Windfarms - Overview

Offshore wind farms consist of a number of wind turbines which sit on foundations, secured to the seafloor, which produce electricity. This electricity is transmitted to where it is needed through a series of cables and substations. The first offshore wind farm was installed in Denmark in 1991 and the industry has grown rapidly since then with 3.3GW installed across Europe (1.8GW of which is in the UK).  China, US, Japan and South Korea have also started to develop offshore wind farms.

In the UK, the sector has developed in a series of leasing rounds undertaken by the Crown Estate, the landlord and owner of the seabed. The first one of these was launched in 2001 and involved 18 sites across England and Wales with a potential capacity of 1GW. 1GW of capacity can power 613,000 homes/annum.

In 2003 the much larger Round 2 was issued totalling 7GW of projects grouped into three strategic areas: Greater Wash, Greater Thames and Irish Sea. The highest profile site is the London Array project which, when it opens in early 2013, will be the largest offshore wind farm in the world.

Scotland had its first leasing Round in 2009 with the Scottish Territorial Waters round providing the potential for 5GW across 6 sites.

This was shortly followed in 2010 by the enormous Round 3, which totalled 32GW across nine zones across the UK. Round 3 represented a slight change in approach with developers granted much larger zones, within which developers would identify a number of projects. It is important to note that these zones will not be covered by turbines. The Zonal approach allow developers greater flexibility when siting projects, giving more opportunity to take on stakeholders concerns and also allow a better assessment of cumulative impacts. The largest zone – Dogger Bank – has the potential to generate up to 13GW of power and is one of the largest energy projects anywhere in the world.

There have also been a number of smaller demonstration sites leased which will allow new technologies to be tested before being used at a commercial scale. The two main sites are NAREC at Blyth and Aberdeen Bay.

Once a developer has obtained a lease they have to undertake various development activities and apply for consent.

The optimal location for an offshore wind farm is a function of a number of different factors including:

• wind speed – the higher the wind speed the more power the turbines generate;
• depth of water – the deeper the water the more expensive the foundations and installation;
• distance to shore – the further from shore the more cable required and the greater the distances to travel for installation and operational vessels and employees;
• environmental and human users of the sea – offshore wind farms have a range of potential impacts and developers will seek to minimise these, however, changes which may benefit one user may hinder another; and
• geology and sea bed conditions – some seabed types are more suitable to offshore wind then others.

Developers therefore have to balance a huge range of often competing factors and impacts in what is in effect a huge optimisation exercise. Unfortunately this means that not all stakeholders can get everything they want.  For instance, turbines spaced further apart may benefit fishermen and reduce impacts on birds, but this will increase the cost of array cables.