1. Introduction
2. Global Environment
3. Biological Impacts
3.1: Birds
3.2: General conclusions
3.3: Sea Mammals
3.4: Fish
3.5: Seabed and benthos
3.6: Hydrography, sea currents and water quality
3.7: Effects from accidents
3.8: New biological impact Studies
4. Noise and Vibration
4.1: Airborne noise
4.2: Underwater noise and vibrations
5. Conflicts of Interest
5.1: Ships
5.2: Air traffic
5.3: Defence
5.4: Radar and radio signals
5.5: Fishing industry
5.6: Raw material deposits
5.7: Marine archaeology
6. Ship Collision Risks
6.1: Effects from accidents
6.2: Environmental impacts
6.3: Collision Risk Analysis
6.4: Risk management
6.5: Further info
7. Visual Impact
7.1: Public opinion
7.2: Visibility
7.3: planning for acceptance
8. Planning and Environmental Assessment
8.1: Planning rules
8.2: Belgium
8.3: Denmark
8.4: Germany
8.5: Ireland
8.6: Netherlands
8.7: UK
8.8: Legal Framework
8.9: Environmental Impact Assessment
9. References


Wind energy replaces the use of fossil fuels and thus reduces emissions of CO2 and other types of air pollution. While wind power thus haves a strong positive influence on the global and regional environment, it poses a potential threat to the local environment, through especially the influence on birds and the deterioration of landscape.

The above statement is particularly true for offshore wind power because:
* offshore wind power is potentially a huge source of CO2 free clean energy and is regarded as the most cost-effective and promising solution to reducing CO2 emissions Global Environment;
* at the same time, offshore wind power poses, due the huge size of the wind farms, a potential threat on the local scale, due to its Biological Impacts, its potential conflicts with other users of the sea (Conflicts" of Interest, Ship Collision Risks;) and its Visual Impact;as seen form the shore.
Since offshore wind power is still in its infancy, not much is yet known of these impacts. Although impacts are generally regarded as acceptable, it is nevertheless crucial to develop offshore wind power with great care by avoiding sensitive areas and developing more knowledge by executing monitoring programs.
Current planning and licensing by authorities is clearly taking this very seriously, see Planning and Environmental Assessment.

The benefits to the environment from using wind power result from reducing atmospheric pollution. As well as a significant reduction in CO2, other pollutants are also reduced; SO2, NOx, CO, Methane and Particulates. The amount of CO2 emitted by various types of power generation during all stages of a power generation plant's life cycle are listed below. The values given are subject to country by country variation, but the main message is that wind power reduces emissions by orders of magnitude compared with conventional thermal power generation.

CO2 Emissions (Tonnes per GWh)

Sour	Fuel Extraction	Construction	Operation	Total
Coal-fired [1]	1	1	962	964
Oil-fired	-	-	726	726
Gas-fired	-	-	484	484
Nuclear [2]	~2	1	5	8
Wind	N/A	7	N/A	7
Photovoltaics	N/A	5	N/A	5
Large hydro	N/A	4	N/A	4
Solar thermal	N/A	3	N/A	3
Wood [3]	-1509	3	1346	-160

[1] Conventional plant [2] Boiling water reactor [3] Sustainable harvest

The actual saving in emissions depends to a large extent on the mix of types of power generation for an individual country or region and the type of plant replaced by wind power. An example: the German energy mix including nuclear power is 600 ton CO2/GWh, whereas the mix excluding nuclear power is 890 ton CO2/GWh

The general conclusion is that wind power has clear global environmental benefits in comparison with fossil fuel powered generation.

The most comprehensive way of comparing environmental impacts is with Life Cycle Assessment (LCA). An LCA gives an inventory of all environmental impacts of a product within its complete lifecycle, including production, use and disposal. The method has been used for onshore wind turbines (main result: energy for production, maintenance and disposal is recovered in ca. 4 months) and has also been applied for the Horns Rev offshore wind farm ; see [2.1].

further info: see: global environmental impact study

The impact of offshore wind farms on birds is generally considered the most important environmental impact .
Much is known of effects of onshore wind turbines on birds, derived from many studies for many different sites, situations and wind turbine characteristics. An extensive database on avian studies can be found at NREL avian database. A recent analysis of the effects of wind farms on birds (both onshore and offshore) and guidance on environmental assessment criteria and site selection issues can be found in [3.1]. The overall finding is that impacts, such as mortality rates, are low in comparison to other manmade structures, with the lowest effect on local bird populations, a medium effect on migrating birds during low visibility conditions and the relative highest effects occur on raptors.

In view of the still limited experience with offshore wind farms, only a few studies have yet been carried out for offshore wind turbines. Examples are:
* In Denmark, at Tuno Knob offshore wind farm , Before-After-Control-Impact and After-Impact studies were conducted from 1994-97 [3.2], but the results - that no effect of the ten 500 kW wind turbines could be detected on the abundance and the distribution of Eider ducks - were only valid for wintering Eiders. A further night radar tracking study showed that Eiders and Common Scoter appeared to maintain a greater distance from the turbines during poor visibility to avoid flying between the turbines.
* In Sweden, two studies on migrating birds at Utgrunden and Yttre Stengrund have been carried out, observations from Utgrunden [3.3], indicate that Eider ducks have no problems avoiding collisions with the turbines, as the ducks discover the turbines already 3-4 km before they reach the farm, and then subsequently pass the farm at safe distance (1 km). Moreover they favour flying at low altitudes (10 m) thereby reducing collision risks.
* In The Netherlands, bird monitoring was undertaken at the Lely wind farm 1 km from the shore of the IJsselmeer lake, primarily using radar techniques. The main finding was that the observed ducks avoided the turbines, even in conditions of darkness, see [3.4].

