A part of BMT in Energy and Environment

Foundations and Moorings for Tidal Stream Systems

Client: The Carbon Trust

Report no.: L.CAR.002W

Date: September 2009

Confidential

Foundations and Moorings for Tidal Stream Systems

The Carbon Trust

BMT Cordah Limited 1 September 2009

Report Title Foundations and Moorings for Tidal Stream Systems

Client The Carbon Trust

BMT Cordah Report No: L.CAR.002W

Status and Version: Public draft

Date of Release: September 2009 (Print Date Monday, 21 September 2009 at 12:39 PM)

Terms:

Name Signature Date

Authors

Michael Starling

Alex Scott

21st September 2009

Approved by Richard Parkinson

BMT Cordah Limited,

4th Floor,

Holland House,

1 4 Bury Street,

London

EC3A 5AW

Tel. +44 (0)20 7015 0300

Fax +44 (0)20 7015 0344

Email: mstarling@fleetech.com

Website: www.bmtrenewables.com

Foundations and Moorings for Tidal Stream Systems

The Carbon Trust

BMT Cordah Limited 2 September 2009

Document log

Version Date Summary of changes Author

Pre-issue 14th October 2008 Skeleton Michael Starling

01 4th December 2008 First Issue Michael Starling

02 2nd January 2009 Second issue following review meeting on 4th December 2008

Michael Starling

03 8th June 2009 Third issue following contract extension

Michael Starling

03a 24th July 2009 Update with responses to Entech comments

Michael Starling

Public Draft

21st September 2009 Edited to be basis of the carbon trust public version of the report

Michael Starling

Foundations and Moorings for Tidal Stream Systems

The Carbon Trust

BMT Cordah Limited 3 September 2009

CONTENTS 1 INTRODUCTION..................................................................................................................8

1.1 About the Report 8

1.2 Overview of the Report 8

2 OVERVIEW OF TIDAL STREAM DEVICES ....................................................................10

2.1 Sources of Information 10

2.2 Characteristics that affect the Foundations and Moorings 10

2.3 Tidal Stream Devices 10

2.4 Conclusions on Tidal Stream Devices 15

3 OVERVIEW OF TYPICAL TIDAL STREAM DEVICE LOCATIONS ..............................16

3.1 Relative Difficulty of Locations 16

3.2 Selection of Environmental Parameters that Drive Difficulty 16

3.3 Classification System for Environmental Parameters 18

3.4 Relative Importance of Environmental Parameters 22

3.5 Selection of Favoured Locations 23

3.6 Classification of the Favoured Locations 24

3.7 Relative Difficulty of Favoured Locations 27

3.8 Conclusions on Location Difficulty 28

4 FOUNDATIONS AND MOORING REQUIREMENT SPECIFICATION ...........................31

4.1 Success Criteria 31

4.2 Life 31

4.3 Loadings 32

4.4 Installation 34

4.5 Operations and Maintenance 34

4.6 Conclusions on Requirement Specification 35

5 REVIEW OF FOUNDATION AND MOORING METHODS ..............................................36

5.1 Characteristics that affect the suitability of a Foundation or Mooring 36

5.2 Potential Foundations and Moorings 36

5.3 Further Information on Foundation Types 40

5.4 Further Information on Moorings Types 44

5.5 Maintenance of Foundations and Moorings 47

5.6 Conclusions on Foundation and Mooring Methods 49

6 INDICATIVE INSTALLATION COSTS .............................................................................51

6.1 General 51

6.2 Cost Bands 52

6.3 Installation Vessel Costs 53

Foundations and Moorings for Tidal Stream Systems

The Carbon Trust

BMT Cordah Limited 4 September 2009

6.4 Base Case Costs 56

6.5 Commentary on the Cost Adjustment Factors 59

6.6 Conclusions on Installation Costs 61

7 COMPARATIVE COSTS OF FOUNDATION AND MOORINGS INSTALLATION .........63

7.1 Basis of the Costing 63

7.2 Summary of the Findings 63

7.3 Limitations of the Cost Modelling 65

8 CONCLUSIONS.................................................................................................................66

