An Analysis of Offshore Grid Connection at Kriegers Flak in the Baltic Sea

Transcription

1 An Analysis of Offshore Grid Connection at Kriegers Flak in the Baltic Sea Joint Pre-feasibility Study By Energinet.dk Svenska Kraftnät Vattenfall Europe Transmission May 2009

2 1. Executive Summary 3 2. Introduction 5 3. Background 5 4. Technical solutions for grid connection of offshore wind power plants Separate solutions Combined solutions Combined, AC-based solution (B) VSC-based multi-terminal solution (C) Hybrid solution based on VSC- and AC-technology (D) Summary of technical concepts Method for calculating socio-economic benefit Description of environmental issues Environmental issues Environmental assessments Cumulative impacts of Kriegers Flak Espoo EIA on combined solution Overview and comparison of alternatives Challenges Co-ordination and commitment are needed Uncertainties about the offshore wind power plants Reinforcements of onshore grids Internal grid reinforcements in Germany Internal grid reinforcements in Sweden Internal grid reinforcements in Denmark VSC technology needs development and standardisation Priority feed-in of wind power may limit day-ahead trade Renewable energy from Kriegers Flak to the power market Balancing TSO agreements on costs and congestion rent National support schemes for wind power Framework for permissions Other regulatory issues Conclusions 25 References 27 2

3 1. Executive Summary The Kriegers Flak area in the Baltic Sea is well-suited for offshore wind power plants. A large number of wind turbines are being considered but at present there are no final decisions to place offshore wind power plants at Kriegers Flak. Spread out over the German, Swedish and Danish parts of Kriegers Flak a total of 1600 MW future wind power generation capacity has been assumed in this study. As always, it is important that this wind energy is connected to the onshore grids in the best possible way. This prefeasibility study presents and discusses four technical concepts for connecting offshore wind power plants at Kriegers Flak in the Baltic Sea. One concept is a classical solution where the offshore power plants are connected nationally. This concept is compared to three combined solutions where the grid connection of the offshore wind power plants would also function as an interconnector between Germany, Sweden and Denmark. This combination is called combined solution throughout the document. A combined solution at Kriegers Flak would: Bring renewable energy to the European consumers, strengthen the energy markets and increase the security of supply by providing transmission capacity. The three combined concepts illustrate how it could be technically possible to design a combined grid solution at Kriegers Flak. It is also stated that e.g. a separate grid solution together with direct interconnectors could represent an alternative to a combined solution at Kriegers Flak. All four concepts are briefly described in this report and so is a rough analysis of the costs and benefits associated with these concepts. These possible concepts must be described and compared in more detail before a decision (including a choice of technology) can be made, and the concepts must also be compared to alternatives like separate interconnectors. The aim of this pre-feasibility study is to investigate the potential for a combined solution for the grid connection of offshore wind power at Kriegers Flak. What are the benefits and obstacles? The key questions are: - Is it technically possible? - Is it economically viable? - What are the environmental issues? - Is it practicable within the current legal, market and regulatory situation? The pre-feasibility study should answer these questions well enough to form a solid basis for a decision on whether to initiate a detailed feasibility study. All in all, the rough cost benefit analysis in this report indicates a positive benefit for a combined solution compared to separate grid connection of future offshore wind power plants at Kriegers Flak. A more precise evaluation of this potential will require further analysis. The results of this pre-feasibility study thus indicate a good potential in an international approach which optimizes the grid connection with a focus on not just national but also regional benefits. A Kriegers Flak combined solution would involve three countries, two market systems, two synchronous zones, and the technical challenge it is to design combined, offshore solutions. So any combined grid solution at Kriegers Flak would involve new and international approaches in many ways. Naturally, there are barriers which must be overcome if such a project is to become a reality. This pre-feasibility study therefore also includes a description of the challenges which will be faced at Kriegers Flak. The following challenges have been identified and must be addressed: 3

4 - Co-ordination and commitment are needed - Uncertainties about the offshore wind power plants - Reinforcements of onshore grids will be necessary - Some concepts need development and standardisation of the VSC technology - Priority feed-in of wind power may limit day-ahead trade - Handling Kriegers Flak in the power market: common procedure needed - Balancing: common procedures or agreements needed - TSO agreements on costs and congestion rent needed - National support schemes for wind power differ - Frameworks for permissions are different, slow and complex - Other regulatory issues exists A combined grid solution at Kriegers Flak would require the involvement and commitment from a number of parties including the political systems. The transmission system operators will play their part in this process and welcome discussions on this pre-feasibility study in particular and on Kriegers Flak in general. 4