Because of the lack of data, it is difficult to draw general conclusions about the possible impacts. Nevertheless the following general impacts may be expected:
* collisions of migrating or feeding birds with turbines (rotor)
* turbines acting as barriers between feeding and roosting grounds or in migrations routes
* ousting birds off their traditional feeding/roosting grounds due to physical changes of habitat

The expected impacts will depend on the following parameters:
* construction work: the impacts on birds during the construction phase are only expected to be temporary and limited. However, the choice of foundation type may be of importance, as it is expected that the hammering of a monopile could cause noise levels up to 150 dB and potentially disturb both breeding and staging birds. If a caisson type of foundation is chosen, the noise level during the construction phase will be lower
* bird species: different bird species react differently and individually to man-made obstacles such as wind turbines. The EIA's for each offshore wind farm must therefore address the avian issues in detail.
* flying heights and migratory paths, depending on the following parameters:
o number of birds: migrating birds in larger amount often fly at higher altitude, thereby encountering less disadvantages of the wind farm. Migrating birds offshore, however, tend to fly at lower altitude than over land.
o weather conditions: during conditions of poor visibility, e.g. in foggy weather, the risk of collisions for birds increases. Furthermore, air pressure, temperature and wind directions influence flying height and direction.
o time of day: birds usually migrate at higher altitudes at night than at daytime, resulting in a decreased collision risk if the flying height then becomes higher than the zone of risk (the rotor height). But in general, as the collision risk increases in situations of poor visibility, the risk of collision will be larger at nigh time than at daytime.
* distance to shore: migrating birds often have their flight path near the coastline, therefore the effects of a near shore wind farm might be larger. In general the number of birds declines with distance to shore, but there is insufficient information available on bird migration away from the coastline
* water depth: as birds prefer shallow water to deep water, due to better feeding possibilities, the risk of collision and ousting should diminish if the farm is placed in deep water.
* feeding conditions: as the foundations prove a good living environment for small fish, mussels etc, this tends to attract bird colonies, feeding from this new fauna. If fishery, as expected, is to be forbidden within the offshore farms, the farm area may serve as feeding ground for birds, thereby improving feeding conditions and minimizing the ousting of birds off their traditional feeding/roosting grounds, but at the same time increasing collision risks.
* dimensions of the wind farm: it is believed that larger turbines, being more visible, will reduce the risk of collision. The negative effects of large-scale offshore wind farms on migrating birds might also be reduced by designing suitable layout arrangements
* operating strategies: the possibility of stopping all turbines at low visibility conditions would reduce collision risks e.g. during times of heavy migrations.
* colour/illumination of turbine: the risk of collision may diminish if the turbines are as visible as possible (which on the other hand may influence the public acceptance negatively, depending on the visibility, i.e. distance to shore). The towers can be painted in bright colours and illuminated appropriately, but concerning illumination this is to be handled with great cautiousness as lights may also attract bird, thereby increasing the risk of collision. Especially the mounting of light on the turbines for ship navigation or repair works may attract nocturnal migrants during conditions of poor visibility, leading to an increased risk of collision [3.5].
* noise/movements during operation: as it is expected that offshore wind turbines will produce more noise than onshore models, e.g. due to increased blade tip speed, this may influence the impact on birds both negatively (ousting) and positively (fewer collisions).
* The noise from maintenance vessels - or helicopters - may cause more disturbances to birds than the noise from the turbines themselves - maintenance should therefore also due to environmental concerns be minimised, using low-noise vessels if the farm is in the vicinity of areas with birds (or other fauna).

Another unsolved question is how close a wind farm can be situated to Bird Protection Areas. In Denmark, the Nysted offshore wind farm will be situated 3 km away from a Special Protected Area, making this farm a very important object in relation to impact studies in relation to birds.

It is obvious that a bird protection area in general cannot be recommended as a suitable area for a wind farm, as collision and ousting risk will be unacceptably high.

As studies regarding the impact of offshore wind farms on birds and general studies on migration patterns are sparse, and as the effects depend on many different parameters, more knowledge is needed, both as general studies concerning bird migration and as site-specific studies: Ecological monitoring programmes/ Before-After-Impact-Studies are highly desirable in order to judge the effect on birds. The public dissemination of such studies is vital to promote good practice through the industry.

Furthermore it will be very important to collect information from different "narrow" site specific studies in order to develop an overall impact description. Fortunately, monitoring of biological impacts, in particular for birds, is included in many of the recently constructed or scheduled offshore wind farms, see "new studies" at the end of this section.

It is important to prevent public concern regarding the effect of offshore wind farms on bird life by careful siting of turbines, away from important migratory paths (where these are clearly defined) and bird habitats and on the basis of serious investigations of populations and behavioural patterns in the specific area, as part of the specific EIA.

If an offshore farm is placed in the vicinity of bird areas, effects on birds should be minimized by considering e.g. type of vessel (low-noise) and time of day and year for construction, maintenance and dismantling work: the collision risk will be lower when carrying out work at daytime and at a time of the year when the number of birds is low, and at a non-sensitive period.

Further info: National Environmental Research Institute (NERI), Denmark: NERI website organised in November 2001 a Workshop on Birds and Offshore Windfarms; proceedings including abstracts of lectures and summary of discussions are expected to become available.

The effect from offshore wind farms on sea mammals (such as seals, dolphins, whales) is generally not considered to be very important. However if the specific site is situated in the vicinity of a sensitive area, such as grey-seal colonies, this question may become crucial in relation to the approval of the project. This was the case for the Swedish Bockstigen project, where a Before-After-Impact-Study was carried out before construction, during construction and two years after start of operation, showing that wind turbines did not affect the seals in any respect [3.6].
The same experience can be drawn from the Tuno Knob Wind Farm , where the seals seem unaffected by the turbines.

At the moment a Danish project is underway by SEAS, where the movements of radio-tagged seals are followed as part of a larger seal surveillance program in relation to the construction of the Nysted offshore wind farm where the population of seals is significant.

Current knowledge regarding sensitivity of sea mammals for disturbances is largely based on work carried out for the oil & gas industry. See for instance [3.7 ]. Although the impact on mammals seems marginal, further investigation is needed in relation to subjects specific for offshore wind farms, such as:

* loss of habitat due to disturbance through noise emission from turbines and from construction and maintenance vessels (or helicopters) and equipment. The disturbance during the construction phase is expected to be only temporary, whereas disturbance from turbines and maintenance vessels might have permanent effects Effects of noise and vibration.
* potential influence from low frequency sound emission and electric and magnetic fields in cables. However, calculations of magnetic fields from submarine cables dug down one metre under the seabed show that the magnetic field on the seabed above the cable will be smaller than the geomagnetic field. Therefore no impacts are expected if the cables are properly buried.
* effect on mammals may increase due to visual impact from large-scale offshore wind farms (moving blades, especially).

