Offshore Transmission Network Feasibility Study

Transcription

1 Offshore Transmission Network Feasibility Study Date: 26 September 2011 Version: 1.0 Cover Photograph: DONG Energy

2 Offshore Transmission Network Feasibility Study Offshore Transmission Network Feasibility Study Section 1 Executive Summary Page 2 Section 2 Background Page 5 Section 3 Methodology and Assumptions Page 7 Section 4 Stakeholder Engagement Page 17 Section 5 Consenting and Planning Page 18 Section 6 Overview radial and radial plus Page 24 Section 7 Overview coordinated Page 29 Section 8 Assessment of Potential Benefits and Challenges Page 32 Section 9 Conclusions Page 41 Appendices Appendix A Further information on scenarios Page 42 Appendix B Generic cable route optimisation Page 48 Appendix C Marine Resource System modelling and datasets Page 53 Appendix D Technology and cost assumptions Page 57 Appendix E Consenting and planning Page 58 Appendix F Assessment of design strategies Page 66 Appendix G East Coast of England Page 82 Appendix H East Anglia Page 98 Appendix I Southern Page 114 Appendix J Irish Sea Page 123 Appendix K Scotland Page 138 Appendix L Assumptions Page 152 Appendix M Glossary of acronyms Page 154 1

3 Offshore Transmission Network Feasibility Study Offshore Electricity Generation Section 1.0 Executive Summary 1.1 Offshore electricity generation will play an important part in meeting the renewable energy and carbon emission targets for 2020 and afterwards toward The Crown Estate s leasing rounds provide the potential to deliver around 46 GW of offshore wind generation in UK waters, and the award of Round 3 Zone Development Agreements in December 2009 marked the start of the biggest single programme in the world. Around 17 GW of Round 3 capacity has now entered into connection agreements with National Grid, demonstrating tangible progress toward the UK s binding commitments on renewable energy. Transmission Infrastructure Requirements 1.2 The potential growth rate, location and size of new offshore generation expected over the remainder of this decade and beyond means that the need to consider the necessary transmission infrastructure requirements to deliver this generation to market is more pressing than ever. In meeting the objectives of sustainability, affordability and energy security, ensuring the deliverability of offshore wind will be critical in facilitating the connection of generation in the required timescale. 1.3 To date, the offshore transmission infrastructure has typically been delivered on a point-topoint or radial basis, reflecting the characteristics of the generation projects as well as timing and technology constraints. However, questions arise as to whether this approach is fit for purpose over the longer term given limited resources and wider issues such as planning and consenting constraints, particularly onshore. 1.4 To this end, The Crown Estate and National Grid Electricity Transmission (NGET) have worked together to produce this Offshore Transmission Network Feasibility Study (the study) to identify and assess the feasibility, benefits and challenges of adopting a more coordinated approach to the development of offshore transmission infrastructure. 1.5 The coordinated design presented in this study is based on the installation of high voltage multi-user assets that interconnect the offshore platforms and generation projects to form an offshore network that is fully integrated with onshore Transmission requirements. This conceptual design highlights how the volume of assets installed offshore could be reduced whilst the need for onshore reinforcement is minimised. Offshore Transmission Network Feasibility Study 1.6 Focused on Round 3 and Scottish Territorial Waters (STW) projects, together with possible interconnection, the study has undertaken a detailed assessment of constraints (onshore and offshore) and network design. It has been additionally recognised that other programmes, notably some Round 2 projects, large marine energy schemes and future interconnectors, could be incorporated into a coordinated network design strategy. 1.7 Three scenarios form the basis of the design work: Accelerated Growth, Gone Green and Slow Progression as per the Offshore Development Information Statement (ODIS). Together, these provide a broad range of scenarios for the deployment of offshore generation. A further sensitivity has been utilised which offers a different build profile of offshore wind generation. 1.8 A number of design strategies are considered against these scenarios and the report offers a comparison between a purely radial design, radial plus (use of larger assets but without inter-zonal interconnection) and a fully coordinated solution. Each design strategy has been built incrementally, with designs illustrated at 2015, 2020, 2025 and Section 1: Executive Summary 2

4 Offshore Transmission Network Feasibility Study 1.9 Through the combined expertise of NGET and The Crown Estate, this has resulted in a detailed report on potential development paths for the electricity transmission system offshore (and associated onshore) in Great Britain to The study represents a view of the future network requirements and direction for potential development using information available at the time of analysis (frozen June 2011). The actual network design will be developed in accordance with user requirements. The designs shown in this report should not be considered as implying actual connection dates or connection routes for new infrastructure and they do not reflect the Transmission Owner s investment decisions regarding the development of their transmission area nor any other parties investment decisions. The designs present an illustrative coordinated transmission design approach and have been developed to allow a comparison between the potential design options. The actual contracted position and development of the offshore and onshore transmission system can and may differ from that illustrated in the study. Headline findings 1.11 The study has identified a number of benefits that are likely to result from the development of a coordinated offshore transmission network. These benefits can be categorised as follows: Environmental and consenting benefits; Improved management of valuable resources including land take, corridor routes, and manufacturing capability; Reduced cost for UK consumer (capital cost reductions and also a reduction in operational costs such as maintenance costs and congestion management costs in relation to system operation); and A flexible offshore transmission network that is better able to respond to future challenges Total potential cost savings associated with the coordinated strategy of 6.9 billion by 2030 have been identified 1, when compared with the development of the offshore transmission network on a radial basis ( 3.6 billion against radial plus by 2030). This includes: 5.6 billion capital cost savings ( 2.4 billion against radial plus); 1.2 billion congestion management cost savings (against both radial and radial plus); 0.1 billion maintenance cost savings ( 0.05 against radial plus) The capital cost savings identified are largely delivered through a reduction in the volume of assets required to connect offshore generation under a coordinated design as opposed to a radial design. The table below summarises aggregate asset requirements and savings under the Accelerated Growth scenario to More detail in respect of the benefits arising under this and the other scenarios is included within the main body of the report. 1 Congestion management and maintenance cost savings beyond 2030 are not reflected in this study. Section 1: Executive Summary 3

5 Offshore Transmission Network Feasibility Study Asset volume and capital cost (Accelerated Growth) radial vs coordinated ( 2010 prices) Radial Coordinated Savings Radial plus Coordinated Savings HVDC cables 6641 km 5216 km 1425 km 21% 5145 km 5216 km -71 km -1% Offshore AC cables 1559 km 2353 km -794 km -51% 1948 km 2353 km -405 km -21% Onshore AC lines (new) km 126 km 321 km 72% 447 km 126 km 321 km 72% Offshore platforms % % Cable landing sites % % Cost 34.8 bn 29.2 bn 5.6 bn 16% 31.6 bn 29.2 bn 2.4 bn 8% 1.14 The study has demonstrated that interconnection between zones (full coordination) is vital to realise the overall savings in relation to both asset and cost - and drives the additional benefits beyond those identified under radial plus. In contrast, the radial plus approach continues to require significant onshore reinforcements and an increased number of landing points to support the offshore developments bringing with it environmental and consenting challenges, as well as greater ongoing operating costs (maintenance and congestion management) The study recognises a number of challenges associated with moving towards a coordinated transmission design offshore: Uncertainty over the rate of deployment of offshore wind; Technology advancement rate; and The ability to consent those new routes required to connect the offshore generation A clear regulatory framework, delivered in a timely manner, will be required to navigate these challenges. Whilst the study does not explicitly consider the regulatory framework changes required to deliver a coordinated offshore transmission design, it does recognise that timescales for delivery and the need for holistic consideration will be key factors. Given the level of uncertainty within the wider energy industry with respect the rate of offshore wind deployment, a small risk of investment stranding is evident in the analysis. This risk however largely occurs at the pre-construction stage of the process, with the stranding risk associated with physical transmission investment occurring as a result of timing issues regarding lead times for new transmission infrastructure. The design and consenting activities will need to progress a coordinated solution, even though there may be varying degrees of certainty as to whether a generator(s) may proceed with a project. 2 The onshore reinforcements (onshore AC lines) referenced in this study relate only to MITS reinforcements (locally or deeper system reinforcements). Section 1: Executive Summary 4