5 2. Introduction This report summarizes the results from a pre-feasibility study on grid connection of future offshore wind power plants at Kriegers Flak in the Baltic Sea. The pre-feasibility study is a joint project carried out by the three Transmission System Operators (TSO) relevant to Kriegers Flak: Energinet.dk (Denmark), Svenska Kraftnät (Sweden) and Vattenfall Europe Transmission (Germany). The Kriegers Flak area is well-suited for offshore wind power plants. Spread out over the German, Swedish and Danish parts of Kriegers Flak a total of 1600 MW future wind power generation capacity has been assumed in this study. As always, it is important that this wind energy is connected to the onshore grids in the best possible way. The three TSO's initiated this pre-feasibility study to investigate the possibility of connecting future wind power plants at Kriegers Flak through a combined, international offshore grid connecting Germany, Sweden and Denmark. Such a combination has never been built, but it would serve three purposes: Bring renewable energy to the European consumers, strengthen the energy markets and increase the security of supply by providing transmission capacity. These synergies would be the result of optimizing grid connection of offshore wind power plants not just nationally but also regionally. This pre-feasibility study compares national, separate grid connection solutions to combined wind power connection and interconnector solutions. The combination of offshore wind power plant grid connection and a three-legged interconnector at Kriegers Flak (KF) is called Kriegers Flak combined solution or simply combined solution throughout the document. Realising that Kriegers Flak would need a close co-operation and co-ordination from the beginning, the three TSO's decided to make these investigations together. The aim of this joint pre-feasibility study is to assess possible technical concepts, additional cost and benefits, and to identify barriers, which could hinder a combined, international solution at Kriegers Flak. Transparency is important to the transmission system operators, and it was decided to make the results of this prefeasibility study public. This was also done in order to enable possible stakeholders to work on identified barriers and to help develop possible solutions. 3. Background With the need for more wind power, wind production has gradually changed from single, onshore wind turbines to offshore wind power plants. As the offshore wind power plants become bigger and are placed further from the coast, a re-evaluation of the way to connect these wind power plants to the electrical grid is needed. One such re-evaluation relates to the technology for connecting wind power plants. For every new offshore wind power plant, the situation is analyzed in detail and the best technical solution chosen. For offshore wind power plants near the coast, that best solu- 5

6 tion has up to now been based on AC-technology 1. However, with increasing distances between the offshore plants and the onshore grid, new technologies based on DCtechnology are becoming more and more interesting. With respect to offshore grids, the new type of DC-technology called VSC (Voltage Source Converter) is particularly suitable. Another re-evaluation questions the prevailing concept of connecting wind power plants radially. New concepts involve ideas about connecting neighbouring wind power plants not only to shore but also to each other and about combining connection of wind power plants with interconnectors. The latter is primarily interesting where wind power plants are placed far from shore and between areas where there is a good potential for electricity trade. Both the Baltic Sea and the North Sea are very interesting in this context. Connection from Norway In progress Coordinated offshore development DC platforms Ekofisk Kriegers Flak 28. april Fig. 1. Map from the Norwegian TSO, Statnett, showing a possible offshore grid development in the North Sea. The original map focuses only on the North Sea and does not include potential interconnectors outside this area. Existing interconnectors are not shown. Kriegers Flak has been included here for comparison. The North Sea is considered for future, large-scale offshore grids which might involve interconnectors, offshore wind power plants and more environmentally-friendly power supply to offshore oil and gas platforms (see Fig. 1). This is a gigantic vision - involving huge investments and huge risks. A modular approach will probably be the key to solving challenges of this magnitude and complexity. This would mean systematically dividing the challenges into smaller and less complex modules. 1 AC: Alternating Current as opposed to DC, Direct Current. Almost the entire electrical grid is based on AC. DC is used for large distances and interconnectors between different synchronous zones. 6

7 A Kriegers Flak combined solution would involve three countries, two market systems, two synchronous zones, and the technical challenge it is to design combined, offshore solutions. So any combined grid solution at Kriegers Flak would involve new and international approaches in many ways. Offshore wind power plants play a decisive role in achieving national and European goals for renewables, and there is a broad interest in promoting offshore wind. This sincere interest is seen in many ways - through declarations, international studies, political initiatives, financial support, research and investments. It is uplifting that this interest embraces all aspects of offshore wind power. From improving the efficiency and profitability of wind power plants - over finding and approving possible sites - to integrating large amounts of wind power into the electricity systems. Two international initiatives are especially relevant for a combined, international solution at Kriegers Flak. The first is the joint declaration by Germany, Sweden, and Denmark that underlines the political willingness to co-operate on offshore wind energy in the Baltic Sea and in the North Sea [1]. This declaration refers to the so-called Berlin Declaration from February 2007 [2]. The other initiative is the Connection to offshore wind power in Northern Europe (North Sea - Baltic Sea) initiative headed by the European Coordinator, Mr. G. W. Adamowitsch. His first annual report [3] was published in October 2008 and Kriegers Flak is strongly emphasized both in the report and in the work plan for In this pre-feasibility study it is important to assess whether there is potential in a Kriegers Flak combined solution as compared to separate, national solutions. This comparison is made under the assumption that all three wind power plants will be erected at Kriegers Flak. Whether this will be the case or not (and on what time scale) is still unclear, so a key question for the transmission system operators is how to handle these uncertainties. In this pre-feasibility study, it was decided to analyse a situation where it is assumed that the following amounts of wind power will be installed: Table 1. Assumptions on installed wind power capacities This represents an ambitious but realistic situation. Any future offshore wind power plants at Kriegers Flak must be connected to the onshore grids and there are certain costs associated with this. The question is whether it is reasonable to invest in a more extensive grid solution which would have both additional benefits and costs. This is what is investigated here, and since the wind power plants would have to be connected under any circumstances, the comparison is made between the additional costs of a Kriegers Flak combined solution and the additional benefits which could be gained. 7