General conclusions
* More studies are needed to evaluate the effect from noise and magnetic fields, and the visual impact on mammals.
* Before-After-Impact-Studies, including seismic surveys and monitoring of underwater noise levels, and studies on noise reception of sea mammals must be carried out.
* When planning offshore wind farms, specific protections areas for sea mammals should be avoided, and duration and quantity of noise minimised during construction (especially at sensitive time periods) and operation. Submarine cables should be properly buried or shielded.

Only a few studies deal with the subject of the impact from offshore wind farms on fish, as most of the early offshore wind farms were erected in areas with no or very few fish.
Preliminary observations seem to indicate that the foundations tend to resemble a natural reef, giving good living conditions for fish, benthic communities (communities living on the sea bed, also known as "Benthos") and fauna. Also the fact that fishing with trawling equipment will not be allowed within and in the vicinity of farms, will affect the fish population in a positive way by improving habitat as breeding and resting grounds for fishery species.

The exclusion of fishery will in many cases lead to conflicts with the fishing industry.

A Swedish study of the first offshore wind power project in the world outside Nogersund, Blekinge (Sweden), showed that there was no negative impact on fish from the 220 kW turbine - the fish population within 400 m from the turbine increased, however the fishermen caught less fish when the turbine was in operation (leading to a conflict of interest).

Potentially negative effects are
* effects of Noise and Vibration; on fish life both in the construction phase and after installation, which may lead to loss of habitat. Maintenance vessel may also have a negative impact, but compared to the "usual" impact from fishing boats this must be considered as a minor impact
* especially during construction, sedimentation and turbidity (degree of cloudiness or opacity of the seawater due to disturbed sediment) of water may impact on fish larvae, however this is regarded as a temporary impact. Construction during sensible periods should be avoided, as this may lead to a high fish mortality rate.
* the fact that foundations will serve as natural reefs, but consist of hard material compared to the sea bed, may lead to changed biotope, and thereby to a change in fish population. If the sea bed is rocky, as for instance at many Swedish offshore locations, the potential alteration of biotope will be limited
* electric and magnetic fields around the cables may influence fish since specific species exploit the electric outputs of organisms in saltwater to detect and capture their prey [3.8].

As the effect of noise, vibrations and magnetic fields on fish is relatively unknown, studies and surveys are needed before, during and after construction. Projects should seek to minimise the effect of structures and cabling on existing stocks, their food sources and spawning activity, e.g. by shielding and burying cables appropriately in order to minimise electromagnetic impacts on fish. Construction works should be avoided during sensible periods.

In general the disturbance of seabed, and thereby of benthic communities, will primarily take place during the construction (and dismantling) phase. During operation the effects from gravity foundations will be higher than the effects of e.g. monopile foundations, both due to the simple fact that gravity foundations will cover an area of the seabed larger than is the case for monopile foundations and due to the risk of scouring of the seabed.
Even though a gravity foundation is chosen, the total seabed area covered by foundations will still be very small compared to the total area of the wind farm.

Expected impacts are:
* loss of habitat and individuals due to construction activities. However, the disturbance of the seabed from sedimentation during the construction phase so far only seems to be temporary, as experience from the Swedish Bockstigen project shows
* changes in sediment structure may in some cases rise from changed water flow around the foundations
* footprint of turbine foundations and cables, maintenance vessels, electromagnetic radiation and noise may reduce abundance and diversity of seabed life
* the foundations act as natural reef and introduce fauna, however these artificial hard substrates may cause changes to the biotope structure with unknown consequences regarding benthos and subsequently food chain
* the absence of fishery and shipping (except for maintenance vessels) will have a positive local effect on fauna and seabed

General conclusions: The quality and quantity of possible impacts on seabed and benthos are not well known, calling for surveys of specific project sites, both as part of the EIA and as generic studies. When designing wind farms, maintaining or improving habitat for local species of importance should be considered.
In general the subject of cables need to be further investigated in relation to impacts due to physical size and electromagnetism; the area around the cables may be included in the fishery exclusion zone.

These topics are only considered important at a very few special locations, due to the typical low ratio between foundation diameter to inter turbine spacing.
However, detailed modelling may be necessary depending on size of project, proximity to shore, shallowness of water and general sensitivity of local hydrography or sea currents.

In order to avoid impacts on hydrography, sea currents and water quality, foundations should be designed to minimise scouring, erosions, sediment redistribution and alteration to current flow. Projects must minimise risk of contamination during construction, operation and decommissioning and avoid use of pollutant chemicals when foundation, tower and turbines are protected against marine environment.

The effects on the environment due to accidents are to be taken seriously, as for instance a collision with an oil tanker may in worst-case cause severe damage to fauna and flora, water quality, coastline etc.
As the consequences of collisions may be very serious, mitigating measures are called for in order to minimise collision risks. Examples are: proper marking of farm/turbines and protection of cables. However it should be noted that the collision frequency is relatively low and that for a properly designed wind turbine support structure, a collision with a tanker should not result in ship damage and thus not in severe environmental damage.
For a further discussion see Ship Collision Risks.

In view of the lack of detailed knowledge on biological impacts of offshore wind farms, many R&D programmes have recently been initiated or are scheduled in the near future, most of them in connection to newly constructed wind farms or wind farms under development.
Extensive monitoring is going on in connection with the Horns Rev wind farm ; both before construction, during construction in 2002 and in current operation.

In Germany, monitoring of the existing situation in the potential offshore wind farm areas in the North Sea and the Baltic started in 2002 and will continue for several years. Key projects are MINOS and BEOFINO. MINOS is a research project which examines whether large scale offshore wind farms within the German parts of North and Baltic Seas affect or endanger harbour porpoises, common seals and sea birds. The research results are expected to provide the knowledge for estimating and assessing the impacts of future wind farms.
BEOFINO will perform platform-based field studies on the impact of offshore wind farms on the marine environment. The main focus of the project is to investigate possible impacts of future offshore windturbines on the marine environment and to develop methods and criteria for the evaluation of such impacts. BEOFINO consists of work packages on the effects on the migration of birds (and bats), on the effects on the benthic communities near the piles and on the effects of the electro-magnetic fields of sub-sea cables on marine organisms.

In The Netherlands extensive impact studies are scheduled for the NSW Nearshore wind farm while studies are also intended to be carried out for the Q7-WP wind farm .