8.1 Integration of Foundation Design with Device Design 66

8.2 Foundation Design - Need to use tried and tested designs 66

8.3 Mooring Design - Need to demonstrate feasibility 66

8.4 Installation of Single Devices and Series Installation 66

8.5 Installation Vessels - Need to investigate the ideal vessels 67

8.6 Maintainability - Need to design for ease of maintainability 67

9 RECOMMENDED ARRAS FOR FURTHER RESEARCH ...............................................68

9.1 Suggested Research to Reduce Risk 68

9.2 Suggested Research to Investigate Opportunities 69

9.3 Research Programme Participants 70

10 OBSTACLES ON THE ROUTE TO MARKET .................................................................71

10.1 Routes to Market Template 71

10.2 Conclusions and Directed Research 71

11 ANNEX A - SCOPE AND PURPOSE OF A REQUIREMENT SPECIFICATION............74

11.1 Phases of Development 74

11.2 Phases of an Installation 75

11.3 Installation Cost Drivers 76

11.4 Phases of Operation 76

11.5 Factors Affecting Operations 77

12 ANNEX B - EXAMPLE ENVIRONMENT IN THE PENTLAND FIRTH ............................78

12.1 Difficulty of the Location 78

12.2 Geology of the Location 81

12.3 Ecology and Marine Life at the Location 82

12.4 Marine Growth On Foundations and Moorings 84

12.5 Anti-Fouling Solutions 89

12.6 Tidal Current Converter 90

13 ANNEX C ADDITIONAL INFORMATION ON COST MODELLING.............................91

13.1 Cost Variability 91

13.2 Technical Parameters used in the Cost Model 92

Foundations and Moorings for Tidal Stream Systems

The Carbon Trust

BMT Cordah Limited 5 September 2009

13.3 Technical Parameters used in the Cost Model 93

TABLES

Table 1 Tidal Devices and their Moorings 14

Table 2 Tidal Currents - Classification of Tidal Speed 18

Table 3 Tidal Currents - Classification of Flow Conditions 18

Table 4 Tidal Currents - Classification of Variation Across Site 18

Table 5 Tidal Currents - Classification of Data Uncertainty 19

Table 6 Water Depths - Classification of Depth at Lowest Astronomical Tide 19

Table 7 Water Depths - Classification of Tidal Range 19

Table 8 Weather Exposure - Classification of Survivability Extremes 20

Table 9 Weather Exposure - Classification of Wave and Wind Windows for Installation 20

Table 10 Bathymetry - Classification of Seabed 21

Table 11 Bathymetry - Classification of Marine Hazards 21

Table 12 Relative Importance of Classifications 22

Table 13 Classification of Favoured Locations 26

Table 14 Relative Difficulty of Favoured Locations 27

Table 15 Potential Foundations for Tidal Stream Devices 38

Table 16 Potential Moorings for Tidal Stream Devices 39

Table 17 Installation Cost Bands - Lump Sum Base Costs 52

Table 18 Installation Cost Bands - Day Rate Base Costs 52

Table 19 Installation Cost Bands - Cost Adjustment Factors 52

Table 20 Installation Vessels and their Costs 55

Table 21 Indicative Bases Costs and Cost Adjustment Factors of Installing a Foundation 58

Foundations and Moorings for Tidal Stream Systems

The Carbon Trust

BMT Cordah Limited 6 September 2009

Table 22 Technology Route to Market 72

Table 23 Project Route to Market 73

Table 24 Density of Marine Growth 85

Table 25 Tidal Current Converter (m/s knots) 90

FIGURES

Figure 1 Normalised Installation Costs 64

Figure 2 Technology Route to Market 71

Figure 3 Project Route to Market 71

Figure 4 Circling in on a Design Solution 74

Figure 5 Phases of a Marine Development 75

Figure 6 Phases of a Marine Installation 75

Figure 7 Installation Cost Drivers 76

Figure 8 Phases of Marine Operations 76

Figure 9 Operations Cost Drivers 77

Figure 10 Tidal Currents Cycles in the Pentland Firth 78

Figure 11 Tidal Currents Cycles in the Pentland Firth - Spring Tide 79

Figure 12 Tidal Currents Cycles in the Pentland Firth - Neap Tide 79

Figure 13 Normalised Installation Cost Variability - Foundations 91

Figure 14 Normalised Installation Cost Variability - Moorings 91

Figure 15 Technical Parameters - Foundations 92

Figure 16 Technical Parameters - Moorings 92

Figure 17 Cost Parameters - Foundations 93

Figure 18 Cost Parameters - Moorings 93

Foundations and Moorings for Tidal Stream Systems

The Carbon Trust

BMT Cordah Limited 7 September 2009

MAPS

Map 1 Map of Favoured Locations 23

Foundations and Moorings for Tidal Stream Systems

The Carbon Trust

BMT Cordah Limited 8 September 2009

1 INTRODUCTION

1.1 About the Report

The tidal stream energy system developers share a common challenge. Each device needs

to be held on station in a tidal flow in a practical and cost-effective way. The foundations or

mooring systems required can form a significant part of the life-cycle cost of the system

since they contribute to the capital cost and the ease of