8 Another assumption is that the transmission capacity of the cable to each country is the same as the installed wind power capacity - so that e.g. the cable to Sweden is assumed also to be 600 MW. Because of the lower capacity of 400 MW towards Germany and experience with the price structure in Northern and Central Europe, it was decided also to include concepts with increased transmission capacity of 600 or 1000 MW on the connection towards Germany. The aim of this pre-feasibility study is to investigate the potential for a combined solution for the grid connection of offshore wind power at Kriegers Flak. What are the benefits and obstacles? The key questions are: - Is it technically possible? - Is it economically viable? - What are the environmental issues? - Is it practicable within the current legal, market and regulatory situation? The pre-feasibility study should answer these questions well enough to form a solid basis for a decision on whether to initiate a detailed feasibility study. It is not within the scope of this pre-feasibility study to make detailed comparisons between a combined solution at Kriegers Flak and other ways of providing additional transmission capacity across the Baltic Sea. 4. Technical solutions for grid connection of offshore wind power plants The traditional way to connect offshore wind power plants to the onshore grids is to use a radial connection. This means that there is a single connection between the offshore power plant and the onshore connection point (see Fig. 2). If each country decides to connect separately to their Kriegers Flak offshore wind power plant, it is very likely, that it will be through a radial connection. At Kriegers Flak, however, an alternative presents itself. Because of the position of the future wind power plants and the distances to the onshore grids, it might be advantageous to connect the offshore wind power plants through a combined solution which would also serve as an interconnector between Germany, Sweden and Denmark. A combined offshore solution has never been built, and so it is a key question to find a suitable technical concept. This has been analysed and is discussed below. 8

9 Fig. 2. Separate, radial connection of the wind power plants (on the left) and a Kriegers Flak combined solution (on the right). At this stage, only technical concepts have been investigated, and more detailed studies and plans must follow before decisions can be made. The analyses have resulted in three potential concepts for a Kriegers Flak combined solution, and these are described below. Both the technical consequences and rough cost estimations have been analysed. The rough cost estimations are based on a number of assumptions regarding cable prices and other important factors and are hence associated with large uncertainties. Because of the advanced stage of the project in Germany, it is assumed in all variants that the wind power plant Kriegers Flak 1 (KF1) will be connected by AC cables to the onshore grid. The grid connection of Kriegers Flak 1 will be combined with the connection of the Baltic 1 offshore power plant. The permission for this connection is for AC only and since most components have been ordered, there will be some financial losses involved if this technical solution is not chosen. That KF1 will be connected by an AC connection has been included in the analyses and is based on the responsibility to be able to connect KF1 to the German onshore grid by 2011 in case it will be decided that KF1 offshore wind power plants (as expected) will be built by then. 4.1 Separate solutions When deciding on a radial solution for the grid connection for a particular wind power plant, the main issues are the technical choices between AC or DC and between different voltage levels. For each new offshore wind power plant the situation must be analysed in detail. Both specific circumstances for the given wind power plant (such as distance to the onshore grid) and global circumstances (such as current cable prices) will affect the final choice of how to connect that particular wind power plant. If Kriegers Flak 1-3 will be connected separately by a radial connection, the technical choice for each wind power plant can be made independently of each other, and it is quite possible that the detailed technical solutions will be different for the three wind power plants. A later interconnection of these three systems might then be difficult. 9

10 In this study, we have analysed separate grid connection solutions based either on AC or on DC. Based on the distances to shore, the estimated cable prices and other assumptions, the separate solutions based on AC came out as the cheapest option. The total cost of three, separate AC connections was approximately 500 million (excl. offshore platforms), and this is used as the reference point when calculating the additional costs for various combined solutions. The difficulty in assessing offshore platforms is discussed further in Chapter 7. If separate solutions are chosen, the cables can only be used for transmitting wind power to the national onshore grids, and the full capacity of the cables will only be used when the wind is strong enough for the power plants to be producing at maximum capacity. On average, the wind production is so that the cables will be used at a level of less than half of the maximum capacity. If additional interconnector capacity is needed across the Baltic Sea, this can be provided through new direct, classical and bilateral interconnectors. 4.2 Combined solutions The challenge is to find solutions for an interconnector solution which has three legs, wind power plants attached, and which can be operated between two synchronous zones (Nordel and UCTE). Fig. 3 shows four different concepts for connecting future offshore wind power plants at Kriegers Flak. The concept involving separate grid connections (A) was described above, whereas three concepts (B-D) for a combined solution at Kriegers Flak will be briefly described below. Fig. 3. Diagram showing four technical concepts for grid connection of the Kriegers Flak offshore wind power plants. Separate connections (A), AC-based solution (B), multiterminal HVDC solution (C), and a hybrid solution combining multi-terminal HVDC with AC (D). AC cables are shown in dark blue and DC cables in light blue Combined, AC-based solution (B) This solution for grid connection is based on AC technology and all three connections to the onshore grids are made by AC cables. Germany (UCTE), Sweden (Nordel) and the eastern part of Denmark (Nordel) are part of different synchronous zones, and the Nordel and UCTE systems cannot be connected directly by an AC link. The interconnection between the two asynchronous systems is realized through an AC-to-DC-to-AC conversion in a so-called back-to-back converter station. This conventional converter station is assumed to be placed in Germany because that would be cheaper than to place it offshore or to build two stations in Denmark and Sweden. The power flow on the AC connections between Sweden and Denmark can be controlled by installing a phase shifting transformer on either the Swedish or the Danish side. Whether it will actually be possible to use the 10