6 Offshore Transmission Network Feasibility Study Section 2.0 Background Offshore Wind, National Grid and The Crown Estate 2.1 The Crown Estate has extensive marine assets, including ownership of approximately 55% of the UK s foreshore and the majority of the seabed within the 12 nautical mile UK territorial limit. It also has the right to exploit natural energy resources, excluding fossil fuels, on the continental shelf within the Renewable Energy Zone. The Crown Estate has a responsibility to ensure an efficient and sustainable use of seabed in relation to marine activities, including corridors for cables and pipelines within 12 nautical miles and those cables associated with renewable energy infrastructure in the Renewable Energy Zone. The Crown Estate is obligated to enhance the capital value and the revenue return of the assets it has responsibility for. This includes the seabed and therefore it is the view of The Crown Estate that consideration needs to be given to the most efficient (within environmental, technical, commercial and other constraints) use of the seabed, coastal and other assets within its responsibility. 2.2 Offshore wind farm developers lease an area of seabed from The Crown Estate within which their infrastructure is to be constructed. There have been five commercial allocation rounds to date: Round 1, Round 2, Round 3, extensions to Rounds 1 and 2 projects, and projects in Scottish Territorial Waters (STW). 2.3 The first allocation, in 2001, acted as a demonstration round to allow potential developers to gain an understanding of the technological, environmental and economic issues associated with developing and operating offshore wind farms. 2.4 Further allocation rounds were conducted in 2003 (Round 2), 2008 (Scottish Territorial Waters), 2009 (Round 3), and 2010 (Round 1 and 2 extensions). The combined generation capacity for all of these rounds amounts to over 46 GW by National Grid Electricity Transmission (NGET) owns and operates the high voltage electricity transmission system in England and Wales and, as National Electricity Transmission System Operator (NETSO), operates the Scottish high voltage transmission system. Following activation of the offshore transmission regime in June 2009, NGET s system operator role was extended to cover offshore waters. NGET s system operator role brings responsibility for the day-to-day management of the flow of electricity onto and over the National Electricity Transmission System including developing and maintaining an efficient, coordinated and economical system of electricity transmission. NGET also has an obligation to provide information on offshore developments through the publication of a non-binding Offshore Development Information Statement (ODIS). 2.6 The Crown Estate and NGET have contributed their relative experience and expertise to the findings of this study. The Crown Estate has used its award-winning Geographic Information System (GIS) based Marine Resource System (MaRS) to identify the offshore constraints relevant to the portion of illustrative cable routes under each of network design strategies identified for each scenario, taking into account constraints and exclusions for each region. It has also reviewed the current consenting framework in relation to offshore developments. NGET has identified electrical requirements and preliminary illustrative routing for onshore and offshore including landing points, interface points and offshore platform positioning, and has modelled the cost and technology assumptions to these illustrative designs in order to assess potential benefits and challenges. Further detail on the underlying assumptions is provided in section 3 and relevant appendices. Project objective and scope 2.7 The potential growth rate, location and size of new generation raises a number of challenges in terms of grid connections, which has resulted in the requirement to consider a coordinated design of the offshore and onshore transmission system. In order to Section 2: Background 5

7 Offshore Transmission Network Feasibility Study investigate the feasibility of such an approach The Crown Estate and NGET worked together on this offshore transmission network feasibility study, to: Identify how the coordinated development of the offshore (and associated onshore) network could be developed across a range of scenarios; Compare the coordinated approach against a radial and a radial plus approach where appropriate 3 ; Assess the benefits and challenges of a coordinated network, in particular, the impact on overall volume of assets, cost, flexibility, consenting, network security and resilience. 2.8 The study sought to present illustrative designs which: Optimise deliverability of offshore generation; Minimise overall cost to consumers; Optimise network resilience and security; Identify incremental development to minimise the risk of asset stranding; Facilitate flexible network development; and Mitigate the consent risk. 2.9 The study focused on the potential network development associated with the offshore wind programmes of Round 3 and STW projects, together with possible additional European interconnection. However, it has been additionally recognised that other programmes, notably some Round 2 projects, large marine energy schemes and future interconnectors, could be incorporated into a coordinated network design strategy The designs shown in this study should not be considered as implying actual connection dates or connection routes for new infrastructure and they do not reflect the Transmission Owners (TOs) investment decisions regarding the development of their transmission area or imply any other parties investment decisions. The designs present an illustrative coordinated transmission design approach using information available at the time of analysis (frozen June 2011) and have been developed to allow a comparison between the potential design options. The constraints presented in this study are those identified by high level (desktop based) analysis using the available information known at the time of analysis. The actual constraints, which would be applicable to the individual connection route, can and may be different following completion of further detailed site analysis. The actual contracted position and development of the offshore and onshore transmission system can, and may, differ from that illustrated in the study. The study represents a view of the future network requirements and direction for potential development, the actual network design will be developed in accordance with user requirements The study does not consider the legal and regulatory mechanisms which would be required for the delivery of the designs or the specific impact on individual transmission connections. It is, however, recognised that Ofgem and DECC are currently reviewing the existing framework through the Offshore Transmission Coordination Group. 3 A description of these design strategies is provided in section 3.14 of this report. 4 For this study, the STW projects of Beatrice, Inch Cape and Neart na Gaoithe were not included in the coordinated design and therefore are not included in the asset volume and cable route assessment. Some benefits of coordination of these projects is likely, but has not been captured in this study. Section 2: Background 6

8 Offshore Transmission Network Feasibility Study Overview Section 3.0 Methodology and Assumptions 3.1 The study undertook an assessment of the constraints and network design by region to allow a detailed assessment to be made. The following regions (as illustrated in Figure 3.1) were identified and developed: Irish Sea; East Coast of England; Southern; East Anglia; Scotland. 3.2 For each region, three full generation and demand scenarios and an additional sensitivity analysis have been considered. A snapshot of the network design has been taken for each design strategy for 2015, 2020, 2025 and A holistic review of the entire network across the regions was undertaken to ensure that the interactions between regions (and associated onshore reinforcements or avoidance thereof) could be fully reflected. This approach allowed a view to be presented on investment required and incremental development of the system. Section 4: Stakeholder Engagement 7

9 Offshore Transmission Network Feasibility Study Figure 3.1: Regions Assessed Within Study Section 4: Stakeholder Engagement 8

10 Offshore Transmission Network Feasibility Study Future Generation and Demand Scenarios 3.3 In order to appropriately assess the need for future transmission system development, it is necessary to make assumptions regarding the future generation and demand background that the electricity transmission system will need to accommodate. Three generation and demand background scenarios, plus an additional sensitivity, have been used 5 : Slow Progression; Gone Green; Accelerated Growth; and Tuned Transmission Entry Capacity sensitivity (Tuned TEC). 3.4 In each of the scenarios, demand is included at its assumed peak level. The assessment of the electricity system adequacy tends to focus on transmission system peak demand as this is often the most onerous demand condition the network needs to be able to accommodate and will drive many of the required reinforcements. 3.5 All scenarios cover the period from 2011 to 2030 and consider the anticipated range of potential offshore developments from nearly 23 GW of offshore transmission wind generation installed capacity (Slow Progression) rising to approximately 49 GW (Accelerated Growth). Slow Progression 3.6 In this scenario, the emphasis is on a slow progression towards the EU 2020 targets for renewable energy, carbon emissions reduction and energy efficiency improvements. The EU 2020 renewable targets are not met until around Gone Green 3.7 The Gone Green 6 scenario represents a potential generation and demand background that meets the environmental targets in 2020 and maintains progress towards the UK s 2050 carbon emissions reduction target. 3.8 The scenario takes a holistic approach to the meeting of the targets, assuming a contribution from the heat and transport sectors towards the renewable energy target. Accelerated Growth 3.9 The Accelerated Growth scenario uses the Gone Green onshore generation background as a base with the assumption that offshore generation builds up far more quickly due to a rapidly established supply chain, higher carbon prices and strong government stimulus The key comparison to the onshore background against the two scenarios above is that the nuclear advanced gas-cooled reactor (AGR) plant is consistent with the Slow Progression scenario and that existing gas plant remains open for longer to maintain the plant margin and act as a back-up for the significant amount of wind generation that may be built. Sensitivity Tuned Transmission Entry Capacity (Tuned TEC) 3.11 The Tuned TEC sensitivity was developed with a view to reflecting The Crown Estate offshore leasing capacity. It was derived primarily using publicly available information. 5 These scenarios are based on the 2011 ODIS Future Scenarios: More information is provided in Appendix A. 6 Please note that there is close correlation between the Gone Green 2011 scenario and the Renewables Roadmap which was published with the 2011 Electricity Market Reform White Paper. Section 4: Stakeholder Engagement 9

11 Installed Capacity (GW) Offshore Transmission Network Feasibility Study 3.12 For projects that currently do not have a Connection Agreement with NGET for their maximum generation capacity, the Tuned TEC sensitivity depicts an alternative planning view regarding the connection dates for the development zones/projects, based on the aggregated proposed development rates for projects considered by this study Figure 3.2 illustrates a comparison of the three scenarios and the Tuned TEC sensitivity comprising Round 3 and STW projects. Figure 3.2: Future Scenarios Comparison: Round 3 & STW Offshore Wind Developments Slow Progression: R3 & STW Offshore Wind Accelerated Grow th: R3 & STW Offshore Wind Gone Green: R3 & STW Offshore Wind Tuned TEC Register: R3 & STW Offshore Offshore and Associated Onshore Connection Designs 3.14 The study includes a number of conceptual desktop design strategies that demonstrate how different design and technology assumptions can influence the offshore transmission development for each scenario (and sensitivity). The different design strategies presented are: Radial: point-to-point connections from the offshore generation to suitable onshore Main Interconnected Transmission System (MITS) collector substations using currently available technology; Radial plus: similar to radial in the use of point-to-point connections for connecting the offshore generation to the onshore MITS, but utilising anticipated future transmission technology capability (e.g. 2 GW capacity converter stations and high capacity offshore cables) in line with technology projections for the next five years. Coordinated: an interconnected offshore design using AC cable and HVDC interconnection between MITS, offshore platforms and offshore wind development areas, using the same advanced technology as the radial plus strategy These design strategies are consistent with those identified in the 2010 Offshore Development Information Statement 7 (ODIS) and are illustrated in Figure A D12F/43325/2010ODIS_Chapters_Final.pdf Section 4: Stakeholder Engagement 10

12 Offshore Transmission Network Feasibility Study Figure 3.3: Design strategies Network design an overview 3.16 In undertaking the network design, the study sought to demonstrate a network that can: Meet user requirements at the most economic and efficient cost (considering onshore and offshore costs) - taking account of all user requirements (including onshore generation, offshore generation, interconnectors); Be developed incrementally and flexibly (to minimise stranding risk) - incorporating an appropriate level of extendibility (with snapshots taken at 2015, 2020, 2025 and 2030); Optimise network resilience and security - facilitating flexible development and use of the transmission system; Be considered against a credible range of scenarios Slow Progression, Gone Green, Accelerated Growth - and Tuned TEC sensitivity; Be compared across radial, radial plus (where appropriate) and coordinated design strategies This was achieved by: Desktop analysis of known offshore, foreshore and onshore constraints; Assessment of the consenting implications of alternative network design strategies; Utilisation of appropriate technology assumptions, Discussion with developers to gain their input (through an initial workshop and individual developer meetings); Focusing on Round 3 and STW projects, together with possible additional European interconnection The following National Electricity Transmission System Security and Quality of Supply Standards (NETS SQSS) assumptions were used for the offshore element of the study: Radial elements: Up to 1800 MW can be connected by a single circuit; Radial connections rated at 100% generation capacity; Section 4: Stakeholder Engagement 11

