Which Irish Wind Farm has the best site?

Developers of offshore wind farms in Ireland must get approval from the Irish government by winning a contract in an Offshore Renewable Electricity Support Scheme (ORESS) competition. These were outlined by the Irish government in 2018 in an attempt to reach their goal of 5 GW of offshore wind energy by 2030. To date, there have been two ORESS auctions.

The first of these, ORESS 1, concluded in 2023 and awarded contracts to four new wind farms: The North Irish Sea Array (NISA), Dublin Array, Codling Wind Park, and the Scierde Rocks Offshore Wind farm. Three of these four are currently still in the planning phase, while Scierde Rocks was forced to withdraw their plans in April 2025, citing poor site suitability as a primary factor.

ORESS 2 took place in 2025, and the results are expected to be released soon. This auction is slightly different compared to the ORESS 1 auction in that the site had already been chosen as part of the national Designated Maritime Area Plan (DMAP) outlined in 2021 by the Maritime Planning Act. The ORESS 2 site, known as Tonn Nua, is a 310 square kilometer area located offshore of County Waterford, and it is much larger than the other planned sites.

Seeing as the results of Tonn Nua should be out in the near future I thought it could be fun to “score” the planned ORESS sites using my new MCDA/stakeholder engagement model for evaluating offshore wind site suitability. I’ll also include Arklow Bank, Ireland’s only active wind farm, in my evaluation.

My model works by using 11 site suitability factors and weighting them with an MCDA approach. This is assisted by the stakeholder interviews and surveys that I conducted as part of my MSc dissertation. In addition to each wind farm’s overall rankings, I will also show how well they scored with respect to each individual factor. These factors are listed in order of how they are weighted by the model, with criteria deemed most important (like Wind Power Density and Grid Connection) at the top and criteria deemed least important at the bottom.

6th: North Irish Sea Array (NISA)

The NISA site scores the lowest overall with my model, and it also possesses the two lowest scores in any individual criteria (Distance to Port and Fishing overlap) of any of the windfarms considered. The closest port that my model considers viable as a primary deepwater construction port is Rosslare Harbour in County Wexford. While the Port of Dublin is highly developed and closer, it seems that the industry consensus is that this port does not have the capacity to accommodate offshore wind farm development. Currently, the NISA project plans on developing Greenore Port in County Louth to use as its primary service point, but this is not complete yet and so Distance to Port will remain unsuitable for the NISA site currently. Additionally, the site is in an area of high fishing intensity, and this has been apparent throughout the development project as the NISA site has faced strong backlash from the fisheries. That said, I’m sure the NISA developers, Statkraft and Copenhagen Infrastructure Partners, have their reasons for choosing this site, but I would be very interested to know why they chose to pass up other locations that seem far more feasible.

5th: Sceirde Rocks

The ill-fated Sceride Rocks Wind Farm is number five in overall suitability, and this site selection has confounded industry experts and academics alike. No one could really understand the rationale to attempt development on the western coast, which had essentially always been deemed unviable with fixed foundation technology. An article by the Irish Times states that the primary reasons for bailing on the project were site suitability concerns, namely, issues with rocks in the construction site and every strong wave conditions. This corresponds quite well with what my model outputs: poor substrate quality, and low serviceability (Wave Height and Days with Serviceable Conditions). Very high visual impact added to the poor score, and local communities were strongly against the Sceride Rocks project due to the impact it would have on the view from shore. Projects like this one show that good site selection is extremely important for offshore wind, and that more research is needed into accurate site suitability models.

4th: Tonn Nua

The subject of the ORESS 2 auction is challenging to score using my model, as the massive site contains significant variation in its suitability through its borders. There are areas with extremely low suitability (mainly due to rock substrate), but there are also areas with favorable conditions as well. It’s my assumption that developers won’t try to build out 100% of the Tonn Nua DMAP, and if that is the case then the site’s suitability is actually a little higher than this mean overall suitability score might suggest. Still, the bathymetry will likely present problems, with the site possessing a mean depth of 50m. Additionally, most of the shallow areas are also the areas with rocky substrate, forcing developers to consider deeper waters. However, advances in fixed foundation technology are steadily increasing the economical depth limit for these wind farms, and a long term project like Tonn Nua may have access to better foundations by the time they start construction.

3rd: Codling Wind Park

The Codling Wind Park scores very well in most categories, and it is only held back from top tier ranking by its poor port proximity, fisheries overlap, and mid-level wind power density. In terms of port proximity the situation is somewhat similar to that of the NISA project in that the closest port considered by my model is Rosslare Harbour. Like with NISA, this will not be used as the port of construction. Codling Wind Park will use Wicklow Harbour as its primary construction port, and while some work is needed to develop Wicklow into an offshore wind construction base, it will be located just 15km from the wind farm site. If the developers are able to effectively develop Wicklow’s infrastructure, they would have one of the most ideal port proximity situations of any Irish wind farm, and the site would deserve a higher suitability score. The other downside of the site is that it is located in a high fishing intensity area, which has caused backlash from fisheries. Overall, my model indicates that Codling Wind Park’s location is a generally good site to build on.

2nd: Dublin Array

The Dublin Array site is located very close to the Codling Wind Park site, and there are a lot of similarities between the two. However, one key advantage of the Dublin array site is that it has very low fishing intensity, which has resulted in much less high profile fisheries conflict than the Codling project. However, its current plan for construction is to use the Port of Dublin as its primary base, which was not included as a viable port in my model because it is generally assumed to be too busy to accommodate offshore wind construction. It seems likely that this could pose significant problems for developers, and I wonder about the possibility of using Wicklow in conjunction with the Codling Wind Park, assuming the developers of the two wind farms could build the needed infrastructure in Wicklow harbour. Aside from this, the site is excellent, and has one of the best grid connection setups of any planned/existing Irish wind farm due to substation proximity and proximity to Dublin.

1st: Arklow Bank

Arklow Bank wind farm has been in service since 2004, and its site scores higher than any of the planned sites. The biggest issue with the Arklow Bank site is its substrate. While the Arklow Bank seabed consists of shallow sand, which is the perfect substrate for fixed offshore wind, the sand bank that Arklow Bank is built on is highly mobile, which caused problems during construction and servicing. While this is partially reflected in the Slope category (only Sceride Rocks had a lower slope score than Arklow Bank), slope is not a perfect proxy for substrate mobility. This is an issue with my model that I hope to fix as better substrate mobility maps come out for Irish waters. Aside from this, however, the Arklow bank site is excellent. It is interesting that even though Wind Power Density is the heaviest-weighted variable in my model, Arklow Bank with the lowest Wind Power Density has the most suitable location. This is due to the less important variables combining to outweigh WPD.

That concludes my site suitability ranking of Irish offshore wind farm sites! If you are interested in the particulars of my model, linked my dissertation here. Additionally, please feel free to reach out to me via email or the contact box below if you have any questions!

Happy Wind Farming!