Multidimensional optimisation of O

1
Multi-dimensional optimisation of OM provisions
for offshore wind projects
Jerome Jacquemin Garrad Hassan and Partners
Ltd European Offshore Wind Berlin - December
2007
2
Overview

• Background and motivation
• Model
• Optimisation approach
• OM decision support tool
• Conclusions

3
Background and Motivation (1)
Additional operational risks compared to
onshore projects

• Weather / access risk

• Equipment risk

• Export system risk

• Assess these risks
• Eliminate, reduce or transfer
• Minimise the impact through adequate OM
  resources and strategies

4
Background and Motivation (2)

• Some key questions that a modelling approach
  helps to answer.
• General
• Is it worth investing more / less in OM
  resource ?
• Transport / Access strategy
• What is the right balance between investment in
  transport and investment in manpower?
• Scheduled maintenance strategy
• Is seasonal campaigning a cost effective
  approach ?
• Change-out strategy
• Should a crane vessel be chartered for the
  project ? Shared with neighbouring projects?
• Which and how many strategic spares ?

5
O2M model

• Closely based on work of Bossanyi and
  Strowbridge (ETSU 1994)
• Model dubbed O2M,Optimisation of Operations
  Maintenance

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Optimisation objective

• OM Direct Cost plus Lost Production Cost

• Optimum is a function of
• Project size
• Distance from port
• Wave climate
• Intrinsic turbine reliability
• Off-take energy price

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Optimisation variables and method

• Variables / dimensions
• Manpower
• Access strategy (onshore, offshore
• accommodation, helicopters)
• Access vessels
• Crane barge contracting
• Shift length / number of shifts
• Repair philosophy
• Seasonal campaigning (y / n)
• Base ports
• Spares

• Methods
• Trial and error
• Outcome is uncertain, time-consuming
• Univariate search
• Convergence to poor local optima, time-consuming
  
• Systematic multivariate optimisation
• Robust
• Significant effort involved but can be
  computerised

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Proposed Wind Farm Site GHbank
GHbank Wind Farm
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OM Modelling Univariate 1
AV Availability DC Direct Costs LP Lost
Production TC Total Cost (DCLP) All costs in
Euro 000,000s / annum
BASIC ASSUMPTIONS
Crane Barge Contracting
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OM Modelling Univariate 2
AV Availability DC Direct Costs LP Lost
Production TC Total Cost (DCLP) All costs in
Euro 000,000s / annum
BASIC ASSUMPTIONS
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Univariate / Multivariate optimisation Comparison
BASIC ASSUMPTIONS
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Strategy Inter-Dependency
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OM decision support tool
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Conclusions
The role of modelling ? Interactions between
weather, failures and OM provisions ? OM
strategy lt?gt availability The benefit of a
multi-dimensional approach ? Complex couplings
between OM provisions are encapsulated ?
Optimisation of OM provisions / sensitivity
studies Further Work ? Better understanding of
corrective maintenance requirements for WTG ?
Time-varying OM costs throughout the project
life ? Validation