13 Offshore Transmission Network Feasibility Study Loss of single connection circuit may cause loss of all generation on connection. Interconnected elements: Links can be greater than 1800 MW provided alternate power paths are available to redistribute power following loss; Local connections based on 100% generation capacity, other elements are based on scaled generation as onshore; Up to 1800 MW can be lost for a cable loss; Wider infrastructure requirements based on scaled generation, as onshore By extending the interconnected transmission system to include parallel offshore circuits through a coordinated design, the offshore transmission assets become an integral part of the wider transmission system. The transmission focus changes from simply transporting power away from the generation to that of meeting both the generators requirements and those of the wider transmission system to ultimately satisfying demand. This is in contrast to point-to-point radial connections transporting power from offshore generation to the onshore MITS (with connections to the MITS based on 100% generation capacity), which then must take the role of onward transport to the demand centres. In the coordinated strategy, the offshore system assists in the wider system power transfer and is required to respond dynamically to changing power flow conditions on the system (including demand and generation changes and fault outages). With the coordinated strategy, the local offshore generator connection must still satisfy the local generation capacity (i.e. local connections are based on 100% generation capacity), but the transmission capacity beyond that may be shared with wider system power flows (i.e. the scaling approach (as detailed in 3.18) does not require the same connection capacity). This is the same as experienced by onshore generation connections joining the onshore MITS A generic exercise in cable and platform position optimisation (as shown in Appendix B) has also been used in developing the designs It is important to note that all of the design strategies illustrated in this report will involve development of both offshore and onshore infrastructure. Whilst some offshore strategies may facilitate the requirement for fewer additional onshore reinforcements, the onshore system will still be required to meet the electricity requirements of Great Britain s homes and businesses. Interfaces between the onshore and offshore elements of the transmission system will need to be robust to facilitate power flows. Technology 3.22 The study takes a relatively cautious approach to the technology development, with only those technological advancements available in the next three to five years included within the design. These are consistent with those outlined in Appendix 4 of ODIS A sample of the technology assumptions are as follows: Only technology that is already available or is reasonably expected to be available within the next 3-5 years with appropriate supplier engagement has been considered. DC Technology assumptions: Offshore HVDC links will be Voltage Sourced Converter (VSC); HVDC converters up to 2 GW capacity will be available by ; Multi-terminal VSC links with off-line DC switching will be available by AC technology assumptions: Platforms will have a maximum of 600 MW of generation connected; AC transmission to shore and between platforms will be at 220 kv using 3 core bundled, 300 MVA cables; This assumes focused development commences early Section 4: Stakeholder Engagement 12

14 Offshore Transmission Network Feasibility Study Greater design efficiencies may be obtained by increasing voltage and utilising 3 single core cables (300 MVA plus); Maximum distance considered for AC will be ~ 60km cable length. Technology not considered in the study 10 : HVDC on-load circuit breakers have not been considered; AC cables with ratings greater than 300MVA; HVDC cables exceeding 2 GW The designs presented in the report utilise DC cabling to an AC platform and therefore do not require the use of a HVDC circuit breaker. Amendment to these assumptions, facilitated by research and design to support the coordinated solution, would result in further reductions in both required asset volumes and the overall cost, e.g. increased ratings of AC cables or more compact, cheaper offshore platforms. Cost Assumptions 3.25 All designs have been costed using the specific cost ranges and unit cost assumptions included within ODIS 2010 (a summary of which is provided in Appendix D). In some instances, these costs have been grouped to provide an installed cost, for example to give the total cost of an offshore platform rather than its component parts. Where pricing information has been available as part of NGET s day-to-day operations, this information has been used to validate the cost assumptions. For offshore assets and next generation technologies, the cost assumptions have been validated through discussions with suppliers. Given the lack of information available regarding the cost of offshore platforms, only conservative cost efficiencies have been taken into account as the size of offshore platforms is increased Staging 3.26 The designs present a staged development, with each stage assigned against a particular year for the scenario under consideration (2015, 2020, 2025 and 2030). The analysis assumes that pre-construction engineering takes place in a timely manner 11, to allow the commencement of major construction work within the same lead-time as the development of generation projects. By ensuring the design stages are consistent for each scenario, it is possible to make the design robust against changes in the generation background. For example, this means that design stages can be brought forward should the generation background move from a predominantly Gone Green generation background to an Accelerated Growth generation background (or vice versa). Cost Model 3.27 To enable analysis of the economics associated with asset volume for each of the illustrative offshore network designs, NGET has developed a scheme and capital cost model. The cost model applies average costs for each equipment type (as detailed in Appendix D). When calculating the cost of cabling offshore, the analysed cable statistics from The Crown Estate s Marine Resource System (MaRS) has been used to account for difficult conditions like deep water, hard seabed material, obstacle avoidance and existing infrastructure crossings. The offshore platforms have been assumed to typically be in a water depth of 35-40m and to include sufficient electrical equipment to accept multiple transmission connections The unit costs represent an installed cost and, therefore, include an estimate for such things as consenting, land purchase, materials, installation and construction. 10 Development in these areas would significantly increase the benefits of a coordinated network. 11 By undertaking pre-construction engineering the lead time for the delivery of the major transmission projects can be aligned with the offshore development and significantly reduce stranding risk while ensuring transmission capacity can be made available in accordance with generator requirements. Section 4: Stakeholder Engagement 13

15 Offshore Transmission Network Feasibility Study 3.29 To determine the cost of each of the design components, the cost model calculates the sum of the average cost for each equipment type and multiplies it by quantity. The total design cost of building everything was then determined by the cumulative cost of all of the elements required for the selected scenario Each of the scenarios and the sensitivity specify the year of commissioning for each element allowing the determination of a cost profile. The cost model utilises a four year cost profile for each scheme to spread the scheme cost over time. Cumulative costs for a selected scenario are determined by summing the costs from all of the applicable individual schemes The resulting cost analysis (both component assessment and capital cost over time) is provided in section 8 for Accelerated Growth. The cost analysis for the other scenarios and sensitivity is provided in Appendix F and for the individual regions in Appendices G K. Offshore constraints 3.32 MaRS is a Geographic Information System (GIS) based decision support tool that can be used to identify areas with potential development opportunity within UK waters. The tool utilises a range of datasets to allow the user to determine areas of exclusion or potential restriction. Exclusions must be avoided when planning cable routes and include any activity or obstacle that will inhibit cable routing such as current The Crown Estate assets, oil and gas infrastructure and other structures. Restrictions of varying degree are prioritised (weighted) in order to capture other sensitivities, interests and marine users considered to be relevant or to represent a potential constraint for cable infrastructure. The full range of datasets considered in the MaRS model is outlined in Appendix C In some instances it is not appropriate to incorporate a dataset directly into the MaRS model. This may be due to the format/completeness of the data or due to a lack of supporting detail about how to prioritise the information shown. Such information has been incorporated into the study analysis as a series of review layers, which have been analysed separately in the GIS for each of the routes identified. The review layers include bathing beaches, military interests and shipping densities (a full list of these is available in Appendix C) Following the initial iteration of the network design for each region, the MaRS modelling outputs were used to underpin a detailed assessment of illustrative routes (where relevant outlined within the regional reports in Appendices G - K). Input from individual developers also contributed to a fuller appreciation of potential constraints offshore. This allowed a thorough desktop assessment of the constraints/exclusions against the chosen route to shore reflected in the network design shown in sections 6 and Figure 3.4 provides an overview of the entire GB coastline to demonstrate the constraints and exclusions identified through the MaRS modelling. It should be noted that this analysis is based on a desktop study and actual constraints may be found to differ from those illustrated As per the key outlined in Figure 3.4 the green shading on the map illustrates the varying levels of constraint offshore, with the six shades from pale through to dark illustrating a low level of constraint through to highly constrained as determined by the desktop analysis undertaken. Areas of exclusion are shown in black. There are also a number of areas where no data was available which have been highlighted accordingly It should be emphasised that the constraints analysis undertaken is acceptable for the purposes of this feasibility study. It is not sufficiently detailed, however, to provide any certainty on the suitability of those routes illustrated (technical, environmental or consenting). Furthermore, the data used for constraints are necessarily at a national/regional scale and are therefore coarser in their resolution that would be required Section 4: Stakeholder Engagement 14

16 Offshore Transmission Network Feasibility Study as part of a specific project. The constraints presented in this study are those identified through high-level desktop analysis. Actual constraint analysis may differ upon completion of further detailed work. Consideration of planning and consenting issues 3.38 As part of the study, the consenting of related aspects of transmission have been considered. This consideration included an analysis of those consents required and an assessment of the consenting benefits and challenges associated with different design strategies. The outcome of this is detailed in sections 5 and 8. Section 4: Stakeholder Engagement 15

17 Offshore Transmission Network Feasibility Study Figure 3.4: Offshore Constraints and Exclusions Section 4: Stakeholder Engagement 16