11 full 400 MW cable capacity towards Germany in the day-ahead market will be discussed in Section 8.5. This concept is based on well-proven technology. Although the challenge of long AC cables, especially at sea, must be addressed. This is a flexible and scalable modular concept VSC-based multi-terminal solution (C) This concept involves a separate, AC-based grid connection for the planned German Kriegers Flak wind power plants (KF1), and a combined solution for connecting Kriegers Flak 2 and 3 to Germany, Sweden and Denmark. This concept for a Kriegers Flak combined solution is based on a multi-terminal HVDC connection with VSC-technology. This is the state-of-the-art technology relevant for large and more complex HVDC-based offshore grids such as the one shown for the North Sea in Fig. 1. Multi-terminal VSC connections use a new technique which is very promising but which has not been demonstrated yet (see also Section 8.4). Hence, concepts based on this technology are associated with larger uncertainties and risks compared to well-proven technology. This means that special attention must be given to handling and limiting these risks. The best measure is probably to find a flexible solution based on a modular design. A Kriegers Flak combined solution would in any case be built gradually and not in one step. An overall plan with a modular approach will ensure that each solution along the way is a good solution in itself and also compatible with a complete Kriegers Flak combined solution. In the beginning of this pre-feasibility study, a purely VSC-based combined solution was also considered, but had to be abandoned because of the advanced stage of KF1. Such a solution would, in principle, have been very similar to concept C. The main difference would be whether two or three offshore wind power plants would be connected to the hub at Kriegers Flak. If Kriegers Flak 1 is significantly delayed and other parts of a combined VSC-based solution are built in the mean time, it may become an option to connect Kriegers Flak 1 to the VSC-grid instead of by AC. This would of course have to be evaluated in detail. The VSC-based concept with a bus bar at sea where both offshore wind power plants and the interconnector cables are connected is a flexible and scalable modular concept Hybrid solution based on VSC- and AC-technology (D) This concept is essentially the same as the concept described above except that the 400 MW wind power at Kriegers Flak 1 is also part of the combined solution. This concept is more extensive but the additional offshore converter means that the total interconnector capacity of the cables to Germany will be up to 1000 MW as compared to the 600 MW in concept C. Whether it will actually be possible to use the full 400 MW cable capacity towards Germany in the day-ahead market will be discussed in Section 8.5. The hybrid solution providing increased total interconnector capacity is a flexible and scalable modular concept. 11

12 4.2.4 Summary of technical concepts Different technical concepts for a combined solution have been investigated, and the conclusion is, that each of these three concepts is expected to be able to solve this technical challenge. Some of the concepts require the development of techniques and technical standards, because they are based on technology which has not been proven yet. These possible concepts must be described and compared in more detail before a decision on the choice of technology can be made. The concepts must also be compared to alternatives like separate interconnectors. If it is decided to make a combined grid solution at Kriegers Flak, then a technical choice will also have to be made. An important difference between the concepts is that concept B is associated with lower risk than concepts C/D, which are based on technology that is under development. Concepts C/D have, on the other hand, technical aspects which could be transferable to future offshore grids in the North Sea. A combined solution at Kriegers Flak would, regardless of the choice of the technical concept, also face e.g. regulatory and market-related challenges, and experiences from this would also be transferable to the North Sea. Concept C might experience fewer challenges because of the clearer distinction between interconnector and wind power grid connection on the German part. The analysis has also included cost estimations for each concept. The rough cost estimations are presented in Chapter 7 where they are compared to the benefits from having additional transmission capacity available between Germany, Sweden and Denmark. 5. Method for calculating socio-economic benefit The ambition to improve market integration and to increase the amount of renewable energy sources is accompanied by a need to strengthen both national and cross-border transmission systems. The transmission systems for electricity are the backbone of both power markets and security of supply. Together with flexible and intelligent market systems for production and consumption, a strong and modern transmission system will make it possible to reach the European ambitions for renewable energy. It is essential to have good planning tools to assess the value of new transmission capacity. The Nordic transmission system operators have a long tradition of using market modelling tools to analyse the potential of new transmission capacity and other changes in the power system. The corner stone of these analyses is the EMPS (EFI's Multi area Power Scheduling) model. The EMPS model simulates the day-ahead (spot) power market. It calculates the price cross in twenty price areas based on the production system and consumption in each area and the transmission capacities between the areas. The model is especially strong in modelling the large amounts of Nordic hydro power and uses 51 years of historic inflow to take account of the variability of hydro power. Fig. 4 shows the countries which are included in this model. 12

