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Conference programme 

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Poster session

Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Andrew Henderson Senior Lead Offshore Wind Engineer, DONG Energy, United Kingdom
Andrew Henderson (1) F P Nick Baldock (2) Iván Arana (1) Chris Newton (2)
(1) DONG Energy, London, United Kingdom (2) , , (3) DNV.GL Garrad Hassan, Bristol, United Kingdom

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Presenter's biography

Biographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited

Andrew Henderson is Senior Lead Offshore Windfarm Engineer at DONG Energy Windpower with responsibilities for windfarm design and optimisation. Andrew has worked in offshore wind for around 15 years starting with research work at University College London (Ph.D.) and TUDelft in the Netherlands (European R&D projects). Subsequently Andrew worked on Spanish-led deepwater offshore wind projects at CEASA (now part of EdPR) and Acciona whilst most recently Andrew led the offshore wind due diligence work at Garrad Hassan (now part of DNV-GL).


Low-hanging fruit for reducing the Cost of Energy: Optimising the Electrical Export Capacity


The most immediate and direct ways of reducing the Cost of Electricity from offshore wind include the offshore windfarm design itself, with one such design approach being to optimise the ratio between the windturbine generating capacity and the electrical infrastructure export capacity (also known as "overplanting"). This optimisation of the physical wind-farm provides several good cost reduction possibilities and can be considered ‘low-hanging-fruit'.


Through two separate models, previously developed fully independently of each other by DONG Energy and DNV.GL, this paper will explore how the ratio of electrical infrastructure capacity to the wind turbine capacity affects the project's cost of energy. Optimal windfarm sizing, for given sets of design criteria, are identified, along with the associated reduction in the cost of energy and robustness of the design to uncertainties in design and operating parameters.

Main body of abstract

Since the electrical infrastructure is a considerable part of the overall CapEx, since windspeed and hence energy production varies in time, since windturbines will be out of operation at times for scheduled maintenance and repairs, and since electrical losses are more significant for larger wind farms, it makes good economic sense to build a small number of extra windturbines in the windfarm.

In order to ensure wider industry understanding and support for this design approach, this paper will:
• introduce the rationale
• present results from the two fully-independent approaches (i.e. from DNV-GL and DONG Energy)
o hence provides confidence in the conclusions
• examine some of the sensitivities and drivers;
o how the benefits may change depending on windfarm characteristics and assumptions
o and hence which projects can benefit
• consider potential impacts on other offshore windfarm as well as package design aspects
• consider the regulatory dimension
o examine whether any regulatory complications might halt this initiative
To examine the technical robustness of the design process, a number of key sensitivities for the assumptions will be examined. The purpose being to:
• identify which assumptions are important
• identify confidence in the optimal design and value generated
• identify which of the near-optimal design options identified above (i.e. N or N+1 additional windturbines) are most robust to changes in the assumptions


This paper will present the case for optimising the ratio between the windturbine generating capacity and the electrical infrastructure export capacity, presenting evidence of potential cost of energy reductions for offshore wind energy in the range of ½% to 1%.

This evidence can be deployed when supporting arguments are required, across Europe as well as the wider World, acknowledging that particular regulatory structures can exclude this design initiative.

Learning objectives
The objective of this proposed paper is to allow the audience to:
• understand the principals of this design approach
• appreciate the benefit of reductions to the cost of electricity and the technical ease with which this initiative can be deployed
• acknowledge some of the challenges, in particular relating to regulation