18 Offshore Transmission Network Feasibility Study Section 4.0 Stakeholder Engagement 4.1 As part of the process, developers (Round 3 and STW in particular) were invited to input into the study in order to maximise the data available and ensure relevant information was reflected. 4.2 A challenge and review of the findings has sought to allow the results to be reflective of the latest public information and include credible (illustrative) offshore routing designs for each zone. 4.3 The stakeholder engagement process with developers was initiated by a launch event workshop in February 2011, followed by individual sessions (which discussed the study in the context of anticipated projects) and a closing seminar in July 2011 to discuss the outcome of the study. 4.4 During the stakeholder engagement process, key principles of the study were discussed, including: The need to take a holistic view of the development of the onshore and offshore network to ensure the most appropriate solution across the system is presented; To clearly articulate assumptions used to allow review by interested parties; The study does not consider how the illustrative designs presented would be delivered; Future routes and locations are illustrative, based on desktop analysis and not representative of actual positioning. Detailed positioning and identification of the infrastructure required will be subject to detailed survey and consultation, taking into account the latest developments on the network; Although the focus was on Round 3 and STW, other projects such as the remaining Round 2 projects and large marine energy projects, could be included in future coordinated solutions if the analysis found this approach to be of benefit for that site; Assumptions on platform positions were acceptable on the basis that it was made clear that they were illustrative only and therefore subject to change and finalisation. 4.5 All Round 3 developers were given the opportunity to discuss the study with regards to their own zone. These one-to-one sessions, with representatives from NGET and The Crown Estate, facilitated more detailed discussion on how the individual zones could be developed utilising the different transmission design strategies and different electricity (generation and demand) backgrounds. The sessions enabled NGET and The Crown Estate to explain and illustrate their respective methodology on the transmission design and offshore routing and how this influenced the study findings. The sessions also enabled the developers to provide specific feedback on the regional designs, which may influence the methodology utilised by NGET and The Crown Estate in the study analysis. 4.6 In July, a seminar was held to present the findings arising from the joint study. In addition to the developers who attended the February session, other interested parties were also invited such as those attending Ofgem/DECC s Offshore Transmission Coordination Group as well as devolved government departments 12. The seminar saw the presentation of illustrative designs for all regions, an early view of the benefits arising thereof and some of the consenting practicalities likely to be faced, allowing for a full question and answer session. Questions raised at the seminar have been addressed in this report. 12 Attendees included developers, OFTOs, supply chain representatives, trade bodies, government departments and Ofgem. Section 4: Stakeholder Engagement 17

19 Offshore Transmission Network Feasibility Study Section 5.0 Consenting and Planning 5.1 Construction and operation of offshore windfarms, transmission links to the onshore MITS and system reinforcement works require the acquisition of consents and rights under a variety of legislation. Significant information requirements and the involvement of multiple parties can all add to the complexity of the process. Consents legislation and environmental regulations prescribe the information that must be submitted with consent applications. Certain legislation requires mandatory pre-application consultation through the project development process. This requires considerable levels of design to be undertaken early in the process to support the consultation activities, with consultation responses influencing the development of the project. In addition, environmental regulations may require the assessment of cumulative and in-combination effects with other projects, which may be at different stages of project development, adding complexity and uncertainty to the consents process. 5.2 With a typical consents process including effective pre-application consultation, project design development, environmental impact assessment (where appropriate), examination of the application, consultation comments and decision-making, obtaining consents is dependent on many factors. These must be carefully balanced by the determining authority in weighing up the merits of the application, which is likely to include consideration of relevant policy, environmental and socio-economic effects, technical issues and, where relevant, cost. It is therefore essential that the consenting process, and the issues which are considered in that process, are included as part of the review of potential offshore grid strategies. 5.3 This section describes the consenting requirements for the different design strategies. The benefits and challenges involved with consenting the different strategies are also summarised in this section and detailed in section 8 of this report. Consenting/planning aspects of the offshore transmission network 5.4 Whilst the acquisition of any onshore and offshore consent broadly follows similar processes, there are subtle differences between the different legislation and determining bodies, for example, devolution of planning responsibility or type of infrastructure to be consented. The specific consents required for offshore and onshore elements are dependent on four main factors: The location of the infrastructure (terrestrial or marine; marine within territorial waters or in the Renewable Energy Zone); The planning system(s) 13 which applies to the geographical location of the infrastructure (English/Welsh/Scottish); The nature of the infrastructure (e.g. Nationally Significant Infrastructure Project (NSIP)); and The nature of the organisation seeking consent (for example, NGET has certain Permitted Development rights, as would OFTOs once they are licensed). 5.5 Figure 5.1 sets out the typical infrastructure requirements along with the existing responsibilities for development and ownership of the assets. Appendix E provides detail of the applicable consenting legislation, and also includes information about the individual pieces of legislation, along with a brief summary of other relevant regulations, in particular the requirements of the Environmental Impact Assessment. 13 Described in Appendix E. Section 5: Consenting and Planning 18

20 Offshore Transmission Network Feasibility Study Figure 5.1: Typical infrastructure requirements Development and Consent Construction Ownership & Operation 1 Offshore Transmission Owner MITS reinforcements (locally or deeper system reinforcements) Transmission Owner Transmission Owner Substation connecting to MITS Transmission Owner Transmission Owner DC converter station (if required) and substation Offshore wind developer or OFTO 1 Offshore wind developer or New project company or OFTO Jointing pit and onshore cable Offshore wind developer or OFTO Offshore wind developer or New project company or OFTO Offshore substations and cable connection to landfall point Offshore wind developer or OFTO Offshore wind developer or New project company or OFTO Transmission Owner Transmission Owner OFTO OFTO OFTO Offshore Generating Station Offshore wind developer Offshore wind developer or New project company Offshore wind developer or New project company Section 5: Consenting and Planning 19

21 Offshore Transmission Network Feasibility Study Consenting requirements for the radial strategy 5.6 A significantly greater volume of onshore and offshore infrastructure will typically be required under this approach 14, relating both to the offshore generating station and to its associated transmission connection requirements. Furthermore, consents applications will be submitted to determining authorities by multiple parties in similar timescales and locations, affecting similar communities. Given this, a number of challenges are evident for the radial strategy: The volume of consents sought means that consultation respondents are likely to challenge the need for, location of and design of the transmission infrastructure and request demonstration of the overall strategy for the delivery of the generating station, the offshore works and the onshore works; To demonstrate that the most appropriate solution is being pursued different organisations working to different timescales and programmes must coordinate with each other in terms of engineering design and consenting/construction programmes (currently facilitated by the relationship between the generator and NGET as part of the connection agreement); Multiple applications for consents could be required over a prolonged time frame resulting in interlinked consent applications being run by different organisations on different programmes. This could result in a delay to the consenting programmes and add to confusion for the public and statutory bodies, with whom the consultation is taking place. 5.7 Figure 5.2 shows three examples of the different routes that could be followed to obtain the necessary consents for the main infrastructure requirements for a radial connection within English waters. This report explores these considerations in the light of the English planning system, but the principles also apply to planning systems under the devolved administrations. 5.8 A number of important assumptions have been made in drawing up the consent options shown in this Figure and the subsequent coordinated option, notably: The transmission link is related to an offshore wind farm of 100MW and could therefore be considered associated development to an NSIP; The onshore transmission links (connecting to the MITS) would be buried cables rather than overhead lines (if overhead lines greater than 132kV were required these would form an NSIP project in their own; Transmission licence holders will have permitted development rights for certain aspects of the onshore elements of an offshore transmission link, so the timing of when OFTOs are involved plays an important role in the development of a project. 5.9 The transmission link referred to above, relates only to the link connecting the offshore wind farm to the onshore MITS, additional onshore reinforcements is likely also to require consents. 14 Information on the infrastructure requirement of the design strategies is presented in section 8 of this report. Section 5: Consenting and Planning 20

22 Offshore Transmission Network Feasibility Study Figure 5.2: Radial consent examples 5.10 In the case of a radial plus strategy, some additional consenting considerations apply in bringing forward the separate generating stations for connection and/or consenting the transmission link itself. However, the options for consenting in terms of the legislative regimes applied are consistent with the radial strategy and are influenced largely with issues of ownership and any association with an NSIP generating station as such no separate figure for radial plus has been prepared. Consenting requirements for the coordinated strategy 5.11 Under a coordinated strategy, a number of differences are apparent which will impact on the consents process. Onshore, the key difference is that fewer cables come ashore, requiring fewer land fall points, fewer converter stations and substations. There is also less likely to be a requirement for deeper system reinforcement works Offshore, the key difference is the requirement for fewer transmission connections to shore, more interconnection between offshore wind developments and an overall reduction in infrastructure requirement The legislative framework for radial or radial plus could equally be applied to consent the coordinated strategy. This is illustrated (for English projects) in Figure 5.3. For radial plus and coordinated designs, the main variations in consent strategy arise in relation to the ownership of the various assets and their association or otherwise with an NSIP, the timing of projects coming forward for development, the need case and the provision of any anticipatory infrastructure. It is uncertain under current arrangements whether a need case which contains elements of anticipatory infrastructure would be sufficiently robust to meet the challenge of key stakeholders, consultees and the determining authorities. Section 5: Consenting and Planning 21