13 Fig. 4. The region included in the power simulation tool used to estimate the socio-economic benefit of a combined solution at Kriegers Flak. In this study, the EMPS model is used to quantify the expected socio-economic benefit of a combined solution compared to the situation where each country makes their own, separate connection from the Kriegers Flak wind power plants to the respective onshore grid. The analyses are based on the expected production system, consumption and transmission system in The data set is an updated version of the business-as-usual scenario for 2015 from the Nordic Grid Master Plan 2008 made by Nordel [4]. The most significant changes are updated fuel prices and the inclusion of a more detailed description of the German system. The expected fuel prices in 2015 are based on the IEA World Energy Outlook from November 2008 [5]. As described in Chapter 3, it has been assumed that in total 1600 MW of wind power will be installed at Kriegers Flak. In these market simulations on Kriegers Flak it is assumed, that the capacity which is not used by the wind power will be available to the day-ahead market. This is done in order to assess the potential of a combined solution which can be used simultaneously for connection of wind power and day-ahead cross-border trade of electricity. It is, however, important to note that this may only be partly possible due to the present German RES Act (see Section 8.5). The assumption is, none the less, made here to illustrate the potential of a Kriegers Flak combined solution. The simulations show that there is a benefit in combining the connection of the Kriegers Flak offshore wind power plants with interconnection of Germany, Sweden and Denmark. The results are presented in Chapter 7 where they are compared to the additional costs associated with building a combined solution instead of three separate connections for the wind power only. A Kriegers Flak combined solution has other advantages compared to separate connections, but these cannot be easily quantified. One advantage is the increased security of supply which comes from the additional transmission capacity between Germany, Sweden and Denmark. In situations with little wind production (low wind or too strong wind), the additional interconnector transmission capacity could support the security of supply. Es- 13

14 pecially the eastern part of Denmark and the southern part of Sweden are expected to benefit from this increased level of security of supply. A Kriegers Flak combined solution would also improve the integration of wind in the region by spreading the wind power production from Kriegers Flak between three countries in a more optimal way. Another advantage of a combined solution is seen in the case of a faulty connection to one of the countries. In that situation, it would still be possible to collect at least some of the wind power from the unfortunate wind power plant. If separate solutions are chosen, that wind power plants would have to be stopped until the fault has been repaired. There is a general advantage in wind power generation being spread out over larger areas, and having offshore wind power in both the Baltic Sea and the North Sea will be beneficial when weather fronts pass Northern Europe. 6. Description of environmental issues Another important topic is the environmental impacts inevitably caused by the construction, operation and decommission of the grid connection. The environmental impacts will carefully be examined in the course of the permit process described below. Regardless of the chosen technical concept, the focus will always be on the principle of prevention and minimization of negative environmental impacts as far as possible. 6.1 Environmental issues A combined solution may on the one hand lead to negative impacts (e.g. through the laying of additional cables or construction of additional offshore stations), but does on the other hand improved transmission of electricity from the wind power plants and utilization of the connection for international transmission of electricity. Thus a combined solution may reduce the need for other bilateral grid connections and thereby avoid the negative environmental impacts caused by these. As a general principle, it can be stated that the number and size of offshore stations and the number and type of cables are the key criteria that determine the significance of the impacts on the environment. The impacts related to the wind power plants at the Swedish and German parts of Kriegers Flak have been described in the national environmental impact assessments (EIAs). The following description of environmental issues therefore only covers the cables and stations related to a combined solution. The most important environmental impacts caused by a combined solution are expected to be: - Installation of cables. The number of cables and size of cable trenches will affect the level of impacts on the sea bed - primarily caused by dredging during the construction of the grid connections. In the operation phase, a protection zone will be established around each cable corridor to minimize the risk of damage to the cables caused by anchors, fishing equipment etc. These protected zones will affect e.g. fishing activities and raw material exploration in the areas. A combined solution is expected to affect a larger part of the sea bed. 14