In the UK, the Collaborative Offshore Wind Research into the Environment (COWRIE) project has been set-up in 2001 with funds based on financial deposits made by offshore wind farm developers. Current topics include effect studies of electromagnetic fields on fish, of noise on marine mammals, displacement of birds from feeding areas and development of bird study methodologies.

Much work is being carried out on development of methodologies and monitoring techniques, in particular regarding the impact on birds. Radar, infra red video and acoustic detection are examples of new high tech techniques.
For a recent summary see [3.1].

Noise from wind turbines arises from the movement of the blades through the air (aerodynamic noise) and the consequent transmission of power and momentum in the nacelle (mechanical noise). Furthermore, noise may arise from the control equipment within the tower (power electronics).

The degree of noise effects is primarily dependent upon the level and character of the noise emitted, the distance from the turbines to potential sensitive receivers, wind directions and background noise levels.
It is expected that airborne noise may have the following impacts:
* ousting of birds
* loss of habitat for marine mammals
* decrease in public acceptance if turbine noise is audible to humans from the shore

Noise is also an issue of public concern, although the noise from offshore wind farms will not generally be audible on shore. Nevertheless, it appears that wind power has received a reputation for being noisy, which, together with the fact that noise propagates much easier over the sea than over land, is reflected in the public attitude towards wind power, including offshore wind.

Turbine manufacturers may be tempted to place less emphasis on noise control, because the noise impact from offshore wind farms is not perceived as a significant problem with the turbines being placed far enough from shore to give what is believed to be inaudible levels of noise. Such an attitude, combined with increases in turbine size and the blade tip speed might, however, lead to the problem arising anew.

During construction of offshore farms, airborne noise from construction work (vessels, ramming etc.) is expected to effect birds and marine mammals (ousting), but as the effects are of limited duration, the effects are expected only to be temporary. However, sensitive time periods like breeding or nursery periods should be avoided if the construction site is placed near important biological areas - which may be in conflict with the intentions of the developers to establish offshore wind farms when stormy weather is least probable.

During construction, underwater noise from construction vessels and drilling or piling equipment may have a detrimental effect on marine mammals, fish and benthos. These effects are especially evident, when hammering down mono piles - experience from Sweden indicates that this construction method results in a shock reaction from fish, actually loosing conscience and drifting in the water surface as were they dead. However, the effect is temporary, but sensitive time periods should absolutely be avoided - in the case of fish larvae, construction work at sensitive periods may result in a very high fish mortality rate.

During operation, noise from offshore turbines can be transmitted into the water in two ways: the noise either enters the water via the air as airborne sound, or the noise is transmitted into the water from tower and foundation as structural noise. The frequency and level of underwater noise is thereby to a certain degree determined by the way the tower is constructed and by the choice of foundation type and material (monopile/steel - or caisson type/concrete - foundation).
Underwater noise from offshore wind turbines must of course exceed the level of underwater background noise (ambient noise, especially from ships) in order to have any impacts on marine fauna.

The following frequency areas were used for measurements during the EIA process for the Horns Rev offshore wind farm :

Porpoises:
Produce pulsed sounds: 2 kHz (perhaps communication)
Echo localization sounds: 13-130 kHz
Fair hearing: 1-150 kHz
Good hearing: 8-30 kHz

Speckled Seals:
Produce sound: 0,1-40 kHz
Fair hearing: 0,1-60 kHz
Good hearing: 1-50 kHz

Fish: 0-130 kHz

Generally speaking, porpoises and seals are sensitive to high frequency noises, seals in the range from 100 Hz to 40 kHz, porpoises at 100kHz and higher. Fish are sensitive to low frequency noises, below 20 kHz.

The effects on marine life from vibrations of the turbines are rather unknown, but as the developers seek to avoid resonance in the tower, the effects on especially fish and benthos may be limited.

Measurements from Vindeby (caisson foundation type) and Bockstigen (monopile) offshore farms indicate that underwater noise is primarily a result of the structural noise from tower and foundation. When the results were scaled up, based on measurements from a 2MW onshore wind turbine, it was concluded that the underwater noise might be audible to marine mammals within a radius of 20 metres from the foundation. Generally it is believed that for frequencies above 1 kHz, the underwater noise from offshore turbines will not exceed the ambient noise, whereas it is expected that for frequencies below 1kHz, noise from turbines will have a higher level than the background noise.

Only measurements and impact studies after the construction will reveal if underwater noise will really affect marine mammals.

The impact on fish from low frequency sounds (infrasound, below 20 Hz) was not estimated, and in general this area is covered with much uncertainty. A planned study at Vindeby , carried out by SEAS, investigating the effects from noise and electromagnetic fields on fish communities living at the seabed, may yield valuable information regarding this subject.


Some areas may definitively be excluded from consideration for use for offshore wind power. These are major ship lanes, areas close to airports, oil & gas pipelines, cable routes, raw material deposits, military restricted areas and areas of importance in relation to fauna, e.g. Important Bird Areas. However, most other suitable sites will confront a number of potential conflicts of interests with other uses and users of the locations. Most potential conflicts of interest apply to areas already known in the planning phase, thus severe conflicts of interest which could stop a project can theoretically be avoided through careful, open planning.

Interference with maritime traffic is generally seen as the most important issue regarding potential conflicts of interest. Obviously major shipping lanes and anchoring sites will not be allowed for siting offshore wind farms, but interference with traffic remains an issue for most other sites. Offshore wind farms must undoubtedly be marked properly and effectively, in accordance with national or international guidelines (AISM/IALA Recommendations for the marking of offshore structures, 1984, 2000). However ship collision risks will remain present and should be dealt with accordingly.

Civil air traffic does not appear to be a major critical issue [5.1], although certain areas will be prohibited for use as offshore wind farm sites where protection of air navigation demands this (by Civil Aviation Authorities, either national or international (ICAO))
The requirements posed by helicopter traffic seem to be the most important concern, such as the case of a rescue helicopter having to access an offshore wind farm in heavy weather. As the wind farms may have quite heavy turbulence, helicopter manoeuvres within the area are difficult, making marking lights and ability to switching off all turbines immediately a serious safety issue.