23 Offshore Transmission Network Feasibility Study Figure 5.3: Coordinated consent examples Benefits and challenges associated with consenting a coordinated strategy 5.14 The key consenting benefits from the development of a coordinated strategy are derived from the requirement for fewer cables coming ashore and the requirement for fewer, more strategic onshore reinforcements and offshore infrastructure Whilst the consenting of radial connections may be better understood by developers, consenting bodies, and stakeholders, the consenting of offshore generation is yet to be taken through the development consent order process under the Planning Act. Furthermore, consents for radial links are only likely to be granted if the consenting body believes development to be sustainable. The consenting burden and associated risk is likely to increase as the volume of radial connections increases, particularly in relation the extensive onshore reinforcements required. In contrast, the coordinated strategy would demonstrate that consideration has been given to the overall solution, which would minimise the cumulative effect of projects seeking to connect It is important to note that as part of the coordinated strategy, some wind farm connections would be connected on a radial basis where this offers the most economic and efficient solution. However, through being considered as part of the wider coordinated strategy, the consenting of these radial elements will see the same consenting benefits The benefits and challenges of consenting a coordinated strategy are detailed in Section 8 and Appendix E of this report. Consenting summary 5.18 Obtaining consent for offshore and onshore transmission is an essential step in the connection of offshore wind generation capacity to the transmission network. The existing legislation under which consents for transmission are obtained is appropriate for both the Section 5: Consenting and Planning 22

24 Offshore Transmission Network Feasibility Study radial and coordinated strategies. However, the consenting burden for Round 3 and STW is likely to become unmanageable. The sequential consenting of radial connections allows no scope for minimising the cumulative effects of transmission links, which could result in delay or consents not being obtained. On balance, the coordinated strategy is likely to give rise to fewer planning and environmental issues, thus resulting in consents being more easily acquired. However, to support the consents for a coordinated solution it would be helpful if policy or guidance existed to endorse the development of anticipatory infrastructure. It is essential that the consenting process forms a fundamental element of the development of the coordinated strategy. In particular: Investigating the most appropriate way to incorporate the transmission infrastructure requirements within the marine planning process; Establishing whether the move to a coordinated approach suggests the need for enabling anticipatory consenting; and Considering whether transitional arrangements are necessary in respect of projects already in the consenting process. Section 5: Consenting and Planning 23

25 Offshore Transmission Network Feasibility Study Section 6.0 Overview: radial and radial plus 6.1 This section provides an overview of the illustrative network designs envisaged for the radial and radial plus design strategies under Accelerated Growth. 6.2 Figures 6.2 to 6.3 illustrate the designs in subsequent five year periods of development, with Figures 6.4 and 6.5 providing an overview of the radial and radial plus designs in The key associated with Figures 6.2 to 6.5 is illustrated in Figure 6.1 below: FIGURE 6.1: Key for Figures Section 7: Overview coordinated 24

26 Offshore Transmission Network Feasibility Study Figure 6.2: Overview, Time Series, Radial, Accelerated Growth Section 7: Overview coordinated 25

27 Offshore Transmission Network Feasibility Study Figure 6.3: Overview, Time Series, Radial Plus, Accelerated Growth Section 7: Overview coordinated 26

28 Offshore Transmission Network Feasibility Study Figure 6.4: Overview, Radial, Overview, Accelerated Growth, 2030 Section 7: Overview coordinated 27

29 Offshore Transmission Network Feasibility Study Figure 6.5: Overview, Radial Plus, Accelerated Growth, 2030 Section 7: Overview coordinated 28

30 Offshore Transmission Network Feasibility Study Section 7.0 Overview: coordinated 7.1 This section provides an overview of the illustrative network designs prepared for the coordinated design strategy under Accelerated Growth. 7.2 Figure 7.2 illustrates the design in subsequent five year periods of development, with Figure 7.2 providing an overview of the coordinated design in The key associated with Figures 7.2 to 7.3 is illustrated in Figure 7.1 below: Figure 7.1: Key for Figures Similar figures are provided in Appendix F for the Gone Green and Slow Progression scenarios, and Tuned TEC sensitivity. 7.4 It is recognised that offshore generation could, depending on the volume of generation connecting, lead to the requirement for significant onshore reinforcements to accommodate the increased transfers required. For the radial strategy, the network capacity requirements have been provided by the use of point-to-point circuits to accommodate generation capacity supported by additional onshore reinforcements. By developing a coordinated strategy, which links together the offshore developments and integrates fully with onshore, it is possible to accommodate all generation requirements whilst significantly reducing the onshore transmission reinforcement requirements. An alternative network solution that could be considered is to coordinate within development areas, but without coordinating between areas. However, this approach would fail to realise many of the potential benefits of coordination as detailed in section 8. This is particularly apparent in the East Coast and East Anglia regions considered in this study. Section 7: Overview coordinated 29

31 Offshore Transmission Network Feasibility Study Figure 7.2: Overview, Time Series, Coordinated, Accelerated Growth Section 7: Overview coordinated 30

32 Offshore Transmission Network Feasibility Study Figure 7.3: Overview, Coordinated, Accelerated Growth, 2030 Section 7: Overview coordinated 31

33 Offshore Transmission Network Feasibility Study Section 8.0 Assessment of Potential Benefits and Challenges Comparison of design strategies 8.1 For the purpose of comparison, this section focuses on the Accelerated Growth scenario in order to assess the benefits and challenges associated with the various design strategies. 15 The benefits and challenges hold true for the other scenarios and sensitivity (to varying degrees depending of the rate of offshore wind deployment), the data relating to the other scenarios and sensitivity are provided in Appendix F The benefits and challenges identified in this section are for the overall network design. The specific regional findings are detailed within the regional Appendices (Appendices G - K.) Potential benefits associated with the coordinated strategy 8.3 In meeting the objectives of sustainability, affordability and energy security, ensuring the deliverability of offshore wind will be critical. The benefits of pursuing a coordinated transmission network design, highlighted as part of this study, help to facilitate deliverability of offshore wind. They can be categorised under the following headings: Environmental and consenting benefits, Improved management and utilisation of valuable resources; Reducing costs for the UK consumer; and Future proofing the transmission network. Environmental and consenting benefits 8.4 A key aspect to the deliverability of offshore wind will be the ability to consent the necessary transmission infrastructure to allow for connection of the wind farm. Whilst the process of consenting under both the radial and coordinated strategy will present its challenges, the study demonstrates that there are tangible consenting benefits that arise from a coordinated approach. With a reduction in consenting complexity due to fewer onshore reinforcements and offshore assets being required, this allows for: The improved management of valuable environmental resources - minimising potential for route sterilisation by reducing the number of cables and landing points required and facilitating the ability to take a holistic view of requirements. This will allow assets to be sized and located accordingly, with consents obtained once whilst recognising future developments as projects are deployed and/or re-optimisation of the network takes place; The coordination of works and associated consents to allow demonstration that an appropriate solution was being sought beyond that required for an individual project. Option evaluation and demonstration of alternatives is challenged rigorously by interested parties, in particular for onshore developments; Reduced consenting burden on stakeholders with whom the relevant applicant organisation is undertaking consultation. 8.5 This is in contrast to the radial (and radial plus) strategy where the requirement for multiple radial connections would result in a number of highly interlinked applications being run by different organisations on different programmes. This would: Increase the consenting burden and requirement to demonstrate the correct solution is being sought; Result in cumulative and increased risk for later projects; and 15 Unless otherwise stated, the benefits and challenges associated with radial/radial plus are the same. 16 Appendix F also includes a comparison between the output from this study and the study prepared by NGET in 2010 to allow tracking of the findings between studies. Section 8: Assessment of Potential Benefits and Challenges 32

34 Offshore Transmission Network Feasibility Study Make robust assessment of alternatives difficult (for both those seeking consents and those considering consents applications). 8.6 Further detail on the benefits of consenting a coordinated strategy is included within Appendix E. 8.7 There is further environmental benefit from the coordinated strategy through a reduced footprint delivered through a reduction in land area required for substations and HVDC converters. For the East Coast region for example, there is approximately 25% reduction in land area required. Improved management and utilisation of valuable resources 8.8 The coordinated strategy reduces the overall volume of assets installed with respect to offshore and associated onshore transmission. Onshore 17 : the coordinated strategy requires significantly reduced onshore reinforcements. This not only brings with it cost savings, but facilitates deliverability of the required network in terms of reduced construction challenge and reduced planning/consenting requirements. The overall reduction in asset volume also reduces the overall environmental impact of the design. Offshore/foreshore: the reduced offshore cabling, platforms and landing points required under the coordinated approach will also minimise environmental impact and reduce the likelihood of route sterilisation. 8.9 Figure 8.1 shows the asset volume (and associated capital cost) required for the coordinated strategy compared to the radial and radial plus strategies under the Accelerated Growth scenario (as determined by the methodology outlined in section 3). The cost information presented is taken from NGET s scheme and capital cost model (as described in section 3), and has been populated with cost data based on information in the 2010 ODIS. Figure 8.1: Asset volume and capital cost (Accelerated Growth) radial Vs coordinated Radial Coordinated Savings Radial plus Coordinated Savings HVDC cables 6641 km 5216 km 1425 km 21% 5145 km 5216 km -71 km -1% Offshore AC cables 1559 km 2353 km -794 km -51% 1948 km 2353 km -405 km -21% Onshore AC lines 447 km 126 km 321 km 72% 447 km 126 km 321 km 72% (new) Offshore platforms % % Cable landing sites % % Capital cost (2010 prices) Capital cost based on 2010 prices bn 29.2 bn 5.6 bn 16% 31.6 bn 29.2 bn 2.4 bn 8% 17 The onshore reinforcements (onshore AC lines) referenced in this study relate only to MITS reinforcements (locally or deeper system reinforcements). Section 8: Assessment of Potential Benefits and Challenges 33