15 - Electromagnetic fields. Submarine cables expose marine life to electromagnetic fields. The electromagnetic fields depend on the number of cables and the type of current (AC / DC). However, the small number of existing field studies indicate that the effects might be negligible. - Warming of the sea bed. The submarine cables may lead to a warming of the sea bed and thereby affect micro organisms. In Germany, for example, the submarine cables may generally not lead to a warming of the sea bed of more than 2K in a depth of 20 cm in the sea bed. - Visual impact. Even though the distance to the mainland is mostly more than 20 kilometres, the construction of the offshore stations may cause visual impacts. These impacts are, however, minor compared to the visual impacts of the much taller wind power plants. Furthermore, cumulative impacts regarding e.g. risk of ship collision and water currents must be assessed. Cumulative impacts will be a result of both the offshore wind power plants and the chosen type of grid connection. From an environmental point of view, the differences between the alternative concepts would not be of such significance that they would amount to a decisive aspect for the comparison of the discussed alternatives. In fact, the environmental impact of any of the discussed solutions would probably be considerably smaller than the impact caused by the wind power plants. 6.2 Environmental assessments The three countries (Sweden, Germany and Denmark) do not have identical legislation and norms for dealing with these issues. Clarification of the differences is key to ensure a coordinated planning process in the case of a combined solution. A harmonized and coordinated planning and permit process would be vital for a successful realization of a combined project. The permission procedures are handled by the authorities. In the course of these procedures, environmental assessments including systematic analyses and hearings ensure a high level of transparency and legitimacy. If separate, national solutions are chosen for the wind power plants at Kriegers Flak, the national permission procedures will be similar to those for other wind power plants projects. A combined solution is expected to entail an environmental assessment of the interconnection according to the Espoo convention (see 6.2.2) Cumulative impacts of Kriegers Flak 1-3 The location of the three wind power plants at Kriegers Flak is likely to cause significant cumulative impacts. The Danish strategic environmental assessment of the location of future domestic wind power plants (Future Offshore Wind Power Sites ) [6] states that cumulative assessments must be included in a Danish environmental assessment of Kriegers Flak. By making use of the environmental impact assessments of the German and Swedish wind power plants at Kriegers Flak, a cumulative assessment of the activities 15

16 at Kriegers Flak could be made. Conducting a cumulative impact assessment reduces the risk of under- or overestimating impacts can be reduced. Choosing a combined grid connection solution will add to the cumulative impacts of the wind power plants. The Nordic Council of Ministers has established NordVind to investigate conditions for wind power in the Nordic region. In "Status for Kriegers Flak Projects" [7], NordVind states that "a separate assessment of the environmental issues for the three projects will hold the risk of doing the same work more than once and the danger of underestimating the true effects of the three projects as a whole" and "If important cumulative effects are found this would furthermore raise the question of which part of the wind park will be permitted and which will not" Espoo EIA on combined solution The Espoo convention requires that EIAs are extended across the borders between parties of the convention when a planned activity may cause significant adverse transboundary impacts. The criteria for significance are size, location and effects. If the impacts of a combined solution at Kriegers Flak are considered significant, the interconnection falls under the Espoo Convention. The cumulative assessment mentioned above can be included as part of the Espoo EIA and the analyses in the national EIAs may contribute to the assessments in the Espoo EIA for a combined solution. For the projects in Swedish and German waters, EIAs have already been carried out. An overview of environmental assessments is shown in Table 2. Table 2. Overview of environmental assessments for separate and combined solution for grid connection of offshore wind power plants at Kriegers Flak 7. Overview and comparison of alternatives An overview of the alternatives for grid connection of offshore wind power plant at Kriegers Flak is presented in Table 3. The rough costs have been estimated for each concept and are based on a number of assumptions regarding cable prices and other important factors and hence associated with large uncertainties. The method for estimating the socio-economic benefit from increased day-ahead trading was described in Chapter 5. 16

17 Also these estimations are sensitive to the assumptions made, and the estimations are associated with large uncertainties. Especially the expected fuel prices and production system in 2015 will influence the calculated value of the combined solutions. The total socio-economic benefit given in Table 3 is for the entire region (see Fig. 4). The effects are, however, mainly within Germany, Sweden and Denmark. Table 3. Overview of technical alternatives for grid connection of offshore wind power plants at Kriegers Flak. These are rough estimates and associated with large uncertainties. As described earlier, the comparison is made between the additional costs and additional benefits of a combined solution compared to traditional, separate solutions. The additional costs include the additional construction costs of a combined solution, while any additional costs from changes in maintenance costs or losses have not been included yet. The need for reinforcements of the national onshore grid must be seen in a larger context and the costs for these are also not included in the costs for grid connection of Kriegers Flak. The need for additional reinforcements of the national onshore grids is discussed in Section 8.3. It is particularly difficult to estimate the cost of platforms for the offshore grid-stations, as these depend both on the number of platforms, the size of the platforms and the water depth. Platforms for gathering power from the individual wind turbines are needed in all concepts. A coordinated planning involving e.g. common platform(s) placed at low water depth might result in significant savings when it comes to platforms for gathering power from the individual wind turbines. Additional platforms will be needed in concepts C and D for the offshore HVDC substations, whereas additional platforms may be needed to compensate the long AC cables in concepts A and B. The total costs for offshore platforms are expected to be the highest in concepts C and D, but because of the complexity this has 17