Military area restrictions disqualify a number of feasible sites from being developed. Especially for Sweden and Finland this is considered problematic as a significant part of potential wind power areas have a military destination. Practical solutions for co-existence between military and wind power are called for, but a solution must come through the political system.

As an example of the importance of and need for political solutions, the British Ministry of Defence has objected to certain sites on land and offshore as they would interfere with low flying aircraft, even though these sites were not in close vicinity to military airports or equipment, but apparently just due to the fact that the height of the turbines represents a danger in itself.

The disturbance of radio and radar signals has been subject of negotiation in several countries, and in general the issue of radar is approached with much concern, as the disturbance of radar signal from offshore wind farms may become a serious obstacle to future development.

Based on preliminary Swedish studies [5.2] the following conclusions can be drawn:
* The effect of wind turbines vary with different radar systems - the radar defence systems of NATO countries are less affected by disturbance from wind turbines than for instance the Swedish radar system, because NATO's radar system is primarily based on satellites and airborne radar equipment, whereas some parts of the Swedish radar defence system consists of older units and hence less advanced equipment. With modern radar equipment, disturbances should be minimal.
* The disturbance of (Swedish) radar equipment from turbines is only related to moving blades:
* the movements of the blades are registered by the radar as false echoes, giving rise to several dots on the operator's screen, which may be confused with the echoes from an aircraft.
* For experienced radar operators this disturbance should be easily handled when the radar installation is not situated within the wind farm, and if the exact coordinates of the wind turbines are known, the radar system/operator should be able to compensate from the false signals, [5.1].
* If the turbines are stopped, there will be no disturbance of the radar system.
* The disturbance of radio signals is primarily caused by reflections from the tower and is depending of the frequency band of the radio links - influence from wind turbines may impair the performance for radio relay links for frequencies between 2 and 10 GHz.
* The potential disturbance effect of radar and radio signals increases with the number of turbines

As an example of measures to mitigate the effect of wind turbines on radar systems and to decrease the collision risk, it can be mentioned that in the UK, whenever relevant, wind farms will be equipped with radar reflectors/intensifiers and fog signalling devices, as specified by the Department of Environment, Transport and the Regions [5.3].
Another example: the Norwegian Armed Forces (March 2002) claimed that 8 of the 23 planned wind power plants in Norway may lead to major problems for their radar and telecommunication systems, and therefore shouldn't be build. Another 8 plants have to be adjusted before the defence is willing to accept them.

It can be concluded that although solutions seem to be available, it will be important for the development of large-scale offshore wind farms that the subject of interference with radar and radio systems is more closely investigated, as the potential effects are system- or country-specific.

The conclusions from the following studies may contribute with valuable information:
* A UK study carried out by Ministry of Defence, undertaking a number of trials to determine the extent of interference with radars from wind turbines, but these data have not been published yet. A BWEA working group has been convened to address this issue.
* A Swedish study concerning impacts on radar and radio systems finalised in 2001.

Restrictions to fishing rights from offshore wind power are bound to be an area of conflicting interests as the fishermen will lose trawling ground and possibly areas for pot fisheries. Up to now this conflict has not excluded any projects from being carried through, but financial compensation must be given to the fishermen, often without much evidence that fishing is actually reduced. This conflict appears to be especially problematic for France, where the fishing lobby is very strong and do not hesitate to block harbours, if they feel their interests threatened, but such problems may also occur elsewhere since the fishermen are generally well organised all over Europe.

On the other hand, there is also a positive effect. Preliminary observations seem to indicate that the foundations tend to resemble a natural reef, giving good living conditions for fish and fauna. Also the fact that fishing with trawling equipment will not be allowed within and in the vicinity of farms, will affect the fish population in a positive way by improving habitat as breeding and resting grounds for fishery species.


In order to minimise impacts on fish, and thereby reducing the risk of conflicts with fishermen, it is recommended to
* avoid construction of wind farm in sensitive spawning areas, areas with species of commercial or conservation importance and areas with a very high value for fisheries
* avoid construction during important breeding, nursery or feeding periods
* carry out site-specific and species-specific monitoring studies in order to investigate the effect of offshore wind farms on fish, e.g. investigate if foundations may indeed serve as natural reefs, as indicated from previous studies Vindeby wind farm , thereby increasing fish life, and investigate the consequences on fish population/fishing possibilities when fishing is restricted within and in the vicinity of the wind farm.

The siting of offshore wind farms may interfere with existing raw material deposits. As these deposits are well known already, this should however not lead to any significant conflict of interests. It is furthermore believed that offshore farms do not exclude extraction of, for instance, oil in the same area and that there may be possible synergies from simultaneous energy production in offshore wind farms and raw material extraction.

Seismic site surveys and historical records investigation during the planning phase prior to the decision of the exact location of the turbines should avoid possible conflicts of interest. Specific areas of archaeological interest should be avoided. If, however, for instance a wreck is found during installation, this may lead to a serious delay of the whole project. Measures must therefore be taken to avoid such incidents by carrying out the investigations necessary in the EIA.

Accidents between ships and wind farms could results in damage to both the wind farm, the ship and the local environment, as illustrated below.

Although the probability of occurrence of ship collisions is (or should be) very low, the scale of the consequences could be extremely large. For instance, a collision with a HV station could (in an extreme case) result in a loss of hundreds of millions euro's as loss of investment, loss of energy sales and penalties.
Also the effects on the environment due to accidents are to be taken seriously, as for instance a collision with an oil tanker may in worst-case cause severe damage regarding fauna and flora, water quality, coastline etc.
As the consequences of collisions may be very serious, mitigating measures are called for in order to minimise collision risks and collision damage.

Accidental impacts on the environment may origin from collision between a ship (such as an oil tanker or a maintenance vessel) and wind turbine/foundation, substation, or submarine cable.

The effect of such accidents may be a pollution of the environment caused by substances from the offshore farm (turbine/substation/cable) or substances from the colliding ship. The consequences of such a collision depend on many parameters, such as type of ship/, collision angle, ship speed at collision and design of the structure itself.
If larger ships, such as oil tankers, collide with a turbine, in many cases it is to be expected that only the turbine and foundation will be seriously damaged and the ship will remain undamaged. Several manufacturers even design their support structures such as to cause minimal damage to colliding ships. A ship collision does thus not necessarily mean leakage of huge amounts of harmful substances.
In case leakage of polluting substance occurs, the degree of impact on the environment will depend on weather conditions (temperature, wind speed) and the physical properties of the polluting substances.

