next position x x x

14 Positioning x x x




Sensitivity

Programme

Example


Net time Cost of Spread

120 days 0.2 M€/day

1.5 2 1.5 2 1.5 2

72 40% 59% 300 203 60 41

24 58% 74% 207 162 41 32

4 71% 84% 169 143 34 29

2 72% 86% 167 140 33 28

Availability

Hs limit [m]Weather

window [hr]

Total time [days] E.g. budget M€

Hs limit [m] Hs limit [m]




Sensitivity

Budget

Example: indicative day rate of installation spread:

200,000 €/day


Net time Cost of Spread Cost of Spread

120 days 0.2 M€/day 0.5 M€/day

1.5 2 1.5 2 1.5 2 1.5 2

72 40% 59% 300 203 60 41 150 102

24 58% 74% 207 162 41 32 103 81

4 71% 84% 169 143 34 29 85 71

2 72% 86% 167 140 33 28 83 70

Hs limit [m]

E.g. budget M€Availability

Hs limit [m]Weather

window [hr]

Total time [days] E.g. budget M€

Hs limit [m] Hs limit [m]



3. Potential R&D Work Lines

a) WDT assessment

Objective of WDT assessment:

Reliable information for risk management and investment decision

Methods:

• Based on rates: for early development phases, average

• Based on simulation: for detailed planning, budget allocation

(process simulated for historical records).





a) WDT assessment


Duration,

Cost

100%

50%

No

n e

xce

ed

an

ce

pro

ba

bili

ty

Strategy

A

Strategy

B




a) WDT assessment

Work lines (simulation models):

• Improved usage and results post-processing

• Sensitivity analysis

• Presentation of results

• Simulation of other risks.

• Accuracy estimations, based on the quality of the input data.

• Influence of the quality of the weather forecasts expected.

• Customization to specific vessels.





b) Monitoring

Movement = f ( Metocean agents

Characteristics of vessels and equipment

Interaction between them- movements )

Work lines:

• Systems to monitor metocean conditions and movements

during execution.

• Methodologies to define operational limits based on monitoring.





b) Monitoring

Subjectivity:

• Captain

• Marine Warranty Surveyor

New systems need an implementation process, with the

involvement of the different stakeholders (consensus, certification,

experience, confidence).





c) Improved operational limits

• Proprietary, for example.:

• Onshore Pre-commissioning.

• Dimensions and weight optimization.

• Blades installation tools.

• Widely applicable

• Equipment manufacturers.

• New vessels.

• Joint initiatives (e.g. ORE Catapult, CT OWA)




4. Conclusions

• There is still margin for improve WDT assessment and to

optimize operations.

• Innovation must be inclusive for the different stakeholders.

• The applicability due to manufacturer-specific conditions should

be taken into account.


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