INTEGRATION OF OFFSHORE WIND FARMS TO THE GREEK TRANSMISSION SYSTEM VIA AN ISLAND INTERCONNECTION GRID A. Koronides J. Kabouris M. Efstathiou M. Tsili Hellenic TSO M. Papadopoulos Em. Prof. of NTUA President of the Hellenic TSO

INTRODUCTION (1) Existing submarine cable interconnections:Existing submarine cable interconnections: - AC 150kV: All Ionian islands (1964 – 76) - AC 150kV: All Ionian islands (1964 – 76) - AC 15 – 20kV: About 65 islands (since 1960) - AC 15 – 20kV: About 65 islands (since 1960) - DC 500kV: Greece – Italy (2002) - DC 500kV: Greece – Italy (2002) Under construction: Cycladic InterconnectionUnder construction: Cycladic Interconnection Planned island interconnection of all the Aegean islands, in order to:Planned island interconnection of all the Aegean islands, in order to: (a) Eliminate the existing oil powered stations (a) Eliminate the existing oil powered stations (b) Exploit the excellent wind potential (b) Exploit the excellent wind potential

DEVELOPMENT STAGES Three main stages:Three main stages: (A) Preliminary planning of the “Aegean sea grid”, based on existing projections (island loads and proposals for RES installations) (A) Preliminary planning of the “Aegean sea grid”, based on existing projections (island loads and proposals for RES installations) (B) Detailed design of the interconnection of each group of islands, to accommodate the RES plants with installation licenses (B) Detailed design of the interconnection of each group of islands, to accommodate the RES plants with installation licenses (C) Construction of each interconnection, when the proper conditions (economic feasibility, technical maturity etc) are obtained. (C) Construction of each interconnection, when the proper conditions (economic feasibility, technical maturity etc) are obtained.

ISLAND GROUPS and expected wind power Four main interconnections – island groupsFour main interconnections – island groups and expected wind capacity (on the islands): and expected wind capacity (on the islands): (1) Cycladic islands (construction stage) (1) Cycladic islands (construction stage) Production licenses: 650MW Production licenses: 650MW (2) North Aegean islands (2) North Aegean islands Production licenses: 700MW Production licenses: 700MW (3) Crete (3) Crete Production licenses: 2.200MW Production licenses: 2.200MW (4) Dodecanese (4) Dodecanese Expected wind power on the islands: 700MW Expected wind power on the islands: 700MW Stand-alone interconnection – SkyrosStand-alone interconnection – Skyros with expected wind power 333MW with expected wind power 333MW

Applications for offshore wind farms

GRID INTERCONNECTION EHV Substations (400/150 kV) have been chosen as connection points to the mainland gridEHV Substations (400/150 kV) have been chosen as connection points to the mainland grid –Robust system nodes (high short-circuit power) –Enough transmission capacity to absorb large wind power capacity Limitations to the absorbed wind powerLimitations to the absorbed wind power –Transmission system reinforcements for the accommodation of wind power –Restrictions in the total installed wind capacity due to the transfer capacity limits between North and South Greece

WIND POWER PENETRATION LIMITS of EHV Substations (400/150kV) of the mainland gridof EHV Substations (400/150kV) of the mainland grid

AEGEAN ISLANDS PROPOSED INTERCONNECTION SCHEME

Accommodation of onshore wind farms (4583MW)Accommodation of onshore wind farms (4583MW) AEGEAN ISLANDS PROPOSED INTERCONNECTION SCHEMES Island Group Expected Wind Farms Installed Capacity (MW) Connection Point (EHV Substation) Cyclades650Pallini/Lavrio North Aegean 700Larymna/Filippoi Crete2200Megalopoli/Aharnes Dodecanese700Aharnes Skyros333Larymna

AEGEAN ISLANDS PROPOSED INTERCONNECTION SCHEMES Accommodation of offshore wind farmsAccommodation of offshore wind farms Island Group Expected Wind Farms Installed Capacity (MW) Connection Point (EHV Substation) Fanari-Thasos500Filippoi Alexandroupoli – Samothraki – Limnos- Agios Efstratios 1000 To be further investigated in conjunction with possible onshore wind farm developments in Thrace Karpathos70Dodecanese Kymi75Aliveri Petalioi180 possibility of connection to Aharnes or Pallini must be investigated Kerkyra-Lefkada160Ahelwos/Arahthos

Grid Interconnection Issues Connection of the offshore parks in islands Alexandroupoli – Samothraki – Limnos- Agios Efstratios must be further investigated – reduction of the installed capacity of onshore parks in the North Aegean islands or ThraceConnection of the offshore parks in islands Alexandroupoli – Samothraki – Limnos- Agios Efstratios must be further investigated – reduction of the installed capacity of onshore parks in the North Aegean islands or Thrace The possibility to accommodate the above offshore wind farms by connection to EHV substations (400/150 kV) of the South system is limited due to the overall onshore installed capacities in Cyclades/DodecaneseThe possibility to accommodate the above offshore wind farms by connection to EHV substations (400/150 kV) of the South system is limited due to the overall onshore installed capacities in Cyclades/Dodecanese The offshore wind farms in Karpathos can be accommodated by the interconnection of Dodecanese islands to the mainland gridThe offshore wind farms in Karpathos can be accommodated by the interconnection of Dodecanese islands to the mainland grid The connection of offshore wind farms in Petalioi must be investigated due to the overall onshore installed capacities in Cyclades/Dodecanese that are connected to 400/150 kV of the South system (Aharnes/Pallini)The connection of offshore wind farms in Petalioi must be investigated due to the overall onshore installed capacities in Cyclades/Dodecanese that are connected to 400/150 kV of the South system (Aharnes/Pallini) No special considerations for the connection of offshore wind farms in the rest of the considered islandsNo special considerations for the connection of offshore wind farms in the rest of the considered islands

There are possibilities of integration of offshore wind farms to the greek transmission system via an island interconnection grid in order to support Maritime Spatial PlanningThere are possibilities of integration of offshore wind farms to the greek transmission system via an island interconnection grid in order to support Maritime Spatial Planning The potential from offshore parks that can be accommodated by the existing or planned submarine cable interconnections is highly dependent on the onshore wind farm developments (mainland/islands)The potential from offshore parks that can be accommodated by the existing or planned submarine cable interconnections is highly dependent on the onshore wind farm developments (mainland/islands) Limitations to the absorbed wind power in the mainland gridimposed by the transmission system infrastructure should be consideredLimitations to the absorbed wind power in the mainland gridimposed by the transmission system infrastructure should be considered Conclusions