35 Offshore Transmission Network Feasibility Study 8.10 Taken together, this overall reduction should help alleviate constraints on the supply chain s ability to meet demand for both the onshore and offshore infrastructure requirements, thus increasing confidence from a deliverability perspective 18. Reducing costs for the UK consumer 8.11 The total potential overall savings associated with the coordinated strategy are identified as being 6.9 billion by 2030 (2010 prices) 19 when compared to a radial transmission design (and 3.6 billion against radial plus by 2030). This consists of: 5.6 billion real capital cost savings ( 2.4 billion against radial plus); 1.2 billion congestion management cost savings (against both radial and radial plus); 0.1 billion maintenance cost savings ( 0.05 billion against radial plus) It is important to note that the technology assumptions considered in the study could be viewed as conservative. Amendment to these assumptions facilitated by further technological development to support the coordinated solution would result in further reduction in both the asset volume required and the overall cost of the coordinated solution for instance through increasing the rating for AC cables or the development of more compact, cheaper offshore platforms 20. Similarly, amendment to the other assumptions, such as undergrounding, will have a significant impact on the capital cost 21. The assumptions used within this study are detailed in Appendix L Further detail of these cost savings is provided below. Real capital cost savings 8.14 By implementing a coordinated strategy, the study has demonstrated that there are capital cost savings due to the deployment of larger, standardised, multi-user offshore transmission assets and optimisation of onshore and offshore transmission reinforcements. All capital cost savings are in 2010 prices Figure 8.2 provides a comparison of the capital cost of the coordinated strategy against both the radial and radial plus strategies to It is clear that the coordinated strategy provides a significant capital cost reduction in comparison to the other two design strategies. Figure 8.2: Capital cost comparison (Accelerated Growth) Coordinated Capital Cost Coordinated Capital Savings Radial 34.8bn 29.2bn 5.6 bn 16% Radial Plus 31.6 bn 29.2bn 2.4 bn 8% 8.16 A breakdown of the capital expenditure differential between each of the key component classifications of the radial and coordinated strategy under Accelerated Growth is illustrated in Figure It is widely recognised within the industry that supply chains will come under significant pressure as they ramp up production capability to meet demand for increased HVDC cable and offshore wind assets. Moreover, the volume of onshore reinforcements required across GB irrespective of energy source as we transition to meeting the 2020 targets means that onshore the supply chain is also under considerable pressure. 19 Congestion management and maintenance cost savings beyond 2030 are not reflected in this study. 20 For instance if the delivery of HVDC cables with greater capacity then 1.2GW could be advanced, from 2017 (as has been used in the study) to 2015, this would result in more then 0.5 billion of additional savings. Similarly, any further delay in the development of technology would see the potential savings eroded. 21 For instance amending the existing undergrounding assumption of 10% down to 5% under the radial strategy would reduce the total capital cost by 0.4 billion, similarly increasing the assumption to 15% would add an extra 0.4 billion. Section 8: Assessment of Potential Benefits and Challenges 34

36 Offshore Transmission Network Feasibility Study Figure 8.3: Capital expenditure assessment by components (Accelerated Growth) 8.17 Figure 8.3 identifies that whilst the coordinated design incurs additional capital cost in offshore AC cables (largely driven by the additional interconnection between zones and a change to the assumed MVA rating), there are significant capital cost savings associated with HVDC cables, converters and onshore reinforcements. The interconnection between zones is vital to realise the overall savings in both asset and cost reduction (and drives the additional benefits beyond those identified under radial plus) Figure 8.4 illustrates the capital expenditure profile across the years to 2030 under Accelerated Growth for all three of the design strategies. It demonstrates that the profile associated with the coordinated strategy mirrors those associated with radial and radial plus, which is a result of the design facilitating incremental delivery. Figure 8.4: Capital expenditure assessment (Accelerated Growth) Section 8: Assessment of Potential Benefits and Challenges 35

37 Cost M Offshore Transmission Network Feasibility Study Capital Costs 40,000 35,000 30,000 25,000 20,000 15,000 10,000 5,000 Cumulative Coordinated Cumulative Radial Cumulative Radial Plus Delivery Year Operational cost savings congestion management 8.19 As part of the day-to-day operation of the wider transmission network, additional generating plant is held in reserve to cover possible generation loss as result of operational faults across the wider network. The risk of loss of generation is exacerbated where connection is facilitated via a single connection, as no alternative route to market for the power is possible. In such instances, generation held in reserve will be instructed to generate to cover the loss in electrical output, thus affecting operational costs passed back to the market (called congestion management) A coordinated offshore transmission network has the potential to reduce the risk of loss of output because of wider network issues, with a significant positive effect on system operation costs. Figure 8.5 provides an estimate of the annual energy curtailment cost associated with the Round 3 and STW projects in the Accelerated Growth scenario for four individual years from 2015 to 2030 for each design strategy For the three design strategies, a high-level analysis of constrained generation was assessed against an assumed average offshore wind generation load factor of 40% (a widely used level of load factor assumption). It was also considered against an average transmission asset availability of 98% (the minimum OFTO availability target set by Ofgem). The energy curtailment, and its associated constraint cost estimate, reflects the value of the renewable energy that may be incurred due to transmission unavailability. A constraint index of 75/MWh has been assumed based on recent energy and ROC values The analysis detailed in Figure 8.5 illustrates that there would be significantly higher congestion management costs associated with the radial and radial plus approaches through energy curtailment. This is attributable to the onshore reinforcements necessary to facilitate the radial strategies wider within the network. Therefore, through the coordinated strategy, as time progresses and the volume of offshore wind connected rises, increasingly efficient operation of the network will be facilitated. Extrapolating this out from 2015 to 2030 could result therefore, in cumulative congestion management savings in the region of 1.2 billion under Accelerated Growth for the coordinated strategy. For the purposes of this study, the assessment has only extended to 2030, however the requirement for congestion management and the associated constraint cost will continue beyond 2030 a quantification for which is not provided here. Section 8: Assessment of Potential Benefits and Challenges 36

38 Offshore Transmission Network Feasibility Study 8.23 A change to the assumed transmission asset volume availability would significantly impact on the constraint cost. For instance, amendment from 98% to 95% would see by 2030 the constraint cost savings increasing from 1.2 billion to approximately 3 billion. Figure 8.5: Congestion Management (Accelerated Growth) 250 Annual Curtailment (40% wind load factor & 98% availability factor) M 100 Coordinated Radial Radial Plus 50 0 AG 2015 AG 2020 AG 2025 AG 2030 Operational cost - maintenance 8.24 It follows that the asset reduction will result in a reduction in maintenance costs associated with the coordinated solution. This is illustrated in Figure The total maintenance cost has been calculated by considering three major categories of infrastructure, which are offshore cables, offshore platforms and the remaining assets (onshore and other). The maintenance cost (calculated on present money value) is assumed as a percentage of the installed capital cost as follows: Offshore Cables 0.5% Offshore Platform 2.0% Onshore and Other 1.0% 8.26 The figure demonstrates maintenance cost savings in the region of 0.1 billion by 2030 against the radial strategy. Section 8: Assessment of Potential Benefits and Challenges 37

39 Cost M Offshore Transmission Network Feasibility Study Figure 8.6: Maintenance Cost Total Maintenance Cost Losses Delivery Year Cumulative Coordinated Cumulative Radial Cumulative Radial Plus It follows that with a reduction in assets and pushing the technology to run at higher voltages there should be a reduction in losses (although it is difficult to quantify the full impact of transmission losses). The interconnected nature of the coordinated approach with HVDC also provides the opportunity to actively manage transmission losses by controlling power distribution and shutting down redundant elements under lightly loaded conditions. Future proofing the transmission network 8.28 The profile of investment identified in Figure 8.4 demonstrates that the three design strategies can equally be developed incrementally. This will allow opportunity for reoptimisation as developments occur and thereby minimise the risk of stranding. Reoptimisation is critical, as it is important to note that the commitment to spend will follow a less smooth profile due to the timing associated with taking the investment decisions The added resilience (through the additional redundancy provided) in the coordinated strategy facilitates greater security of supply of the network. It also helps to facilitate greater European interconnection by allowing the potential for future connection to an international platform. This is in line with the North Seas Countries Grid Initiative being implemented by the member states surrounding the North Sea. This allows for greater flexibility in the effective management of the wider transmission network, minimising the need for generation curtailment and future proofing the transmission network. Potential challenges associated with the coordinated strategy 8.30 The study has identified a number of potential benefits that could be delivered through the adoption of a coordinated strategy. There are also a number of challenges associated with the delivery of the coordinated strategy, which require careful management. The challenges can be categorised under the following headings: Delivery of an appropriate framework for coordination; Uncertainty over the rate of deployment of offshore wind; 22 Sections provide details of how such flexibility can be achieved. Section 8: Assessment of Potential Benefits and Challenges 38

