Ocean energy technologies
Offshore Renewable Energy has the potential to provide a substantial amount of sustainable, renewable energy around the world. Find out more about the key technologies.
Offshore wind energy
With a seabed area seven times its landmass and excellent wind and wave conditions, Ireland has access to a huge offshore renewable energy (ORE) resource to help decarbonise the economy. ORE can potentially provide more energy than projected Irish Ireland, therefore Ireland has the opportunity to export significant low-carbon power to consumers across Europe. Offshore wind will play a significant role in Irelands decarbonised electricity system with a government stated ambition to deliver 5 GW of offshore wind by 2030, and 20 GW by 2040, and 37 GW by 2050.
Offshore wind uses two broad technology types, Fixed-bottom and Floating offshore wind.
Fixed-bottom offshore wind
Fixed-bottom offshore wind projects are those using wind turbines on monopile, jacket or gravity-base foundations fixed to the seabed. Fixed offshore wind has TRL 9 and CRI 6 in accordance with AREAs Commercial readiness index. To date, fixed projects have been installed in water depths of up to 60 m, but maximum depths will likely continue to increase. In Ireland, the only project in operation is the 25 MW Arklow Bank phase 1 project , a small project of 7 turbines, installed in 2004. A further 3.1 GW offshore wind energy have been awarded exclusive rights for development agreement in the Offshore Renewable Energy Support Scheme (ORESS) round 1 auction of 2023.
| Project Name | Awarded Capacity (MW) |
|---|---|
| Codling Wind Park | 1300 |
| Dublin Array | 824 |
| North Irish Sea Array | 500 |
| Sceirde Rocks | 450 |
The CRU has also announced a route to market for 1.175GW of offshore wind projects which were unsuccessful in the ORESS 1 auction. Oriel Wind Farm (375MW) and Arklow Bank Wind Park 2 (800MW) have a route to market via a corporate power purchase agreement (CPPA).
Fixed offshore wind is already playing a significant role in many markets, with 61 GW operating globally across about 250 projects by the start of 2024. This technology has a high degree of commercial readiness, and is considered fully bankable, enabling access to significant volumes of finance.
Floating offshore wind
Floating wind projects use turbines mounted on floating hulls, attached to the seabed through mooring systems and anchors. So far, the same turbines as for fixed offshore wind have been used, except for changes in tower design and control systems to account for different loading patterns. The key advantage of floating offshore wind over fixed is its ability to deploy in deeper waters, thereby increasing the opportunity for offshore wind. Floating offshore wind technology is much less well established than fixed. Floating offshore wind is at TRL 8 or 9 (depending on foundation concept) and CRI 2. Semi-submersible and Spar buoy foundations are TRL 9 and Tension leg platforms and Barge foundations are TRL 8.
Given the extensive deep-water area in Ireland's exclusive economic zone with high wind resource, floating offshore wind provides a significant opportunity for the Irish energy sector. To grow the offshore wind industry beyond 10 GW in Ireland, floating offshore wind will likely need to be deployed off the Irish coasts. Ireland's chosen pathway and division between fixed and floating deployment will be clarified through forthcoming marine area spatial plans, which will account for wider environmental and social considerations.
Wave energy
Waves are formed by winds blowing over the surface of the sea. The size of the waves generated will depend upon the wind speed, its duration, and the distance of water over which it blows (the fetch), bathymetry of the seafloor (which can focus or disperse the energy of the waves) and currents. The resultant movement of water carries kinetic energy which can be harnessed by wave energy devices.
The best wave resources occur in areas where strong winds have travelled over long distances. For this reason, the best wave resources in Europe occur along the western coasts which lie at the end of a long fetch (the Atlantic Ocean). Nearer the coastline, wave energy decreases due to friction with the seabed, therefore waves in deeper, well exposed waters offshore will have the greatest energy.
Ireland's wave energy resource
The Offshore Renewable Energy Development Plan published in 2014 identified a total theoretical development potential of 31,100MW of wave energy in Ireland that could be extracted without having likely significant adverse effects on the environment.
The Offshore Renewable Energy Technology roadmap has assessed the potential for wave energy to play a role in Irelands decarbonised electricity system. The roadmap recognises that wave energy could play a role in meeting Ireland's 37GW ambition if sufficient progression in technology readiness and price reduction is achieved.
