Multipurpose artificial islands
Island Concepts
Wim Klomp
7 April 2021
Multipurpose artificial islands | 7 April 2021
Content
1. Functionality of energy islands
2. Concepts for offshore islands
3. Evaluation of concepts
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Multipurpose artificial islands | 7 April 2021
Multifunctional island (25 – 100 ha)
◼ HVDC substation & cable entries
◼ P2G for electricity conversion
◼ Operation & maintenance base for windfarms
◼ Data centres
◼ Search and Rescue base
◼ Aquaculture
◼ …..
Functionality of energy island
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Small HVDC island (6 – 20 ha)
◼ HVDC substation
◼ Cable entries and connections
◼ Quay for Installation and access
Multipurpose artificial islands | 7 April 2021
Area demand for different functions
◼ Substation (HVDC)
Area is needed for HVDC substation, AC switch yard, cable entries from windfarms and cables to mainland and other countries
(interconnections), operations building, workshops and accommodation. Present assumption is that substations for 2 GW are
efficient and these are being developed for platform as well as for island concept. Typical area demand for 2GW “island
concept” is 8 ha land. Access to the island is arranged via a sheltered port basin (shared with others) and a berth of 100 m, with
terminal area of some 1 ha.
◼ Power to Gas
For efficient use of all power from offshore wind farms it is believed that generated power needs to be used for generation of
Hydrogen or other gases to be able to store the energy and transport it more efficiently via power cables. Technology for large
scale conversion is to be developed. For hydrogen production, seawater is used as resource and area is needed for
desalination, hydrogen generation and hydrogen storage. An area of 11 ha is estimated for transformation of 2GW capacity. Use
of a available quay (occasionally) is assumed.
◼ Energy storage
Several systems storage systems are currently being developed, for example Pumped Hydro storage to Thermal storage and
Compressed Air Energy Storage (CAES). Required surface area and subsoils volumes are very different. A surface area of
some 10 to 15 ha will give possibilities and flexibility for energy storage systems.
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Multipurpose artificial islands | 7 April 2021
Area demand for different functions
◼ Operation & maintenance base for Wind farms
Accommodation for maintenance crew, storage for spare parts, workshops for repairs/testing. Port basin and safe mooring for crew vessels and maintenance jack-ups. A helipad needs to be included to move personnel to the island.
A land area of some 3 ha per 2 GW windfarms and a berth (150 m) and port area of some 1 ha per 2 GW wind farms. In case island is also used as basis for construction of new windfarms a larger area is to be expected.
◼ Data centres
An offshore energy island would also be a good location for data centres. Data centres required electricity and cooling water, which is both available on the island. Data cables can be part of an international network of data connections.
Land area needed for a datacentre is expected to be small, 1 ha per data centre.
◼ Other uses
Other uses can be support for aquaculture (drying area for weeds and/or processing facilities), search and rescue services, military/coast guard base. Most have only a small area demand on land and in the basin.
For artificial islands located further from the coast (say 250 to 300 km from shore) a offshore supply base to support construction of wind farms could be beneficial. This does require a significant area on land (10 ha for 1 GW/year installation) and in the port basin (5 ha for 1 GW/year installation).
Especially for multipurpose use of the island, some additional area is required for roads, utilities and or recreational. An increase of the net area of some 10 - 20% is recommended.
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Multipurpose artificial islands | 7 April 2021
Multifunctional island (10 GW)
Functionality on energy island
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Small HVDC island (2 - 4 GW)
HVDC (4 GW) 16 ha
Power to Gas (6 GW) 33 ha
Energy storage 10 ha
O&M wind farms (10 GW) 15 ha
Accommodation/utilities 5 ha
Other uses 10 ha
Roads/corridors 6 ha
Port basin/quay 25 ha
Total 120 ha
HVDC (2 GW) 8 ha
P2X (2 GW) 11 ha
Road/utilities 1 ha
Quay or Port basin 1 to 5 ha
Total 10 - 25 ha
Multipurpose artificial islands | 7 April 2021
Island concepts
Revetment type
◼ Sand base / pancake
◼ Traditional revetment of rock and
armour units
◼ Crest height typically 12 to 15 m
◼ Sand fill above high water level
Caisson type
◼ Gravel berm underneath caisson
◼ Caisson with wave wall
◼ Crest height typically 15 to 20 m
◼ Drainage canal behind caisson
◼ Sand fill above high water level
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Caisson type
Revetment type
Multipurpose artificial islands | 7 April 2021
Island concepts
Laguna type
◼ Sand berm / pancake
◼ ‘sustainable’ reef breakwater of sand and rock, gentle slopes
◼ Crest height typically 6 to 10 m
◼ Small island with ‘light’ revetment and floating pontoons in sheltered conditions
◼ Large footprint, but more variability in environmental ecotopes
◼ Flexible, especially for functions which can be placed on floating pontoons
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Laguna type
Multipurpose artificial islands | 7 April 2021
Evaluation of concepts
Revetment type Caisson type Laguna type
Costs + + 0
Ecology 0/+ 0 +
CO2 - footprint 0 -/0 +
Flexibility / extension 0 -/0 +
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• Laguna type is relatively expensive, especially for smaller islands• Caissons may be more favourable in deeper water, higher wave conditions and smaller
islands• Laguna type less CO2-footprint due to less concrete volume.• Laguna type can be more easily expanded in area. This can be done either by floating units or
increasing the size of ring construction. Caisson type is less flexible as the toe construction would have to be removed.
Multipurpose artificial islands | 7 April 2021
Discussion
Energy transition in the North Sea should be developed with a vision for long-term use and
possibly extension areas and future function changes. Also the ecological aspects and
work & living conditions on the island should be taken into account. The oil & gas platforms
in the North Sea should therefore not been taken as example.
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VindØ Consortium, Denmarkhttps://www.flickr.com/photos/22437367@N00/944354
Multipurpose artificial islands | 7 April 2021
Poll question
What do you estimate an island (in the North Sea, about 50 ha; in 25 m water
depth, without applications on it) will cost to build?
a) around 100 million euro
b) less than 500 million euro
c) around 1 billion euro
d) more than 2 billion euro
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