40 Offshore Transmission Network Feasibility Study Technology advancement rate; and Consenting. Framework for coordination 8.31 Realisation of the coordinated design depends on an appropriate legal and regulatory framework to enable delivery. Whilst this study does not consider the detail of what this should be, amendment to the current provisions is likely to be required The coordinated design illustrated includes all potential offshore wind seeking to connect, in line with the scenarios identified. As discussion over the delivery of an appropriate framework to facilitate coordination progresses, there is a risk that timing will result in it no longer being possible to capture all projects as part of the coordinated strategy, with some of the value associated with this strategy becoming eroded. Timely resolution is therefore paramount. Uncertainty over the rate of deployment of offshore wind 8.33 This study considers a range of scenarios to illustrate the impact of the future deployment of offshore wind. Whilst this provides a useful illustration of potential developments, the actual deployment of wind out to 2030 cannot be predicted. The designs presented are illustrative based on desktop analysis, as further analysis is undertaken the actual constraints, which are applicable to the individual connection route, can and may be different A radial strategy connecting individual wind farms will ensure only those transmission assets required for the wind farms under development will be taken forward. The coordinated strategy requires a much more holistic view to be taken on the transmission requirements, which may include elements of anticipatory investment It is critical that the design and deployment of future GB offshore transmission assets are able to evolve against an uncertain and changing future onshore/offshore generation backdrop. Given the level of uncertainty within the wider energy industry with respect the rate of offshore wind deployment, a small risk of investment stranding is evident in the analysis. This risk however largely occurs at the pre-construction stage of the process. The detailed design, Invitation to Tender and consenting process will need to consider a coordinated design even though certainty as to whether the generator will proceed is not yet evident In practice, the stranding risk associated with physical transmission investment is more limited. This largely occurs as a result of timing issues in relation to the lead-times required for new transmission infrastructure, in particular HVDC cable, being slightly longer (approximately one year) than that required for the generation assets. In such instances, standardisation will be important as this will allow the asset to be utilised within another project should the original development change course within the intervening lead-time period A key tool in mitigating the stranding risk in the process will be the ability to re-optimise the proposed transmission design as necessary to ensure incremental build is possible using the optimal design. The ability to design holistically and flexibly across both the onshore and offshore transmission systems is critical to delivering the right offshore transmission network at any point in time As part of the study, a variation to the Irish Sea offshore transmission design has been prepared as an example as to how flexibility in design might be pursued. This design (included as Figure F22 in Appendix F) is intended to illustrate how a design might change should the generation mix deviate from the scenarios expected. Should the offshore wind generation within the Irish Sea not develop in line with either timing or volume assumptions, then the onshore requirements relating to the commissioning of new nuclear generation in the North Wales region would require a different solution. It is this kind of flexibility in Section 8: Assessment of Potential Benefits and Challenges 39

41 Offshore Transmission Network Feasibility Study design at the pre-construction stage that, whilst it may incur some additional cost, allows for the minimisation of stranding risk at the point of actual investment. This flexibility in approach will allow for the right procurement strategies and ensure that investment occurs in a timely manner thus minimising the risk arising from uncertainty. Technology advancement rate 8.39 The technology assumptions associated with both the coordinated and the radial plus design strategies require technological progress if the designs are to be realised indeed further development will be required to ensure the necessary timescale can be met. It is essential that the supply chain be provided with appropriate signals to ensure this development occurs. The analysis has already demonstrated that some of the potential benefits of a coordinated strategy (under Accelerated Growth) in the early years cannot be realised Discussion with equipment manufacturers has led to conservative assumptions being taken with respect to offshore VSC HVDC circuits larger than 1.2GW, i.e. not deliverable before For the Accelerated Growth scenario and Tuned TEC, this means the initial stages for some projects will be restricted to using currently available technology. Commitment to focused research and development will allow for faster technology development, with the potential for more than 500 million capital benefit. Similarly, delays to technological development will reduce potential capital savings by similar magnitudes. Consenting 8.41 The achievement of the necessary consents is vital to facilitate project realisation, which therefore brings consenting challenges to the delivery of any infrastructure both onshore and offshore. It is important to be mindful that such challenges exist under both the coordinated and radial strategies. In particular, for the coordinated strategy, it would be helpful if policy or guidance existed to endorse the development of anticipatory infrastructure. Moreover, marine spatial planning must take account of the coordinated strategy (a matter that requires timely attention due to the ongoing development of marine plans). It is also important that the impact on ongoing consents programmes is taken into account A further consideration of the challenges of consenting a coordinated strategy is included within Appendix E. 23 HVDC convertor suppliers have indicated that 12 months development work is required before they are likely to be in a position to offer greater than a 1.2GW HVDC link, making the earliest deployment 2016/17. Section 8: Assessment of Potential Benefits and Challenges 40

42 Offshore Transmission Network Feasibility Study Section 9.0 Conclusions 9.1 Offshore power generation will play an important part in meeting the renewable energy and carbon emission targets for 2020 and afterwards towards The potential growth rate, location and size of new offshore generation means that it is important to reflect on how best to connect offshore wind to the wider transmission system while balancing the three key policy objectives of decarbonisation, security of supply and affordability. 9.2 The coordinated design presented in this study is one that is based on the installation of high voltage multi-user assets that interconnect the offshore platforms and generation projects to form an offshore network. This conceptual design highlights how the volume of assets installed offshore could be reduced whilst the need for onshore reinforcement is minimised. 9.3 As a result of the study, a number of benefits have been identified arising from the development of a coordinated offshore transmission network and can be categorised as follows: Environmental and consenting benefits; Improved management and utilisation of valuable resources including land take, corridor routes and manufacturing capability; Reduced costs for UK consumer (capital cost reductions as well as a reduction in operational costs such as maintenance costs and congestion management costs in relation to system operation); and A flexible offshore transmission network that is better able to respond to future challenges. 9.4 The study also recognised a number of challenges associated with moving towards a coordinated transmission design offshore including: Uncertainty over the rate of deployment of offshore wind; Technology advancement rate; and The ability to consent those new routes required to connect the offshore generation. 9.5 A clear regulatory framework, delivered in a timely manner, will be required to navigate these challenges. The existence of these challenges should not detract from the potential benefits associated with a coordinated design strategy, and in order for the benefits to be realised, the timescales for delivery will be key. The ability to re-optimise the proposed transmission design as necessary to ensure incremental build using the optimal design has been demonstrated in this study and this will be crucial to ensure that the most appropriate network is delivered. 9.6 To ensure that the benefits identified in this report can be achieved it is recognised that: Pre-construction work should commence early 2012 for the initial key elements of the coordinated network; Further detailed steady state and transient system studies must be undertaken to allow protection and control requirements for HVDC equipment to be fully specified; Functional specification must be produced to enable focused development to take place; Focused development with all key suppliers must be undertaken to ensure equipment is available in the required timescale. 9.7 To conclude, the study has demonstrated that the coordinated strategy will facilitate balancing of the three key policy objectives of decarbonisation, security of supply and affordability by: Maximising deliverability of offshore wind - providing a means through which the significant volumes of offshore wind can connect which minimises risk of route sterilisation, maximises supply chain deliverability and facilitates the consents process; Strengthening security of supply through delivery of a more resilient network; Delivering at a lower overall cost to consumers. Section 9: Conclusions 41

43 Installed Capacity (GW) Offshore Transmission Network Feasibility Study Appendices Appendices Appendix A: Further information on scenarios Future Scenario: Slow Progression A.1 In this scenario, the emphasis is on a slow progression towards the EU 2020 targets for renewable energy, carbon emissions reductions and energy efficiency improvements and the UK s unilateral carbon emissions reduction targets. EU 2020 renewable targets are not met until around A.2 This scenario has been developed against a background of lower carbon prices. This results in a slower build-up of lower carbon generation and a greater reliance on gas-fired plant. The scenario also assumes a slower rate of development for coal generation plant with carbon capture and storage (CCS) functionality, compared to the other scenarios. Future Scenario: Slow Progression Offshore Transmission Generation (Wind) A.3 In the Slow Progression scenario, there is 11.5 GW of offshore transmission wind generation capacity included in 2020 (with a further 11.5 GW connecting by 2030). A.4 The build-up of offshore transmission wind developments in this scenario includes: 6.0 GW of Round 1 and Round 2 (inclusive of Round 1 and 2 extensions) offshore transmission wind capacities by 2020; 0.5 GW of STW offshore transmission wind capacity by 2020 An additional 5 GW of Round 3 offshore transmission wind capacity by 2020; and A further 11.5 GW of Round 2, 3 and STW developments by the end of the study period A.5 The build-up of Round 3 and STW offshore wind developments in this scenario is shown in Figure A1: Figure A1: Slow Progression - Offshore Transmission Generation Wind Vs Round 3 & STW Offshore Wind Developments Slow Progression: Offshore Transmission Wind Slow Progression: R3 & STW Offshore Wind Appendix A: Further information on scenarios 42

44 Installed Capacity (GW) Offshore Transmission Network Feasibility Study Appendices Future Scenario: Slow Progression Generation and Demand (Transmission) Backgrounds A.6 The generation mix for this scenario is detailed in Figure A2. Generation is shown at full capacity with the total rising to account for the intermittent nature of wind generation and thus the need for back-up plant. Figure A2: 2011 Slow Progression: Generation (Transmission) Backgrounds Nuclear Coal Gas Offshore Transmission Wind Onshore Transmission Wind Other Renew ables Other A.7 A summary of Slow Progression s key points: AGR (Advanced Gas-cooled Reactor) nuclear plants receive five-year life extensions to that publicly announced; First new nuclear plant connects in 2021/22; A significant amount of existing coal plant closes by 2023 due to a combination of the Industrial Emissions Directive (IED) and the age of the plant; Carbon Capture and Storage (CCS) is retro-fitted at one coal plant as part of the government funded scheme with no further CCS coal plant included in the scenario over the study period; Existing gas-fired plant remains open for longer than in the Gone Green scenario; A total of 26 GW of new gas plant is included in the scenario by 2030, with 7 GW already under construction / commissioning; 6 GW of new gas plant with CCS is included in the scenario; The build-up of wind generation is lower in this scenario with 20 GW of wind capacity in 2020 (11 GW offshore) and 32 GW (23 GW offshore) in 2030; Marine generation is assumed to develop very slowly with some larger scale generation not connecting until around Future Scenario: Gone Green A.8 The Gone Green scenario represents a potential generation and demand background that meets the environmental targets in 2020 and maintains progress towards the UK s 2050 carbon emissions reductions target. The scenario takes a holistic approach to the meeting of the targets, assuming a contribution of the heat and transport sectors towards the renewable energy target. A.9 This scenario includes a more rapid build-up of wind generation, with the supply chain and thus growth in offshore wind, maintained post Nuclear AGR plant is assumed to receive ten years life extension, maintaining the level of nuclear capacity until the advent of new nuclear plant and assisting in lowering the level of carbon emissions from the generation sector. CCS plant is envisaged at both coal and gas plants into the future, with Appendix A: Further information on scenarios 43

