The effort to reduce greenhouse gas emissions is receiving global attention. The most efficient method to achieve this is to reduce fossil fuel energy generation (coal, oil and gas) and increase the development of renewable energies. The European Union therefore has established a common framework to support energy generation from renewable sources (Directive 2009/28/EC on the promotion of the use of energy from renewable sources 23 April 2009), which sets mandatory national targets for the overall share of energy from renewables in terms of national gross final consumption of energy and for the share of energy from renewable sources used in transport.
The introduction of renewable energies within the European energy framework has already made an impact. The analysis of the EU evolution of renewable energy demands has revealed an increase from 6 to 9% of gross inland energy consumption by renewable energies during the last ten years, which have been replacing mainly solid fuels, petroleum products and natural gas (Fig. 1).
Figure 1. Gross inland energy consumption by fuel - 1000 toe, 1999 and 2009. Adapted from data source: EUROSTAT.
According to recent studies, the greatest potential for offshore renewable energies in the North Sea, Baltic Sea and Western Mediterranean Sea lies in wind energy. Offshore wind generation is efficient at producing energy since offshore winds are stronger and steadier than on land. Strongest offshore wind locations are off the coastlines of Norway, the UK and Ireland. In addition to offshore wind, tidal and wave powered generation has potential in the dynamic coasts of the North Sea, particularly the seas of the Northern reaches of Scotland (Orkney and Shetland Isles).
In the Western Mediterranean, there is potential for solar energy to be successful in addition to the projected wind farm projects. Ocean currents may also provide enough energy for power plants in the north-west and south-west coast of Sardinia and the Sicily Channel.
In the Baltic Sea conventional energy production (such as nuclear, gas, oil and coal) is relevant to the marine sector because of the placement of generation sites in coastal areas.
Marine energy developments will claim more space in coastal areas and at sea which has the added complexity of sharing requirements with other sectors such as fisheries, transport, aquaculture and leisure use.
The North Sea is composed of soft (mostly sandy) sediment and has anthropologically heavily disturbed sea bed (years of trawling) making benthic fauna of the North Sea not especially vulnerable to industrial energy installations. In the Baltic Sea, provision of solid platforms will not change the balance of species occurrence and dispersal, as the seabed in this frequently visited marine area is scattered with ship wrecks. Outbreak forming species are mostly pelagic, so the technology that influences the seabed is unlikely to influence their distribution. Productivity in the vicinity of extensive wind farms may be impacted, as such installations may cause eddy patterns influencing planktonic production and also modify the wind which can affect the mixing depth of surface waters. In the Western Mediterranean area, special attention should be focussed on the endemic species Posidoniaceae, which is very sensitive to turbidity and therefore to marine excavation. Moreover, the existence of migratory bird routes is also an important factor to be considered when wind farms are developed.
The increasing development of renewable energy will have multiple social benefits including the reduction of global CO2 emissions, the improvement of regional energy security and will support the creation of new economic/employment opportunities.
Compatibility of energy installations with the marine environment is possible if potential impacts are well assessed from an early stage of the projects, mitigation measures are successfully implemented and effects are monitored after construction. Marine spatial planning and mapping sensitive areas are highlighted as significant tools to minimise potential impacts at an early stage, since they help for careful siting and preconstruction assessment of energy infrastructures in the offshore area. Well-managed environmental impact assessments and monitoring plans will facilitate the avoidance or reduction of impacts.