18 not yet been analysed in detail and the platform prices are not included in the rough cost estimations. As described above, the differences in environmental impact between the alternative concepts would not be of such significance that they would amount to a decisive aspect for the comparison of the discussed alternatives. In fact, the environmental impact of any of the discussed solutions would probably be considerably smaller than the impact caused by the wind power plants. All in all, the rough cost benefit analysis in this report indicates a positive benefit for a combined solution at Kriegers Flak. A more precise evaluation of this potential will require further analysis. The analyses indicate a positive economy for interconnector capacity across the Baltic Sea between Denmark/Sweden and Germany. This was also one of the conclusions of the Nordic Grid Master Plan 2008 [4]. For separate grid connection solutions (concept A), there is no increased interconnector capacity between the Nordic region and Central Europe. New interconnector capacity could also be supplied (without including the wind power plants at Kriegers Flak) by e.g. 600 MW, direct HVDC connection from Denmark to Germany or from Sweden to Germany. The investment costs for one of these separate interconnectors would be approximately 270 M (not including the investment costs for the separate grid connection at Kriegers Flak). With such a solution there will be full transmission capacity available to the market independently of the wind production. Concept A or B in parallel to separate interconnectors could be another approach to reinforce interconnector capacity. 8. Challenges A number of challenges would have to be met before a Kriegers Flak combined solution would be able to become a reality. The list is long and each challenge alone induces an elevated risk that an international solution at Kriegers Flak cannot be reached, and it will be important to address all challenges. But that being said, there is no reason to believe that the challenges cannot be resolved. 8.1 Co-ordination and commitment are needed A successful international Kriegers Flak combined solution cannot be accomplished by the transmission system operators alone. It is a task which requires sincere, long-term commitment from a number of parties: - The constructors and owners of the offshore wind turbines - The transmission system operators responsible for designing and building the grid connections - Those responsible for preparing the market for electricity trade across Kriegers Flak - The regulators and authorities being responsible for making regulatory decisions and for issuing the large numbers of different approvals needed for a project of this magnitude - The politicians. The degree of political willingness is important. Together we face a number of challenges. It is clear that one of the most important challenges is the issue of timing and co-operation because of the limited time available to develop a good, international solution. 18

19 Though a complete, international solution (with all, possible offshore wind turbines spinning, all modules of the grid connection in operation, and electricity being traded efficiently) is still some years into the future, the first building blocks and the most important decisions are not that far away. 8.2 Uncertainties about the offshore wind power plants As transmission system operators we work towards integrating new wind power plants into the electricity systems, but we do not decide when or how many that will be built. This is one of the reasons why co-ordination is important when it comes to offshore wind power, and why this would be especially important at Kriegers Flak. Usually, one wind power plant owner, one TSO and one set of authorities are involved, but for a combined solution at Kriegers Flak, this would be tripled. The following is an overview of the three wind power plant areas Kriegers Flak 1-3: Kriegers Flak 1 (Germany): Permission has been given for up to 80 wind turbines of up to 5 MW each - which would mean a total installed capacity of up to 400 MW. The wind turbines have not been ordered, but planning is far advanced and a decision could come as soon as 2009, and a time for start of operation is expected around 2011/2012. The permission does not include an obligation to build, but if the developer decides to build a wind power plant at Kriegers Flak 1, the current German support scheme gives great incentive to build before Vattenfall Europe Transmission is obliged to have the connection to the onshore grid ready by the time the wind power plant at Kriegers Flak 1 is ready to produce electricity. The grid connection of KF1 has already been optimized and will share a combined AC-connection with the smaller wind power plants Baltic 1 (approx. 50 MW), which will be commissioned in For realizing the offshore grid concepts B and D, an expansion of the KF1 offshore platform is necessary: additional assets like SF6-circuit breaker, SF6-Bus expansion, additional cable route on the platform, relay and reactive compensation etc. With a view of the planned commissioning of KF 1, the dimensions of the offshore platform must be determined at the end of Kriegers Flak 2 (Sweden): Permission has been given to Vattenfall AB for 640 MW wind power. Detailed studies have been performed and the investment potential is being analysed. An investment decision could be made in Vattenfall AB has a right but no obligation to install wind power at Kriegers Flak 2, as the permission does not specify that wind turbines must be installed at Kriegers Flak 2 within a certain time frame. In Sweden, the owner of the offshore wind power plants (Vattenfall AB) has the responsibility for making the connection to the onshore grid. It is, on the other hand, the Swedish transmission system operator (Svenska Kraftnät) who is responsible for new interconnectors from Sweden. It is at this stage not decided whether Vattenfall AB or Svenska Kraftnät (or both) would be the Swedish party involved in a future Kriegers Flak combined solution. Thus, there would be a particular need for co-operation between the owner of the Swedish offshore wind power plant and the Swedish TSO if it is decided to make a combined grid solution at Kriegers Flak. 19

