Wind and Wave Atlas for Ireland
11 November 2014
Met Éireann and UCD create a high-resolution wind and wave atlas for Ireland
Researchers in the UCD School of Mathematical Sciences, in collaboration with Met Éireann, have created a new wind and wave atlas for Ireland for the period 2000-2012. The study was supported by the Sustainable Energy Authority of Ireland (SEAI) through the Renewable Energy Research Development & Demonstration Programme.
Ireland is uniquely placed in terms of its ocean renewable energy resource, with a highly energetic wave and wind climate. The western coast of Ireland possesses one of the best wave energy resources in the world and consequently, is a promising location for the future deployment of wave energy converters (devices that extract energy from the incoming waves). Quantifying the wave climate and energy resource can aid in the selection of adequate locations for potential deployment and for the planning and design of those marine operations. In addition, up-to-date knowledge of the wind and wave climate of Ireland is very desirable for all marine activities.
- The wind energy resource is consistent around the coast with the highest values off the northwest.
- Winter averages for wind power at 100m are generally over 1100Wm-2, spring averages over 800Wm-2, summer over 500Wm-2 and autumn over 900Wm-2, even close to the shore (Fig. 1 left)
- In contrast to the wind energy resource, the wave resource is restricted to the Atlantic coast and to a lesser, but still substantial, extent off the Celtic Sea coast as shown in Fig. 1 (right). Winter wave energy can reach over 100kWm-1. This drops dramatically to 20kWm-1 in summer.
- Notably, the west and northwest benefit from exceptional levels of wave energy. The mean winter significant wave height can reach over 4m off the western coast.
The wind atlas was derived by downscaling the ERA-Interim atmospheric re-analysis to a 2.5km horizontal resolution with 65 vertical levels using the mesoscale HARMONIE model, a well-established atmospheric model used by Met Éireann for operational forecasting. Downscaling describes the process of deriving finer resolution data from coarser resolution model data. This allows local conditions to be simulated in greater detail. The downscaling area covers all of Ireland and its coastal waters ensuring that physically consistent wind fields are generated for both land and sea areas.
The wave climate was estimated using the WAVEWATCH III wave model. The resolution of the wave model varied from approximately 10km offshore to a maximum resolution of 250m in the nearshore. In order to provide a realistic description of the nearshore waves, the wave model was driven by the HARMONIE downscaled winds at 10m height, which have sufficient resolution to reflect the small scale orographic features associated with the coastlines and the sheltering effects of bays and islands. The wave hindcast was also forced at the model grid boundaries by wave directional spectra from the ERA-Interim wave re-analysis. This ensured that realistic ocean swells entered the model domain from the North Atlantic.
Fig. 1: (left) Seasonal averages of wind power at 100m. (right) Seasonal averages for wave power per metre of wave crest (kWm-1). (images © Met Éireann).
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