45 Installed Capacity (GW) Offshore Transmission Network Feasibility Study Appendices thermal plant developed after 2023 required to have CCS technology. The increased lifespan of the AGR plant results in existing Combined Cycle Gas Turbine (CCGT) plant closing earlier than in the Slow Progression and Accelerated Growth scenarios. A.10 This scenario is set against a background of potentially higher energy prices with the price of carbon and the level of government subsidies stimulating low carbon generation and increasing the levels of energy efficiency. Future Scenario: Gone Green Offshore Transmission Generation (Wind) A.11 In the Gone Green scenario, there is 16.5 GW of offshore transmission wind generation capacity included in 2020 (with a further 20.3 GW connecting by 2030). A.12 The build-up of offshore transmission wind developments in this scenario includes: 7.0 GW of Round 1 and Round 2 (inclusive of Round 1 and 2 extensions) offshore transmission wind capacities by 2020; 1.3 GW of STW offshore transmission wind capacity by 2020; An additional 8.2 GW of Round 3 offshore transmission wind capacity by 2020; and A further 20.3 GW of Round 3 and STW developments by the end of the study period. A.13 The build-up of Round 3 offshore and STW transmission wind developments in this scenario is shown in Figure A3: Figure A3: Gone Green - Offshore Transmission Generation Wind Vs Round 3 & STW Offshore Wind Developments Gone Green: Offshore Transmission Wind Gone Green: R3 & STW Offshore Wind Future Scenario: Gone Green Generation and Demand (Transmission) Backgrounds A.14 The level of demand in this background is consistent with the wider Gone Green scenario and represents a level of electricity demand where the 2020 targets are met. There is a greater level of energy efficiency (than that included in the Slow Progression scenario) and potentially higher power prices. The impact of new demand sectors is also considered, namely heat pumps and electric vehicles. A.15 The impact of the electrification of heat and transport has been assessed in more detail, with demand increasing towards the end of the period post This includes an assessment of the impact of smart metering and time of use tariffs, which are assumed to flatten the load profile to some degree. Appendix A: Further information on scenarios 44

46 Installed Capacity (GW) Offshore Transmission Network Feasibility Study Appendices A.16 The overall generation mix for this scenario is detailed in Figure A4. Generation is shown at full capacity with the total rising to account for the intermittent nature of wind generation and thus the need for back-up plant. Figure A4: Gone Green: Generation (Transmission) Backgrounds Nuclear Coal Gas Offshore Transmission Wind Onshore Transmission Wind Other Renew ables Other A.17 A summary of Gone Green s key points: AGR nuclear plant receives additional five-year life extension to that assumed in the Slow Progression scenario; First new nuclear plant connects in 2019/20; Significant amount of coal plant closes due to IED and age; 4 GW of coal with CCS connects post-2023 in addition to the development of CCS at original demonstration site; Existing gas-fired plant assumed to close at around 25 years of age; A total of 19 GW of new gas-fired generation connects over the period with 7 GW already under construction / commissioning; 7 GW of new gas plant with CCS is included in the scenario from 2023; The build-up of wind generation reaches nearly 26 GW of wind capacity in 2020 (16.5 GW offshore) and 47 GW (nearly 37 GW offshore) in 2030; Marine generation develops more quickly than in the Slow Progression scenario reaching 4 GW in Future Scenario: Accelerated Growth A.18 The Accelerated Growth scenario uses the Gone Green onshore generation background as a base with the assumption that offshore generation builds up far more quickly due to a rapidly established supply chain, higher carbon prices and strong government stimulus. A.19 The key differences in the onshore background are that the AGR plant assumptions are consistent with the Slow Progression scenario (AGR nuclear plant receive five-year life extensions) and that existing gas plant remains open for longer to maintain the plant margin and act as a back-up for the significant amount of wind generation. Future Scenario: Accelerated Growth Offshore Transmission Generation (Wind) A.20 In the Accelerated Growth scenario, there is 32.9 GW of offshore transmission wind generation capacity included in 2020 (with a further 16.0 GW connecting by 2030). Appendix A: Further information on scenarios 45

47 Installed Capacity (GW) Offshore Transmission Network Feasibility Study Appendices A.21 The build-up of offshore transmission wind developments in this scenario includes: 8.8 GW of Round 1 and Round 2 (inclusive of Round 1 and 2 extensions) offshore transmission wind capacities by 2020; 2.8 GW of STW offshore transmission wind capacity by 2020; An additional 21.3 GW of Round 3 offshore transmission wind by 2020; and A further 16.0 GW of Round 2, Round 1 and 2 Extensions, Round 3 and STW developments by the end of the study period. A.22 The build-up of Round 3 and STW offshore transmission wind developments in this scenario is shown in Figure A5: Figure A5: Accelerated Growth - Offshore Transmission Generation Wind Vs Round 3 & STW Offshore Wind Developments Accelerated Grow th: Offshore Transmission Wind Accelerated Grow th: R3 & STW Offshore Wind Future Scenario: Accelerated Growth Generation and Demand (Transmission) Backgrounds A.23 The electricity demand in this scenario is the same as that used in the Gone Green scenario. A.24 The overall generation mix for this scenario is detailed in Figure A6: Appendix A: Further information on scenarios 46

48 Installed Capacity (GW) Offshore Transmission Network Feasibility Study Appendices Figure A6: 2011 Accelerated Growth: Generation (Transmission) Backgrounds Nuclear Coal Gas Offshore Transmission Wind Onshore Transmission Wind Other Renew ables Other A.25 A summary of Accelerated Growth s key points: AGR nuclear plant receives five-year life extensions to that publicly announced; First new nuclear plant connects in 2019/20; Significant amount of coal plant closes due to IED and age; 4 GW of coal with CCS connects post-2023 in addition to the development of CCS at original demonstration site; Existing gas-fired plant remains open for longer as a back-up for the significant amount of wind capacity; A total of 17 GW of new gas-fired generation connects over the period with 7 GW already under construction / commissioning; 5 GW of new gas plant with CCS is included in the scenario from 2023; The build-up of wind generation reaches 42 GW of wind capacity in 2020 (32 GW offshore) and 59 GW (49 GW offshore) in 2030; Marine generation develops at a slightly quicker rate than in the Gone Green scenario albeit reaching the same level by Appendix A: Further information on scenarios 47

49 Appendix B: Generic cable route optimisation B.1 This Appendix investigates possible configurations of electrical connection to offshore collector platforms with the objective of generic optimisation to minimise the overall length of cable required. Many factors influence the selection of offshore platform and cable, but for this generic assessment a uniform grid layout has been considered with a nominal AC platform spacing of 15km. Despite the generic nature of this assessment, the same optimisation principles should still apply when considering practical examples on a real world geographic layout. The basic layouts here may be seen in the different regional designs for radial, radial plus and coordinated designs. B.2 A set of standard building blocks/modules have been assumed when assessing the design options. These are: 500MW AC wind farm collection/substation platform with AC switching; 600MVA capable AC interconnecting cables (which may consist of 6 separate single core cables or a pair of multi-core cables); 1 GW HVDC offshore converter platform with AC switching; 2 GW HVDC offshore converter platform with AC switching; 1 GW offshore HVDC bipole cable; 2 GW offshore HVDC bipole cable. B.3 The base assumption for the following electrical designs is to ensure sufficient transmission capacity to allow the generation capacity (with minimum transmission losses) to reach shore under intact conditions. B.4 The design layouts shown in Figure B1 expand from a small group of AC collector platforms in a string to expanding to include additional HVDC interconnection to the joining of more platforms into different grid configurations. Appendix B: Generic cable route optimisation 48

50 Figure B1: Generic route optimisation design layouts 2GW HVDC connection. 15km grid spacing Option A AC Platforms 4 (500MW) DC Platforms 1 (2GW) AC Cable 60 km HVDC Cable - km Option B AC Platforms 4 (500MW) DC Platforms 2 (1GW) AC Cable 45 km HVDC Cable +16 km (an increase of 16km from configuration A) Addition of a 2GW interconnector shared with the windfarm connection Option A AC Platforms 4 (500MW) DC Platforms 2 (2GW) AC Cable 61 km (assuming HVDC platforms within 1km of each other) HVDC Cable - km Option B Appendix B: Generic cable route optimisation 49

51 AC Platforms 4 (500MW) DC Platforms 4 (1GW) AC Cable 47 km HVDC Cable +32 km (an increase of 32km from configuration A) Expanding to a 2 x 4 grid Option A AC Platforms 8 (500MW) DC Platforms 2 (2GW) AC Cable 150 km HVDC Cable - km Option B AC Platforms 8 (500MW) DC Platforms 4 (1GW) AC Cable 90 km HVDC Cable +30 km (an increase of 30km from configuration A) Option C Appendix B: Generic cable route optimisation 50

52 AC Platforms 8 (500MW) DC Platforms 2 (2GW) AC Cable 115 km HVDC Cable - km 4GW of wind connection and a 2GW interconnector Option A AC Platforms 8 (500MW) DC Platforms 3 (2GW) AC Cable 151 km HVDC Cable - km Option B AC Platforms 8 (500MW) DC Platforms 6 (1GW) AC Cable 120 km HVDC Cable +45 km (an increase of 45km from configuration A) Appendix B: Generic cable route optimisation 51