The most possible polluting substance in these cases is regarded to be oil from ships. Diesel oil from fishing boats and maintenance vessels is less a problem than oil from larger ships, because diesel oil will evaporate to a relatively high degree compared to bunker oil. The most critical event would be the pollution resulting from a collision with an oil tanker, as this collision would result in the leakage of considerable amounts of jet fuel and bunker oil. The bunker oil is the more destructive due to its low evaporation rate. The consequences of such a collision calls for development of special emergency procedures with a short reaction time for each large offshore farm.
Oil spillage deriving from the turbine is not an issue of major concern, as the turbines contain only small amounts of oil. Also the diesel oil inside the substation is not regarded as being a major source of risk, as the oil amount is limited and the diesel oil will relatively easy evaporate. damage on submarine cables may cause release of mineral oil isolating the cable, is this type of cable is chosen. During the construction of the Middelgrunden Offshore Wind Farm , the submarine cables were damaged three times, however without environmental impacts, as the cables did not contain oil as isolating material.

Collision risk analyses are to be carried out as part of the EIA and are moreover of great use for choosing cost effective and balanced risk mitigation measures.
The phenomenon of ship collisions with offshore wind farms is more or less comparable to other ship collision issues, such as with ship/ship collisions, collisions with offshore oil/gas platforms, or collisions with large bridges (Oresund Link). Use can therefore be made of knowledge and models developed for these other issues. The few currently available studies on ship collision risks for offshore wind farms are indeed based on such models, such as in the EIA's for the 160 MW wind farm at Horns Rev [6.1], the 100 MW Near Shore Wind Farm at Egmond aan Zee and the 120 MW Q7-WP wind farm at the Q7 block of the Dutch EEZ. For these projects extensive studies have been made on ship traffic statistics, ship collision scenario's and probabilities, oil spill and oil pollution scenario's.

Notwithstanding the wide use of probability models for ship collision problems, a number of elements should be improved or developed in order to make such models suitable for analysing ship collision risks with offshore wind farms, as can be expected, taking the lack of experience with collisions of this kind into consideration.
With support from the EU FP5 programme, a consortium of a wind farm developer. a wind turbine manufacturer, maritime R&D institutes and a wind energy certification institute started February 2003 the SAFESHIP project, aiming to develop a comprehensive and dedicated model for the analysis of risks associated with ship collisions with offshore wind farms. See for actual info the website of the SAFESHIP co-ordinator E-Connection project BV

As the consequences of collisions may be very serious (although the collision frequency is relatively low) mitigating measures are called for in order to minimise collision risks, collision damage and potential environmental impact:
* Collision risks can be reduced by passive measures, such as proper marking of the wind farm and the individual wind turbines or by active measures such radar based ship detection in combination with emergency towing capabilities.
* Collision damage can be reduced by classical fendering techniques and damage reduction design optimisation.
* Environmental impact can be reduced by proper oil spill contingency and mitigation planning.
An overall risk management approach is to be followed to develop a cost effective balanced package of measures. Such an approach combines risk assessment, design measures and active risk control measures. In addition to the development of a risk analysis tool, the above mentioned SAFESHIP project follows such an approach to develop a catalogue of cost-effective risk reducing technologies and methodologies.

recent event: 1e Fachtagung "Offshore WindEnergie - Schifffahrt, Windpark, Umwelt"
17 June 2002, Hamburg (Germany), Germanischer Lloyd WindEnergie, Germany
info: Gundula Fischer, gfi@germanlloyd.org

The visual impact, along with the impact on birds, is considered the most important environmental impact. This reflects the growing public concern in Europe on the visual effects of wind power on the landscape in general. This is illustrated by the situation in Denmark, where policy has banned the further development of wind power from onshore to offshore locations. However, offshore farms raise new concerns regarding visual effects as wind turbines here represent man-made structures in an otherwise open landscape.
For the offshore farms already established at near shore locations, concerns on the visual impacts have played a major role in the public hearings. Also the visual impact is a determining factor for public acceptance at locations renown for their scenery or close to recreational areas.

A public opinion survey in the Netherlands concluded that visual disturbance was the most important impact factor, but would not necessarily result in fewer visit to the affected location - the wind farm may also have positive effects on the visiting public, becoming a tourist attraction with visitor centres onshore and boat trips to the farm. The fact that offshore farms may become tourist attractions is probably one on the reasons why the mayor of Nysted (the municipality closest to the has insisted on renaming the planned Rodsand wind farm in "Nysted Offshore Wind Farm" ). The same results were found in Germany [7.1] where it was concluded that offshore wind farms would have no negative impacts on tourism as long as the farms were at least 15 km from shore

As the visual impact is a matter of the viewer's taste, it must be expected that there will always be public resistance, especially for near-coast projects, but even offshore projects invisible from the shore may experience public resistance in connection with being seen from ships, boats and ferry lines.

Obviously the visual impact diminishes with the distance to shore, and in general it is assumed that the visual impact to viewers at sea level is negligible when the farms are located more than 8 km from shore. At 45 km from shore, wind farms will not be visible due to the curvature of the earth's surface. These distances will be greater where there are elevated viewpoints, but may also be much less, depending on the weather and atmospheric clarity.

The visibility from shore will also depend on navigational marking lights and painting. In order to minimise the risk of collision with naval or air traffic, authorities put requirements on blade painting and marking lights. In most cases nacelle lights are required as a minimum, following the standards for onshore turbines and other high buildings.
In Germany, for instance, buildings larger than 100 m must have marking lights, and colours on the blades are mandatory for wind turbines larger than this size.
The subject of marking lights and visual impacts is illustrated in an example from Denmark, where the Danish Forest and Nature Agency has recommended that the turbines chosen for the Nysted Offshore Wind Farm should not exceed 100 m. (from sea level to upper blade tip), in order to avoid marking light requirements set by the Danish Civil Aviation Administration. The recommendation of the Agency was purely motivated by visual impact concerns.

In Denmark research is carried out on how to colour the turbines to appear as neutral as possible in relation to the surrounding nature. This obviously could conflict with navigational requirements.