The amount of this resource which Ireland ultimately realises will depend on:
- The cost effectiveness of the wave energy technology.
- The amount of power which can be practically connected to the network from the western seaboard locations.
- The amount of capacity available on the network when other intermittent generation sources such as onshore/offshore wind energy are considered.
- Impacts on the environment and Interactions with other users of the marine resource.
Wave energy converters
Wave energy technology captures the kinetic energy contained within ocean waves using wave energy converters (WECs). Unlike other more established renewable energy generation technologies, there is yet to be a convergence in the design of WECs. There are a range of devices suitable for location in the nearshore and offshore environment. All wave energy converters (WECs) comprise a sub-surface component (moorings, lines, anchors, foundation) and some have a surface or above surface component). WECs may be installed as a single device or an array of devices depending on the technology. There are a range of devices currently being tested and the technology remains novel. Ireland's wave resource is greatest on the west, south and north coast where environmental conditions are more extreme. The design archetypes for wave energy converters include the following:
- Attenuator
- Point Absorber
- Over-topping Device
- Oscillating Water Column
- Submerged Pressure Differential
- Oscillating Wave Surge Converter
- Water Pressure/ Bulge Sytems
- Rotating Mass Point Absorber
Tidal energy
Tidal energy uses the kinetic energy of the free movement of water due to tides to generate electricity. Tides are driven by the relative movement of the earth, moon and sun and can be predicted years in advance. Tidal range (the difference between the largest and smallest tidal heights) is greatest during spring tides, and smallest during neap tides.
Tidal energy can be captured by Tidal Stream or Tidal Barrage technologies. In tidal stream Tidal energy converter (TEC) devices are placed in environments to capture the kinetic energy of water movement. In tidal barrage a barrier with integrated turbines is constructed transecting the body of water (typically an estuary or man made basin) which captures the motion of water as the tide rises and falls.
Tidal stream
Tidal stream TRL is 7-9 and CRI is 1.
Most tidal energy converters (TECs) function similarly to wind turbines, capturing energy from water rather than air, though some designs act more like rigid-wing airborne wind devices. TECs are generally placed in areas with high flow speeds due to suitable bathymetry (such as tidal lagoons, estuaries or channels), though some designs are emerging that are optimised for lower flow speeds.
Tidal stream resources are generally largest in areas where a good tidal range exists, and where the speed of the currents are amplified by the funnelling effect of the local coastline and seabed, for example, in narrow straits and inlets, around headlands, and in channels between islands.
TECs are placed directly into the tidal current and may be fixed (with a range of different foundation types) or floating.
Tidal energy devices
Tidal devices are located in tidal streams, such as narrow straits and inlets, around headlands, in channels between islands. Devices are mainly subsurface but there may also be a surface component. A single or a number of devices may be located within a tidal stream. Ireland tidal stream resource is limited, the best locations being on the north and north east coast, and discrete sites such as the Shannon Estuary.
- Horizontal axis
- Vertical axis
- Reciprocating Devices (Oscillating hydrofoils)
- Venturi effect
- Archimedes Screw
- Tidal Kite
The main barrier to Tidal stream development remains cost with Offshore wind remaining more competitive.
Tidal barrage
Generation using tidal barrages uses turbines integrated directly into the barrage wall. As water flows in and out of an estuary, natural or man-made basin due to tidal activity, water will flow through the barrage, driving the turbines, similar to in hydroelectric dams, but with much reduced pressure head.
Tidal barrage generation is not likely to play a large role in the future of Ireland's energy supply due to limited applicable environments for development. Tidal barrages are most suited to be placed across rivers or tidal basins with high tidal ranges, without the need for regular vessel navigation, and in areas without sensitive coastal ecosystems that would be disrupted by changes in water level and reduced access through the barrage.
Ireland's tidal energy resource
In 2005 SEAI undertook a review of the tidal resource in Ireland. This report identified a number of areas around Ireland coastline suitable commercial for tidal deployment, primarily the East coast, and Shannon estuary.
A total theoretical development potential of 3000MW of tidal energy was identified in OREDP I across these the SE coast, NW coast and Shannon Estuary areas. A strategy for the deployment of tidal energy is yet to be developed due to remaining challenges regarding cost competitiveness.