20 Kriegers Flak 3 (Denmark): In Denmark, all new offshore wind power plants have been decided by parliament. So far three sites (Horns Rev, Rødsand and Anholt) have been decided over the years. Kriegers Flak 3 was analysed in the "Future Offshore Wind Power Sites " study from 2007 [6] as well as in the follow-up study from 2008 and is being considered as one of the next sites. The results of a more detailed study headed by the Danish Energy Agency are expected during The permissions for Danish offshore wind power plants usually include a "use it or loose it" condition to promote a speedy realization of the wind power plants. It is possible to apply for the right to construct offshore wind power plants without a decision in parliament, but such projects are, however, obliged to pay for their own grid connection. An application regarding permission to construct wind power plants at Kriegers Flak 3 has been sent to the Danish Energy Agency and the application is being processed. Energinet.dk is responsible for connecting wind power plants decided in parliament. The establishing of offshore grid connection always demands a concession from the Danish Energy Agency (except voltage level) cf. "The Danish Act on electricity supply" 22 a and the "Act on Energinet.dk" 4 a. Concession is mandatory regardless of which form of offshore grid connection in question; Connectors to wind power plants and interconnectors between Denmark and third countries are therefore subject to the same legal regulation. This status for Kriegers Flak 1-3 illustrates well a number of challenges involved in connecting offshore wind power plants to the onshore grids. There is a will and a need for long-term planning in order to do this in the best way, but it is still quite open for what, or even if, connections have to be built. Again, co-ordination, modular design and the willingness of all parties to commit to a long term project are key issues. 8.3 Reinforcements of onshore grids The wind power and additional interconnector capacity at Kriegers Flak must be integrated into the existing onshore grid. Given the magnitude of wind power (and hence cable capacity) being considered at Kriegers Flak, this will put additional strain on the onshore grids and may be responsible for a need to reinforce the onshore grids. Onshore grid reinforcements are challenging and very time consuming. It is particularly worrying that the expected time from decision to operation is much longer for onshore grid reinforcements than it is for e.g. connection of offshore wind power plants. A shorter and smoother permit process for construction of onshore grid would help. The need for new internal grid reinforcements must be seen in a larger context, as reinforcements in the transmission system can have many reasons (e.g. new generation capacities, new connections or other changes in power flows). 20

21 8.3.1 Internal grid reinforcements in Germany The station in Bentwisch is expected to be the onshore connection point in Germany. Previous studies have so far shown that a wind power and cable capacity of 400 MW will not require additional grid reinforcements going beyond Vattenfall Europe Transmission s current investment plans. Concepts C and D will require reinforcements of the German onshore grid - especially to handle 1000 MW of southbound power flow. A 400 kv overhead line from Bentwisch to Güstow would be needed, but this line would also accommodate additional generation capacity in Greifswald and (due the advantageous harbour facilities) also possible future power plants around Rostock as well as additional wind power in that region. It would be possible to have 1000 MW of northbound power flow without reinforcements, and this is relevant when looking at the improved security of supply in eastern Denmark and southern Sweden from a combined solution. In this region of Germany, a total of more than 4000 MW offshore wind power along with new generation and interconnector capacity has been applied for. This would require a replacement of the 220 kv double line Bentwisch-Lüdershagen-Lubmin by a 400 kv double line and its extension to a new 400 kv substation (Pasewalk). Moreover, the realization of new interconnections to the nort-east Pommerian region (from Lubmin to Pasewalk) and reinforced long-distance northeast-southwest connections are necessary to integrate the load flow and to transfer this bulk power to the load centres in the south and west of Germany. A decision has not been made, and the expected time from decision to operation is 8-10 years Internal grid reinforcements in Sweden In Sweden, a separate solution connecting the wind power at Kriegers Flak 2 to the Swedish system using AC cables would be made by two cables connected to the 130 kv system. A connection with HVDC would most likely be connected to the 400 kv system in one of several possible locations. One location would mean that the 400 kv AC grid would have to be reinforced with a new line, another would require a longer HVDC cable. More detailed studies have to be carried out before a decision can be made. The expected time to get permission and build a 400 kv AC overhead line is 8 10 years. An interesting alternative connection is to take advantage of the new SouthWest Link that is planned in order to reinforce the grid between Norway and Sweden as well as the grid in southern Sweden and which is to be built using VSC-HVDC. For that to be possible it is necessary for VSC-HVDC technology to become more standardised (voltages, controls etc) so that an existing VSC-HVDC connection can be extended with new converters. This also means that fast and economically realistic HVDC-breakers need to be developed. The potential to export power from southern Sweden depends on the transfer capacity through a critical cross-section between the southern and middle part of the Swedish grid. This so-called cross-section 4 is today at times limiting the export on the existing cables to Germany and Poland and to Denmark. The SouthWest Link is built partly to increase the capacity through this cross-section. The link is part of the Nordic Grid Master Plan [4] and is expected to be taken into operation in However, additional interconnector capacity out of southern Sweden would increase the pressure on cross-section 4, and so both a Kriegers Flak combined solution and e.g. an interconnector between Sweden and Lithuania will lead to periods with limitations between middle and southern Sweden. Even more so, if both interconnectors should be built. Depending on the market solution in 21