The general conclusion is that turbines must be marked properly and effectively in accordance with national and/or international guidelines in order to minimise risk of collision with ships, low flying aircraft or helicopters. Consequently, painting and illumination/marking lights may have negative consequences for the visual impact and increase the risk of collision with birds, both subjects resulting in the fact that the public acceptance of the farm may decrease. Therefore the safety issue should be well balanced with the environmental impacts, and the consequences of marking lights etc. on visual aspects and bird interests should be thoroughly investigated in the EIA.

Visualisation with digital imaging techniques has become rather popular for wind farm visualisation purposes and has also frequently been used for offshore purposes.
The enclosed example is an Artist impression of the Dutch Nearshore wind farm (NSW) project near Egmond aan Zee. [Source: Haalbaarheidsstudie Near Shore Windpark, Novem]

A word of care regarding the value of visualisations. Swedish investigations indicate that visualizations can cause problems with acceptance because pictures do not always present the true visual impact of wind turbines on a landscape.
Offshore wind farms should in general be placed as far away from the coast as possible, and in particular proximity to recreational areas and/or coastal settlements should be avoided.

Experience from Denmark (Middelgrunden Wind Farm) ) indicates that local involvement in the ownership of the wind farm may have an important role for the acceptance of the visual impact close to a city. Early local involvement in the planning phase is thus essential and community involvement in ownership of the wind farm will be beneficial.

Furthermore, an open and careful planning process with detailed visualizations may result in less public resistance. In the case of the Middelgrunden project, as a result of visualizations and public hearings, the farm layout was changed from 3 rows with 9 turbines to a single curved row with 20 turbines. This change of farm layout and thereby of the visual impact gave rise to increased public acceptance. Thus farm lay-out, number and size of turbines and cumulative effects should be thoroughly and openly analysed and discussed before decision is taken.

The political attitude towards offshore wind power is in many EU countries very positive, which is reflected in the fact that several countries have established ambitious targets for the exploitation of offshore wind power. In the most ambitious plans many thousands of MW offshore wind power plants are planned within the coming 10-25 years.
In most countries, however planning rules and regulation did not yet exist when those targets were formulated. See for instance the study carried out by Ecofys [8.1] describing the situation in many countries around the year 2000. Since than, much effort has been devoted in formulating strategies and implementing resulting planning rules and regulations for permitting offshore wind farms.

The situation for some countries is (summer 2003) as follows:

In 1999 already, Belgium provided regulation, which a.o. resulted in quick permitting and development of the Seanergy 100 MW wind farm at the Vlakte van Raan . However, an irregularity in the legal procedures has enabled opponnets to postpone the project.
A Green Certificate system has also been introduced with positive support potentials for offshore wind farms. Unfortunately several details of the system remain to be clarified before project developers and investors will be in a position to proceed with go-ahead decisions. As a result of both these procedural problems, offshore wind developments are stagnating.

The "old" Danish Government's Action Plan for Energy called for an accelerated development of offshore wind power up to 4000 MW in 2030, and a first agreement between the government and the utilities, which obliged the utilities to build a total of 750 MW offshore wind power during the period from 2001 to 2008. The Horn Rev wind farm ), currently under construction, is scheduled to be the first wind farm under this program, to be followed in 2003 by Nysted Offshore Wind Farm ).
The new Danish liberal-conservative government concluded in 2001 however that the RES targets for 2003 has already been surpassed and for this reason it cancelled the installation of the next three offshore wind farms (totalling 450 MW).

Germany has an ambitious target of 3000 MW of offshore wind power in 2010, while for 2030 even 25.000 MW is mentioned. As most near shore sites are either nature protection area's or have important tourist values, the German development are focused on deep water with water depths between 20 and 40 meter.
The legal framework for offshore wind parks within the 12 nautical miles zones is rather confusing because both federal and state law is applicable. Further away from the coast only federal law is applicable. The federal law foresees at this moment no specific guidelines. As such one has to deal with a set of rules that make several governmental instances competent for granting approvals. Locations are identified by eliminating areas for several reasons (environmental, military, shipping, etc.). The Environmental Impact Assessment is of central importance for obtaining a concession in German territorial waters or the exclusive economic zone.
Government support is currently focussed on dealing with environmental issues, such as with the execution of extensive ecological monitoring programmes in prospective offshore wind farm areas in both the North Sea and the Baltic and with the development of harmonised EIA procedures.

The Irish Republic was quick to issue a coherent set of rules regarding licensing of offshore wind farms. It has made clear that offshore wind parks are eligible everywhere in Irish waters unless it is forbidden. Licenses are approved in 2 phases. Phase 1, "the Site Investigation License', allows consortia to investigate whether the targeted site is suitable and economically viable. Under phase 2 a full license can be granted in case all approvals have been obtained. The first such license was issued January 2002 for the Arklow Bank wind farm ). Environmental and safety prescriptions are in place although it is still allowed that the Minister may include additional requirements. Financial support for renewable energy cones from the Alternative Energy Requirement (AER) competitions. The latest, AER 6 (announced February 2003) gives funding to several offshore wind farm developments.

Although the Dutch Government is convinced of the importance of offshore wind energy, the actual implementation is increasingly lagging behind targets. Even the long awaited Nearshore wind farm NSW is delayed until at least 2004. The NSW is a government initiative for a demonstration wind farm to obtain the necessary experience to further develop offshore wind parks. The site has been selected, the conditions to build the wind park were defined and a tender procedure was started in 2001 to select a consortium. This tender was won by the Shell/NUON consortium, but go-ahead stalled as a result of reduction in production incentives, uncertainties regarding tax benefits and procedural delays.
The financial uncertainties have also delayed the construction of the private initiative Q7-WP wind farm .
More information regarding the Dutch situation can be found in the Dutch Corner of this site.

The UK is, from a wind resource point of view, by far the best place to install offshore wind parks. A subsidy program for offshore wind energy development is in place as part of the NFFO, de Non Fossil Fuel Obligation Act. In 2001, some 18 companies have been selected (for 13 sites in territorial waters) which received rights to develop wind farms with NFFO financial support, with a total power of approx. 1600 MW. In the summer 2003. most of these projects were still alive and even 6 project are close to realisation. In the 2nd round of offshore wind development, the UK Government called for proposals to develop another 6000 MW of offshore wind farms in 3 strategic zones around the UK.
Much effort is also being given to streamlining legislative processes with emphasis on environmental issues. Strategic EIA's (SEA))for a number of areas are being carried out, unified environmental procedures (monitoring, EIA, assessment criteria) are being developed and joint research on environmental issues is going on, see (COWRIE).


