Where to install offshore wind farms

Offshore wind energy is a form of renewable and clean energy that is generated by capturing, through offshore wind farms, the power of wind on the high seas − where its speed is more constant and higher as there are no physical obstacles. Furthermore, it should be taken into account that space is greater at sea and that ships offer the possibility of transporting larger blades and towers. This means that these offshore wind farms, equipped with the most advanced technical innovations, can optimise this inexhaustible and clean source of energy in an efficient manner. 

However, how do you decide where to install offshore wind farms, and how do you choose whether they should be offshore or floating wind farms? This process involves assessing various key factors whose analysis seeks to maximise the potential for wind energy generation in areas with strong and consistent winds, while considering logistical and environmental feasibility. Learn about the key criteria to ensure the optimal location for renewable energy generation in the marine environment.

Factors to take into account when choosing the location of offshore wind farms 

One of the first criteria to consider when deciding where to install offshore wind farms is the analysis of the wind resource. A good location must have a constant and strong wind, so it is necessary to collect historical data on wind speed and direction at the offshore location of interest. This data can come from onshore weather stations, offshore weather buoys or measurements taken at the specific location. These data are analysed to determine average wind speed, wind variability over the year or seasonal trends, and models are developed to take into account orography, sea temperature and other local factors that may influence the wind.

Another important issue is the depth required for wind farms as this influences the type of foundation required for wind turbines. In shallow waters, fixed foundations can be used, such as monopiles or gravity or jacket foundations, which are fixed on the seabed. In deeper waters, floating solutions are required, which are currently under development and therefore in early projects must take into account the increased costs and technical challenges compared to fixed foundations, which have nearly 20 years of development and accumulated experience.

Another variable to take into account is the distance to the coast, which largely determines the logistics of construction and maintenance, as well as the fact that a shorter distance facilitates interconnection to the electricity grid. 

Finally, we must not forget the shipping lanes. 
 

Floating or fixed offshore wind?

A correlative to the decision of where to install offshore wind farms is what type of technology to use. The choice between floating and fixed offshore wind depends on a number of elements that must be carefully evaluated in the context of a specific project. Water depth has already been mentioned as a determining factor since floating wind farms are needed in deep water, where fixed foundations are not feasible. However, the power generation potential must also be taken into account, as floating wind farms can take advantage of areas with stronger and more constant offshore winds, which rises up the generation potential compared to shallow water foundations.

In terms of environmental impact, floating wind farms potentially have a minor environmental impact on the surroundings. Other specific conditions, such as geology, ocean currents, climate and navigation, must also be assessed, as they can be critical in ensuring the safety and viability of the project.

It should be noted that the combination of both types of technologies can also be a viable option in certain cases, taking advantage of their respective strengths to maximise renewable energy generation in the marine environment.

How can the impact of offshore wind farms be minimised?

Another issue to consider when planning where to install offshore wind farms is how to minimise their environmental impact on marine life and the surrounding ecosystem. Here are some technologies and measures used to reduce the environmental impact of these projects:

Selection of suitable location:

As already mentioned, in addition to significant wind potential it is important that environmental and visual impacts are minimised including the identification of areas of interest and special environmental protection, distance to the coast, water depth and the presence of shipping lanes.

Design of turbines and foundations and floating platforms:

The evolution of wind turbines implies a significant increase in their dimensions: height and span of the blades. This is particularly relevant for offshore turbines, as the transport logistics are carried out by sea, avoiding the size limitations of land transport.

Larger turbines of higher unit power mean fewer units for a wind farm of equal power; for example, a 1,000 MW offshore wind farm needs 100 turbines of 10 MW each, but only 50 units of 20 MW each. This reduction in the number of turbines reduces environmental impacts, especially during the construction of the farm.

Environmental impact assessment during installation and operation:

Conduct comprehensive environmental impact assessments to identify and mitigate potential impacts on marine life, birds and bats, marine habitats and other ecosystems. This may include implementing exclusion areas and scheduling construction to avoid wildlife breeding seasons.

In addition to the turbines and foundations, the electrical infrastructure that evacuates the energy generated in the wind farm to the onshore grid is also taken into account:

Electrical substations: when the power to be evacuated and the distance to the coast require it, it is necessary to install marine substations. The electrical equipment can be installed in relatively shallow water structures, or on floating platforms for deep water. The potential impacts of these substations are minimised and monitored in a similar way as for the substructures supporting wind turbines.

Inter-turbine cables and export cables carrying energy to land: the main measure to minimise the impact of cables is to design their routes over the seabed avoiding environmentally sensitive areas. Cables in fixed foundation wind farms are usually buried in trenches to avoid damage and cable movement during wind farm operation. In floating wind farms, part or all of the cable remains submerged in the water column, avoiding impact on the seabed.

An electrical conductor passing a current of electrons generates heat and a magnetic field. Much has been said over the last 20 years about the impact of such an electric and thermal field on wildlife. Cables are properly shielded with several layers of insulating materials and metallic armour, which minimise the effects of such fields, making the impact not significant for wildlife.
In the case of floating platforms, anchoring or anchor lines are another element that is taken into account in the environmental impact assessment. The design of the platforms and their anchoring is done in such a way as to minimise the impact on sensitive areas of the seabed.

Constant monitoring:

It is essential to implement monitoring systems to continuously track and assess the impact of the offshore wind farm on the environment. This allows corrective or compensatory measures to be taken if unexpected impacts are detected.
 

Underwater noise mitigation:

When it comes to noise impact, this is limited to the construction phase, as the noise during the operation phase due to the turbine blades’ rotation remains at sea thanks to the ambient noise caused by wind and waves.


During the construction phase of wind farms with fixed foundations, noise is mainly produced during the driving or drilling of the foundations, if applicable. This noise is limited in time and space, so the mitigating measures implemented are as follows:

Over time: the presence of fauna and their sensitive periods of activity in the area (mating and breeding) are analysed, avoiding these periods and implementing noise-reducing measures such as double bubble curtains around the pile or structure hammered or drilled into the seabed, monitoring that the immission sound level does not exceed the threshold defined by the environmental authority. In addition, specialised personnel monitor the presence of sensitive fauna, such as cetaceans, during the installation, stopping the noisy activities when necessary.

In space: the planning of marine space and the decision on the location of wind farms takes into account areas of high environmental quality, avoiding and making the implementation of wind farms compatible with the protection of these areas.

 
Floating platforms can reduce the noise impact during installation, especially if drag anchors or suction boxes are used as anchoring elements.

The installation philosophy of the floating platforms is to assemble the turbine on the platform in port and tow the complete unit, platform plus turbine, to the offshore site, minimising offshore activities compared to the installation of the fixed foundations.

Responsible decommissioning:

Plan from the outset for decommissioning offshore wind farm facilities, ensuring proper removal of structures and restoration of the site to its original or enhanced state.