The fact that the legal framework is still under construction and unclear in many countries is to be regarded as a major limiting factor to the development of offshore wind energy.
Moreover, national planning rules may vary significantly within the EU, and even on the national level, different and confusing legal frameworks exist within individual countries. Different regulations regarding the same subject exist in several countries, depending on whether a proposed farm is located inside the 12 nautical mile zone (often referred to as "territorial sea") or outside ("exclusive economic zone", extending from the 12 nm zone seawards to a maximum of 200 nm from the shoreline).

With EU FP5 support, a number of countries (United Kingdom, Ireland, Sweden, Denmark, Germany, Poland, and the Netherlands) initiated started early 2003 the "Concerted action for offshore wind energy deployment (COD)". The objective of the COD group is to speed up the implementation of offshore wind energy in the European Union by early identification and possibly removing non-technical barriers: legal, administrative, policy, environmental and infrastructure issues. COD aims to provide a harmonised European process for deployment, environmental impact analysis and for permission procedures for Offshore Wind Energy Farms. See COD


Within the EU, an Environmental Impact Assessment (EIA) must be carried out before public approval for larger projects can be granted. The term "Environmental Impact Assessment" (EIA) covers the procedure that fulfils the assessment requirements of Directive 97/11/EC. In many countries, e.g. in the UK, the environmental information provided by the developer is presented in the form of an Environmental Impact Statement (EIS), which may then be described as the final product of an EIA. In this report only the term EIA will be used The minimum requirements of the EIA are specified in the EC Council Directive 85/337/EEC amended in Directive 97/11/EC.

The directives require that private and public projects, which are likely to have significant effects on the environment, must be subject to an assessment of their potential effects on the environment before they can be allowed to proceed.

An EIA shall identify, describe and assess the direct and indirect effects of a project on the following factors:
* human beings, fauna and flora
* soil, water, air, climate and the landscape
* material assets and the cultural heritage
* the interaction between these factors mentioned

The directives lay down rules for the EIA procedure, which includes a requirement for public participation: the results are to be made public, and the views of the public taken into consideration in the consenting procedure.

Wind energy projects are specifically mentioned in Annex 2 of the Directive 97/11/EC, indicating that the individual member states shall determine, either through a case-by-case examination or through thresholds or criterions set by the member state, whether wind power projects shall be made subject to an assessment.

In this way member states may exempt a specific project from the provisions in the directives, but it is unlikely that any offshore wind farm may be publicly approved without an EIA because of its size and the public attention regarding its environmental effects.

Developers of offshore wind farms must carry out an EIA on the specific project, with the purpose of providing information about the possible impacts on the environment from the time of installation till the dismantling of the turbines and foundation.
The EIAs from individual offshore wind energy projects will contain much valuable information regarding the effects from wind energy on the environment and provide valuable sources of information:

country	projects with EIA's	examples/information sources
Denmark	Horns Rev; Nysted, Middelgrunden	Horns Rev or:Horns Rev Nysted Middelgrunden
Ireland	Arklow Bank	-
Netherlands	Nearshore Wind Farm (NSW) ; Q7-WP	NSW: contact mr. Ruud de Bruijne: r.de.bruijne@novem.nl , or at NSW Q7-WP: contact Mr. H. den Boon of E-Connection: den.boon@e-connection.nl
United Kingdom	Burbo Offshore Wind Farm	Burbo

[2.1] H. Hassing, Life Cycle Assessment for Wind Turbines, EWEC 2001, pp 131-133, 2001

[3.1] Langston, R.H.W., Pullan, J.D., Windfarms and Birds: An analysis of the effects of windfarms on birds and guidance on environmental assessment criteria and site selection issues, BirdLife Report written on behalf of the Bern Convention, september 2002. Available ad pdf download

[3.2] Clausager, I., Impact assessment studies of offshore wind parks on seabirds with special reference to the Tuno Knob Park, in: Merck & von Nordheim: Technische Eingriffe in Marine Lebensraume, Tagungsband. BFN-Skripten 29. Bundesamt fur Naturschut,z 2000.

[3.3] Petterson J., Bird observation in Southern Kalmar Sound Stage 1, 2001

[3.4] Dirksen, S., Spaans, A.L>, Winden, van der J, Van Den Bergh, L.M.J. Nocturnal flight patterns and altitudes of diving ducks in the IJsselmeer area, Limosa Vol 71 (1998), pp 57-68.

[3.5] Noer, H., Christensen, T.K., Clausager, I., & Petersen, I.K., Effects on birds of an offshore wind park at Horns Rev: Environmental impact assessment. Neri report. Danish Ministry of Environment and Energy & Danish National Environmental Research Institute, 2000.

[3.6] Sundberg, J. & Soderman, M, Windpower and grey seals: An impact assessment of potential effects by sea-based windpower plants on local seal population. Department of Animal Ecology, Uppsala University, 1999.

[3.7] Background Information on Marine Mammals relevant for SEA2, SMRU, August 2001. Available as pdf download

[5.1] Jago, P, Taylor, N., Wind turbines and Aviation Interests - European Experience and Practice, STASYS, published as ETSU report W/14/00624/REP.
Available as pdf download

[5.2] Forsvarsmakten, Vindkraftsprojektet (Forsvaret och vindkraften), en allman beskrivning, {in Swedish: Swedish Armed Forces: The wind power project (The Defense and the wind power): A general presentation}, 2000.

[5.3] UK Department of Trade and Industry, (Contractor Metoc PLC), An assessment of the environmental effects of offshore wind farms, Report ETSU W/35/00543/REP, 2000.

[6.1] Randrup-Thomsen et Al, Risk of Oil Pollution due to Ship Collision with Offshore Wind Farms.

[7.1] Institut fur Tourismus- und Baderforschung in Nordeuropa , Kiel (N.I.T.), Effects on tourism from on- and offshore wind turbines in Schleswig-Holstein, September 2000.

[8.1] Broad, D. et Al, Inventory of Policy Regulations, Administrative Aspects and current projects for Offshore Wind Energy in Northern Europe, Ecofys report E60146, January 2001

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